We present a comprehensive review of the properties of the epitaxial 4H silicon carbide polytype (4H-SiC). Particular emphasis is placed on those aspects of this material related to room, ...high-temperature and harsh environment ionizing radiation detector operation. A review of the characterization methods and electrical contacting issues and how these are related to detector performance is presented. The most recent data on charge transport parameters across the Schottky barrier and how these are related to radiation spectrometer performance are presented. Experimental results on pixel detectors having equivalent noise energies of 144 eV FWHM (7.8 electrons rms) and 196 eV FWHM at +27 deg C and +100 deg C, respectively, are reported. Results of studying the radiation resistance of 4H-SiC are analysed. The data on the ionization energies, capture cross section, deep-level centre concentrations and their plausible structures formed in SiC as a result of irradiation with various particles are reviewed. The emphasis is placed on the study of the 1 MeV neutron irradiation, since these thermal particles seem to play the main role in the detector degradation. An accurate electrical characterization of the induced deep-level centres by means of PICTS technique has allowed one to identify which play the main role in the detector degradation.
We show that a spatially well-defined layer of boron dopants in a hydrogen-enriched silicon target allows the production of a high yield of alpha particles of around 109 per steradian using a ...nanosecond, low-contrast laser pulse with a nominal intensity of approximately 3×1016Wcm−2 . This result can be ascribed to the nature of the long laser-pulse interaction with the target and with the expanding plasma, as well as to the optimal target geometry and composition. The possibility of an impact on future applications such as nuclear fusion without production of neutron-induced radioactivity and compact ion accelerators is anticipated.
The High Energy Modular Ensemble of Satellites (HERMES) project is aimed to realize a modular X/gamma-ray monitor for transient events, to be placed on-board of a nano-satellite bus (e.g. CubeSat). ...This expandable platform will achieve a significant impact on Gamma Ray Burst (GRB) science and on the detection of Gravitational Wave (GW) electromagnetic counterparts: the recent LIGO/VIRGO discoveries demonstrated that the high-energy transient sky is still a field of extreme interest. The very complex temporal variability of GRBs (experimentally verified up to the millisecond scale) combined with the spatial and temporal coincidence between GWs and their electromagnetic counterparts suggest that upcoming instruments require sub-microsecond time resolution combined with a transient localization accuracy lower than a degree. The current phase of the ongoing HERMES project is focused on the realization of a technological pathfinder with a small network (3 units) of nano-satellites to be launched in mid 2020. We will show the potential and prospects for short and medium-term development of the project, demonstrating the disrupting possibilities for scientific investigations provided by the innovative concept of a new “modular astronomy” with nano-satellites (e.g. low developing costs, very short realization time). Finally, we will illustrate the characteristics of the HERMES Technological Pathfinder project, demonstrating how the scientific goals discussed are actually already reachable with the first nano-satellites of this constellation. The detector architecture will be described in detail, showing that the new generation of scintillators (e.g. GAGG:Ce) coupled with very performing Silicon Drift Detectors (SDD) and low noise Front-End-Electronics (FEE) are able to extend down to few keV the sensitivity band of the detector. The technical solutions for FEE, Back-End-Electronics (BEE) and Data Handling will be also described.
Abstract
We present the experimental results of the Application Specific Integrated Circuit (ASIC), called LYRA, specifically designed for the High-Energy Rapid Modular Ensemble of Satellites ...(HERMES) mission concept, a constellation of nano-satellites able to detect and localize high-energy rapid transient events (up to 2.2 MeV) as the Gamma Ray Bursts (GRBs) from the deep space. LYRA has been desied for the detection system composed by a combination of Gadolinium Aluminum Gallium Garnet (GAGG) scintillators for high-energy photons, coupled to a matrix of 120 silicon drift detectors (SDD), used for detecting both scintillation light and low-energy photons. The LYRA ASIC has been conceived with a multi-chip architecture: 120 LYRA Front-End chips (LYRA-FE) are placed in close proximity to the anodes of the SDD matrix for a first processing of the detector signals and trasmit them in current mode to four 32-channel LYRA Back-End chips (LYRA-BE) to complete the elaboration. The requirements that the LYRA ASIC have to fulfill for the HERMES project are challenging: the maximum input energy measured in Silicon must reach 120 keV — corresponding to 2.2 MeV on GAGG — with a linearity error below 1%, the electronic noise must be less then 30 el. r.m.s. and the power consumption less then 1 mW per channel in a system with 120 channels working in parallel. The characterization of LYRA has been carried out on a dedicated test board, coupling one channel of the ASIC with a 25 mm
2
SDD. An input full scale range of 5.2 fC and an electronic noise of 22 el. r.m.s. have been measured at -33
∘
C with a power consumption of 745 µW per channel.
The use of a low contrast nanosecond laser pulse with a relatively low intensity (3 × 1016 W cm−2) allowed the enhancing of the yield of induced nuclear reactions in advanced solid targets. In ...particular the 'ultraclean' proton-boron fusion reaction, producing energetic alpha particles without neutron generation, was chosen. A spatially well-defined layer of boron dopants in a hydrogen-enriched silicon substrate was used as a target. A combination of the specific target composition and the laser pulse temporal shape allowed the enhancing of the yield of alpha particles up to 109 per steradian. This result can be ascribed to the interaction of the long-laser pre-pulse with the target and to the optimal target geometry and composition.
Abstract
X-ray imagers with spectroscopic capabilities and high photon count rates are finding promising applications in industrial real-time inspection systems. In this context, XSpectra
®
combines ...a CdTe-based linear energy-resolved photon counting (ERPC) pixel sensor with real-time image processing techniques to detect low and high density contaminants. The detection unit makes use of a new analog read-out ASIC that has been designed by Politecnico di Milano to meet strict application requirements both in energy resolution and achievable photon count rate. A room-temperature low-rate spectroscopic characterization of the system at a peaking time of 60 ns showed an average equivalent noise charge of 259 electrons r.m.s. (2.72 keV FWHM in CdTe) and an average FWHM of the 59.5 keV
241
Am line of 3.6 keV, with a 3
σ
dispersion in noise performance of ±10% over 256 channels. The detection unit was tested in high incoming photon flux conditions by means of an X-ray tube. Minimal spectral distortion due to pile-up events is obtained up to an Incoming Count Rate of 2.5 Mcps/channel, while the maximum counting capability of energy-resolved events is 2.2 Mcps/channel.
We present a spectroscopic system constituted by a Silicon Drift Detector (SDD) coupled to a CMOS charge sensitive preamplifier, named SIRIO, specifically designed to reach ultimate low noise levels. ...The SDD, with an active area of 13 mm 2 , has been manufactured by optimizing the production processes in order to reduce the anode current, successfully reaching current densities between 17 pA/cm 2 and 25 pA/cm 2 at + 20 ° C for drift fields ranging from 100 V/cm to 500 V/cm. The preamplifier shows minimum intrinsic noise levels of 1.27 and 1.0 electrons r.m.s. at +20 ° C and -30 ° C, respectively. At room temperature (+ 20 ° C) the 55 Fe 5.9 keV and the pulser lines have 136 eV and 64 eV FWHM, respectively, corresponding to an equivalent noise charge of 7.4 electrons r.m.s.; the noise threshold is at 165 eV. The energy resolution, as measured on the pulser line, ranges from 82 eV FWHM (9.4 electrons r.m.s.) at + 30 ° C down to 29 eV FWHM (3.3 electrons r.m.s.) at - 30 ° C.
This work presents an analysis of silicon carbide (SiC) as semiconductor for the realization of detectors for soft X-rays (<20 keV). On the basis of experimental data on prototype SiC junctions, the ...performance in X-ray spectroscopy using planar diode and drift detectors in SiC have been estimated in a wide range of operating temperature (up to 150°C). It has been derived that, due to their extremely low reverse current density (4.7 pA/cm 2 at 300 K and 17 pA/cm 2 at 340 K and at electric field of 100 kV/cm), SiC detectors can potentially reach superior performance with respect to all the other semiconductors presently employed at or above room temperature. In particular, a comparative theoretical analysis, based on experimental data on state-of-the-art silicon and SiC junctions, shows that SiC detectors with areas larger than 1 mm 2 have the potentiality to offer higher energy resolution when operating at temperature above 25°C. An energy resolution of about 700 and 1300 eV FWHM have been estimated for 1 mm 2 and 10 mm 2 SiC pad detectors operating at 100°C with a silicon front-end FET. The contribution of a standard silicon front-end electronics on the system performance has been analyzed. The open issues in SiC technology for X-ray detector development are highlighted.
Abstract The functionality and experimental performance characterization of the latest four channel version of ORION ASIC, a very low noise multichip read out and processing electronics customized ...for the X and Gamma Imaging Spectrometer (XGIS) instrument onboard the Transient High-Energy Sky and Early Universe Surveyor (THESEUS) mission, is presented. XGIS is a set of two coded-masked wide field deep sky cameras using monolithic SDDs (Silicon Drift Detectors) and CsI:Tl (Thallium doped-Cesium Iodide) scintillator-based X-γ ray detectors. This paper highlights the design, working principle and the expected performances of the XGIS, on a small scale 2×2 prototype. Furthermore, the evolution timeline of different versions of ORION with detailed performance observations and analysis for spectroscopic resolution, electronic noise and the operational linear energy ranges of both X and the γ processors of the four-pixel ASIC version bonded to a 2×2 SDD array are emphasized. Each 2×2 SDD array element is electrically and dimensionally equivalent to single elements of the THESEUS 8×8 SDD array.
A system constituted by a Silicon Drift Detector (SDD), fabricated with an innovative technology for minimizing the anode current, and a new CMOS charge sensitive preamplifier (CSA), designed for ...ultimate low noise performance, has been realized and experimentally characterized. The SDD is hexagonal with an active area of 13 mm super(2). The current density measured at the anode with the detector in operating condition is 25 pA/cm super(2) at +20degreesC. The CSA-named SIRIO-has intrinsic Equivalent Noise Charge (ENC) ranging from 2.9 to 1.5 electrons r.m.s. at 0.8 mus and 11 mus peaking times at room temperature, respectively. With the SDD-SIRIO system at +21degreesC, an energy resolution of 141 eV FWHM on the super(55) Fe line at 5.9 keV and 74 eV FWHM on the pulser line with a noise threshold of 170 eV have been measured at 0.8 mus peaking time. The system has been tested from -30degreesC to +30degreesC with energy resolution from 124 eV to 148 eV FWHM at 5.9 keV. A moderate cooling at +10degreesC is sufficient to reach 133 eV FWHM at 5.9 keV.
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