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Register a new userPhysical Design and Monte Carlo Simulations of a Space Radiation Detector onboard the SJ-10 satellite
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A radiation gene box (RGB) onboard the SJ-10 satellite is a device carrying mice and drosophila cells to determine the biological effects of space radiation environment. The shielded fluxes of different radioactive sources were calculated and the linear energy transfers of gamma-rays, electrons, protons and alpha-particles in tissue were acquired using A-150 tissue-equivalent plastic. Then, a conceptual model of a space radiation instrument employing three semiconductor sub-detectors for deriving the charged and uncharged radiation environment of the RGB was designed. The energy depositions in the three sub-detectors were classified into fifteen channels (bins) in an algorithm derived from the Monte Carlo method. The physical feasibility of the conceptual instrument was also verified by Monte Carlo simulations.
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We report the radiation hardness of a p-channel CCD developed for the X-ray CCD camera onboard the XRISM satellite. This CCD has basically the same characteristics as the one used in the previous Hitomi satellite, but newly employs a notch structure of potential for signal charges by increasing the implant concentration in the channel. The new device was exposed up to approximately $7.9 times 10^{10} mathrm{~protons~cm^{-2}}$ at 100 MeV. The charge transfer inefficiency was estimated as a function of proton fluence with an ${}^{55} mathrm{Fe}$ source. A device without the notch structure was also examined for comparison. The result shows that the notch device has a significantly higher radiation hardness than those without the notch structure including the device adopted for Hitomi. This proves that the new CCD is radiation tolerant for space applications with a sufficient margin.
Transition Radiation (TR) plays an important role in particle identification in high-energy physics and its characteristics provide a feasible method of energy calibration in the energy range up to 10 TeV, which is of interest for dark matter searches in cosmic rays. In a Transition Radiation Detector (TRD), the TR signal is superimposed onto the ionization energy loss signal induced by incident charged particles. In order to make the TR signal stand out from the background of ionization energy loss in a significant way, we optimized both the radiators and the detector. We have designed a new prototype of regular radiator optimized for a maximal TR photon yield, combined with the Side-On TRD which is supposed to improve the detection efficiency of TR. We started a test beam experiment with the Side-On TRD at Conseil Europ{e}en pour la Recherche Nucl{e}aire (CERN), and found that the experimental data is consistent with the simulation results.
RADMON is a small radiation monitor designed and assembled by students of the University of Turku and the University of Helsinki. It is flown on-board Aalto-1, a 3-unit CubeSat in low Earth orbit at about 500 km altitude. The detector unit of the instrument consists of two detectors, a Si solid-state detector and a CsI(Tl) scintillator, and utilizes the textDelta{E}-E technique to determine the total energy and species of each particle hitting the detector. We present the results of the on-ground and in-flight calibration campaigns of the instrument, as well as the characterization of its response through extensive simulations within the Geant4 framework. The overall energy calibration margin achieved is about 5%. The full instrument response to protons and electrons is presented and the issue of proton contamination of the electron channels is quantified and discussed.
We report on the design and performance of a mixed-signal application specific integrated circuit (ASIC) dedicated to avalanche photodiodes (APDs) in order to detect hard X-ray emissions in a wide energy band onboard the International Space Station. To realize wide-band detection from 20 keV to 1 MeV, we use Ce:GAGG scintillators, each coupled to an APD, with low-noise front-end electronics capable of achieving a minimum energy detection threshold of 20 keV. The developed ASIC has the ability to read out 32-channel APD signals using 0.35 $mu$m CMOS technology, and an analog amplifier at the input stage is designed to suppress the capacitive noise primarily arising from the large detector capacitance of the APDs. The ASIC achieves a performance of 2099 e$^{-}$ + 1.5 e$^{-}$/pF at root mean square (RMS) with a wide 300 fC dynamic range. Coupling a reverse-type APD with a Ce:GAGG scintillator, we obtain an energy resolution of 6.7% (FWHM) at 662 keV and a minimum detectable energy of 20 keV at room temperature (20 $^{circ}$C). Furthermore, we examine the radiation tolerance for space applications by using a 90 MeV proton beam, confirming that the ASIC is free of single-event effects and can operate properly without serious degradation in analog and digital processing.
After the development of a BoGEMMS (Bologna Geant4 Multi-Mission Simulator) template for the back- ground study of X-ray telescopes, a new extension is built for the simulation of a Gamma-ray space mission (e.g. AGILE, Fermi), conceived to work as a common, multi-purpose framework for the present and future electron tracking gamma-ray space telescopes. The Gamma-ray extension involves the Geant4 mass model, the physics list and, more important, the production and treatment of the simulation output. From the user point of view, the simulation set-up follows a tree structure, with the main level being the selection of the simulation framework (the general, X-ray or gamma-ray application) and the secondary levels being the detailed configuration of the geometry and the output format. The BoGEMMS application to Gamma-ray missions has been used to evaluate the instrument performances of a new generation of Gamma-ray tele- scopes (e.g. Gamma-Light), and a full simulation of the AGILE mission is currently under construction, to scientifically validate and calibrate the simulator with real in-space data sets. A complete description of the BoGEMMS Gamma-ray framework is presented here, with an overview of the achieved results for the potential application to present and future experiments (e.g., GAMMA-400 and Gamma-Light). The evaluation of the photon conversion efficiency to beta particle pairs and the comparison to tabulated data allows the preliminary physical validation of the overall architecture. The Gamma-ray module application for the study of the Gamma-Light instrument performances is reported as reference test case.
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