WO2003029843A1

WO2003029843A1 - Magnetic saturation and coupling

Info

Publication number: WO2003029843A1
Application number: PCT/US2001/030546
Authority: WO
Inventors: K. Amini Bijan
Original assignee: Em-Tech Llc
Priority date: 2001-09-28
Filing date: 2001-09-28
Publication date: 2003-04-10

Abstract

The invention subject of this invention pertains to means and methods for transmitting electromagnetic signals into or through magnetically permeable and electrically conductive materials. The invention also teaches methods and apparatus for receiving return signals from the or through the material, thereby allowing information to be collected pertaining to matter existing on the opposite side of the material. The subject invention teaches various techniques for creating EM wave transparencies in materials such as carbon steel and iron. The invention further teaches methods and apparatus for varying, in a controlled manner, the size of the transparency, the creation of multiple transparencies, the sequential opening and closing of the transparencies, utilzation of one or more transmitting and receiving devices, each of which may be located at its own transparent opening. The invention also teaches methods and apparatus for creating such transparencies in small and confined spaces and that can be moved within small spaces. The invention also teaches methods for inducing a spectrum of magnetic or electromagnetic signals in such permeable and conductive materials that may be used to identify the specific condition and composition of the materials.

Description

TITLE MAGNETIC SATURATION AND COUPLING BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to transmitting and receiving electromagnetic energy through or across materials that have previously been barriers to the penetration and passage of this type of energy. Specifically, the present invention relates to a method and apparatus for transmitting electro-magnetic energy into or across ferromagnetic materials, paramagnetic metals or other electrically conductive materials that are magnetically permeable. These materials are barriers through which electromagnetic energy typically cannot penetrate into or pass through. The invention also relates to a method and apparatus that can concentrate the magnetic flux field lines penetrating into a small region of the barrier material. This reduces the power required to fully or partially saturate the selected region of the barrier material.

Further, the invention relates to a method and apparatus that bends magnetic flux lines as they penetrate through such barrier material. This bending is a result of the changed permeability of the barrier material. This magnetic flux bending can be used to focus the magnetic flux as it penetrates through the barrier material into the matter or objects on the other side of the barrier. More specifically, the controlled focusing of the magnetic flux partially counteracts the normal rapid geometric spreading of the flux field. In turn, concentrating the magnetic flux allows distant sensing of or focusing upon objects using much less power than would otherwise be required.

The invention relates to a method and apparatus comprising at least one electromagnet or permanent magnet capable of at least partially saturating a region of barrier material. The apparatus also comprises one or more transmitter magnets having means to simultaneously create oscillating magnetic flux lines penetrating into the saturated or partially saturated region of the barrier material. The device also contains means for receiving electro-magnetic energy from or across the area of saturation. The apparatus may also include means to vary in a controlled manner the frequencies of the oscillating or non-static magnetic flux field. The degree or level of saturation of the volume area, i.e., region, of the barrier region may be controlled to create a magnetic lens that focuses the flux field lines. More particularly, the present invention relates to a method of studying the properties or characteristics of a barrier material fully or partially saturated with magnetic flux. This is performed by detecting and measuring the magnetic flux field induced by electric current (eddy currents) generated by the passage of the transmitted oscillating magnetic signal permeating into or through the affected region of the barrier material. The method and apparatus of the invention do not require physical contact with the barrier material for the detection or study of the properties of the barrier material or objects on the opposite of the barrier material. The apparatus may be stationary and the barrier material being studied moved in relation to the stationary apparatus, or the apparatus may be moving across a surface of stationary barrier material. The invention also pertains to an apparatus that can be used to determine or measure the electrical characteristics or electrical properties of such objects existing behind or on the opposite side of the barrier material.

2. Description of Related Art

There are many examples of the use of electro-magnetic (EM) energy for sensing and measurement. However, materials that are electrically conductive and are magnetically permeable act as barriers to the use of EM energy for sensing and measurement. (These barriers are hereinafter termed "barrier materials" or "EM barriers".) Magnetic permeability is the ability of a material to absorb magnetic energy: The limitation in sensing or measurement by electro-magnetic energy through EM barriers has prevented utilization of EM energy for sensing or measuring through carbon steel tanks, pipelines, well casings and the like. It is well known that ferromagnetic and paramagnetic materials are electrically conductive. It is also well known that magnetic energy is dissipated by both conductive and ferromagnetic or paramagnetic material. The absorption of magnetic energy is due to the molecules of such material responding to the magnetic component of EM energy. It is this molecular response that consumes or absorbs magnetic energy. The higher the permeability, the greater the capacity to absorb EM energy. Ferromagnetic carbon steel casing has a permeability of about 2,000 to 10,000 webers/amp, depending on the specific chemical structure of the material.

On the other hand, non-ferromagnetic metals such as aluminum, copper, and stainless steel do not absorb magnetic energy from permanent magnets or electromagnets generated by direct current. They have a permeability of one or unity but are also highly conductive of electric energy. Air also has a permeability of one but is significantly less conductive. Transmitting an Electro-magnetic wave through aluminum, therefore, is much different than transmitting an Electro-magnetic wave through air. Since aluminum is an excellent electrical conductor, part of the Electro-magnetic wave is readily dissipated. In the near field to a low impedance transmitter antenna (i.e., within 10 or less wavelengths of the transmitter antenna), the magnetic field predominates. The fact that the magnetic field predominates allows the magnetic signal to penetrate a non-ferromagnetic material, e.g., aluminum. All oscillating EM signals through aluminum will experience attenuation or damping because the electrical conductivity of the aluminum generates eddy currents that dissipate the Electro-magnetic wave.

The situation changes dramatically when aluminum is replaced by a ferromagnetic material, e.g., carbon steel. The much higher carbon steel permeability readily dissipates even the near magnetic field. The inspection or detection of material properties, including but not limited to location, thickness, corrosion, defects, cracks or anomalies, has required the use of Gamma rays, X-rays, conducting a dc electric current through the EM barrier material, use of acoustic devices or other work intensive methods.

Gamma rays require a radioactive source and provide limited penetration. It requires cumbersome equipment and safety precautions. The use of X-rays requires use of relative high electrical power, as well as cumbersome equipment and safety precautions. The evaluation of the data collected from gamma ray and X-ray devices requires the viewing and interpretation of the photos or data by specially trained personnel. Many gamma ray and X-ray devices and methods are also not easily adapted to a continuous recording of data during ongoing industrial operations.

The use of electric current or acoustic signal passing through a barrier material requires the material to be physically contacted. This requires the insulation coating or other covering matter to be wholly or partially removed. It also impedes the prompt or

- continuous measurement of the material in an ongoing industrial or otherwise uncontrolled environment. These methods or devices also have limited reliability or sensitivity. SUMMARY OF THE INVENTION

There has long been a need for a device that can make barrier materials transparent or semi transparent to electro-magnetic energy. Also, there has been a need for a device that can make barrier materials transparent or semi-transparent for a sufficiently broad spectrum of electro-magnetic wave frequencies. This would permit EM energy to be used to obtain useful measurements of the electro-magnetic properties of electrically conductive matter or objects (hereinafter "objects") existing within or on the opposite side of the EM barrier. The present invention allows detection of properties and defects at greater distances from the target of the study. The present invention also allows more detailed description of the EM barrier properties and the detection of smaller defects within or on both sides of the barrier material and within the barrier material. The present invention also allows the detection of objects on the opposite side of the EM barrier. The invention requires minimal power. It also does not require contact with the barrier material.

The present invention utilizes the material properties of the EM barrier materials to achieve transmission of electro-magnetic energy through the EM barrier. It is well known that the strength of the magnetic field in a particular area is related to the density of magnetic flux lines penetrating that area. As the barrier material is subjected to an increasingly strong field of magnetic flux, more and more of the magnetic dipoles of atoms of the barrier material begin to line up uniformly in response to the magnetic field. More specifically, this increasing magnetic energy causes the spin of the "odd" electrons occupying unfilled orbital shells of the atoms to begin to align in the same direction. This response or action of the electrons consumes magnetic energy. When the magnetic energy is increased sufficiently within a region of the barrier material, the spin of all of the odd electrons within that region will be aligned in the same direction. When the electrons of the atoms cannot absorb any more magnetic energy, that volume of the barrier material is in a state termed "magnetic saturation." During magnetic saturation, the relative permeability of the barrier material approaches one. Thus, in a saturation state, the relative permeability of the material approaches the permeability of aluminum or air. However, the EM barrier is still electrically conductive. Therefore an oscillating Electromagnetic wave is still subject to damping by eddy currents generated by conduction of the EM energy through the barrier material.

The portion of the barrier material saturated with magnetic energy is "transparent" with respect to the transmission of additional magnetic energy, for example a second source of magnetic energy. While transparent, the barrier material no longer acts as a complete barrier to the penetration of low frequency magnetic energy or magnetic energy generated by dc current. (There is, however, some loss of magnetic energy resulting from eddy currents being generated in the saturated barrier material. As the frequency increases, the conductive losses increase until the skin depth of penetration becomes much less than the thickness of the barrier material. As used herein, "skin depth" is proportional to the inverse of the square root of the product of permeability, current and frequency.) Therefore, a separate oscillating or non-static source of magnetic energy

(preferably at a different or greater frequency than the magnetic energy utilized to saturate the barrier material) can be transmitted into or through the barrier material. When an electrically conductive "object," as used herein, is within the oscillating magnetic flux field, the oscillating magnetic field induces a corresponding eddy current in the object. This eddy current in turn induces another corresponding (and oscillating) field of magnetic flux that is emitted from the object. This oscillating magnetic flux field, which can be at different frequencies or phases from the magnetic wave transmitted through the saturated or near saturated barrier material, also is able to pass through the saturated area of the barrier material in a return direction and by a reverse process of the original oscillating transmitted signal. This return oscillating magnetic wave can also be detected and measured by a receiver located on the transmitter side of the barrier material when positioned in close proximity to the original or a separate saturated area of the barrier material. The apparatus is therefore allowing the magnetic component of EM energy to "see through" the barrier material. Conversely, it can then be said that the barrier material no longer is a barrier to EM energy. The method and apparatus of this invention is hereinafter termed "saturation flux generator." The saturation flux generator saturates barrier material with the magnetic flux or magnetic component of an EM energy source. A region of a barrier material may be completely saturated or partially saturated in a controlled manner. The region of the barrier material that is in a state of saturation or near saturation is alternately termed herein as "transparent", a "Metallic Transparency™ region", "magnetically transparent" or simply "transparency." The invention may utilize one or more magnetically transparent regions within the barrier material. The term "partial barrier", "partial magnetic transparency" and "partially transparent material" are alternatively used herein to describe the regions of the barrier material that are significantly, but not totally, saturated.

If complete saturation is desired, multiple designs exists for creating the substantial constant or low frequency magnetic flux field. It has been found that energy can be conserved yet still produce a controlled transparent region by bucking field lines outward from the saturation flux generator and into the EM barrier. This can be accomplished by placing at least two like poles together. The field lines repel each other, thereby causing the concentrated field lines to be pushed far into the barrier material. The component of the apparatus utilized in containing the plurality of like magnetic poles is termed the "magnetic culminator."

An alternate application of the invention is utilizing the saturation flux generator to couple with a selected portion of the EM barrier. Coupling does not require the transmission of magnetic flux out from the EM barrier, but rather can achieve the reduction of the permeability of the EM barrier (particularly at the surface) sufficient that the higher frequency oscillating magnetic flux, e.g., transmitter flux, may penetrate into the thickness of the EM barrier between the opposing magnetic poles of the saturation flux generator. In addition, the reduced permeablity of the EM barrier allows oscillating magnetic flux intersecting with the surface of the barrier material at an oblique angle to penetrate into or couple with the barrier material. If a partially transparent region is created, a separate oscillating electro-magnetic wave may be transmitted into this partially transparent region, preferably of a higher frequency than the first electro-magnetic energy source. Eddy currents are generated in the partially transparent material. An oscillating magnetic field is induced by these eddy currents. At least some portion of the magnetic flux from this induced magnetic field may be emitted from the surface of the barrier material. However, the lines or path of flux may bent or altered from the orthogonal as the flux emerges from the surface of the partially saturated material into the surrounding environment. This bending of magnetic flux can be controlled, allowing the lines of magnetic flux to be focused on an object or area existing on the opposite side of the barrier material from the saturation flux generator. This focusing partially counteracts the normal rapid geometric spreading of magnetic flux. Concentrating the magnetic flux allows distant sensing using much less power. When utilized in this manner, the saturation flux generator includes a Magnetic Lens™ capability or device.

If the saturation flux is only sufficient to partially saturate a portion of the barrier material, the partially saturated region may still become transparent, i.e., achieve increased saturation, with the addition of a second source of electro-magnetic energy. Also, barrier material that is partially saturated experiences a significant reduction of permeability. In a state of reduced permeability, the barrier material will more readily allow higher frequency oscillating energy to penetrate through the surface and into the interior of the barrier material. This can allow study or inspection of the interior of the barrier material. It should be noted that this higher frequency energy would only penetrate into the surface of the barrier material proportional to the skin depth when in an unsaturated state. It will be readily appreciated that the geometry of placement of the transmitter generating the second source of EM energy in relation to the transparent region of the barrier material is important. It will also be readily appreciated that the placement of the receiver in relation to the transparent region will also be important. It should also be appreciated that the placement of the receiver in relation to the transmitter of the oscillating magnetic signal will also be important.

The oscillating magnetic flux lines are induced by eddy currents within a barrier material. The eddy currents are induced by an oscillating magnetic flux field generated by a transmitter contained within the apparatus. The partial transparency is accomplished by a magnetic field generated by a strong low frequency or direct current. The Metallic Transparency™ region defines the portion of the EM barrier where at least the permeability of the barrier surface has been sufficiently reduced to allow the oscillating transmitter flux to penetrate into the surface of the barrier material. The same coils may generate the low frequency saturation flux and the oscillating transmitter flux if the impedance matching to amplifiers is observed and the frequencies are near enough to each other.

An alternate embodiment of the invention utilizes separate saturation coils and transmitter coils. In this configuration, the saturation coils can partially or fully saturate the barrier material in a simple or geometric pattern that could vary with time. In this way the bending of the magnetic flux lines could be varied with respect to time and space thereby moving the focal area temporally and spatially. Metallic Transparency would represent full or near complete saturation with a relative permeability approaching one. Partial metallic transparency could allow transmission of a portion of the transmitter energy through the barrier material, the remaining transmitter energy generating powerful internal eddy currents in the barrier material. The invention utilizes one or more saturation flux generators, which may each contain a combination of a low frequency oscillating current or constant dc generated current combined with at least one higher frequency oscillating transmitter or receiver. The relationship of the constant or low frequency oscillating saturation flux and higher frequency transmitter flux is that the higher frequency flux will be at some multiple of the low frequency saturation flux sufficient for measurements desired. The low frequency or direct current is utilized to generate a field of magnetic flux for fully or partially saturating the barrier material. This magnetic flux field causes the barrier material to become transparent or partially transparent to or in conjunction with the addition of at least one higher frequency electro-magnetic wave (transmitter flux). When partially saturated, i.e., state of partial transparency, the transmitter current (oscillating at a constant frequency) causes the level of saturation of the barrier material or object to vary. This, in turn, causes the permeability of the target material (a barrier material or other object) to vary in some manner. This changing permeability, in turn, causes a nonlinear interaction creating a spectrum of frequencies of the eddy currents induced in the target material. This spectrum of varying eddy currents can be detected and measured as described elsewhere in this invention and is useful for the broadband study or determination of the electrical characteristics or other properties of the target material.

Low frequency current or a dc current may be utilized for achieving the desired level of saturation in the barrier material since the flux field and the flux lines comprising the field remain constant in direction in relation to the higher frequency oscillating transmitter flux field. This saturation flux, used to completely or to partially saturate the barrier material, is hereinafter termed "saturation flux."

An ac current generating component (hereinafter "transmitter") of the saturation flux generator device can be used to generate the higher frequency transmitter flux and associated higher frequency oscillating magnetic flux field. As indicated above, multiple higher frequency currents, each with separate frequencies, may be simultaneously utilized. The higher frequency flux is hereinafter termed "transmitter flux." The transmitter flux is able to penetrate into or through the barrier material as a result of the concurrent reduction of surface permeability achieved by the saturation flux. This "transparent" region of the barrier material i.e., partially or completely saturated region, behaves similar to that of aluminum or other material with permeability near 1 weber/amp. As already stated, this barrier material region no longer has the same properties as a barrier to electro-magnetic energy, but remains electrically conductive. It is well known that a fluctuating magnetic field with respect to time or space induces a separate electric current in an electrically conductive material. Oscillating magnetic energy of the transmitter flux (which may be generated by the saturation coils) induces a separate electric current, i.e., eddy currents in the saturated or partially saturated portion of the barrier material or in electrically conductive objects located outside of the now transparent barrier material. These eddy currents also oscillate at a frequency. Accordingly, these eddy currents induce a separate oscillating magnetic field about the barrier material or the object. The characteristics or properties of the oscillating magnetic field may be measured by one or more flux receiving devices. Such devices are included within the scope of the invention. The signal receiving devices (hereinafter "receivers") may receive the object's induced magnetic field signal through the same transparent region of a barrier material utilized by the oscillating transmitter magnetic flux or, alternatively, through at least one additional transparent region.

It will be appreciated that the design of the saturation flux generator geometry will be important. It should also be appreciated that the saturation flux generator must be constructed upon a suitable frame or core. The saturation coil, creating the large magnetic flux needed to saturate or partially saturate the selected region of the barrier material, and the transmitter coil must be wound upon a core with a sufficiently large mass and permeability. This is also required of the material utilized as a magnetic culminator. Accordingly the core framework of the saturation flux generator, referred to herein as "saturation core" must be constructed of a highly permeable ferromagnetic material.

One variation of the invention utilizes an oscillating transmitter flux penetrating a partially transparent (but electrically conductive) material. This oscillating flux induces an eddy current within the electrically conductive material. The eddy current may extend beyond the partially saturated portion of the barrier material. The eddy currents induce a separate oscillating magnetic field within the barrier material. The flux lines of this oscillating magnetic field may be emitted out from the surface of the barrier material. Electrically conductive objects located within this emitted flux field will also generate another and separate eddy current within the object.

In this manner, the EM barrier material serves as an antenna for the transmission of EM energy. In addition, a Magnetic Antenna™ device or capability of the partially transparent barrier material can be utilized in a controlled manner to focus or direct the second and separate induced oscillating magnetic flux field. This feature is termed "lensing" and the component termed a Magnetic Lens™ device.

Other variations of the invention provide energy efficient, reliable and prompt methods and devices to detect and locate micro defects, anomalies or other properties within or upon barrier materials. Examples where such ability is needed include the ability to detect structural defects, anomalies or cracks in barrier material, including welds or other connections or joining of or within the subject barrier material and target materials that are located within or covered by other matter. Examples of covered target materials can include structural reinforcing steel within concrete, multiple layers of target materials and other matter, such as braided or wound metal cables or multiple or overlapping metal plates, and target materials coated or painted with or encased within insulating resinous, plastic or similar diamagnetic matter.

Specifically, there are many applications for a device that could detect micro cracks in target materials. Such examples include but are not limited to the detection of cracks in railroad rails, offshore or underwater structures, bridges, pipelines, storage tanks, pressure vessels, autoclaves, hot isostatic presses, boilers, engines and similar structures subjected to mechanical stress, pressure, wear, heat, cold, variable temperature and pressure, or corrosive environments.

The saturation flux generator provides an apparatus and method for detection that is non-contacting, thereby eliminating the need to remove surface coverings or coatings. It also minimizes the need for adjusting or normalizing the data collected for the specific surface condition of the target material. This allows the measurements to be made more rapidly and at less cost. It also minimizes wear on the apparatus of the invention. It also allows detection of such defects, etc., at distances greater than possible by existing methods. Applications of the invention for use in cased wells or other confined area require an apparatus design capable of generating very strong magnetic flux fields in a narrow diameter, e.g., in a diameter of two (2) inches or less. The high flux densities needed to partially or to completely saturate the barrier material may be generated through long coil windings. The material comprising the core of the winding is preferably a high permeability material. The saturation flux generator device may also utilize a highly permeable component that serves as the junction of a plurality of like magnetic poles. This component is termed a "magnetic culminator."

It is, therefore, an object of this invention to provide a method and device capable of creating a magnetic field sufficient to partially or completely saturate EM barrier materials.

It is therefore another object of this invention to provide a method and device for the measurement of properties of barrier materials. It is another object of the invention to provide a method and device that can detect anomalies in the range of sub-thousandth of an inch. It is yet another object of the invention to provide a method and device that can continuously collect data as the device is passed over the barrier material, thereby allowing the invention to be used in conjunction with other operations and with minimum disruption of the activity.

It is another object of the invention to provide a method and means to determine the electrical properties of objects within or in the vicinity of the EM barrier material.

It is yet another object of the saturation flux generator device to provide resistivity measurements through EM barriers such as steel casings in oil wells, steel storage tank ^■ walls and pipelines.

Another feature of the present invention is to provide resistivity measurements simultaneously through multiple layers of EM barrier materials, including but not limited to ferromagnetic pipelines and casings.

Another feature of the present invention is to determine the thickness, corrosion, location, continuity or the permeability and conductivity of the barrier material.

Another feature of the present invention is to provide detection of liquid interfaces or sedimentation levels through EM barriers, such as but not limited to steel and iron tanks and pipes.

Another feature of the present invention is to provide resistivity and sediment detection in refinery tanks and pipes.

Yet another feature of the invention is to provide through wall flow rate and resistivity measurements and switches in pipelines and tanks without using hot taps or other intrusive methods.

Still another object of the present invention is the measurement of outside casing coating conditions or corrosion from inside the casing or tubing.

Another object of the present invention is to provide resistivity logging through casing and tubing in an oil or gas well.

Another object of the present invention is that it does not require contact with the surface of the barrier material or other objects.

Still another object of the present invention is that surface conditions are not important because inductive fields do not require contact and can be done at a distance. Still other features of the invention will allow application as dip angle of formation measurement, imaging tool, through casing resistivity (in situ), through casing directional resistivity, through casing water flood detection, through casing cross well resistivity, through casing ranging, air weathering layer measurements, rock analysis using spectral sweep, casing thickness measurement, logging tool for cased and open hole, airborne medium and deep exploration and ranging, exploration through salt marsh, casing corrosion measurement and through separator liquid level measurement.

Yet other features of the invention will allow testing or tracking of through pipeline pig tracking, through pipeline hydrate detection, through pipe flow meter, through pipe water detection, and through pipe resistivity.

Yet other features of the invention will allow subterranean pipeline location and ranging, pipeline leak detection, and sub-sea pipeline location.

Yet another feature of the invention is the ability to detect cracks, corrosion and other properties of barrier materials without requiring any physical contact with the barrier material and without requiring removal of protective coatings from the barrier material.

Other applications of the invention in the food processing industry include water and liquid percentage through tank wall, salt content through tank walls, liquid level through tank and non-intrusive flow meter.

Yet other applications of the invention in the pharmaceutical and medical industry include water and/or ion content through vat, chemical salt content through vat, liquid level through tank non-intrusive flow meter, non-intrusive stomach acid measurement and local non-contacting, non MRI imaging and non contacting measurements of electrolytes in the body.

Other medical applications include uses to focus magnetic energy for imaging and without the necessity of contacting the target or subject of the imaging.

Other applications of the invention applicable to turbines, pumps and compressors include through housing blade inspection and water detection in hydraulic lines.

Applications in construction include through concrete detection of re-bar voids and moisture, concrete thickness determination, through metal and concrete measurement and subsurface road and highway inspection. Aircraft applications include through wing detection of flaps, rudder or aileron movement or position, and^'through wing detection of ice. Other applications include detection of water in fuel tanks or lines, long distance ranging, movement detection through structures, rocks, subsurface, wooded areas, through hull proximity detection, through salt water plastic mine detection and through metal or earth ranging.

Yet other applications include determination of depth of water penetration during crop watering, non-contact analysis of chemical fertilizer added in soil and its absorption status, motion detection through structures and determination of water content and consistency through vats or conveyors.

Additional features and advantages of the invention will be set forth in part within the description that follows, and in part will become apparent from the description, or may be learned by practice of the invention. The features and advantages of the invention may be realized by means of the combinations and steps particularly pointed out in the appended claims.

Other variations, changes or modifications of the invention will be recognized by individuals skilled in the art that do not depart from the scope and spirit of the invention described and claimed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the general description of the invention given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. Figures 1A, 1B, 1C and 1 D illustrate several magnetic flux field line geometries of the transmitter flux with respect to the transparent region within an EM barrier material.

Figure 2 illustrates the wave pattern of an oscillating transparency current with a superimposed higher frequency oscillating transmitter flux.

Figure 3 is a block diagram of the components comprising one embodiment of the present invention.

Figure 4A illustrates one embodiment a saturation core component of the invention.

Figure 4B illustrates a configuration of the magnetic signal receiver and the transmitter on the saturation core shown in Figure 4A Figure 4C illustrates the placement of a magnetic transparency device on the outside of a storage tank made of a barrier material.

Figure 4D illustrates a configuration of a receiver on part of saturation core of the present invention.

Figure 5 illustrates the transmitter of the present invention separate from the signal receiver.

Figure 6 illustrates a transmitter and the separate signal receiver of the present invention inside a well casing or pipe.

Figure Ik illustrates a plurality of separate signal receivers in relation to a separate transmitter.

Figure 7B illustrates another embodiment the oscillating magnetic flux transmitter separate from the signal receiver.

Figure 7C illustrates another embodiment with multiple transmitter coils.

Figure 8 illustrates another embodiment of the separate oscillating magnetic flux transmitter and the signal receiver.

Figure 9A and 9B illustrate additional embodiments where the penetration distance outside of the EM barrier is increased proportionally with the length of the coil.

Figures 10A and 10B illustrate the geometry of field considerations for placement and size of the transmitter in relation to the area of the region to be saturated. Figures 11 A, 11 B, 11C and 11 D illustrate examples of various embodiments of the present invention for directional measurement.

Figure 12 is yet another embodiment of the present invention illustrating the use of the invention for profile logging with a separated transmitter and receiver.

Figure 13 illustrates another application of the present invention associated with the measurement of sediment and water in a storage tank.

Figure 14A illustrates yet another embodiment of the present invention for the measurement of sediment and water wherein the transmitter is in association with a polarity of fixed receivers at equal distances from the transmitter and located outside the tank such that resistivities change as the transmitter/receiver signal changes. Figure 14B illustrates yet another embodiment of the present invention for the placement of transmitter/receiver pairs on the outside ofthe tank for measuring sediment and water used as a switch.

Figure 15 illustrates the use of a damping ac signal upon the saturation current for steel casing. Figure 16A is a one-axis device of the present invention for coupling a magnetic field to the surface of a barrier material.

Figure 16B is an alternate one-axis device of the present invention containing a magnetic culminator. .

Figure 17 is a two-axis cross-flux magnetic culminator of the present invention. Figure 18 is a two-axis star-flux magnetic culminator of the present invention.

Figure 19 is a three-axis star-flux culminator of the present invention.

Figure 20A is another embodiment of the present invention for use with well logging through casing where the electromagnet generating the saturation flux contains a single magnetic pole located between two opposite or unlike poles.

Figure 20B is another embodiment of the present invention for use with the well logging through a casing where the saturation flux generator contains a single pair of north-south magnetic poles.

Figure 21 A illustrates magnetic flux lines from dc generated flux field. Figure 21 B illustrates magnetic flux lines from dc generated flux field where like magnetic poles are placed closely together.

Figure 21 C illustrates saturation flux flux lines in conjunction with the placement of transmitter and receiver coils.

Figure 22 illustrates a saturation core by a dc current, around which a transmitter is wrapped, and flux lensing occurs at the surface penetrating length of the core.

Figure 23 illustrates another embodiment of the present invention.

Figure 24 illustrates the embodiment of the invention of Figure 23 with the saturation flux activated. The Figure also shows the intensity spike of transmitted transmitter flux. Figure 25A illustrates the transmitter rotated to be parallel to the metal plate. An intensity plot is also show for the illustrated configuration.

Figure 25B illustrates the transmitter flux of the transmitter when the saturation flux is activated.

Figure 26A illustrates the same embodiment of the invention but with the saturation flux powered "off."

Figure 26B illustrates another embodiment of the invention utilizing a curved metal plate with the saturation flux powered "on."

Figure 27 illustrates another embodiment of the present invention where multiple magnets are utilized and the magnets are of unequal strength. Figure 28 illustrates another embodiment of the present invention wherein two

Transparency magnets and two transmitters of unequal strength are utilized.

Figure 29 illustrates another embodiment of the invention utilizing plurality of saturation magnets of unequal strength and plurality of transmitters also of unequal strength. Figure 30 illustrates another embodiment of the present invention.

Figure 31 illustrates another embodiment of the present invention wherein the transmitter is placed at an angle to the EM barrier.

Figure 32A illustrates an apparatus for a single beam with lensing.

Figure 32B illustrates beam interference with lensing.

The above general descriptions and the following detailed descriptions are merely illustrative of the generic invention, and additional modes, advantages, and particulars of this invention will be readily suggested to those skilled in the art without departing from the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To achieve the foregoing objects, features, and advantages and in accordance with the purpose of the invention as embodied and broadly described herein, a method is described for transmitting EM energy into or across barrier material and receiving a return signal. The first step is creating transparency or partial transparency in the barrier material by a first electro-magnetic wave adjacent to or in close proximity to the EM barrier. This electro-magnetic wave may be generated by a permanent magnet, or an electromagnet powered by dc current or an electromagnet powered by ac current. The ac powered electro-magnetic wave will preferably be of a relatively low frequency oscillation.

The second step is fully or partially saturating a region of the barrier material with the magnetic component of this first electro-magnetic wave. The third step is creating, by means of a transmitter, at least one second oscillating electro-magnetic wave having a higher frequency than the first electro-magnetic wave. The fourth step is engaging the magnetic component of this second electro-magnetic wave with the barrier material when the barrier material is transparent or partially transparent. When almost fully saturated, the EM barrier becomes transparent to electro-magnetic energy. When partially saturated, the barrier material is partially transparent to such energy. For partially transparent barrier material (sometimes termed "partial barriers" herein), the fifth step is the second and oscillating electro-magnetic energy created by the transmitter, inducing eddy currents in the partial barrier. These eddy currents are also oscillating. These eddy currents may extend through the barrier material well beyond the partially saturated region. The sixth step is the oscillating eddy current (within the barrier material) generating a separate field of oscillating magnetic flux. The flux lines of this induced magnetic field also extend beyond the region of the barrier material experiencing the saturation flux. These flux lines may be emitted into the surrounding environment. In this manner, the partial barrier acts as an antenna, broadcasting an oscillating magnetic flux field and is termed a Magnetic Antenna™ device. This oscillating magnetic flux field will induce eddy currents in electrically conductive matter, i.e., objects that are beyond the barrier material but within the induced flux field. The next step is the eddy current generated within the object inducing a separate field of magnetic flux. The lines of this flux field may also extend beyond the object and to the Magnetic Antenna ("antenna"). The permeability of the antenna is lowered as a result of the penetration by saturation flux, the oscillating transmitter flux and the flux induced by the eddy currents. This reduced permeability facilitates the penetration or coupling of the induced magnetic flux from the objects into the antenna. This oscillating flux also generates eddy currents within the antenna. These eddy currents induce a magnetic field that is detected and measured by a receiver contained within and comprising part of the invention.

The invention utilizes the saturation flux generator for creating a transparency or partial transparency in a barrier material. The saturation flux generator comprises one or more magnets to achieve complete or partial saturation of one or more regions of a barrier material, one or more transmitters (or a single coil that can be carrying both the saturation current plus the transmitter current), one or more switches, low noise amplifiers (LNA), receivers, frequency generators, pulsers, and power sources. The saturation flux generator utilizes at least two separate magnetic flux fields. The first magnetic flux field is utilized to create a transparent or partially transparent region within an EM barrier. This is the magnetic flux field of the saturation flux. This magnetic flux field may be generated from either a low frequency oscillating source or from a direct current source, i.e., dc current. The additional magnetic flux field(s) is generated from a transmitter and is termed the transmitter flux. It is preferred that the transmitter flux oscillate at a frequency that is some multiple of the frequency of the saturation flux. In practicing the invention, it is often advantageous to have high concentrations of magnetic flux. It is important that the flux be anisotropic in its direction. That is, it is necessary to have the flux directionally concentrated. In order to conserve power consumption, it is often advantageous to minimize the size of a transparency region. This can be achieved by having a high concentration of flux lines in a small area of the barrier material or an object. The flux densities may be many thousands of Gauss per square centimeter.

There are many geometry's possible to achieve very high concentrations of directional flux. In one embodiment, efficiency is achieved when the device generating the saturation flux, is oriented to the surface of the EM barrier in such a manner that the highest concentration of magnetic flux lines are in close proximity and aligned perpendicular to the surface of the EM barrier.

Another embodiment is a configuration for the device generating low frequency electro-magnetic energy where the magnetic portion of the energy is emitted from a location where a plurality of like magnetic poles are placed in close proximity. This portion of the device incorporates a material (hereinafter the "magnetic culminator") placed between the like poles. The magnetic culminator comprises a material that is highly permeable and of great mass so that the magnetic culminator will not be magnetically saturated prior to the desired transparency or partial transparency being achieved in the EM barrier. The magnetic culminator, containing a plurality of like magnetic poles, achieves a concentration of mutually repulsive lines of magnetic flux which are pushed away from the like magnetic poles and into the EM barrier. The high concentration of magnetic flux causes the flux to be relatively anistropic proximate to the culminator. The geometry of the transparent region is also important in relation to the additional magnetic flux field(s), or transmitter flux(s). It is preferred that the surface area of the transparency in the EM barrier material be sufficiently large to receive at least the most concentrated area of magnetic flux field lines of the oscillating magnetic transmitter flux from the transmitter. The larger this transparency becomes, however, the more power that is required.

Reference will now be made in detail to the present preferred embodiments of the invention as described in the accompanying drawings.

Figure 1A illustrates the oscillating magnetic transmitter flux field line geometry 140 -144 with respect to the location of the transparent area 200 of the cylindrical EM barrier 100 having an upper boundary 221 and a lower boundary 222. The magnet required to create the transparent area is not illustrated. The area of the strongest magnetic flux propagated by the transmitter 300 originates along an axis 315. As used herein, the area of the strongest magnetic flux is the location where the most flux lines are concentrated, i.e., flux line density. This axis is parallel with the central axis 110 of the EM barrier. Note that for a field line to penetrate though the barrier material 100, the field line must exit and return through the EM barrier with the transparent area 200. This area is also represented as the space between 330 and 331 , and the space between 332 and 333 at the intersection of these lines with the EM barrier 100. Lines 330, 331, 332 and 333 originate from the transmitter coil 300. They show the geometric relationship between the field lines from the transmitter 300 to the boundaries of the transparent area 200 of the EM barrier 100. The intersections of lines 331 and 332 with the EM barrier 100 are at points along the upper boundary 221 of the transparency. Note that in Figure 1A, only one 140 of the 5 field lines depicted penetrates through the EM barrier. Figure 1B illustrates another transmitter flux field geometry 140-144. The area of the strongest magnetic flux originates from the oscillating magnetic field generating device 300, propagating the transmitter flux along an axis 315 at right angles to the central axis 110 of the EM barrier 100. The transparent area 200 is created by a separate magnet (not illustrated). The transparent area 200 of the EM barrier 100 has an upper boundary 221 and a lower boundary 222. This configuration of the transmitter 300 to the central axis 110 of the EM barrier results in a greater concentration of the transmitter flux reaching the transparent area of the EM barrier. In Figure 1B, field lines 140 and 141 permeate through the EM barrier within the transparent area 200 enclosed between 221 and 222. Figure 1 C illustrates another embodiment wherein the sensing signal transmitter

300 is placed in close proximity to one side of the EM barrier 100. The axis 315 of the transmitter 300 is parallel to the center axis 110 of the EM barrier 100. Note the angle of the intersection of lines 330 and 331 has broadened. There are 5 field lines 140-144 penetrating the barrier material 100 between lines 330 and 331. The angle of lines 332 and 333 is narrowed. No field lines are penetrating the EM barrier in the transparent area 200 between lines 332 and 333.

Figure 1D illustrates another transmitter flux field line geometry 140-144 from the transmitter 300. As in Figure 1C the transmitter 300 is placed in close proximity to the transparent area of the EM barrier 100. Note that lines 330 and 331 illustrate a significantly broadened area though which field lines may penetrate through the EM barrier 100. Correspondingly, the area for sensing signals to penetrate between lines 332 and 333 has narrowed. Note that 5 field lines penetrate the EM barrier between 330 and 331. Note also that all field lines intersect with the EM barrier in a substantially orthogonal manner, thereby enhancing the coupling or penetration through the transparency. This geometry maybe preferable in many applications of the invention. No field lines penetrate the EM barrier 100 along the opposite direction of the axis 315.

FIG. 2 illustrates the graph of current versus time with respect to the present invention. Illustrated on the graph are the spikes 411 of the higher frequency oscillating electro-magnetic wave of the transmitter flux from the transmitter disposed along a lower frequency oscillating saturation flux 401. In one embodiment, the transmitter flux may be transmitted only during the duration of each cycle of the oscillating saturation flux that is above the level required for saturation 420. Among other advantages, this embodiment minimizes energy consumption. In this embodiment, it is possible to have multiple transmitter flux transmissions during each phase that the saturation flux 401 is above the saturation level 420. Note also that the saturation flux may not achieve the level necessary to saturate the targeted area of the EM barrier. However, the distinctively higher frequency sensing signals will couple, i.e., penetrate, into the EM barrier or, alternatively, be of sufficient magnitude to saturate a region of transparency or partial transparency when combined with the saturation flux and therefore directly penetrate through the barrier material. In other embodiments, the saturation flux may be generated from at least one permanent magnet, low frequency alternating current (ac) or direct current (dc) electro-magnetic device.

As described elsewhere herein, the higher frequency transmitter flux may be generated by a transmitter, comprised of a smaller coil of conductive material, powered by alternating current and at a controlled frequency, wrapped upon or near the larger coil. The larger coil generates the saturation flux. It is wrapped with conductive material and powered either by dc current or an oscillating current. Preferably, the transmitter flux oscillates at a higher frequency than the saturation flux. It is preferred that the frequency be at least a multiple of 10 greater than the frequency of the saturation flux. This higher frequency allows 10 wavelengths of measurement before the transparency is closed.

In Figure 2, the high frequency transmitter flux 411 is demonstrated being pulsed at less than 0.5 milli-seconds rates. If the lower frequency saturation flux 401 , generated by the saturation coil, is pulsed or activated "on" for a period of 10 milli-seconds, there is sufficient time for twenty wave lengths of transmitter flux (e.g., with a wavelength period of only 0.5 millisecond), to go out to a near object and take 10 wavelengths of measurements during the "on" pulse of the saturation flux. During most of this 10 milli- second pulse, the combined saturation flux and transmitter flux will exceed the level of magnetic energy required to achieve saturation 420.

For most applications, a power source of 300 watts or less is sufficient to create the transmitter and saturation flux. For thicker material, strong pulses and signals may be generated by utilizing charge storing capacitors. These capacitors are slowly charged than quickly discharged through a switch contact and then through the low impedance large coil. At the same time, the higher frequency transmitter coil is pulsed.

Figure 3 is a block diagram of one embodiment of an apparatus of the present invention. Figure 3 illustrates an embodiment 500 of the saturation flux generator of the present invention. The saturation flux generator 500 comprises a coil 551 for generating the saturation flux, a second coil, comprising the transmitter 300, a switch 562, a low noise amplifier (LNA) 564, a receiver coil 580, a frequency generator 563, a pulser 566, one or more capacitors 561 , a nulling device 583, and a power source 560. It also incorporates standard electrical power cables and signal wires 568 and 588, as well as housing 572 and 570. One application of this invention is to ascertain or measure the electro-magnetic properties of matter or objects outside a barrier material. An example is obtaining measurements of objects outside of a well casing.

Calculations and experiments have shown a significant transmitted pulse spreading as it passes through a magnetically saturated well casing (an EM barrier material) and into the surrounding geologic formation. This spreading is represented by a transfer function that can be found by mathematical normalization of a measured transmitted pulse (transmitter flux) to the measured received pulse. The frequency dispersion and the extent of flux dispersion are themselves used as a measurement tool for the properties of both the barrier material and the object penetrated by the pulses outside of the transparent barrier material. The electro-magnetic properties of the barrier material are subtracted from the total signals received so that the electro-magnetic properties of the object can be isolated.

It is important to note that an object in which these eddy currents are generated may be a separate barrier material located adjacent to the first saturated barrier material. One example is resistivity logging in a well through the production tubing, i.e., the first barrier material, to ascertain the properties of the reservoir through the well casing, a second barrier material. This example requires a device powerful enough to be capable of completely saturating the inner production tubing while only partially saturating the outer well casing, the second barrier. The conductivity and permeability of the second barrier material may be determined by maintaining a constant transmitter flux while varying the saturation flux from zero to full saturation and measuring the receiver flux. The conductivity can be determined by varying the frequency of the transmitter flux while the saturation flux level is maintained constant. The orientation of the transmitter and receiver is important with respect to the axis of the magnetic culminator or saturating coil, the object to be measured, and the distance to the object.

Many uses exist for the ability to send an Electro-magnetic wave through a barrier material in order to measure EM properties of objects on the other side. Examples are measuring the levels of water or liquids having a magnetic moment or that are slightly conductive, e.g., liquid hydrocarbons, saline solutions, alcohol, through a storage tank wall comprised of a barrier material, detection of water and other such liquids having a magnetic moment or that are slightly conductive in a pipeline also comprised of a barrier material, through casing (another barrier material) resistivity measurements in an oil or gas well, corrosion detection inside storage containers, and many others.

Reducing permeability by magnetic saturation is well known. Others have unsuccessfully attempted to use saturating currents to reduce the permeability of the ferromagnetic casing material for oil well logging using only fixed geometry, time invariant saturation. The production tubing must be removed and the transmitter and receiver must be in the same saturated area. (See patent number 5,038,107). The principles discussed herein, however, may be combined with other embodiments and modifications to utilize barrier material, e.g., ferromagnetic metal, may be itself used to enhance the measurement. This will be done by (1 ) different degrees of saturation that can (2) vary spatially and (3) temporally with (4) transmitter-receiver in separate saturated zones (5) which are nulled electronically. These variations can create magnetic flux concentrations as in a lens.

It has been determined that there are four (4) important factors in the system design of this invention. These factors are as follows:

1. Design of the transparency region.

2. Possible spatial distributions and locations of the magnetic transparencies.

3. Possible temporal variations in opening and closing the magnetic transparency.

4. Nulling techniques to eliminate direct signal coupling between the transmitters and receivers.

Each of these will be discussed below. 1. Design of the magnetic transparency:

There are three (3) aspects to the magnetic transparency design. These are:

(a) Method of design for saturation or partial saturation for creating a magnetic transparency.

(b) Geometric considerations of magnetic transparency size to receiver or transmitter location within the magnetic transparency. The magnetic saturation flux generator device and the flux circuit, which includes the target at which transparency is desired, can only achieve saturation at the point of desired transparency. Thus,

(Vol)(permeability)Mc»(Vol)(permeability)τarget + (Vol)(permeability)_gaps

where "MC" is the magnetic culminator of the magnetic saturation flux generator device subject of this invention. It is preferred that any gaps (e.g. air gaps) should be small with respect to the magnetic culminator diameter or the pole of saturation core emitting the saturation flux if a magnetic culminator is not used. This will include any magnetic culminator utilized in the saturation flux generator.

(c) The local flux density at any location of the saturation core must be less than the local saturation value at that location.

(Vol)(permeability)_saturation _∞re»(Magnetic Flux Density)_satUration core

where "saturation core" is the cross sectional area of any specific location in the saturation core of the saturation flux generator.

1 (a). Method of design for saturation or partial saturation for creating a magnetic transparency:

With respect to full or partial saturation, the volume of the barrier material intended to be saturated must be multiplied by the permeability of the barrier material. Then, the product of the magnetic culminator volume multiplied by its permeability must be calculated. (If a magnetic culminator is not utilized, the volume of the magnetic pole must be calculated and multiplied by the permeability of the pole. The resulting product for the magnetic culminator must be greater than the sum of products for the intended transparency region and any gap. Such a gap may comprise air or materials such as coatings, (including but not limited to insulating materials, paint, cement around carbon steel re-bar) or other barrier materials. This relationship is required for the magnetic flux to be contained and guided to the barrier material to be saturated. Alternatively stated, the product of the volume and permeability of the inducer must be greater than the product of the volume and permeability of the transparency region.

When it is the objective to transmit and receive a transmitter flux through the barrier material in order that the measurements be made of objects on the other side of the barrier material, it is preferred that the volume of the area outside of the EM barrier significantly exceed the transparency region. This volume relationship is preferred in order that the electro-magnetic properties of the object outside the barrier material dominate the received percentage signal and also from the barrier material for maintaining a high signal to noise ratio. Alternately stated, it is intended that the received signal not be significantly influenced by variations in the electrical or physical properties of the transparency region. Changes in the properties of the barrier material that can impact the received signal include but are not limited to variations in thickness, density, corrosion, welds, composition of material.

Figure 4A illustrates the saturation core 501 of one embodiment of the saturation flux generator used to generate the saturation flux required in practicing the present invention, and particularly, for concentrating and directing flux lines orthogonally into the barrier material 100 to achieve full or partial saturation. The magnetic flux generated by the saturation coil 551 will be concentrated in the magnetically permeable core 501 , comprising the saturation core 552, and flanges 504 and 505. The core 552, upon which the coils of the electromagnet are wrapped (not shown), is located between the top flange 504 and bottom 505. The tank wall comprises the barrier materiallOO. The closed loop of magnetic saturation flux, laterally concentrated in each flange, will cross the air gap 950 and into the proximate surface of the EM barrier. The flux across the gap from the flange into the barrier wall will be substantially anistropic in direction and orthogonal to the barrier surface, thereby enhancing the magnetic coupling of the flux into the magnetically permeable barrier wall. Figures 6, 7B and 7C, discussed more fully below, show this path 150 acroos the gap and through the EM barrier wall.

The magnetic flux generator 500 creates a magnetically saturated region, i.e., transparent region, that is illustrated having a width "920", a height "930" and a thickness "960." This region of a barrier material may be termed the "saturation target" or "saturation target material".

Figure 4B illustrates one embodiment of a mono-static application of a magnetic saturation flux generator 500. In this mono-static configuration, the magnetic saturation flux generator incorporates both a transmitter and receiver capability. The power source, display and other components are not shown. Note that the transmitter 300, receiver 580 and saturation coil 551 are all geometrically nulled to each other. The receiver coil 580 and the transmitter coil 300 are each wrapped around or contained within one of the two pole flanges 504 and 505. It will be appreciated that, in this configuration, the receiver and the transmitter will be proximate to areas of the barrier material experiencing large concentration of saturation flux. The saturation target material 600 comprises the volume dimensions 920, 930 and 960. An air gap 950 separating the saturation flux generator from the EM barrier is also shown. As used herein, mono-static embodiment comprises a magnetic saturation flux generator containing both one or more transmitters and one or more receivers.

Figure 4C illustrates a mono-static embodiment of a magnetic saturation flux generator 500 placed upon the outer wall of a storage tank 100. The storage tank wall consists of an EM barrier and the tank contains a volume of an electrically conductive liquid or other substance 150. It will be appreciated that the saturation target material 600 depicted in Figure 4C is part of the Tank 100 and not a component of the saturation flux generator 500.

Figure 4D illustrates a method of placing a coil onto a portion of the saturation flux generator. It will be appreciated that the coil will preferably be a receiver coil 580 or a transmitter coil, not shown. Further, it will be appreciated that the flange 505 of the saturation flux generator will comprise one of the magnetic poles when the transparency coil is activated "on." This flange will comprise a region of relatively high flux density. The placement of a receiver or transmitter coil in this location will enhance its capability to send or receive oscillating magnetic signals into or through the material.

1 (b). Geometric considerations of transmitter-receiver location with respect to the magnetic transparency. The geometric considerations of transmitter-receiver location with respect to the transparency region means that, depending upon whether it is through-tank level gauging or through-well casing logging or some other application, the location of the transmitter- receiver may vary. See Figures 4C, 5, 6, 7A-C, 8, 9A, 11A-C, 12, 13, 14A and 14B, for examples. Therefore, by not wrapping either the transmitter or receiver coils (or both) around the magnetic culminator or magnetic pole of the saturation core, inducing the saturation flux provides a number of advantages, including but not limited to:

1. Mechanical nulling by receiver or transmitter placement or rotation with respect to each other, or with respect to material.

2. Directionality by the transmitter or receiver being nearest tank side of core, or by rotation of the axis of the transmitter or the receiver.

3. Minimization of potential saturation of the magnetic culminator or magnetic pole and allowing uncontrolled dispersion of magnetic field lines. However, there are applications of partial saturation wherein it may be desirable to take walls out of total saturation. This is exactly opposite the concern from cited patent number 5,038,107 which does not want to use an ac current on the core that may take the walls or core out of saturation.

4. Since the transmitter coil can have an air core, laminated core or smaller inductor core than the magnetic culminator or the magnetic pole core, much higher frequencies can be used since the inductive impedance due to the presence of a large metallic core drives up the total impedance to the transmitter flux.

5. Multiple transmitters, each at varying frequencies, maybe used broadcasting simultaneously to perform spectroscopy over a large frequency range.

6. In the same transparency region, transmitter coils of different lengths will have different field lines and can therefore penetrate the surrounding media by the coil length for profiling the near media.

7. For the case of full saturation, the Transparency region to be saturated needs to encompass some portion of the transmitter or receiver. Otherwise, a large amount of the transmitter flux or signal for the receiver is absorbed into the non- transparent area of the barrier material. This concept is shown in Figure 10.

8. Multiple transmitters can be used to "buck" each other so as to push flux lines of the transmitter flux far out into the surrounding environment.

9. Multiple receivers can be either nulled with respect to each other and/or built into an array for improving signal receiving resolution. Figure 5 is an illustration of one embodiment of a flux transmitter and signal receiver configuration used in practicing the present invention. The saturation flux generators 500A and 500B are each separately magnetically coupled with tank wall 100. The transmitter-receiver orientation being one-above-the-other provides effective use of the present invention for through-tank determination of fluid levels and many other applications. The separation between the transmitter and receiver is indicated by "910." The separation "910" acts as a null since the interceding EM barrier 100 comprising the structure of the tank wall is not saturated. Therefore, this portion of the tank wall absorbs magnetic energy emitted from the transmitter. Accordingly, the signal receiver will not receive signals directly from the transmitter, but rather only magnetic energy generated by induced eddy currents in objects inside the tank. Also, the receiver coil 580 is rotated at an orientation 90° to that of the transmitter 300. This geometric or spatial configuration also acts as an additional geometric null to direct the transmitter-receiver coupling.

Figure 6-is another embodiment of the present invention for use with well logging through a casing comprising a barrier material 100. Figure 6 illustrates two saturation flux generators 500A, and 500B separately coupled with the different regions of the casing. The saturation generators are placed apart a distance 910 within the barrier material 100. The transmitter 300 and the saturation flux generator 500 are similarly orientated and an off-core receiver 580 is rotated 90° from the transmitter coil axis 315. Each magnetic saturation flux generator creates a magnetic transparency through which the flux to and from the receiver and transmitter may pass. Figures 5 and 6 are examples of a bi-static embodiment of the invention.

Figure 7A illustrates another embodiment utilizing multiple receivers 580A, 580B, and 580C built into an array for improving signal resolution or detection of induced flux from objects at varying distances from the barrier material. The transmitter 300 and receiver 580A, 580B and 580C may each be incorporated as components of separate magnetic saturation flux generators (not shown). Within the range of distance not exceeding 5 times the diameter of the transmitter coil (not shown), i.e., near field to the transmitter, objects at varying distances within the near field can be detected by a single transmitter flux by measuring the return signals detected alternatively by receivers 580A, 580B, and 580C.

Within the near field, the distance of preferred reception of induced flux will be a function of the distance of the receiver from the transmitter. This relationship is illustrated by receiver 580C, located a distance 915 from transmitter 300 detecting induced oscillating magnetic flux at a distance of 913. It will be appreciated that the separate saturation flux generators will create relatively small transparencies in the barrier material 100. The unsaturated portions of the barrier material will null the direct transmission of the transmitter flux to the receivers. The relatively small transparencies also reduce the energy requirements of the invention.

The arrangement illustrated in Figure 7B provides for a non-saturated section of the wall 100 to be between the saturation flux generators 500A and 500B. The path 150 of the saturation flux across the gap and EM barrier is shown.

Figure 7C illustrates another bi-static embodiment of the invention wherein the saturation flux generator 500A contains a plurality of transmitters 300.

Figure 8 illustrates the orientation of a first saturation flux generator 500A and second saturation flux generator 500B in the associated saturation coil 551 and transmitter coils 300. The transmitter coil 301 and the receiver coil 585 are oriented to be 90° with respect to the saturation flux generator coils 551. Figures 9A and 9B illustrate the concept of utilizing transmitter coils 305 of variable lengths within the same transparency region. Three separate transmitters 300A, 300B and 300C are placed within a magnetic saturation flux generator 500. The saturation flux generator is placed inside a well casing. Figure 9B illustrates that the separate transmitter coils 305 can be converted by closing switches 562A and 562B into a single transmitter coil having the length of the combined coil 940 + 941 + 942. Note that the length of the transmitter core 301 may also be increased by the closing of connections 302A and 302B. It will be noted that additional segments may be used as well as a single combination of 300A and 300B without utilizing 300C. It will be also noted that Figures 9A and 9B do not show the receiver coil or the saturation coil for the saturation flux generator. In Figure 9A, the EM barrier 100 is illustrated to be the well casing but the technique is equivalent for through tank level gauging, pipelines and other related cases. It will be appreciated that the flux generator 500, including transmitter coils 305 and transmitter core 301 are not in electrical contact with the EM barrier 100. 2. Possible Spatial Distributions and Locations of the Magnetic Transparency

Each different application for various problems will have a unique spatial distribution of the magnetic transparency. A few of those many possibilities are shown in Figures 10, 11 , 12, 13 and 14. Therefore, any geometrical combination of transmitters and receivers may be used. Directionality is achieved by creating a transparency in front of different transmitters and receiver combinations to transmit directionally, receive directionally or perform both with transmitters combined with various receivers.

The unsaturated sections that are turned off provide excellent signal damping and nulling for the receiver or transmitter. These time variations of the transparency are discussed herein.

Figures 10A and 10B illustrate embodiments of the invention that utilize the placement of the transmitter 300 in the center of the transparency or partial transparency region of the material 600. The material has a width 920 and a height 930. It will also be appreciated that this may be utilized with a receiver (not shown). It will also be appreciated that placement of the transmitter in the geometric center of the area that is partially transparent will optimize the symmetry or provide other benefits in regard to the Magnetic Antenna device or Magnetic Lensing effect.

Figure 11A is an example of one embodiment of the present invention for directional measurements, such as logging to find resistivity of cement around a casing 100 or from within the interior of a barrier material such as a pipe or shaft. Figure 11A illustrates the use of transmitter- receiver pairs 300E and 580E geometrically nulled by

90° rotation in a magnetically saturated section of the casing. The saturation of the casing is achieved by the saturation flux coupling with the casing wall via the formation of the closed magnetic flux path concentrated in the core of each generator across the air gap and into the casing wall. Note that only the transmitter-receiver pair on saturation flux generator 500E is shown. The transmitter 300E is wrapped around the top flange of saturation flux generator 500E in a manner similar to that depicted in Figure 4B. The receiver 580E is nulled 90° to the transmitter. It will be appreciated that each saturation flux generator may be activated sequentially to allow measurements to be taken in all directions with minimum consumption of power. Also, since the saturation flux generator is not in contact with the wall of the barrier materiaHOO, the device may be moved along the length of the barrier material. Figure 11 B illustrates a bi-static embodiment of the invention wherein multiple transmitter-receiver pairs are placed between production tubing 100 and well casing 110. Each transmitter and each receiver utilizes a separate saturation flux generator. This is shown for saturation flux generator 500A incorporating transmitter 300 and saturation flux generator 500B incorporating receiver 580. The saturation flux generator's are oriented to produce transparencies (or partial transparencies if desired) into or through the well casing 110. This direction of transmitting out of the well casing is shown by vector 825 and the receipt of resulting signals by the vector 826.

Figure 11C illustrates a similar bi-static application but where the transmitter 300 in saturation flux generator 500A is sending an oscillating magnetic signal into the production tubing. This is represented by vector 827. The responding signal is received by the receiver 580 located on saturation flux generator 500B. This is represented by vector 828. It will be appreciated that the transmitter would be located on the inside of the saturation flux generator 500A next to the production tubing wall 100. The receiver would also be located next to the production tubing wall and geometrically nulled to the transmitter.

Figure 11 D shows the saturation flux generator 500 containing the transmitter 300 of Figure 11B. Note that a culminator 555 contains the transmitter and is utilized to increase the energy efficiency of the saturation flux generator. The two flanges 504 are magnetic poles of opposite polarity to the magnetic culminator 555. The generator 500 contains 4 separate saturation coils 551 which each create separate electromagnetic flux circuits or loops that are coupled with the barrier wall. Each flange 504 combines and concentrates flux from two like poles and the culminator concentrates the flux of 4 separate magnets.

Figure 12 is yet another bi-static embodiment illustrating the use of the invention for profile logging with separated transmitter and receiver incorporated into individual saturation flux generator's 500A and 500B. Note that this embodiment does not utilize a magnetic culminator. Note also that the effective signal penetration 915 will be a function of the distance 910 between 500A and 500B, as well as the length of the transmitter coil 300. It will be appreciated that the transmitter 300 and the receiver 580 are components of the saturation flux generator 500A and 500B respectively and not attached to the barrier material 100.

Figure 13 illustrates another application of the present invention associated with the measurement of sediment and water in a storage tank illustrating the placement of a plurality of saturation flux generator devices, each containing transmitter-receiver pairs on the outside of the tank for measuring sediment and water.

Figure 14A illustrates yet another embodiment of the present invention utilizing a bi-static array with a single transmitter 300 and multiple receivers 580-580E for the measurement of sediment and water. The transmitter is in association with a plurality of fixed receivers at equal distances from the transmitter and located outside the tank such that resistivities change as the transmitter-receiver signal changes. It will be appreciated that the vector comprising the vertical distance between each receiver is also equal.

Figure 14B illustrates a bi-static array for a switch. The saturation flux generators are not shown. Figure 15 illustrates the use of an oscillating EM signal 419 for damping the saturation current 420. The damping effect is shown at 418 and occurs within the shaded area. The damping can cause the transparency to close or create only a partial transparency. In this manner, the oscillating wave can act as a switch turning the transparency "on and off". It will also be appreciated that this varying of saturation of the region may be utilized with Magnetic Lensing devices or Magnetic Antenna capabilities. It will also be appreciated that at a level of energy 425, the transparency may be open and the oscillating signal 419 will be transmitted across the barrier material.

Figure 16A is a one-axis saturation flux generator device 500 of the present invention comprised of the saturation coil 551 , and flanges 504 and 505. The one-axis saturation flux generator 500 has magnetic flux lines 140 and 141 , pole orientations "N" 505 and "S" 504. It is of course recognized that the pole orientations may be switched without a change in the subject invention. The closed magnetic saturation flux loop of the saturation flux generator will couple to the EM barrier 100. It is also noted that most, if not all, of the magnetic flux generated by the coil will couple with and travel through the magnetically permeable EM barrier adjacent to the flux generator. .

Figure 16B is another embodiment of a one-dimensional Saturation flux generator 500 but having two cores 551 and south poles 504. The two north poles 505 are combined together into a magnetic culminator 555. The magnetic flux loops 140 and 141 generated by the two saturation coils 551 are concentrated and funneled through the culminator to the magnetically permeable wall of the barrier material 100. The path of the two seprate and closed magnetic flux loops are also illustrated.

Figure 17 is a two-dimensional Cross-Flux Saturation flux generator device 500 of the present invention. The two-dimensional cross-flux saturation flux generator 500 is adjacent to a barrier materiaHOO. The 4 like poles 504 are connected to four separate cores 551. The opposing magnetic poles are contained within a single mass or magnetic culminator 555.

Figure 18 is a two-axis star-flux saturation flux generator device 500 of the present invention. The two-axis saturation flux generator device 500 is adjacent to the barrier material 100. Figure 19 is a three-axis star-flux saturation flux generator device 500 of the present invention. The three-axis saturation flux generator device 500 is adjacent to the barrier material 100. It will be appreciated that all of these configurations create concentrated magnetic flux proximate to the magnetically permeable surface of the EM barrier. This concentration provides an energy and space efficient coupling with the barrier material that allows a second separate flux to readily penetrate into the barrier, either for direct transmission through a fully saturated target material or to induce eddy currents through a broader area of the electrically conductive barrier.

When multiple like magnetic poles are placed or generated in one mass for the purpose of creating a controlled "bulge" or shape in the generated magnetic flux field, it is essential that the magnetic culminator be of adequate capacity or size. The size of the magnetic culminator 555, illustrated in Figures 17, 18, and 19, is determined by the mass and permeability of the intended transparency region of the barrier material to be saturated or magnetically coupled. The magnetic culminator must never become saturated by the saturation flux. In addition, the combined mass and permeability of saturation core inducers, cores and flanges, and magnetic culminator must be sufficiently larger than the mass and permeability of the target region of the barrier material such that the region of the barrier material will become saturated prior to the combined mass and permeability of the magnetic culminator, inducers, cores and flanges. If some part of the saturation core flux circuit is saturated by distance from the barrier material or by local saturation of the saturation core in the flux circuit, the amount of barrier material that can be made transparent is reduced. If the separation distance is small with respect to the magnetic moment of the separated surfaces, the magnetic strength loss is proportional to 1/R, where "R" is the separation distance. However as R increases to be equal to or greater than the magnetic moment diameter then the flux intensity decreases at the rate of 1/R³. Therefore the flux field is rapidly dissipated. Therefore, all magnets used to create the Transparency or partial transparency must be designed so that the total of the magnetic flux generated by the saturation flux generator device remains within the magnetic culminator capacity. The value of R should not exceed the radius of the magnetic culminator. All magnetic flux paths must be complete, i.e., no path must have a large air or low permeability gap in it except in the target metal for enhanced results. It will be appreciated that magnetic culminator will be the location of the greatest magnetic flux density. If a magnetic culminator is not utilized, the magnetic poles intended to created the transparency in the volume area of the barrier material must be constructed of sufficient mass and permeability.

Figure 20A and Figure 20B show a saturation flux generator 500 within a plurality of narrow tubes of barrier material 100 and 110 such as a hydrocarbon production tubing 100 and well casing 110 separated by a gap or spacing 115. These figures also show that long extended coils arms 551 on the magnetic saturation flux generator 500 are important since the complete length of the coils 551 contribute to the magnetic flux field generated between the poles. Figure 20A shows a two like poles (e.g., two north poles) combined in a single culminator 555 and the two opposing south poles 504. Figure 20B shows a simple north-south pole configuration consisting of a single north 504 and south pole 505. The transmitter 300 could be wrapped around one of the poles 505, while the signal receiver 580 could be wrapped around the other 504. This is important since the length of the coils can greatly exceed the space 970 between the magnetic poles. It has been found that electro-magnetic coils wrapped on a core for at least a distance of up to 100 diameters of the core diameter still contribute to the pole strength and amount of magnetic flux existing between the two magnetic poles. This assumes that the core material 552 upon which the coils 551 are wrapped is a highly permeable material. The greater the permeability and length of the core 551 , the greater the flux intensity and that can be achieved by the magnetic poles or culminator of the saturation flux generator 500. The increased strength or intensity achieves greater depth or resolution of flux penetration of the barrier materials 100 and 110 and outside material 155. Such a design is shown in Figures 20A and 20B. Comparison is also made to the design illustrated in Figure 4B. The design of Figure 20A and 20B could be used inside other narrow apertures or other relative inaccessible spaces such as in offshore platforms, bridge decks and the like. It will be appreciated that the gap 970 between the opposing poles 504 and 505 in Figure 20B will also impact the depth of penetration that may be achieved.

Figures 21 A, 21 B and 21 C show the geometry of saturation flux field lines 140 penetrating into the barrier material 100. In Figure 21 A, two opposing magnetic poles 504 and 505 are brought close together adjacent to a ferromagnetic barrier material 100. Note that most, if not all, the lines of magnetic flux 140 travel through the magnetically permeable barrier material 100 to the opposing pole rather than crossing the air gap 970. It will, of course, be appreciated that the flux lines 140 form a closed loop through the poles 504 and 505, saturation cores (not shown) within the saturation coils 551 and the culminators.

In Figure 21 B, two poles of the same polarity are brought together or in close proximity. The opposing poles are not shown. The two sets of magnetic flux field lines 140 emitted from the like poles repel each other and push the flux field further out away from the poles and into the barrier material 100. However a large unsaturated region remains. It is seen that in Figure 21 C that this unsaturated region has been eliminated and the transmitter 300 is more centrally located in the magnetic flux field 140 of the transparency region of the barrier material.

Figure 21 C shows the use of the magnetic culminator 555 containing two like poles 505. It has already been demonstrated that multiple like poles may be combined into a single mass, i.e., a magnetic culminator. Note that the magnetic flux lines 140 permeate the thickness of the barrier material 100. This is also a function of the mutual repulsion of the field lines, and results in the culminator being well suited for placement of a transmitter 300 or a receiver (not shown).

It has been found that enhanced magnetic coupling, i.e., deeper penetration into the barrier material 100, by the saturation flux without saturation, is achieved utilizing this saturation flux generator configuration 500 shown in Figure 21 C. In this case, coupling allows more magnetic energy to be transferred further into to the material 100 from the saturation flux generator 500.

Moreover, it is desired in these application designs to concentrate the magnetic flux energy of the saturation flux into a minimal region. For the configuration illustrated in Figure 21A, this requires closely positioning the north-south poles to each other as the exterior distance measurements allows. Therefore, if the material is "T" inches thick, to saturate all the way through the material the north-south spacing 970 must be at least "T" inches apart. However by "bucking" the poles, the same "T" inches depth of penetration may be achieved but with less than "T" inches separation between like poles. The benefit of minimizing the distances between the poles is that less energy, i.e., amp turns, are required for partial or full saturation of the subtended barrier material. If very long distances are to be measured outside and away from the barrier material, then it is advantageous if the transmitter and receiver are positioned in a bi-static array, i.e., each located within or in conjunction with separate magnetic saturation flux generators creating separate transparencies in the EM barrier.

In Figure 22 illustrates an embodiment of the invention wherein the saturation flux coil 551 and the transmitter coil 300 are separately wrapped around the same saturation core 552. The saturation core is a simple cylindrical shape with both the saturation flux coil and the transmitter coil wrapped in parallel around the axis 515 of the cylinder. Since the saturation coil 551 and transmitter coil 300 may have the same diameter, they may have the same magnetic moment radius. It will be appreciated that the oscillating transmitter flux may generate eddy currents in the saturation core. Further it will be appreciated by persons skilled in the art that the greatest saturation will occur along the circumference of the saturation core. In that manner the permeability of the near saturated or partially saturated saturation core will lowest at the edge. Since the permeability of the barrier material will approach the permeability of air, the angle will increase from the perpendicular. It will be further appreciated that this configuration may be used to create a Magnetic Lensing capacity within the saturation core 552 of the magnetic saturation flux generator. Figure 22 also illustrates the placement of a receiver coil 580 nulled to the transmitter coil. 300.

3. Possible Temporal Variations in opening and closing the Magnetic Transparency

These are the following considerations for the temporal variation of the saturation of the barrier material region in front of a transmitter or receiver.

1. Can use the material as an under-damping device for transmitting pulses for a pseudo-noise radar or reservoir mapping. 2. Transfer function wave form can be made to change with respect to saturation.

3. Can use temporal pairing for directionality measurements as discussed above. 4. Rapid on and off pulsing of the saturation flux generator allows the barrier material to be a time gate for transmitting flux or receiving flux. In addition, a pulsed on non static flux can be used as the source of the transmitter flux. This means the total saturated area becomes a transmitting antenna. It can also allow the frequency of the saturation flux to be matched with the transmitter frequency. Each of these considerations are discussed.

(A) The transmitter flux can be used as an under damping device. In Figure 15, a pulse 418 of a high frequency transmitter flux pulse 425 is superimposed upon the relatively constant saturation flux 420, i.e., steady state dc or low frequency ac current. The shaded area 419 shows the time period of the oscillating transmitter cycle that the barrier material, i.e., carbon steel, may be experience lower saturation due to the direction of the oscillating magnetic transmitter flux opposing the direction of the saturation flux. This means the permeability of the target at that time 419 may be more than one and more of the saturation flux is absorbed into the barrier material. This higher permeability acts as a powerful damping mechanism on the pulse. This is very useful in truncating a transmitted single or signal wave so that the transmitter does not cause "ringing." This ringing or oscillation at the end of the transmitter pulse can obliterate nearby readings.

(B) The saturation flux may be manipulated in such a way that the transparencies are opened in the barrier material as a transfer function wave form filter. This means that the barrier material can be used to allow only a certain upper frequency of a transmitted spectral transmitter flux into the receiver. The receiver transparency may be set to damp out all frequency above a desired range of frequencies. In this way, the barrier material would transmit only the desired upper frequency limit to the receiver when placed in a different location from the transmitter. It will be appreciated that this can be used in many varied and more sophisticated applications than a simple low pass filter illustrated here. For a magnetic flux diode, the current needed to put a material into magnetic saturation is called saturation current. If another current pulse is superimposed on saturation current, the additive part of the pulse will be transmitted, but the negative part of the pulse will reduce the total current below the saturation current. This negative part of the pulse will be severely damped by the metal because it is no longer magnetically saturated. This may be used as a type of diode for positive pulses.

(C) Directional or spatial information can be obtained by having sections of a steel wall equipped with saturating coils. In this way directionality may be obtained by creating a Metallic Transparency region in front of different transmitters, different receivers, or any combination of the two. Figure 11A shows one embodiment of this concept

(D) Combining directionality with the ability to gate electronically the opening and closing of the Metallic Transparency region is another possibility. This gating would also cause the receiver transparency to be off during a pulse from the transmitter, then open after a delay that would correspond to the time more distant induced magnetic flux would be anticipated to return to the receiver. This would be an important part of a pulsed radar system with the gating preventing or allowing, as desired, the near reflections to enter the receiver. Since the gating delays can be changed, in reality different parts of the reservoir are being sampled. Because the wavelengths are so long, this gating could be the useful for long distance mapping of reservoirs.

4. Nulling Techniques to Eliminate Direct Signal Coupling: The direct coupling between the transmitter and receiver is strong enough to overwhelm a secondary signal due to induced eddy currents. Therefore, a nulling technique must be used to de-couple the transmitter and receiver. There are three (3) ways to accomplish this nulling. These are as follows: a. Geometric nulling of the transmitter-receiver by orientation. b. Separation of transmitter - receiver by unsaturated metal. c. Electronic simple nulling of a waveform 180 degrees phase difference and matching amplitude, or by digital means. Each of these is used singly or in combination in the devices used in magnetic transparency.

As shown in Figure 23, a central ferromagnetic core 552 is axially wrapped with insulated wire 551 to create a powerful low frequency or D.C. magnetic field along the longitudinal 515 axis of the core. A ferromagnetic core, having a large mass and permeability, is used so that the magnetic flux lines do not disperse. "Low" frequency is defined by relationship to the frequency of the transmitter flux wavelengths needed to make a measurement, e.g., if ten wavelengths are needed for the measurement, then it is preferred that the low frequency be a least 1/10 of the frequency of the transmitter flux.

Also in Figure 23, one embodiment of the invention shows a separate transmitter

300 wrapped such that the eddy currents 620 generated in the core have their axis 315 perpendicular to the long axis 515 of the core 552. This core is then placed in some gap or distance 950 to the EM barrier plate 100 or in contact to the EM barrier plate 100. This EM barrier can be made completely transparent for the transmitter or, alternatively, an antenna or lens utilizing partial transparency. The optimum size of the gap 950 between the core 552 and the plate 100 is proportional to the magnetic moment of the transmitter/core diameter 990 and any lensing derived from the surface of the core 552 by the transmitter flux being focused by the saturation flux.

As previously mentioned, when a gap is present, e.g., insulation causing the space between the core 552 and EM barrier plate 100, the wrapping of the transmitter 300 on the core 552 utilizes this gap to create the Magnetic Lensing affect at the surface of the core, analogous to the lensing created at the EM barrier surface. This Magnetic Lensing counteracts the dispersion of the transmitter flux field with distance. This is illustrated by the relationship of magnetic flux intensity 180 decreasing to zero along the plot of intensity 181 as the inverse cubed of the distance (D) 910 away from the surface, i.e., Intensity Plot = 1/D³.

There is little lensing in the gap 950 and on the EM barrier plate 100 achieved by the transmitter flux alone. However, the transmitter flux will also generate eddy currents 610 within the EM barrier 100. These eddy currents will also induce magnetic flux lines 140 - 143 within the EM barrier. The transmitter 300 induced eddy currents 610 in the EM barrier 100 are shown in Figure 23. The resulting magnetic flux lines 140, 141, 142 and 143 generated from these electrical eddy currents inside the EM barrier are shown in Figure 23 intersecting the barrier surface perpendicularly 139.

Figure 24 depicts the change caused by the activation of the saturation flux coil 551. In this embodiment, as shown in Figure 23 and Figure 24, the transmitter 300 is a separate coil from the saturation coil 551. In another embodiment, it is possible to have the transmitter flux be superimposed electronically on the saturation flux used to achieve coupling with the barrier material. There are separate advantages to each approach. It is preferred to utilize the transmitter coupling magnet-separated embodiment. Both embodiments, however, are claimed as part of the subject invention of this application. It is also assumed that the saturation magnet is powered either by dc current or low frequency ac current, i.e., low relative to the frequency of the oscillating transmitter flux. The lines 150 of the magnetic flux field within the EM barrier 100 generated by this constant or low frequency magnetic saturation flux are shown. This magnetic flux lowers the permeability of the barrier material. The region of greatest influence of this magnetic field 151 is shown nearest the surface of the barrier material 100 and the saturation core 552 and decreasing into the EM barrier. As the permeability of the EM barrier plate is reduced, the transmitter flux lines (from 144 continuing to 140) begin to change their surface angle of impingement away from the perpendicular 139. It can be readily appreciated that the impingement angle 138 of flux line 140 at the surface will be the limited to the flux angle that would exist if the EM barrier was not present. This limit is approached as the permeability of the EM barrier approaches unity with the permeability of the matter or media in the gap or space, e.g., air, adjacent to the EM barrier. This changed impingement angle is shown in Figure 24 near the region of the core's greatest influence in having reduced the permeability on the EM barrier plate. Further away radially from the core, the magnetic flux lines 144 again impinge perpendicularly 139 to the plate surface.

Also shown in Figure 24 is a plot 181 of the resulting flux intensity 180 variation along the centerline 910. This shows an intensity spike 185 due to the concentration of the field at some fixed distance away from the plate surface. This flux field concentration is the same effect as would be obtained from an optical "lens" and is termed "magnetic lens" effect. The distance away from the EM barrier plate at which these flux lines are concentrated is called the "magnetic focal length." The place these flux lines are focused is called the "magnetic focal point" 186. This focal point may be moved toward or away from the barrier material 100 by reducing or increasing the magnetic moment of the transmitter and the saturation coil or the geometry of the magnetic fields in the metal plate.

In Figure 25A, the transmitter coil 300 is rotated to be parallel to the EM barrier 100. The transmitter induced eddy currents 620 within the EM barrier 100 generate the magnetic flux field having a geometry illustrated by field lines 140-143. Note the density of the magnetic flux field lines along line 910 as the flux field emerges from the partially saturated EM barrier plate 100. Supplemented on the Figure 25A is the plot 181 of the decrease in magnetic field intensity 180 as the distance 910 from the surface of the barrier material increases. The magnetic flux field intensity 180 decreases to zero along the plotted line 181. This illustrates that the intensity decreases in relation to the distance (D) 910 away from the surface, i.e., Intensity Plot = 1/D³.

Figure 25B shows the transmitter induced magnetic flux field 140, 141, 142 and 143 when the saturation coil 551 of the saturation flux generator 500 is turned on. There is a concentration of the flux lines off the centerline 910 and magnetic lensing occurs in a different geometry from Figure 24. The shape of the transmitter induced magnetic flux field has changed. The focused flux fields create a "focal circle" 187 or "focal plane" instead of the focal point geometry illustrated in Figure 24.

There are advantages to winding the transmitter coils 300 in this manner with respect to the EM barrier plate 100. The main advantage is that all elements of the transmitter coils can be made equidistant from the EM barrier plate 100, therefore inducing an eddy current uniformly parallel or perpendicular to the surface of the EM barrier plate and inducing a symmetrical magnetic flux field. If non-uniform eddy currents were desired, then it would be possible to rotate the axis of the transmitter coil 300 to be some angle between perpendicular (as in Figures 23 and 24) or parallel (as in Figures 25A and 25B) to the metal plate. (This geometry is illustrated in Figure 31.)

It will be appreciated that there is an eddy current generated in the core 552 of the saturation flux generator 500 and opposing the transmitter flux. As the transmitter coil 300 is moved axially along the core 552 and away from the end of the cylindrical core, more of the energy of the transmitter is consumed by this opposing eddy current. Note that this decrease of transmitter energy is experienced in spite of the gap 950 between the core 552 and the barrier plate 100 remaining constant.

Using this Magnetic Lensing technique has allowed the transmitter power to be minimized yet allowing detection of objects at distances not possible without the consumption of much greater power and increased size of the magnetic saturation generator subject of this invention.

Figure 26A and Figure 26B, illustrate another embodiment of the invention with a curved EM barrier 100. Due to the EM barrier 100 being only partially saturated, the induced magnetic flux field lines 140 - 143 emerge perpendicular 139 or near perpendicular to the EM barrier surface. As result of the geometry of the EM barrier curvature, this angle of emergence of the field lines helps concentrate the flux field. Note that the magnetic flux field lines 140 - 143 illustrated in Figure 26B (with the saturation flux generator activated "on") remain perpendicular 139 to the surface in the regions distant from the center of the Metallic Transparency effect within the barrier 100. This helps concentrate the flux field since even these flux lines are contributing to the field strength at the focal point or focal plane (depending upon the orientation of the transmitter coils to the EM barrier plate). This embodiment of fixed curvature for the metallic plate antenna obviously predetermines the focal distance. For many applications, this embodiment would be ideal. Also, by concentrating these flux field lines through the curved EM barrier plate 100, now acting as a magnetic antenna device, the decrease in flux field density with respect to an increase in distance is mitigated. It will be appreciated that known techniques for creating flexible ferromagnetic shapes of parabolic or similar geometry may be used to allow adjustment of the magnetic focal distance.

Figure 27 shows beam directivity along vector 956 achieved by controlled interplay of a plurality of saturation flux generators, e.g., 500A, 500B and 500C and each comprised of a saturation coil 551 and saturation core 552, but with one saturation flux generator also incorporating a transmitter 300. In this Figure, saturation flux generator 500A and 500B are creating the maximum permeability reduction within the Barrier 100 proximate to transmitter 300 and saturation flux generator 500A. The is illustrated by the greater concentration of flux lines 150 between 500A and 500B, in contrast to the flux lines 151 coupling between 500B and 500C. This creates the maximum bending of the flux lines 140 - 143 induced by transmitter 300 towards saturation flux generator 500A. The directionality of the beam is reflected in the distinct patterns of magnetic flux proximate 500A and 500C. This flux is achieved by the eddy currents 610 induced within the partially saturated barrier 100 by the oscillating transmitter flux. Note that Note the angle of impingement remains orthogonal 149 at the most distant line of magnetic flux. The flux lines emerging from the barrier material proximate to 500C show little deflection from the orthogonal as a result of the minimal reduction of permeability of the barrier material 100. There is a maximum beam steering available by this single transmitter technique.

Figure 28 shows two transmitters, 300A and 300B with bucked saturation coils 551 A and 551 B. The transmitters are both wound with their coils parallel to the EM barrier plate 100. If the oscillations of the separate transmitters flux are bucked, the eddy currents 610 and 611 induced within the paritally saturated barrier will have opposite directions. To deflect the transmitting flux 150 and 151 from 300A to the top, transmitter 300B should be increased in strength (at the same frequency) and saturation flux of 500B must be increased over saturation flux of 500A. In Figure 29, another transparency magnet 500C is added to increase the current to the distance D_2,3. 910. This will bend the flux field 140 - 143 downward along vector 956 while transmitter 300A is made much more powerful than transmitter 300B to push the flux field down. The increased concentration of saturation flux 151 between 500B and 500C is reflected in the concentration of flux lines, in contrast to the flux 150 proximate to 500A and 500B. The increased strength of the transmitter flux generated by 300A is illustrated by the greater concentration of eddy current proximate to 500A, in contrast to the concentration of eddy current proximate to 500B. It will be appreciated that the transmitters are bucked by the opposite direction of the eddy currents 610 and 620.

In Figure 30, another embodiment of beam movement is shown. This embodiment utilizes the transmitters 300A and 300B having equal diameters but oriented at 90° to the other. Again, it is possible to use combinations of transmitters and saturation flux generators 500A and 500B having unequal saturation strengths to bend the flux field.

Figure 31 shows the transmitter 300 at an oblique angle to the metal plate 100. It is also oblique to the saturation coil 551 and saturation core 552. The metal plate, constituting an EM barrier, is not fully saturated and the oscillating magnetic flux field of the transmitter 300 induces eddy currents 610. These eddy currents are also at an oblique angle to the surface of the plate 100. Further, the eddy currents 610 induce a corresponding magnetic flux field radiating out of the EM barrier plate. It should be noted that the field lines do not extend out of the EM barrier plate toward the saturation flux generator but rather field lines stay in close proximity of the EM barrier surface.

It is obvious that a variety of combinations of permeability changes, transmitter placements in 2D or 3D can be used with straight or curved metallic surfaces to create a large variety of beam forming devices.

Figures 32A and 32B show another embodiment for directing flux fields through a transparent region of a barrier material 250 incorporated into the saturation flux generator 500. It will be appreciated that this barrier material component 250 can be used for creating an antenna or for focusing the transmission of magnetic flux, induced within component, by variable adjustment of the saturated regions and strengths of one or more transmitters. It will be further appreciated at the antenna, comprised of a permeable material receptive to conveying magnet flux, may be used for the purpose receiving oscillating magnetic flux from other locations, which can then be processed and amplified. Directionality may be accomplished with orientation of the transmitter or by beam forming using multiple transmitter coils, 300A, 300B and 300C.

Additional advantages and modification will readily occur to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus, and the illustrative examples shown and described herein. Accordingly, departures may be made from the details without departing from the spirit or scope of the disclosed general inventive concept.

Claims

WHAT IS CLAIMED IS:

1. AA method of reducing the magnetic permeability of an electrically ccoonndduuccttiivvee aanndd mr agnetically permeable barrier material comprising the steps of:

(a) generating a first magnetic flux,

(b) engaging the first magnetic flux with the barrier material for reducing the magnetic permeability of at least a portion of the barrier material,

(c) generating a second magnetic flux at a frequency different from the first magnetic flux,

(d) engaging the second magnetic flux with the barrier material engaged by the first magnetic flux for generating eddy currents within the barrier material,

(e) inducing a third magnetic flux from the eddy currents within the barrier material,

(f) emitting the third magnetic flux from the barrier material,

(g) engaging the third magnetic flux with the electrically conductive and magnetically permeable objects in the vicinity of the barrier material,

(h) inducing eddy currents in the electrically conductive and magnetically permeable objects in the vicinity of the barrier material,

(i) inducing a fourth magnetic flux from the eddy currents within the electrically conductive and magnetically permeable objects,

(j) emitting the fourth magnetic flux from the electrically conductive and magnetically permeable objects, and

(k) receiving the fourth magnetic flux induced by the eddy currents generated within the objects for analysis.

2. The method of reducing the magnetic permeability of an electrically conductive and magnetically permeable barrier material as defined in claim 1 wherein the step of generating a second magnetic flux at a frequency different from the first magnetic flux comprises generating a second magnetic flux at a frequency greater than the first magnetic flux.

3. A method for creating a transparency in a material comprising the steps of: (a) creating a first electromagnetic wave adjacent to the material, (b) engaging the material with the first electromagnetic wave, (c) creating a second electromagnetic wave having a frequency higher than the first electromagnetic wave, and (d) engaging the second electromagnetic wave with the material when the material is saturated by the first electromagnetic wave, (e) creating a resulting wave from the engagement of the second electromagnetic wave with the material which resulting wave is available for detection because a transparency in the material is created.

4. A method for creating a transparency in a first material so that a second material can be evaluated, the method comprising the steps of: (a) lowering the permeability of the material with an initial electromagnetic wave, (b) creating a transmitted electromagnetic wave adjacent to the material having a frequency higher than the initial electromagnetic wave, (c) engaging the transmitted electromagnetic wave with, at least one of, the material or another material for creating a resulting wave, (d) detecting the resulting wave for creating a received signal, and (e) evaluating the received signal to determine the characteristics of, at least one of, the material or another material.

5. The method for creating a transparency in a first material so that a second material can be evaluated as defined in claim 1 wherein the step of lowering the permeability of the material with an initial electromagnetic wave comprises creating full saturation of the material.

6. The method for creating a transparency in a first material so that a second material can be evaluated as defined in claim 5 wherein the step of creating full saturation of the material comprises rendering the material at least one of transparent or partially transparent.

7. The method for creating a transparency in a first material so that a second material can be evaluated as defined in claim 1 wherein the step of lowering the permeability of the material with an initial electromagnetic wave comprises creating partial saturation of the material.

8. The method for creating a transparency in a first material so that a second material can be evaluated as defined in claim 1 wherein the step of creating partial saturation of the material comprises rendering the material at least one of transparent or partially transparent.

9. An apparatus for creating a transparency in a material, the apparatus comprising: (a) means for lowering the permeability of the first material with an initial electromagnetic wave, (b) a transmitter for generating a transmitted electromagnetic wave and engaging the transmitted electromagnetic wave with the material for creating a resulting wave, (c) a receiver for detecting the resulting wave, the receiver for creating a received signal which is available for detection because a transparency in the material is created.

10. An apparatus for creating a transparency in a first material so that the first or a second material can be evaluated, the apparatus comprising: (a) means for lowering the permeability of the first material with an initial electromagnetic wave, (b) a transmitter for generating a transmitted electromagnetic wave and engaging the transmitted electromagnetic wave with, at least one of, the first material or the second material for creating a resulting wave, (c) a receiver for detecting the resulting wave, the receiver for creating a received signal, and (d) means for evaluating the received signal to determine the characteristics of, at least one of, the first material or the second material.