Abstracts:This work describes MexSIC, a data acquisition (DAQ) channel designed for silicon photomultipliers (SiPMs), composed of a mixed-mode application-specific integrated circuit (ASIC) front end, a field programmable gate array (FPGA)-based processing stage, and a user interface. The ASIC provides a 1-bit sigma-delta modulator ( $\Sigma \Delta -M$ ) digital equivalent of the input SiPM current, a flag indicating the start/end of the SiPM pulse, and a clock reference generated by an internal phase-locked loop (PLL). At the ASIC input stage, the SiPM current is converted to voltage by means of a 1.57-GHz bandwidth (BW) transimpedance amplifier (TIA), the gain of which can be switched between 21 and 48 dB, allowing for an input current range between $20~\mu $ A and 20 mA. The generated voltage signal is then fed to a trigger unit (TU) implemented to discriminate between desired signals and the spurious ones and, in parallel, also to a second-order $\Sigma \Delta $ modulator providing 6.1 effective number of bits (ENOB). The TU circuit sends a start/end bit flag by comparing the SiPM voltage signal with an 8-bit programmable voltage reference. $\Sigma \Delta $ was selected to have a single output line instead of using a data bus with many lines, which is important in applications where the number of SiPM channels being read out is very large. The 10-MHz BW $\Sigma \Delta -M$ uses an oversampling ratio (OSR) of 50 and a 1-GHz sampling clock that is generated by a PLL using an off-chip 100-MHz reference. The FPGA receives the ASIC $\Sigma \Delta $ modulated output signal and performs a decimation process by means of a cascade integrator comb (CIC) filter to complete the data recovery. The recovered signal is visualized in a MATLAB-programmed graphical user interface (GUI). The MexSIC ASIC was designed in a 180-nm CMOS standard process using Cadence software, and the processing stage was implemented in a Kintex-7 FPGA.

Abstracts:Measuring the high-power proton beam distribution on the target is critical for the stable operation of a spallation neutron source or an accelerator-driven subcritical system (ADS). This work preliminarily implemented a step of a proposed methodology for indirectly measuring the proton beam spot using pinhole imaging by detecting back-streaming secondary gammas. A prototype gamma imaging system based on pixelated cadmium zinc telluride (CdZnTe) detectors was developed to serve as a foundation for implementing the proposed method. Each detector consists of an $11\times 11$ pixel array, with a pixel pitch of 1.72 mm. Readout electronic modules for two detectors were designed and realized. The energy and timing information of anode channels is obtained by analog application-specific integrated circuits (ASICs) called JCF032EB based on charge-sensitive amplifiers (CSAs), while the cathode channel signals are read out using CSAs and analog-to-digital converters (ADCs). The anode channels have a maximum input charge of up to 49 fC, while the equivalent noise charge (ENC) of most channels is less than 0.1 fC. Energy correction methods based on depth sensing using the cathode-to-anode (C/A) ratio and election drift time were applied. According to test results using radioactive sources, more than half of the anode channels achieve an energy resolution [full-width at half-maximum (FWHM)] better than 1.8% at 662 keV after depth correction, with the best channel reaching better than 1.1%. The imaging results of a 137Cs point source verified the functioning of the gamma imaging system. To verify the practical feasibility of the imaging method, a nickel target was activated on the proton beam line of the Associated Proton beam Experiment Platform (APEP) at the China Spallation Neutron Source (CSNS) and then imaged by the prototype system, which produced the expected results.

Abstracts:In this article, a waveform-sampling front-end application-specific integrated circuit (ASIC) for 3-D position-sensitive detectors (PSDs), called H3DD-UM, is presented. The ASIC integrates 128 channels for anode events and two channels for cathode events. Each channel provides low-noise charge amplification with an adjustable dynamic range to cover up to 10 MeV, followed by two programmable antialiasing filters with different gains, each feeding a 256-cell waveform-sampling circuit. The sampling architecture makes use of a single rail-to-rail amplifier configured to cancel offset errors and achieve high sampling uniformity. A dedicated circuit in the channel provides analog shaping for low-noise discrimination of the events. The number of stored samples before and after discrimination is fully programmable. The ASIC integrates numerous functions, including pixel leakage current measurement, analog monitoring, test pulse generators, temperature sensor, and interchip communication for use in systems with multiple modules.

Abstracts:The Thermo Scientific P385 Neutron Generator is a compact neutron source, producing 14-MeV neutrons through the deuterium-tritium (D-T) fusion reaction. It is important to measure and understand the dependence of the neutron production rate on the accelerator current and voltage. In this study, we evaluated neutron production with an absolutely calibrated liquid scintillator neutron spectrometer (BTI N-Probe), an absolutely calibrated He-3 detector surrounded by high-density polyethylene (HDPE) shells [Detec nested neutron spectrometer (NNS)], and two uncalibrated zinc sulfide (ZnS) fast neutron scintillators (EJ-410), for both A3082 and A3083 sealed tubes. We also modeled the neutron yield using the Transport of Ions in Matter (TRIM) code, which calculates the trajectory and the energy loss of deuterons and tritons in the target. Experimental results showed an essentially linear dependence on the beam current, as expected. A $3.59~\pm ~0.08$ power law dependence on the operating voltage was measured, in effective agreement with the modeled value of 3.5. A series of absolute NNS and N-Probe measurements, matched against Monte Carlo N-Particle (MCNP) calculations, showed that the A3083 and A3082 tubes provide a maximum neutron yield of $ 8.2 \times 10^{8}$ and $4.7 \times 10^{8}$ n/s, respectively, with an estimated uncertainty of ±10%. We showed, through modeling, that tritium decay is not a significant consideration for tubes, such as these, with lifetimes of less than ten years.

Abstracts:Single- and dual-layer arrays of single-photon avalanche diodes (SPADs) fabricated in a 150-nm CMOS technology have been irradiated with neutrons up to a fluence of $4.29 \times 10 ^{10}~1$ -MeV neutron equivalent cm−2. Neutron irradiation is found to induce a notable rise in the dark count rate (DCR) noise of single-layer chips. The dual-layer configuration is demonstrated to be more robust, showing a comparatively smaller DCR degradation. DCR and breakdown voltage measurements have been performed at various temperatures, ranging from - 40°C to 40°C, both before and after irradiation. While the breakdown voltage is not significantly affected by neutron damage, the average activation energy of the defects responsible for DCR is found to decrease to about 0.2 eV after irradiation. Eventually, a model based on the nonionizing energy loss (NIEL) hypothesis and taking into account damage annealing with time is proposed, providing an accurate estimate of the DCR increase with fluence.

Abstracts:This article investigates the effects of cumulative damage, specifically negative bias temperature instability (NBTI), on the transient phenomenon known as single-event burnout (SEB) in power vertical diffused metal-oxide–semiconductor field-effect transistors (VDMOSFETs). Tantalum heavy ion irradiation (THII) experiments were conducted on devices subjected to various pretreatments: negative bias temperature stress (NBTS), hydrogen, low temperature, and a combination of hydrogen and NBTS. The results indicate that devices pretreated with NBTS exhibit increased sensitivity to SEB, whereas those subjected to other pretreatment methods demonstrate decreased sensitivity. In addition, the subthreshold mid-gap technique (SMGT) was employed to differentiate between interface traps and oxide charges, with subsequent technology computer-aided design (TCAD) simulations analyzing their impacts on SEB. The findings reveal that NBTS pretreatment primarily reduces the built-in potential ( $\varphi _{\text {B}}$ ) of parasitic bipolar junction transistor (BJT) conduction by generating oxide charges, thereby increasing SEB sensitivity. Conversely, pretreatments with hydrogen and low temperature promote the conversion of oxide charges into interface traps, resulting in decreased SEB sensitivity. Although the change in SEB sensitivity is relatively small, this research reveals a synergistic interaction between NBTI and SEB, which may lead to premature SEB occurrences and reduce the operational lifespan of power VDMOS transistors.

Abstracts:The environment generated in a high-altitude nuclear explosion (HANE) can cause damage to critical infrastructures, such as space vehicles, communication systems, and power systems. The mechanisms of the instantaneous and long-term environments caused by the HANE and their damage factors to the targets are analyzed. Research works on the numerical simulation of the HANE environment by the author’s team in recent years have been introduced. Many key technologies on the numerical simulation are developed, such as the model of stripped region formation by X-ray peeling extra-nuclear electrons, the integration simulation of the early-time and intermediate-time high-altitude electromagnetic pulse (HEMP) based on the current source provided by the Monte Carlo (MC) method, the model of asymmetric fireball evolution, the model of debris movement and the atmospheric ionization by delayed radiation, and the model of electron injection and diffusion loss in the artificial radiation belt. The numerical simulation method for HANE is presented, including the instantaneous environments (such as nuclear radiation, X-ray, HEMP, and optical radiation) and the long-term environments (such as debris, additional ionosphere, and artificial radiation belt). The environmental parameters of the HANE under typical height of burst (HOB) and yield are given. The characteristics and laws of the HANE environment are summarized.

Abstracts:Commercial solid-state drives (SSDs) were subjected to broad-spectrum neutron exposure at the China Spallation Neutron Source (CSNS) to analyze radiation-induced errors in components and functional interruptions in non-volatile memory express (NVMe) and serial advanced technology attachment (SATA) SSDs. The experiments revealed apparent sensitivity differences, with NVMe SSDs demonstrating better resistance at the module level due to advanced controller technology and enhanced error correction capabilities than SATA SSDs. For NVMe SSDs, functional interruptions were primarily identified as nand Flash faults, such as timeouts, and dynamic random access memory (DRAM) errors, such as stuck bits, while controller vulnerabilities contributed minimally. Moreover, this article examines the dominance of read errors as the primary failure mode in nand Flash and explores how the cumulative characteristic of these errors correlates with functional interruptions.

Abstracts:Good linearity and radiation resistance of conductance updates in memristive synapses are crucial for their use in neuromorphic computing chips in space. Here, the Au/Al:HfOx/TiOx/Ti memristive synapses with good linearity are prepared. The effects of irradiation on the memristive performances are studied through 60Co $\gamma $ -ray irradiation experiments. The effect of irradiation on the image recognition accuracy of the neural network based on the memristive synapse crossbar array is predicted. The results show that the devices maintained good conductance update linearity under irradiation. When the 60Co $\gamma $ -ray irradiation reaches 1 Mrad(Si), the nonlinearity (NL) of conductance update only increases from 0.096 to 0.163, and the image recognition accuracy of the memristor neural network decreases by about 2% (from 91% to 89%). The initial value of oxygen defect content in HfOx resistive materials after Al doping modification is relatively high (36%), which can explain why irradiation has little effect on conductance update linearity and recognition accuracy. These results suggest that the Au/Al:HfOx/TiOx/Ti memristors show good radiation resistance under 60Co $\gamma $ -ray irradiation, which makes them promising candidates for artificial synapses in space applications.

Abstracts:In this article, we mainly report the radiation response of n-channel depletion-mode gallium arsenide (GaAs) metal-semiconductor field-effect transistors (MESFETs) under heavy ion, proton, and electron irradiation. The maximum transconductance ( ${G} _{\text {MAX}}$ ) and drain saturation current ( ${I} _{\text {DSS}}$ ), which can reflect the carrier removal and mobility degradation induced by displacement damage, are selected as evaluation indicators, and two kinds of damage factors are derived: ${K} _{G}$ and ${K} _{I}$ . The nonionizing energy loss (NIEL) of different particles deposited in the epitaxial channel layer of GaAs MESFETs is calculated and used to correlate ${K} _{G}$ and ${K} _{I}$ , respectively. The good linear relationship between damage factors and NIEL makes it possible to predict the degradation of ${G} _{\text {MAX}}$ and ${I} _{\text {DSS}}$ . On this basis, two semiempirical damage equations describing GaAs MESFETs displacement damage are derived and verified by 27-MeV F. We also derive the damage coefficient “ $\gamma $ ” in the more general damage equation, which has a value of $5.5\times 10^{-13}$ g/MeV for ${G} _{\text {MAX}}$ and $8.9\times 10^{-13}$ g/MeV for ${I} _{\text {DSS}}$ . Besides, MESFETs made from other materials may also align with the damage equation. A single irradiation experiment can determine the damage coefficient $\gamma $ values in principle. This work extends the application of the NIEL-based displacement damage dose (DDD) method in GaAs MESFETs.