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POLAR-2 -- Latest Developments of the Next Generation GRB Polarimeter
Authors:
Johannes Hulsman,
Philipp Azzarello,
Joerg Bayer,
Franck Cadoux,
Mariachiara Celato,
Nicolas De Angelis,
Yannick Favre,
Aaron Feder,
Jochen Greiner,
Alejandro Guzman,
Coralie Husi,
Vishal Kumar,
Hancheng Li,
Mobin Mobaseri,
Gabriel Pelleriti,
Agnieszka Pollo,
Nicolas Produit,
Dominik Rybka,
Andrea Santangelo,
Jianchao Sun,
Chris Tenzer,
Xin Wu,
Shuang-Nan Zhang
Abstract:
Gamma-Ray Bursts (GRBs) are among the most energetic events in the Universe. Despite over 50 years of research and measurements their prompt emission remains poorly understood, with key questions surrounding the structure of relativistic jets, magnetic field configurations, and dominant radiation mechanisms. Polarization measurements are critical in resolving these uncertainties. The POLAR mission…
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Gamma-Ray Bursts (GRBs) are among the most energetic events in the Universe. Despite over 50 years of research and measurements their prompt emission remains poorly understood, with key questions surrounding the structure of relativistic jets, magnetic field configurations, and dominant radiation mechanisms. Polarization measurements are critical in resolving these uncertainties. The POLAR mission, operational in 2016-2017 on Tiangong-2, provided the most statistically significant GRB polarization data. Its results indicated low time-averaged polarization with hints of temporal evolution. However, POLAR's limited sensitivity, small effective area, and restricted energy range prevented more detailed time- and energy-resolved analyses in addition to a larger sample of GRB polarization measurements. POLAR-2 is designed to address these limitations by offering a fourfold increase in effective area (at least) and an extended energy range of 30-800 keV by utilizing Silicon Photomultipliers (SiPMs) and an updated module design, enabling the differentiation of competing GRB emission models. The instrument comprises of 100 polarimeter modules (each with 64 plastic scintillator bars), wherein the polarization angle is extracted through Compton Scattering of the gammas. The polarimeter module design was validated during an ESRF beam test campaign in 2023. The instrument was developed by a joint effort of Switzerland, China, Poland and Germany and is planned for launch in 2027. Currently, POLAR-2 is in its production phase with the first module targets being produced. We will provide an overview of the current status of the development.
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Submitted 20 November, 2025; v1 submitted 12 November, 2025;
originally announced November 2025.
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Measurements of the Birks' coefficient of GAGG:Ce using hard X-rays
Authors:
Merlin Kole,
Nicolas De Angelis
Abstract:
Inorganic scintillators continue to be widely used within astrophysical X-ray and gamma-ray detectors. This is in part thanks to the development of new scintillators, such as GAGG:Ce, as well as the availability of new scintillator readout sensors such as Silicon Photomultipliers and Silicon Drift Detectors. In order to use such scintillator materials for spectrometry or polarimetry, a detailed un…
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Inorganic scintillators continue to be widely used within astrophysical X-ray and gamma-ray detectors. This is in part thanks to the development of new scintillators, such as GAGG:Ce, as well as the availability of new scintillator readout sensors such as Silicon Photomultipliers and Silicon Drift Detectors. In order to use such scintillator materials for spectrometry or polarimetry, a detailed understanding of their response is important. One parameter that can affect the scintillator performance, particularly at lower photon energies, is their Birks' coefficienct, which correlates the relative light yield to the ionization energy. While for many high-Z inorganic scintillators this effect can be ignored, for GAGG:Ce this appears to not be the case. Here we provide a measurement of the Birks' coefficient for GAGG:Ce using data from two different detectors irradiated in the 20-80 keV energy range at the LARIX-A X-ray beam in Ferrara, Italy. While the effects due to Birks' law are visible below 30 keV, they also significantly influence the performance of GAGG:Ce performance near one of the K-edges, affecting both the measured gain and the energy resolution. Here, we use beam test data to derive the Birks' coefficient from GAGG:Ce. The results indicate that for usage in hard X-ray and soft gamma-ray missions, this coefficient has a significant effect on the measurements.
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Submitted 3 October, 2025;
originally announced October 2025.
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Design and Scientific Prospects of the POLAR-2 Mission
Authors:
Merlin Kole,
Nicolas de Angelis,
Jiang He,
Hongbang Liu,
Jianchao Sun,
Fei Xie,
Jimmy Zaid
Abstract:
The POLAR-2 mission consists of 3 instruments designed with the combined aim of producing a deeper understanding of Gamma-Ray Bursts. To achieve this, POLAR-2 relies on polarisation measurements and, for the first time will provide these using 2 separate polarimeter detectors. The first of these is a payload optimised to perform Compton polarimetry measurements in the 40-1000 keV energy range usin…
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The POLAR-2 mission consists of 3 instruments designed with the combined aim of producing a deeper understanding of Gamma-Ray Bursts. To achieve this, POLAR-2 relies on polarisation measurements and, for the first time will provide these using 2 separate polarimeter detectors. The first of these is a payload optimised to perform Compton polarimetry measurements in the 40-1000 keV energy range using a combination of plastic scintillators and SiPMs. The development of this payload, the design of which is based on lessons learned from the POLAR mission, included optimization of plastic scintillator design. In addition, its development included detailed characterization, space qualification and radiation damage and mitigation strategies for the large number of silicon photo-multipliers included in the design. We will present these along with an overview of the readout electronics. These electronics were developed with flexibility in mind, as well as low cost and low power consumption. As such, its design is of interest beyond this polarimeter and is also used on the spectrometer instrument of POLAR-2 where it is used to read out an array of GAGG:Ce scintillators. This readout, in combination with a coded mask, allows this secondary instrument to provide detailed spectral and localization measurements. The final instrument used in the mission aims to use gas-based detectors to perform polarization measurements in the keV energy region. The novelty of this design is that it will be optimized to use these for wide field of view observations. The combination of the three instruments will allow to perform detailed spectral, localization and polarization measurements of these transient phenomena together for the first time. Here we provide an overview of the technologies employed in the mission along with detailed predictions on its capabilities after its launch currently foreseen in 2027.
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Submitted 7 November, 2025; v1 submitted 2 October, 2025;
originally announced October 2025.
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Addressing Selected Gamma-Ray Burst Science Topics with Future Space Instruments
Authors:
Nicolas De Angelis
Abstract:
Gamma-ray bursts (GRBs) are among the most energetic events in the universe, offering insights into stellar collapse, extreme matter behavior, and cosmic evolution. The advent of multi-messenger astronomy, combining electromagnetic, gravitational wave, and neutrino observations, alongside advances in high-energy polarimetry, is revolutionizing GRB research, enabling deeper exploration of their phy…
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Gamma-ray bursts (GRBs) are among the most energetic events in the universe, offering insights into stellar collapse, extreme matter behavior, and cosmic evolution. The advent of multi-messenger astronomy, combining electromagnetic, gravitational wave, and neutrino observations, alongside advances in high-energy polarimetry, is revolutionizing GRB research, enabling deeper exploration of their physical mechanisms.
This manuscript summarizes how upcoming and proposed space-based missions will tackle key challenges in GRB science, focusing on four areas: (i) identifying high-redshift GRBs to probe the early universe, (ii) enhancing multi-messenger detection and localization, (iii) improving multi-wavelength follow-up of GRB afterglows, and (iv) studying prompt emission polarization to understand jet dynamics and magnetic fields. Highlighting planned missions and their advancements, this work provides a snapshot of current GRB research frontiers, with updates on the evolving status of these missions.
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Submitted 3 October, 2025; v1 submitted 1 October, 2025;
originally announced October 2025.
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Solar Flare Hard X-ray Polarimetry with the CUbesat Solar Polarimeter (CUSP) mission
Authors:
Nicolas De Angelis,
Andrea Alimenti,
Davide Albanesi,
Ilaria Baffo,
Daniele Brienza,
Riccardo Campana,
Valerio Campamaggiore,
Mauro Centrone,
Enrico Costa,
Giovanni Cucinella,
Andrea Curatolo,
Giovanni De Cesare,
Giulia de Iulis,
Ettore Del Monte,
Andrea Del Re,
Sergio Di Cosimo,
Simone Di Filippo,
Giuseppe Di Persio,
Immacolata Donnarumma,
Sergio Fabiani,
Pierluigi Fanelli,
Nicolas Gagliardi,
Abhay Kumar,
Alessandro Lacerenza,
Paolo Leonetti
, et al. (21 additional authors not shown)
Abstract:
The CUbesat Solar Polarimeter (CUSP) project is a CubeSat mission planned for a launch in low-Earth orbit and aimed to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP will allow us to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star. CUSP is a project in the framework o…
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The CUbesat Solar Polarimeter (CUSP) project is a CubeSat mission planned for a launch in low-Earth orbit and aimed to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP will allow us to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed at developing new CubeSat missions. It is undergoing a 12-month Phase B that started in December 2024.
The Compton polarimeter on board CUSP is composed of two acquisition chains based on plastic scintillators read out by Multi-Anode PhotoMultiplier Tubes for the scatterer part and GAGG crystals coupled to Avalanche PhotoDiodes for the absorbers. An event coincident between the two readout schemes will lead to a measurement of the incoming X-ray's azimuthal scattering angle, linked to the polarization of the solar flare in a statistical manner. The current status of the CUSP mission design, mission analysis, and payload scientific performance will be reported. The latter will be discussed based on preliminary laboratory results obtained in parallel with Geant4 simulations.
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Submitted 16 September, 2025;
originally announced September 2025.
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Gamma-Ray Burst Polarimetry with the POLAR and POLAR-2 missions
Authors:
Nicolas De Angelis,
Philipp Azzarello,
Franck Cadoux,
Kurt Dittrich,
Yannick Favre,
Jochen Greiner,
Johannes Hulsman,
Coralie Husi,
Merlin Kole,
Hancheng Li,
Slawomir Mianowski,
Gabriel Pelleriti,
Agnieszka Pollo,
Nicolas Produit,
Dominik Rybka,
Jianchao Sun,
Xin Wu,
Shuang-Nan Zhang
Abstract:
Gamma-Ray Bursts are among the most powerful and violent events in the Universe. Despite over half a century of observations of these transient sources, many open questions remain about their nature and the physical emission mechanisms at play. Polarization measurements of the GRB prompt gamma-ray emission have long been theorized to be able to answer most of these questions. Early polarization me…
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Gamma-Ray Bursts are among the most powerful and violent events in the Universe. Despite over half a century of observations of these transient sources, many open questions remain about their nature and the physical emission mechanisms at play. Polarization measurements of the GRB prompt gamma-ray emission have long been theorized to be able to answer most of these questions. Early polarization measurements did not allow to draw clear conclusions because of limited significance.
With the aim of better characterizing the polarization of these prompt emissions, a compact Gamma-Ray polarimeter called POLAR has been sent to space as part of the Tiangong-2 Chinese space lab for 6 months of operations starting September 2016. The instrument detected 55 GRBs as well as several pulsars. Time-integrated polarization analysis of the 14 brightest detected GRBs has shown that the prompt emission is lowly polarized or fully unpolarized. However, time-resolved analysis depicted strong hints of an evolving polarization angle within single pulses, washing out the polarization degree in time-integrated analyses. Energy-resolved polarization analysis has shown no constraining results due to limited statistics. Hence, a more sensitive $γ$-ray polarimeter is required to perform detailed energy and time-resolved polarization analysis of the prompt gamma-ray emission of GRBs.
Based on the success of the POLAR mission, a larger-scale instrument, approved for launch to the China Space Station (CSS) in 2027, is currently being developed by a Swiss, Chinese, Polish, and German collaboration. Thanks to its large sensitivity in the 20-800~keV range, POLAR-2 will produce polarization measurements of at least 50 GRBs per year with a precision equal to or higher than the best results published by POLAR, allowing for good quality time and energy resolved analysis.
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Submitted 8 September, 2025;
originally announced September 2025.
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The multi-physics analysis, design and testing of CUSP, a CubeSat mission for space weather and solar flares x-ray polarimetry
Authors:
Giovanni Lombardi,
Sergio Fabiani,
Ettore Del Monte,
Andrea Alimenti,
Riccardo Campana,
Mauro Centrone,
Enrico Costa,
Nicolas De Angelis,
Giovanni De Cesare,
Sergio Di Cosimo,
Giuseppe Di Persio,
Abhay Kumar,
Alessandro Lacerenza,
Pasqualino Loffredo,
Gabriele Minervini,
Fabio Muleri,
Paolo Romano,
Alda Rubini,
Emanuele Scalise,
Enrico Silva,
Paolo Soffitta,
Davide Albanesi,
Ilaria Baffo,
Daniele Brienza,
Valerio Campamaggiore
, et al. (23 additional authors not shown)
Abstract:
The space-based CUbesat Solar Polarimeter (CUSP) mission aims to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed at developing new CubeSat missions. As part of CUSP's Phase B study, which began in December 2024 and will last one year, we pre…
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The space-based CUbesat Solar Polarimeter (CUSP) mission aims to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed at developing new CubeSat missions. As part of CUSP's Phase B study, which began in December 2024 and will last one year, we present the current development status of the design solutions adopted for the mission's most critical multi-physics design drivers. These solutions have been formulated and applied to demonstrate compliance with system requirements at both the spacecraft and platform levels. In particular, we describe the mechanical design of each structural component, the results of static, dynamic finite element analyses, and a proposal for topological optimization of the interface between the platform and payload and some fixture for test, and the preliminary environmental testing campaign (e.g., vibration, shock) that will be carried out on a mechanical demonstrator.
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Submitted 4 August, 2025;
originally announced August 2025.
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CUbesat Solar Polarimeter (CUSP) Sensitivity Estimation and Performance Optimization using Geant4
Authors:
Abhay Kumar,
Giovanni Lombardi,
Giovanni De Cesare,
Nicolas De Angelis,
Sergio Fabiani,
Ettore Del Monte,
Andrea Alimenti,
Riccardo Campana,
Enrico Costa,
Paolo Soffitta,
Mauro Centrone,
Sergio Di Cosimo,
Giuseppe Di Persio,
Alessandro Lacerenza,
Pasqualino Loffredo,
Fabio Muleri,
Paolo Romano,
Alda Rubini,
Emanuele Scalise,
Enrico Silva,
Davide Albanesi,
Ilaria Baffo,
Daniele Brienza,
Valerio Campamaggiore,
Giovanni Cucinella
, et al. (23 additional authors not shown)
Abstract:
The CUbesat Solar Polarimeter (CUSP) aims to measure the linear polarization of solar flares in the 25-100 keV X-ray band using a Compton scattering polarimeter. CUSP will allow us to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star by providing high-sensitivity polarization measurements. CUSP is a project in the framework of the Alcor Progra…
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The CUbesat Solar Polarimeter (CUSP) aims to measure the linear polarization of solar flares in the 25-100 keV X-ray band using a Compton scattering polarimeter. CUSP will allow us to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star by providing high-sensitivity polarization measurements. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed to develop innovative CubeSat technologies and missions. As part of CUSPs Phase B study, which began in December 2024 and will continue for one year, we present the development status of the Geant4 based simulator to accurately simulate the detectors response and initial results on the sensitivity of the instrument. Geant4 Monte Carlo simulation is used to assess the physical interactions of the source photons with the detector and the passive materials. We implemented a detailed CUSP Mass Model within Geant4 to simulate and estimate the instruments sensitivity, correcting the geometric effects of the instrument. We also evaluated the effect of backscattering shielding on the sensitivity to optimize the mass model of the instrument.
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Submitted 1 August, 2025;
originally announced August 2025.
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The CUbesat Solar Polarimeter (CUSP): mission overview II
Authors:
Sergio Fabiani,
Ettore Del Monte,
Andrea Alimenti,
Riccardo Campana,
Mauro Centrone,
Enrico Costa,
Nicolas De Angelis,
Giovanni De Cesare,
Sergio Di Cosimo,
Giuseppe Di Persio,
Abhay Kumar,
Alessandro Lacerenza,
Pasqualino Loffredo,
Giovanni Lombardi,
Lorenzo Marra,
Gabriele Minervini,
Fabio Muleri,
Paolo Romano,
Alda Rubini,
Emanuele Scalise,
Enrico Silva,
Paolo Soffitta,
Davide Albanesi,
Ilaria Baffo,
Daniele Brienza
, et al. (24 additional authors not shown)
Abstract:
The CUbesat Solar Polarimeter (CUSP) project is an Earth-orbiting CubeSat mission designed to measure the linear polarization of solar flares in the hard X-ray band using a Compton scattering polarimeter. CUSP will enable the study of magnetic reconnection and particle acceleration within the Sun's flaring magnetic structures. This project is being developed within the framework of the Italian Spa…
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The CUbesat Solar Polarimeter (CUSP) project is an Earth-orbiting CubeSat mission designed to measure the linear polarization of solar flares in the hard X-ray band using a Compton scattering polarimeter. CUSP will enable the study of magnetic reconnection and particle acceleration within the Sun's flaring magnetic structures. This project is being developed within the framework of the Italian Space Agency's Alcor Program, which aims to foster new CubeSat missions. CUSP entered its Phase B in December 2024, a phase scheduled to last 12 months. This paper reports on the current status of the CUSP mission design, mission analysis, and payload scientific performance.
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Submitted 1 August, 2025;
originally announced August 2025.
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Study of the HV power supply modules for the CUbesat Solar Polarimeter (CUSP)
Authors:
Alessandro Lacerenza,
Alda Rubini,
Andrea Alimenti,
Sergio Fabiani,
Ettore Del Monte,
Riccardo Campana,
Mauro Centrone,
Enrico Costa,
Nicolas De Angelis,
Giovanni De Cesare,
Sergio Di Cosimo,
Giuseppe Di Persio,
Abhay Kumar,
Pasqualino Loffredo,
Giovanni Lombardi,
Gabriele Minervini,
Fabio Muleri,
Paolo Romano,
Emanuele Scalise,
Enrico Silva,
Paolo Soffitta,
Davide Albanesi,
Ilaria Baffo,
Daniele Brienza,
Valerio Campamaggiore
, et al. (23 additional authors not shown)
Abstract:
The CUbesat Solar Polarimeter (CUSP) project is a CubeSat mission orbiting the Earth aimed to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star. CUSP is a project in the framework of the Alcor Program of the I…
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The CUbesat Solar Polarimeter (CUSP) project is a CubeSat mission orbiting the Earth aimed to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed to develop new CubeSat missions. CUSP undergoing the Phase B started in December 2024 that will last for 12 month. The Compton polarimeter of the CUSP payload performs coincidence measurements between plastic scintilaltors and GaGG(Ce) crystals to derive the polarization of X-rays. These sensors are readout by Multi Anode Photomultiplier Tubes (MAPMTs) and Avalanche Photodiodes (APDs) respectively. Both sensors need an HV power supply up to -1~kV (for the MAPMT) and +500~V (for the APD). We tested precision regulated High Voltage DC/DC Converters by HVM Technology Inc. with Sub-Miniature Case Size ($0.85''\times0.85''\times0.60''$) of the SMHV series. These modules are compact and suited for CubeSat missions.
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Submitted 1 August, 2025;
originally announced August 2025.
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Prototype Development and Calibration of the CUbesat Solar Polarimeter (CUSP)
Authors:
Nicolas De Angelis,
Abhay Kumar,
Sergio Fabiani,
Ettore Del Monte,
Enrico Costa,
Giovanni Lombardi,
Paolo Soffitta,
Andrea Alimenti,
Riccardo Campana,
Mauro Centrone,
Giovanni De Cesare,
Sergio Di Cosimo,
Giuseppe Di Persio,
Alessandro Lacerenza,
Pasqualino Loffredo,
Gabriele Minervini,
Fabio Muleri,
Paolo Romano,
Alda Rubini,
Emanuele Scalise,
Enrico Silva,
Davide Albanesi,
Ilaria Baffo,
Daniele Brienza,
Valerio Campamaggiore
, et al. (23 additional authors not shown)
Abstract:
The space-based CUbesat Solar Polarimeter (CUSP) mission aims to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star with its unprecedented sensitivity to solar flare polarization. CUSP is a project in the frame…
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The space-based CUbesat Solar Polarimeter (CUSP) mission aims to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star with its unprecedented sensitivity to solar flare polarization. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed to develop new CubeSat missions. It has been proposed as a constellation of a two Cubesat mission to monitor the Sun for Space Weather, and will proceed with a single-satellite asset in its baseline implementation.
In the frame of CUSP's Phase B study, that started in December 2024 for a 1-year period, we present the development status of this dual-phase polarimeter. Preliminary laboratory results using two chains of acquisition will be discussed. The first chain of acquisition, based on the Hamamatsu R7600 multi-anode photomultiplier tubes coupled to plastic scintillator bars and read out by the MAROC-3A ASIC, is used to detect the Compton scattering of incoming photons. On the other hand, GAGG crystals coupled to avalanche photo-diodes with a readout based on the SKIROC-2A ASIC are used to absorb the scattered photons. By reconstructing the azimuthal scattering direction for many incoming photons, one can infer the linear polarization degree and angle of the source. We will discuss the calibration results obtained with our prototype detector by using well-known radioactive isotopes, allowing us to assess the performances of our detector over the full 25-100 keV energy range.
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Submitted 1 August, 2025;
originally announced August 2025.
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Design and Performance of a Universal SiPM Readout System for X- and Gamma-Ray Missions
Authors:
Merlin Kole,
Nicolas De Angelis,
Nicolas Produit,
Philipp Azzarello,
Franck Cadoux,
Yannick Favre,
Jochen Greiner,
Vishal Kumar,
Johannes Hulsman,
Sebastian Kusyk,
Hancheng Li,
Dominik Rybka,
Jerome Stauffer,
Adrien Stil,
Jianchao Sun,
Jan Swakon,
Damian Wrobel,
Xin Wu
Abstract:
The advent of both multi-messenger and time-domain astrophysics over the last decade has seen a large interest in the development of small-scale, cheap, and robust gamma-ray detectors. This has been further encouraged by the availability of CubeSat platforms. Of particular interest are detectors capable of producing spectral and localization measurements of X and gamma-ray transients to allow for…
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The advent of both multi-messenger and time-domain astrophysics over the last decade has seen a large interest in the development of small-scale, cheap, and robust gamma-ray detectors. This has been further encouraged by the availability of CubeSat platforms. Of particular interest are detectors capable of producing spectral and localization measurements of X and gamma-ray transients to allow for accurate follow-up measurements at different wavelengths. A vast number of the instruments developed for such purposes in the last years use a combination of scintillators and Silicon Photomultipliers (SiPMs) for photon detection. Here, we present the design, performance, and space qualification of a readout system capable of reading out 64 SiPM channels. This low-power and low-cost system was originally designed for the POLAR-2 mission, a large scale gamma-ray polarimeter. However, its flexible design makes it equally suitable for use on various CubeSat missions. The system was found to perform well when reading out both plastic and high Z scintillators using a total of 1.8~W. The space qualified design furthermore relies on commercial off-the-shelf components, thereby also removing most international export issues. In this paper, we will present the overall design, the performance of the electronics, its performance when reading out various scintillators and the successful space-qualification of this design.
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Submitted 17 June, 2025; v1 submitted 13 January, 2025;
originally announced January 2025.
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STROBE-X High Energy Modular Array (HEMA)
Authors:
Anthony L. Hutcheson,
Marco Feroci,
Andrea Argan,
Matias Antonelli,
Marco Barbera,
Jorg Bayer,
Pierluigi Bellutti,
Giuseppe Bertuccio,
Valter Bonvicini,
Franck Cadoux,
Riccardo Campana,
Matteo Centis Vignali,
Francesco Ceraudo,
Marc Christophersen,
Daniela Cirrincione,
Fabio D'Anca,
Nicolas De Angelis,
Alessandra De Rosa,
Giovanni Della Casa,
Ettore Del Monte,
Giuseppe Dilillo,
Yuri Evangelista,
Yannick Favre,
Francesco Ficorella,
Mauro Fiorini
, et al. (42 additional authors not shown)
Abstract:
The High Energy Modular Array (HEMA) is one of three instruments that compose the STROBE-X mission concept. The HEMA is a large-area, high-throughput non-imaging pointed instrument based on the Large Area Detector developed as part of the LOFT mission concept. It is designed for spectral timing measurements of a broad range of sources and provides a transformative increase in sensitivity to X-rays…
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The High Energy Modular Array (HEMA) is one of three instruments that compose the STROBE-X mission concept. The HEMA is a large-area, high-throughput non-imaging pointed instrument based on the Large Area Detector developed as part of the LOFT mission concept. It is designed for spectral timing measurements of a broad range of sources and provides a transformative increase in sensitivity to X-rays in the energy range of 2--30 keV compared to previous instruments, with an effective area of 3.4 m$^{2}$ at 8.5 keV and an energy resolution of better than 300 eV at 6 keV in its nominal field of regard.
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Submitted 10 October, 2024;
originally announced October 2024.
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Optimizing the light output of a plastic scintillator and SiPM based detector through optical characterization and simulation: A case study for POLAR-2
Authors:
Nicolas De Angelis,
Franck Cadoux,
Coralie Husi,
Merlin Kole,
Sławomir Mianowski
Abstract:
The combination of plastic scintillators with Silicon Photo-Multipliers (SiPMs) is widely used for detecting radiation in high-energy astrophysics, particle physics, neutrino physics, or medical physics. An example of application for this kind of detectors are Compton polarimeters such as POLAR-2 or LEAP, for which a low-Z material is needed for the Compton effect to be dominant down to as low ene…
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The combination of plastic scintillators with Silicon Photo-Multipliers (SiPMs) is widely used for detecting radiation in high-energy astrophysics, particle physics, neutrino physics, or medical physics. An example of application for this kind of detectors are Compton polarimeters such as POLAR-2 or LEAP, for which a low-Z material is needed for the Compton effect to be dominant down to as low energy as possible. Such detectors aim to measure low energy Compton depositions which produce small amounts of optical light, and for which optimizing the instrumental optical properties consequently imperative.
The light collection efficiency of such a device was studied with a focus on the POLAR-2 GRB polarimeter, in which the conversion of incoming $γ$-rays into readable signal goes through the production and collection of optical light, which was to be optimized both through measurements and simulations. The optical elements of the POLAR-2 polarimeter prototype module were optically characterized and an optical simulation based on Geant4 was developed to fully model its optical performances. The results from simulations were used to optimize the design and finally to verify its performance. The study resulted in a detector capable of measuring energy depositions of several keV. In addition an important finding of this work is the impact of the plastic scintillator surface roughness on the light collection. It was found that a plastic scintillator with a higher scintillation efficiency but made of a softer material, hence with a rougher surface, was not necessarily the best option to optimize the light collection. Furthermore, in order to optimize the optical crosstalk between different channels, a production technique for very thin ($\sim$150$~μ$m) and reusable silicone-based optical coupling pads, which can be applied for other experiments, was developed.
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Submitted 15 July, 2024;
originally announced July 2024.
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The CUbesat Solar Polarimeter (CUSP) mission overview
Authors:
Sergio Fabiani,
Ettore Del Monte,
Ilaria Baffo,
Sergio Bonomo,
Daniele Brienza,
Riccardo Campana,
Mauro Centrone,
Gessica Contini,
Enrico Costa,
Giovanni Cucinella,
Andrea Curatolo,
Nicolas De Angelis,
Giovanni De Cesare,
Andrea Del Re,
Sergio Di Cosimo,
Simone Di Filippo,
Alessandro Di Marco,
Giuseppe Di Persio,
Immacolata Donnarumma,
Pierluigi Fanelli,
Paolo Leonetti,
Alfredo Locarini,
Pasqualino Loffredo,
Giovanni Lombardi,
Gabriele Minervini
, et al. (13 additional authors not shown)
Abstract:
The CUbesat Solar Polarimeter (CUSP) project is a future CubeSat mission orbiting the Earth aimed to measure the linear polarization of solar flares in the hard X-ray band, by means of a Compton scattering polarimeter. CUSP will allow us to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star. The project is in the framework of the Italian Space…
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The CUbesat Solar Polarimeter (CUSP) project is a future CubeSat mission orbiting the Earth aimed to measure the linear polarization of solar flares in the hard X-ray band, by means of a Compton scattering polarimeter. CUSP will allow us to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star. The project is in the framework of the Italian Space Agency Alcor Program, which aims to develop new CubeSat missions. CUSP is approved for a Phase B study that will last for 12 months, starting in mid-2024. We report on the current status of the CUSP mission project as the outcome of the Phase A.
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Submitted 4 July, 2024;
originally announced July 2024.
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The multi$-$physics analysis and design of CUSP, a two CubeSat constellation for Space Weather and Solar flares X-ray polarimetry
Authors:
Giovanni Lombardi,
Sergio Fabiani,
Ettore Del Monte,
Enrico Costa,
Paolo Soffitta,
Fabio Muleri,
Ilaria Baffo,
Marco E. Biancolini,
Sergio Bonomo,
Daniele Brienza,
Riccardo Campana,
Mauro Centrone,
Gessica Contini,
Giovanni Cucinella,
Andrea Curatolo,
Nicolas De Angelis,
Giovanni De Cesare,
Andrea Del Re,
Sergio Di Cosimo,
Simone Di Filippo,
Alessandro Di Marco,
Emanuele Di Meo,
Giuseppe Di Persio,
Immacolata Donnarumma,
Pierluigi Fanelli
, et al. (16 additional authors not shown)
Abstract:
The CUbesat Solar Polarimeter (CUSP) project aims to develop a constellation of two CubeSats orbiting the Earth to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter on board of each satellite. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures. CUSP is a project approved f…
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The CUbesat Solar Polarimeter (CUSP) project aims to develop a constellation of two CubeSats orbiting the Earth to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter on board of each satellite. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures. CUSP is a project approved for a Phase B study by the Italian Space Agency in the framework of the Alcor program aimed to develop CubeSat technologies and missions. In this paper we describe the a method for a multi-physical simulation analysis while analyzing some possible design optimization of the payload design solutions adopted. In particular, we report the mechanical design for each structural component, the results of static and dynamic finite element analysis, the preliminary thermo-mechanical analysis for two specific thermal cases (hot and cold orbit) and a topological optimization of the interface between the platform and the payload.
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Submitted 4 July, 2024;
originally announced July 2024.
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The evaluation of the CUSP scientific performance by a GEANT4 Monte Carlo simulation
Authors:
Giovanni De Cesare,
Sergio Fabiani,
Riccardo Campana,
Giovanni Lombardi,
Ettore Del Monte,
Enrico Costa,
Ilaria Baffo,
Sergio Bonomo,
Daniele Brienza,
Mauro Centrone,
Gessica Contini,
Giovanni Cucinella,
Andrea Curatolo,
Nicolas De Angelis,
Andrea Del Re,
Sergio Di Cosimo,
Simone Di Filippo,
Alessandro Di Marco,
Giuseppe Di Persio,
Immacolata Donnarumma,
Pierluigi Fanelli,
Paolo Leonetti,
Alfredo Locarini,
Pasqualino Loffredo,
Gabriele Minervini
, et al. (13 additional authors not shown)
Abstract:
The CUbesat Solar Polarimeter (CUSP) project is a CubeSat mission orbiting the Earth aimed to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star. CUSP is a project in the framework of the Alcor Program of the I…
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The CUbesat Solar Polarimeter (CUSP) project is a CubeSat mission orbiting the Earth aimed to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed to develop new CubeSat missions. It is approved for a Phase B study. In this work, we report on the accurate simulation of the detector's response to evaluate the scientific performance. A GEANT4 Monte Carlo simulation is used to assess the physical interactions of the source photons with the detector and the passive materials. Using this approach, we implemented a detailed CUSP Mass Model. In this work, we report on the evaluation of the detector's effective area as a function of the beam energy.
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Submitted 4 July, 2024;
originally announced July 2024.
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Response of the first POLAR-2 Prototype to Polarized Beams
Authors:
Merlin Kole,
Nicolas de Angelis,
Ana Bacelj,
Franck Cadoux,
Agnieszka Elwertowska,
Johannes Hulsman,
Hancheng Li,
Grzegorz Łubian,
Tomasz Kowalski,
Gilles Koziol,
Agnieszka Pollo,
Nicolas Produit,
Dominik Rybka,
Adrien Stil,
Jianchao Sun,
Xin Wu,
Kacper Zezuliński,
Shuang-Nan Zhang
Abstract:
POLAR-2 is a dedicated gamma-ray polarimeter currently foreseen to be launched towards the China Space Station around 2027. The design of the detector is based on the legacy of its predecessor mission POLAR which was launched in 2016. POLAR-2 aims to measure the polarization of the Gamma-ray Burst prompt emission within the 30-800 keV energy range. Thanks to its high sensitivity to gamma-ray polar…
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POLAR-2 is a dedicated gamma-ray polarimeter currently foreseen to be launched towards the China Space Station around 2027. The design of the detector is based on the legacy of its predecessor mission POLAR which was launched in 2016. POLAR-2 aims to measure the polarization of the Gamma-ray Burst prompt emission within the 30-800 keV energy range. Thanks to its high sensitivity to gamma-ray polarization, as well as its large effective area, POLAR-2 will provide the most precise measurements of this type to date. Such measurements are key to improve our understanding of the astrophysical processes responsible for Gamma-Ray Bursts. The detector consists of a segmented array of plastic scintillator bars, each one of which is read out by a Silicon PhotoMultiplier channel. The flight model of POLAR-2 will contain a total of 6400 scintillators. These are divided into 100 groups of 64 bars each, in so-called polarimeter modules. In recent years, the collaboration has designed and produced the first prototypes of these polarimeter modules and subjected these to space qualification tests. In addition, in April 2023, the first of these modules were calibrated using fully polarized gamma-ray beams at the European Synchrotron Radiation Facility (ESRF) in France. In this work, we will present the results of this calibration campaign and compare these to the simulated performance of the POLAR-2 modules. Potential improvements to the design are also discussed. Finally, the measurements are used, in combination with the verified simulation framework, to estimate the scientific performance of the full POLAR-2 detector and compare it to its predecessor.
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Submitted 9 June, 2024;
originally announced June 2024.
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Future Perspectives for Gamma-ray Burst Detection from Space
Authors:
Enrico Bozzo,
Lorenzo Amati,
Wayne Baumgartner,
Tzu-Ching Chang,
Bertrand Cordier,
Nicolas De Angelis,
Akihiro Doi,
Marco Feroci,
Cynthia Froning,
Jessica Gaskin,
Adam Goldstein,
Diego Götz,
Jon E. Grove,
Sylvain Guiriec,
Margarita Hernanz,
C. Michelle Hui,
Peter Jenke,
Daniel Kocevski,
Merlin Kole,
Chryssa Kouveliotou,
Thomas Maccarone,
Mark L. McConnell,
Hideo Matsuhara,
Paul O'Brien,
Nicolas Produit
, et al. (13 additional authors not shown)
Abstract:
Since their first discovery in the late 1960s, Gamma-ray bursts have attracted an exponentially growing interest from the international community due to their central role in the most highly debated open questions of the modern research of astronomy, astrophysics, cosmology, and fundamental physics. These range from the intimate nuclear composition of high density material within the core of ultra…
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Since their first discovery in the late 1960s, Gamma-ray bursts have attracted an exponentially growing interest from the international community due to their central role in the most highly debated open questions of the modern research of astronomy, astrophysics, cosmology, and fundamental physics. These range from the intimate nuclear composition of high density material within the core of ultra-dense neuron stars, to stellar evolution via the collapse of massive stars, the production and propagation of gravitational waves, as well as the exploration of the early Universe by unveiling first stars and galaxies (assessing also their evolution and cosmic re-ionization). GRBs have stimulated in the past $\sim$50 years the development of cutting-edge technological instruments for observations of high energy celestial sources from space, leading to the launch and successful operations of many different scientific missions (several of them still in data taking mode nowadays). In this review, we provide a brief description of the GRB-dedicated missions from space being designed and developed for the future. The list of these projects, not meant to be exhaustive, shall serve as a reference to interested readers to understand what is likely to come next to lead the further development of GRB research and associated phenomenology.
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Submitted 17 April, 2024;
originally announced April 2024.
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POLAR-2, the next generation of GRB polarization detector
Authors:
Nicolas Produit,
Merlin Kole,
Xin Wu,
Nicolas De Angelis,
Hancheng Li,
Dominik Rybka,
Agnieszka Pollo,
Slawomir Mianowski,
Jochen Greiner,
J. Michael Burgess,
Jianchao Sun,
Shuang-Nan Zhang
Abstract:
The POLAR-2 Gamma-Ray Burst (GRB) Polarimetry mission is a follow-up to the successful POLAR mission. POLAR collected six months of data in 2016-2017 on board the Tiangong-2 Chinese Space laboratory. From a polarization study on 14 GRBs, POLAR measured an overall low polarization and a hint for an unexpected complexity in the time evolution of polarization during GRBs. Energy-dependent measurement…
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The POLAR-2 Gamma-Ray Burst (GRB) Polarimetry mission is a follow-up to the successful POLAR mission. POLAR collected six months of data in 2016-2017 on board the Tiangong-2 Chinese Space laboratory. From a polarization study on 14 GRBs, POLAR measured an overall low polarization and a hint for an unexpected complexity in the time evolution of polarization during GRBs. Energy-dependent measurements of the GRB polarization will be presented by N. de Angelis in GA21-09 (August 2nd). These results demonstrate the need for measurements with significantly improved accuracy. Moreover, the recent discovery of gravitational waves and their connection to GRBs justifies a high-precision GRB polarimeter that can provide both high-precision polarimetry and detection of very faint GRBs. The POLAR-2 polarimeter is based on the same Compton scattering measurement principle as POLAR, but with an extended energy range and an order of magnitude increase in total effective area for polarized events. Proposed and developed by a joint effort of Switzerland, China, Poland and Germany, the device was selected for installation on the China Space Station and is scheduled to start operation for at least 2 years in 2025.
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Submitted 1 September, 2023;
originally announced September 2023.
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Energy-dependent polarization of Gamma-Ray Bursts' prompt emission with the POLAR and POLAR-2 instruments
Authors:
Nicolas De Angelis,
J. Michael Burgess,
Franck Cadoux,
Jochen Greiner,
Merlin Kole,
Hancheng Li,
Slawomir Mianowski,
Agnieszka Pollo,
Nicolas Produit,
Dominik Rybka,
Jianchao Sun,
Xin Wu,
Shuang-Nan Zhang
Abstract:
Gamma-Ray Bursts are among the most powerful events in the Universe. Despite half a century of observations of these transient sources, many open questions remain about their nature. Polarization measurements of the GRB prompt emission have long been theorized to be able to answer most of these questions. With the aim of characterizing the polarization of these prompt emissions, a compact Compton…
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Gamma-Ray Bursts are among the most powerful events in the Universe. Despite half a century of observations of these transient sources, many open questions remain about their nature. Polarization measurements of the GRB prompt emission have long been theorized to be able to answer most of these questions. With the aim of characterizing the polarization of these prompt emissions, a compact Compton polarimeter, called POLAR, has been launched to space in September 2016. Time integrated polarization analysis of the POLAR GRB catalog have shown that the prompt emission is lowly polarized or fully unpolarized. However, time resolved analysis depicted strong hints of an evolving polarization angle within single pulses, washing out the polarization degree in time integrated analyses. Here we will for the first time present energy resolved polarization measurements with the POLAR data. The novel analysis, performed on several GRBs, will provide new insights and alter our understanding of GRB polarization. The analysis was performed using the 3ML framework to fit polarization parameters versus energy in parallel to the spectral parameters. Although limited by statistics, the results could provide a very relevant input to disentangle between existing theoretical models. In order to gather more statistics per GRB and perform joint time and energy resolved analysis, a successor instrument, called POLAR-2, is under development with a launch window early 2025 to the CSS. After presenting the first energy resolved polarization results of the POLAR mission, we will present the prospects for such measurements with the upcoming POLAR-2 mission.
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Submitted 1 September, 2023;
originally announced September 2023.
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Proton irradiation of plastic scintillator bars for POLAR-2
Authors:
Slawomir Mianowski,
Nicolas De Angelis,
Kamil Brylew,
Johannes Hulsman,
Tomasz Kowalski,
Sebastian Kusyk,
Zuzanna Mianowska,
Jerzy Mietelski,
Dominik Rybka,
Jan Swakon,
Damian Wrobel
Abstract:
POLAR-2, a plastic scintillator based Compton polarimeter, is currently under development and planned for a launch to the China Space Station in 2025. It is intended to shed a new light on our understanding of Gamma-Ray Bursts by performing high precision polarization measurements of their prompt emission. The instrument will be orbiting at an average altitude of 383 km with an inclination of 42°…
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POLAR-2, a plastic scintillator based Compton polarimeter, is currently under development and planned for a launch to the China Space Station in 2025. It is intended to shed a new light on our understanding of Gamma-Ray Bursts by performing high precision polarization measurements of their prompt emission. The instrument will be orbiting at an average altitude of 383 km with an inclination of 42° and will be subject to background radiation from cosmic rays and solar events. In this work, we tested the performance of plastic scintillation bars, EJ-200 and EJ-248M from Eljen Technology, under space-like conditions, that were chosen as possible candidates for POLAR-2. Both scintillator types were irradiated with 58 MeV protons at several doses from 1.89 Gy (corresponding to about 13 years in space for POLAR-2) up to 18.7 Gy, that goes far beyond the expected POLAR-2 life time. Their respective properties, expressed in terms of light yield, emission and absorption spectra, and activation analysis due to proton irradiation are discussed. Scintillators activation analyses showed a dominant contribution of $β^+$ decay with a typical for this process gamma-ray energy line of 511 keV.
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Submitted 5 July, 2023;
originally announced July 2023.
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Temperature dependence of radiation damage annealing of Silicon Photomultipliers
Authors:
Nicolas De Angelis,
Merlin Kole,
Franck Cadoux,
Johannes Hulsman,
Tomasz Kowalski,
Sebastian Kusyk,
Slawomir Mianowski,
Dominik Rybka,
Jerome Stauffer,
Jan Swakon,
Damian Wrobel,
Xin Wu
Abstract:
The last decade has increasingly seen the use of silicon photomultipliers (SiPMs) instead of photomultiplier tubes (PMTs). This is due to various advantages of the former on the latter like its smaller size, lower operating voltage, higher detection efficiency, insensitivity to magnetic fields and mechanical robustness to launch vibrations. All these features make SiPMs ideal for use on space base…
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The last decade has increasingly seen the use of silicon photomultipliers (SiPMs) instead of photomultiplier tubes (PMTs). This is due to various advantages of the former on the latter like its smaller size, lower operating voltage, higher detection efficiency, insensitivity to magnetic fields and mechanical robustness to launch vibrations. All these features make SiPMs ideal for use on space based experiments where the detectors require to be compact, lightweight and capable of surviving launch conditions. A downside with the use of this novel type of detector in space conditions is its susceptibility to radiation damage. In order to understand the lifetime of SiPMs in space, both the damage sustained due to radiation as well as the subsequent recovery, or annealing, from this damage have to be studied. Here we present these studies for three different types of SiPMs from the Hamamatsu S13360 series. Both their behaviour after sustaining radiation equivalent to 2 years in low earth orbit in a typical mission is presented, as well as the recovery of these detectors while stored in different conditions. The storage conditions varied in temperature as well as in operating voltage. The study found that the annealing depends significantly on the temperature of the detectors with those stored at high temperatures recovering significantly faster and at recovering closer to the original performance. Additionally, no significant effect from a reasonable bias voltage on the annealing was observed. Finally the annealing rate as a function of temperature is presented along with various operating strategies for the future SiPM based astrophysical detector POLAR-2 as well as for future SiPM based space borne missions.
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Submitted 16 December, 2022;
originally announced December 2022.
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Characterisation of the MUSIC ASIC for large-area silicon photomultipliers for gamma-ray astronomy
Authors:
Nicolas De Angelis,
David Gascón,
Sergio Gómez,
Matthieu Heller,
Teresa Montaruli,
Andrii Nagai
Abstract:
Large-area silicon photomultipliers (SiPMs) are desired in many applications where large surfaces have to be covered. For instance, a large area SiPM has been developed by Hamamatsu Photonics in collaboration with the University of Geneva, to equip gamma-ray cameras employed in imaging atmospheric Cherenkov telescopes. Being the sensor about 1 cm$^2$, a suitable preamplification electronics has be…
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Large-area silicon photomultipliers (SiPMs) are desired in many applications where large surfaces have to be covered. For instance, a large area SiPM has been developed by Hamamatsu Photonics in collaboration with the University of Geneva, to equip gamma-ray cameras employed in imaging atmospheric Cherenkov telescopes. Being the sensor about 1 cm$^2$, a suitable preamplification electronics has been investigated in this work, which can deal with long pulses induced by the large capacitance of the sensor. The so-called Multiple Use SiPM Integrated Circuit (MUSIC), developed by the ICCUB (University of Barcelona), is investigated as a potential front-end ASIC, suitable to cover large area photodetection planes of gamma-ray telescopes. The ASIC offers an interesting pole-zero cancellation (PZC) that allows dealing with long SiPM signals, the feature of active summation of up to 8 input channels into a single differential output and it can offer a solution for reducing power consumption compared to discrete solutions. Measurements and simulations of MUSIC coupled to two SiPMs developed by Hamamatsu are considered and the ASIC response is characterized. The 5$^{th}$ generation sensor of the Low Cross Talk technology coupled to MUSIC turns out to be a good solution for gamma-ray cameras.
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Submitted 16 December, 2022; v1 submitted 25 November, 2022;
originally announced November 2022.
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Proton Irradiation of SiPM arrays for POLAR-2
Authors:
Slawomir Mianowski,
Nicolas De Angelis,
Johannes Hulsman,
Merlin Kole,
Tomasz Kowalski,
Sebastian Kusyk,
Hancheng Li,
Zuzanna Mianowska,
Jerzy Mietelski,
Agnieszka Pollo,
Dominik Rybka,
Jianchao Sun,
Jan Swakon,
Damian Wrobel,
Xin Wu
Abstract:
POLAR-2 is a space-borne polarimeter, built to investigate the polarization of Gamma-Ray Bursts and help elucidate their mechanisms. The instrument is targeted for launch in 2024 or 2025 aboard the China Space Station and is being developed by a collaboration between institutes from Switzerland, Germany, Poland and China.
The instrument will orbit at altitudes between 340km and 450km with an inc…
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POLAR-2 is a space-borne polarimeter, built to investigate the polarization of Gamma-Ray Bursts and help elucidate their mechanisms. The instrument is targeted for launch in 2024 or 2025 aboard the China Space Station and is being developed by a collaboration between institutes from Switzerland, Germany, Poland and China.
The instrument will orbit at altitudes between 340km and 450km with an inclination of 42$^{\circ}$ and will be subjected to background radiation from cosmic rays and solar events. It is therefore pertinent to better understand the performance of sensitive devices under space-like conditions.
In this paper we focus on the radiation damage of the silicon photomultiplier arrays S13361-6075NE-04 and S14161-6050HS-04 from Hamamatsu. The S13361 are irradiated with 58MeV protons at several doses up to 4.96Gy, whereas the newer series S14161 are irradiated at doses of 0.254Gy and 2.31Gy. Their respective performance degradation due to radiation damage are discussed. The equivalent exposure time in space for silicon photomultipliers inside POLAR-2 with a dose of 4.96Gy is 62.9 years (or 1.78 years when disregarding the shielding from the instrument). Primary characteristics of the I-V curves are an increase in the dark current and dark counts, mostly through cross-talk events. Annealing processes at $25^{\circ}C$ were observed but not studied in further detail. Biasing channels while being irradiated have not resulted in any significant impact.
Activation analyses showed a dominant contribution of $β^{+}$ particles around 511keV. These resulted primarily from copper and carbon, mostly with decay times shorter than the orbital period.
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Submitted 5 October, 2022; v1 submitted 4 October, 2022;
originally announced October 2022.
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Gamma-Ray Polarimetry of the Crab Pulsar Observed by POLAR
Authors:
Han-Cheng Li,
Nicolas Produit,
Shuang-Nan Zhang,
Merlin Kole,
Jian-Chao Sun,
Ming-Yu Ge,
Nicolas De Angelis,
Johannes Hulsman,
Zheng-Heng Li,
Li-Ming Song,
Teresa Tymieniecka,
Bo-Bing Wu,
Xin Wu,
Yuan-Hao Wang,
Shao-Lin Xiong,
Yong-Jie Zhang,
Yi Zhao,
Shi-Jie Zheng
Abstract:
The X/$γ$ ray polarimetry of the Crab pulsar/nebula is believed to hold crucial information on their emission models. In the past, several missions have shown evidence of polarized emission from the Crab. The significance of these measurements remains however limited. New measurements are therefore required. POLAR is a wide Field of View Compton-scattering polarimeter (sensitive in 50-500 keV) onb…
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The X/$γ$ ray polarimetry of the Crab pulsar/nebula is believed to hold crucial information on their emission models. In the past, several missions have shown evidence of polarized emission from the Crab. The significance of these measurements remains however limited. New measurements are therefore required. POLAR is a wide Field of View Compton-scattering polarimeter (sensitive in 50-500 keV) onboard the Chinese spacelab Tiangong-2 which took data from September 2016 to April 2017. Although not designed to perform polarization measurements of pulsars, we present here a novel method which can be applied to POLAR as well as that of other wide Field of View polarimeters. The novel polarimetric joint-fitting method for the Crab pulsar observations with POLAR, allows us to obtain constraining measurements of the pulsar component. The best fitted values and corresponding 1$σ$ deviations for the averaged phase interval: (PD=$14\substack{+15 \\ -10}$\%, PA=$108\substack{+33 \\ -54} ^{\circ}$), for Peak 1: (PD=$17\substack{+18 \\ -12}$\%, PA=$174\substack{+39 \\ -36} ^{\circ}$) and for Peak 2: (PD=$16\substack{+16 \\ -11}$\%, PA=$78\substack{+39 \\ -30} ^{\circ}$). Further more, the 3$σ$ upper limits on the polarization degree are for the averaged phase interval (55\%), Peak 1 (66\%) and Peak 2 (57\%). Finally, to illustrate the capabilities of this method in the future, we simulated two years observation to the Crab pulsar with POLAR-2. The results show that POLAR-2 is able to confirm the emission to be polarized with $5σ$ and $4σ$ confidence level if the Crab pulsar is polarized at $20\%$ and $10\%$ respectively.
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Submitted 22 February, 2022;
originally announced February 2022.
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Development and science perspectives of the POLAR-2 instrument: a large scale GRB polarimeter
Authors:
N. De Angelis,
J. M. Burgess,
F. Cadoux,
J. Greiner,
J. Hulsman,
M. Kole,
H. C. Li,
S. Mianowski,
A. Pollo,
N. Produit,
D. Rybka,
J. Stauffer,
J. C. Sun,
B. B. Wu,
X. Wu,
A. Zadrozny,
S. N. Zhang
Abstract:
Despite several decades of multi-wavelength and multi-messenger spectral observations, Gamma-Ray Bursts (GRBs) remain one of the big mysteries of modern astrophysics. Polarization measurements are essential to gain a more clear and complete picture of the emission processes at work in these extremely powerful transient events. In this regard, a first generation of dedicated gamma-ray polarimeters,…
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Despite several decades of multi-wavelength and multi-messenger spectral observations, Gamma-Ray Bursts (GRBs) remain one of the big mysteries of modern astrophysics. Polarization measurements are essential to gain a more clear and complete picture of the emission processes at work in these extremely powerful transient events. In this regard, a first generation of dedicated gamma-ray polarimeters, POLAR and GAP, were launched into space in the last decade. After 6 months of operation, the POLAR mission detected 55 GRBs, among which 14 have been analyzed in detail, reporting a low polarization degree and a hint of a temporal evolution of the polarization angle. Starting early 2024 and based on the legacy of the POLAR results, the POLAR-2 instrument will aim to provide a catalog of high quality measurements of the energy and temporal evolution of the GRB polarization thanks to its large and efficient polarimeter. Several spectrometer modules will additionally allow to perform joint spectral and polarization analyzes. The mission is foreseen to make high precision polarization measurements of about 50 GRBs every year on board of the China Space Station (CSS). The technical design of the polarimeter modules will be discussed in detail, as well as the expected scientific performances based on the first results of the developed prototype modules.
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Submitted 7 September, 2021;
originally announced September 2021.
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Gamma-Ray Polarization Results of the POLAR Mission and Future Prospects
Authors:
M. Kole,
N. de Angelis,
J. M. Burgess,
F. Cadoux,
J. Greiner,
J. Hulsman,
H. C. Li,
S. Mianowski,
A. Pollo,
N. Produit,
D. Rybka,
J. Stauffer,
J. C. Sun,
B. B. Wu,
X. Wu,
A. Zadrozny,
S. N. Zhang
Abstract:
Despite over 50 years of Gamma-Ray Burst (GRB) observations many open questions remain about their nature and the environments in which the emission takes place. Polarization measurements of the GRB prompt emission have long been theorized to be able to answer most of these questions. The POLAR detector was a dedicated GRB polarimeter developed by a Swiss, Chinese and Polish collaboration. The ins…
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Despite over 50 years of Gamma-Ray Burst (GRB) observations many open questions remain about their nature and the environments in which the emission takes place. Polarization measurements of the GRB prompt emission have long been theorized to be able to answer most of these questions. The POLAR detector was a dedicated GRB polarimeter developed by a Swiss, Chinese and Polish collaboration. The instrument was launched, together with the second Chinese Space Lab, the Tiangong-2, in September 2016 after which it took 6 months of scientific data. During this period POLAR detected 55 GRBs as well as several pulsars. From the analysis of the GRB polarization catalog we see that the prompt emission is lowly polarized or fully unpolarized. There is, however, the caveat that within single pulses there are strong hints of an evolving polarization angle which washes out the polarization degree in the time integrated analysis. Building on the success of the POLAR mission, the POLAR-2 instrument is currently under development. POLAR-2 is a Swiss, Chinese, Polish and German collaboration and was recently approved for launch in 2024. Thanks to its large sensitivity POLAR-2 will produce polarization measurements of at least 50 GRBs per year with a precision equal or higher than the best results published by POLAR. POLAR-2 thereby aims to make the prompt polarization a standard observable and produce catalogs of the gamma-ray polarization of GRBs. Here we will present an overview of the POLAR mission and all its scientific measurement results. Additionally, we will present an overview of the future POLAR-2 mission, and how it will answer some of the questions raised by the POLAR results.
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Submitted 7 September, 2021;
originally announced September 2021.
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POLAR-2: a large scale gamma-ray polarimeter for GRBs
Authors:
J. Hulsman,
N. de Angelis,
J. M. Burgess,
F. Cadoux,
J. Greinerd,
M. Kole,
H. Li,
S. Mianowski,
A. Pollo,
N. Produit,
D. Rybka,
J. Stauffer,
X. Wu,
A. Zadrozny,
S. N. Zhang,
J. Sun,
B. Wu
Abstract:
The prompt emission of GRBs has been investigated for more than 50 years but remains poorly understood. Commonly, spectral and temporal profiles of γ-ray emission are analysed. However, they are insufficient for a complete picture on GRB-related physics. The addition of polarization measurements provides invaluable information towards the understanding of these astrophysical sources. In recent yea…
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The prompt emission of GRBs has been investigated for more than 50 years but remains poorly understood. Commonly, spectral and temporal profiles of γ-ray emission are analysed. However, they are insufficient for a complete picture on GRB-related physics. The addition of polarization measurements provides invaluable information towards the understanding of these astrophysical sources. In recent years, dedicated polarimeters, such as POLAR and GAP, were built. The former of which observed low levels of polarization as well as a temporal evolution of the polarization angle. It was understood that a larger sample of GRB polarization measurements and time resolved studies are necessary to constrain theoretical models. The POLAR-2 mission aims to address this by increasing the effective area by an order of magnitude compared to POLAR. POLAR-2 is manifested for launch on board the China Space Station in 2024 and will operate for at least 2 years. Insight from POLAR will aid in the improvement of the overall POLAR-2 design. Major improvements (compared to POLAR) will include the replacement of multi-anode PMTs (MAPMTs) with SiPMs, increase in sensitive volume and further technological upgrades. POLAR-2 is projected to measure about 50 GRBs per year with equal or better quality compared to the best seen by POLAR. The instrument design, preliminary results and anticipated scientific potential of this mission will be discussed.
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Submitted 7 January, 2021;
originally announced January 2021.
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The POLAR Gamma-Ray Burst Polarization Catalog
Authors:
Merlin Kole,
Nicolas De Angelis,
Francesco Berlato,
J. Michael Burgess,
Neal Gauvin,
Jochen Greiner,
Wojtek Hajdas,
Han-Cheng Li,
Zheng-Heng Li,
Nicolas Produit,
Dominik Rybka,
Li-Ming Song,
Jian-Chao Sun,
Jaszek Szabelski,
Teresa Tymieniecka,
Yuan-Hao Wang,
Bo-Bing Wu,
Xin Wu,
Shao-Lin Xiong,
Shuang-Nan Zhang,
Yong-Jie Zhang
Abstract:
Despite over 50 years of research, many open questions remain about the origin and nature of GRBs. Polarization measurements of the prompt emission of these extreme phenomena have long been thought to be the key to answering a range of these questions. The POLAR detector was designed to produce the first set of detailed and reliable polarization measurements in an energy range of approximately 50-…
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Despite over 50 years of research, many open questions remain about the origin and nature of GRBs. Polarization measurements of the prompt emission of these extreme phenomena have long been thought to be the key to answering a range of these questions. The POLAR detector was designed to produce the first set of detailed and reliable polarization measurements in an energy range of approximately 50-500 keV. During late 2016 and early 2017, POLAR detected a total of 55 GRBs. Analysis results of 5 of these GRBs have been reported in the past. The results were found to be consistent with a low or unpolarized flux. However, previous reports by other collaborations found high levels of polarization. We study the polarization for all the 14 GRBs observed by POLAR for which statistically robust inferences are possible. Additionally, time-resolved polarization studies are performed on GRBs with sufficient apparent flux. A publicly available polarization analysis tool, developed within the 3ML framework, was used to produce statistically robust results. The method allows to combine spectral and polarimetric data from POLAR with spectral data from the Fermi GBM and Swift-BAT to jointly model the spectral and polarimetric parameters. The time integrated analysis finds all results to be compatible with a low or zero polarization with the caveat that, when time-resolved analysis is possible within individual pulses, we observe moderate polarization with a rapidly changing polarization angle. Thus, time-integrated polarization results, while pointing to lower polarization are potentially an artifact of summing over the changing polarization signal and thus, washing out the true moderate polarization. Therefore, we caution against over interpretation of any time-integrated results and encourage one to wait for more detailed polarization measurements from forthcoming missions such as POLAR-2 and LEAP.
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Submitted 10 September, 2020;
originally announced September 2020.
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Large scale characterization and calibration strategy of a SiPM-based camera for gamma-ray astronomy
Authors:
C. Alispach,
J. Borkowski,
F. R. Cadoux,
N. De Angelis,
D. Della Volpe,
Y. Favre,
M. Heller,
J. Juryšek,
E. Lyard,
D. Mandat,
L. David M. Miranda,
T. Montaruli,
A. Nagai,
D. Neise,
T. R. Njoh Ekoume,
M. Pech,
P. Rajda,
Y. Renier,
V. Sliusar,
R. Walter,
K. Zietara
Abstract:
The SST-1M is a 4-m diameter mirror Davies-Cotton gamma-ray telescope. It has been designed to cover the energy range above 500 GeV and to be part of an array of telescopes separated by 150-200 m. Its innovative camera is featuring large area hexagonal silicon photo-multipliers as photon detectors and a fully digital trigger and readout system. Here, the strategy and the methods for its calibratio…
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The SST-1M is a 4-m diameter mirror Davies-Cotton gamma-ray telescope. It has been designed to cover the energy range above 500 GeV and to be part of an array of telescopes separated by 150-200 m. Its innovative camera is featuring large area hexagonal silicon photo-multipliers as photon detectors and a fully digital trigger and readout system. Here, the strategy and the methods for its calibration are presented, together with the obtained results. In particular, the off and on-site calibration strategies are demonstrated on the first camera prototype. The performances of the camera in terms of charge and time resolution are described.
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Submitted 14 September, 2020; v1 submitted 11 August, 2020;
originally announced August 2020.
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Calibration and operation of SiPM-based cameras for gamma-ray astronomy in presence of high night-sky light
Authors:
Imen Al Samarai,
Cyril Martin Alispach,
Matteo Balbo,
Anastasia Maria Barbano,
Vasyl Beshley,
Adrian Biland,
Jiri Blazek,
Jacek Błocki,
Jerzy Borkowski,
Tomek Bulik,
Frank Raphael Cadoux,
Ladislav Chytka,
Victor Coco,
Nicolas De Angelis,
Domenico Della Volpe,
Yannick Favre,
Tomasz Gieras,
Mira Grudzińska,
Petr Hamal,
Matthieu Heller,
Miroslav Hrabovsky,
Jakub Juryšek,
Jerzy Kasperek,
Katarzyna Koncewicz,
Andrzej Kotarba
, et al. (34 additional authors not shown)
Abstract:
The next generation of Cherenkov telescope cameras feature Silicon Photo Multipliers (SiPM), which can guarantee excellent performance and allow for observation also under moonlight, increasing duty-cycle and therefore the physics reach. A 4 m-diameter Davies-Cotton prototype telescope with a 9-degree optical FoV and a 1296-pixel SiPM camera, has been designed to meet the requirements of the next…
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The next generation of Cherenkov telescope cameras feature Silicon Photo Multipliers (SiPM), which can guarantee excellent performance and allow for observation also under moonlight, increasing duty-cycle and therefore the physics reach. A 4 m-diameter Davies-Cotton prototype telescope with a 9-degree optical FoV and a 1296-pixel SiPM camera, has been designed to meet the requirements of the next generation of ground-based gamma-ray observatories at the highest energies.
The large-scale production of the telescopes for array deployment has required the development of a fully automated calibration strategy which relies on a dedicated hardware, the Camera Test Setup (CTS). For each camera pixel, the CTS is equipped with two LEDs, one operated in pulsed mode to reproduce signal and one in continuous mode to reproduce night-sky background.
In this contribution we will present the camera calibration strategy, from the laboratory measurement to the on-site monitoring with emphasis on the results obtained with the first camera prototype. In addition, key performances such as charge resolution, time resolution and trigger efficiencies and their degradation with increasing night-sky background level will be presented.
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Submitted 19 August, 2019;
originally announced August 2019.
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Monte Carlo study of a single SST-1M prototype for the Cherenkov Telescope Array
Authors:
Jakub Jurysek,
Imen Al Samarai,
Cyril Alispach,
Matteo Balbo,
Anastasia Maria Barbano,
Vasyl Beshley,
Adrian Biland,
Jiri Blazek,
Jacek Błocki,
Jerzy Borkowski,
Tomek Bulik,
Frank Raphael Cadoux,
Ladislav Chytka,
Victor Coco,
Nicolas De Angelis,
Domenico Della Volpe,
Yannick Favre,
Tomasz Gieras,
Mira Grudzińska,
Petr Hamal,
Mathieu Heller,
Miroslav Hrabovsky,
Jerzy Kasperek,
Katarzyna Koncewicz,
Andrzej Kotarba
, et al. (34 additional authors not shown)
Abstract:
The SST-1M telescope was developed as a prototype of a Small-Size-Telescope for the Cherenkov Telescope Array observatory and it has been extensively tested in Krakow since 2017. In this contribution we present validation of the Monte Carlo model of the prototype and expected performance in Krakow conditions. We focus on gamma/hadron separation and mono reconstruction of energy and gamma photon ar…
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The SST-1M telescope was developed as a prototype of a Small-Size-Telescope for the Cherenkov Telescope Array observatory and it has been extensively tested in Krakow since 2017. In this contribution we present validation of the Monte Carlo model of the prototype and expected performance in Krakow conditions. We focus on gamma/hadron separation and mono reconstruction of energy and gamma photon arrival direction using Machine learning methods.
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Submitted 18 July, 2019;
originally announced July 2019.