Particle Energy Deposition Research Articles

Spaceborne particle identification platform and its application based on convolutional neural network

The identification of particle types in space radiation particle detection is a problem of great concern in scientific research and engineering applications. At present, the particle types are mainly identified by the difference in energy deposition of particles in the sensor, the difference in waveform in the sensor, the flight time and energy of particles, and the difference in the deflection path of particles in the electric field, such as traditional telescope detectors, particle pulse waveform analysis, flight time TOF system and electrostatic analyzer. However, the current on-orbit particle identification logic is relatively simple and the identification accuracy is limited. Convolutional neural networks have powerful target classification capabilities and are good at capturing and extracting target feature details, which can improve the accuracy of particle energy measurement and identification. Based on the environment commonly used in space environment detection payloads, this paper proposes a method for building an on-orbit convolutional neural network particle identification platform to achieve particle type identification. The platform first constructs a multi-dimensional input data set, completes the model training and weight derivation with the help of the software platform, and completes the waveform inference and data set expansion through the hardware platform. The established identification platform is used to train and test the neutron and gamma waveform data obtained in actual tests, and the accuracy of the identification of the software and hardware platforms is analyzed, completing the verification of the platform. The establishment and application of this platform provides a new idea and method for particle measurement and identification in future space environment detection, and has strong engineering practice significance.

Scintillator-SiPM detector for tracking and energy deposition measurements

An innovative particle detector that offers a compelling combination of cost-effectiveness and high accuracy is introduced. The detector features plastic scintillators paired with a sparse arrangement of SiPMs, strategically positioned within a unique opto-mechanical framework. This configuration delivers precise measurements of spatial impact position and energy deposition of impinging particles. The manuscript describes the detector’s physical model complemented by an analytical representation. These calculations underpin a numerical algorithm, facilitating the estimation of particle impingement position and energy deposition. The results of the numerical calculations are compared with the output of GEANT4 simulations and evaluated by rigorous laboratory testing. An array of these detectors, intended for deployment in a spaceborne experiment, underwent detailed design, manufacturing, and testing. Their performance and alignment with the physical model were validated through meticulously conducted ground-based laboratory experiments, conclusively affirming the detector’s properties.

Research on a Neutron Detector with a Boron-Lined Multilayer Converter

3He is a splendid neutron detection material due to its high neutron reaction cross section, gaseous state, and nonelectronegative and nonpoisonous nature. With the worldwide problem of the “3He supply crisis” arising, boron-lined gaseous neutron detectors are being widely used in neutron detection to replace 3He neutron detectors. In this work, to reduce the scattering neutron background coming from the substrate of a boron-lined neutron detector in the application of neutron scattering, a new design of the boron-lined gaseous neutron detector composed of a boron-lined multichip converter and a multiwire proportional chamber was proposed. The electron drift efficiency matrix simulated by Garfield++ (Version 2023.4) and the values and positions of electron energy deposition simulated by Geant4 were obtained. The α, 7Li, and total charged particle energy deposition spectra were acquired via coupling calculations of the electron drift efficiency matrix and the values and positions of electron energy deposition, and the width of the slit was selected as 3 mm. The boron-lined multilayer converter neutron detector (BMCND) was tested using a 241Am–239Pu mixture α source, and the total count rate of α charged particles was measured as 599.5 s−1, which is 89% of the theoretical α particle emission rate of 672.9 s−1. The drift voltage experiments showed that 1200 V is enough to acquire a relatively ideal count, and a 2500 V drift voltage was confirmed, considering the higher count and instrument safety. We also performed the neutron detection experiments using a photo-neutron source, and a characteristic spectrum shape of “two stairs” was measured. When borated polyethylene was used to shield the BMCND, the detected total count decreased while keeping the characteristic spectrum shape, demonstrating that the BMCND was equipped with the ability to detect neurons, indicating that BMCNDs have the potential to be an outstanding 3He alternative neutron detector.

A [formula omitted]-radioisotope battery based on betavoltaic and beta-photovoltaic dual effects

Betavoltaic batteries with strontium sources are expected to achieve higher output power because of their high energy density and low self-absorption rate with the development of MEMS. However, the high energy of beta particles emitted from 90Sr/90Y can prone to radiation damage of the semiconductor. In order to exploit the high energy of beta particles emitted from 90Sr/90Y and to avoid radiation damage to the semiconductor, this paper presents a 90Sr/90Y-radioisotope battery based on betavoltaic (BV) and beta-photovoltaic (BPV) dual effects. In the work, the energy deposition of beta particles in LYSO:Ce and GaAs was simulated by Monte Carlo code, and thickness of the scintillator was determined. And the doping concentrations and junction depth of semiconductor were optimized based on the theoretical calculations to obtain the best output performance of device. When the thickness of LYSO:Ce is 0.158 cm, the output power density Pm of the optimized dual-effect battery is 0.61 μW/cm2. And the conversion efficiency of the device is 0.92%. At this time, the doping concentrations are Na=1.58×1017cm−3 and Nd=3.16×1018cm−3, and the junction depth xj=0.05μm. All calculated parameter values are considered as theoretical limit values. In addition, the contribution of BV effect and BPV effect to the output performance of the dual-effect radioisotope battery was investigated. Different scintillator thicknesses lead to different percentages of the two mechanics. In addition, the BV effect and BPV effect output proportion is also affected by the average energy of the radiation source. In the case that the average electron energy on the semiconductor surface is 0.27 MeV, the higher the radioactive source energy, the thicker the scintillator is required, resulting in more BPV effect and less BV effect.

Abstract 6034: PSMA targeted alpha radiopharmaceutical [211At]PSAt-3 inhibits tumor growth in a preclinical model of prostate cancer

Abstract Introduction: Prostate cancer continues to be a highly prevalent cancer diagnosis among men and a leading cause of cancer related deaths worldwide. With the introduction[177Lu]Lu-PSMA-617, targeted radionuclide therapy has proven successful in increasing survival time for patients with metastasized castration resistant prostate cancer. However, despite encouraging results, such patients tend to develop progressive disease, and thus, enhanced efficacy is warranted. To this end, the use of radiopharmaceuticals harnessing alpha-emitters is a promising venue due to the potent energy deposition and short range of alpha particles in tissue. Here, we employ the PSMA targeting vector, [211At]PSAt-3, for targeted alpha radionuclide therapy in a preclinical prostate cancer model. Methods: [211At]PSAt-3, a structural derivative of PSMA-617, in which the L-2-naphtylalanine was replaced by L-3-[211At]astato-phenylalanine, was obtained by electrophilic [211At]astatodesilylation. Evaluation of [211At]PSAt-3 was conducted in male inbred nude mice of Balb/c background xenografted subcutaneously with human prostate cancer cells (LNCaP). Prior biodistribution studies were carried out with approximately 100 kBq intravenous injections, and subsequent biodistribution 2, 6 and 24h post injection (P.I.). For establishment of therapeutic effect, a single intravenous dose of [211At]PSAt-3 was administered. To asses hematological toxicity, blood cell composition was assessed weekly. Results: Favorable tumor uptake of 15.2±6 %ID/g was observed 2h after injection of [211At]PSAt-3 in LNCaP xenografted nude mice, with subsequent 9±5.1% ID/g and 6.4±2.4% ID/g 6 and 24h P.I., respectively. [211At]PSAt-3 cleared mainly by the kidneys, in which uptake was 72, 38 and 6% ID/g at 2, 6 and 24h P.I., respectively. Thyroid/throat uptake remained low at ~0.1% ID for all timepoints investigated, indicating a low degree of de-astatination. Initial efficacy studies using a single intravenous dose of 0.5 MBq (~20 MBq/kg) demonstrated significant growth delay and tumor volume reduction compared with control mice (saline). Blood platelet count was reduced after administration of [211At]PSAt-3 and subsequently recovered. No signs of severe toxicity, and no significant weight loss between control and treated mice was observed, suggesting that the treatment is well tolerated. Conclusion: 0.5 MBq [211At]PSAt-3 was well tolerated in mice and demonstrated tumor volume reduction and significant delay of tumor growth. These findings suggest [211At]PSAt-3 as a promising candidate for clinical translation. Citation Format: Lars Hvass, Marius Müller, Anne Clausen, Matthias Herth, Andreas Kjaer. PSMA targeted alpha radiopharmaceutical [211At]PSAt-3 inhibits tumor growth in a preclinical model of prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6034.

Laser-directed energy deposition of ZrH2 particles reinforced Al7075 alloy: Cracks elimination and strength enhancement

Metal-based laser additive manufacturing, particularly Laser-Directed Energy Deposition (LDED), holds great promise for producing high-strength aluminum alloy components used in industries such as automotive manufacturing, aerospace, and biomedicine. However, achieving defect-free and superior mechanical strength in high-strength aluminum alloys, especially 7XXX series Al alloys, through LDED remains challenging. In this study, the LDED of ZrH2 particles reinforced Al7075 alloy was investigated. Results indicated that the addition of ZrH2 particles to the Al7075 alloy facilitated the columnar-to-equiaxed transition and effectively prevented hot-crack formation during the solidification process, leading to a crack-free and fine equiaxed-grain microstructure. The as-deposited Zr-modified Al7075 alloy demonstrated a favorable combination of strength and ductility, a yield strength of 266 MPa, a strength of 321 MPa, and an elongation of 21.0% in the Al7075–3%ZrH2 sample, which represents promising performance among the reported LDED-fabricated Al alloys. Contributions of four different strengthening mechanisms to yield strength were calculated, showing that the introduction of ZrH2 particles highlighted the effects of grain refinement and geometrically necessary dislocation strengthening. Moreover, the grain reinforcement mechanism in the Al7075 alloy with ZrH2 particles reinforced was elucidated after adequate material characterizations including SEM, EDS, TEM, and XRD. Needle-like Al3Zr and angular-like Al3Zr were observed in the equiaxed and ultrafine grain regions of the LDED-fabricated Al7075–3%ZrH2 samples, corroborating the truth that Al3Zr serves as heterogeneous nucleation sites during the solidification and plays a significant role in grain refinement. The successful manufacturing of crack-free, equiaxed high-strength 7XXX series Al alloys lays the foundation for LDED production of high-strength aluminum engineering components.

Luminescence principle and characteristics of imaging plate

The imaging plate (IP) is a reusable detector for detecting radiation particles in a complex electromagnetic field environment, and it is widely used as a detection medium in laser-accelerated particle beam diagnostic equipment. Therefore, it is necessary to study the performance characteristics and physical mechanism of IP. An electron source with known activity is used to explore the performance characteristics of IP. A <sup>90</sup>Sr/<sup>90</sup>Y electron source is used to measure the time attenuation curve, calibrate the absolute sensitivity, and study the law of multiple scanning of BAS-SR and BAS-TR. In the case of a longer irradiation, the fading cannot be neglected, and the attenuation curves are modified. The time attenuation characteristics indicate that the IP should be cooled after irradiation, and the scanning should be carried out in the slow decay process to reduce the influence of the reading error in the decay process. The absolute sensitivity of BAS-SR and BAS-TR to <sup>90</sup>Sr/<sup>90</sup>Y source are (0.033±0.002) PSL/<i>e</i> and (0.018±0.0038) PSL/<i>e</i> (photostimulated light, PSL), respectively, which are consistent with the results of most absolute sensitivity. The absolute sensitivity is closely related to the type of IP, scanning equipment, and experimental environment. In addition, the energy spectrum integral effect of the broad spectrum <i>β</i> source has a significant influence on the absolute sensitivity. This method is only suitable for the rough evaluation of the sensitivity characteristic parameters of the IP. Multiple scanning approximately satisfies the double exponential function distribution, which is consistent with the physical model. The characteristics of IP are determined by its storage principle. The fluorescence layer of IP is composed of typical electron trapping materials <i>M</i>F<i>X</i> (<i>M</i> = Ca, Sr, Ba; <i>X</i> = C1, Br, I) alkaline earth metal fluorhalide BaFBr. When the IP is irradiated, a large number of free electron-hole pairs are excited by the deposited energy in the material, and the free electrons will be captured by the electron trap, so the fluorescence layer of the IP records the radiation particles’ information through the energy deposited. In this paper, we study three kinds of models. Based on the models, a photo-stimulated luminescence model is proposed to describe the electron transfer process. The photo-stimulated luminescence model describes the physical mechanism of energy deposition, information storage, and information scanning of radiation particles. The relationship between the physical mechanism and characteristics is explained effectively by combining the microscopic mathematical model with the macroscopic physical phenomenon. It provides a specific data basis for the subsequent application of IPs in laser plasma diagnostic experiments.

Toward a Monolithic Pixel Sensor for Heavy Ion Spectroscopy—Pixel Structure Design and Optimization

Detection and classification of cosmic particles is essential for many scientific and engineering applications. Currently available heavy ion detectors necessitate an external readout integrated circuit when conducting both measurements of particle energy deposition and particle incident position. In this paper, we propose an innovative monolithic pixel detector topology capable of distinguishing between particles in a predefined LET range. The analog and digital readout circuitry are incorporated into the pixel region while maintaining almost an 100% detection fill factor over the entire pixel array. We present comprehensive CAD 3D simulations of the device to verify the applicability of the detector for galactic cosmic rays with the specified LET levels and induced charge distribution. We evaluate the charge collection performance under heavy-ion hit conditions and provide an assessment of the impact on charge collection from the particle impinging position, particle LET, angle of penetration and circuit bias. The results indicate a linear relationship between particle LET and collected charge, regardless of the ion hit position and almost independent of the circuit voltage bias. The simulation results for various particle incident angles show correlations between charge collection and particle trajectory length. We propose an implementation which makes it possible to determine the particle angle of penetration and particle LET attributes. The radiation tolerance of the sensor was estimated. Its applicability to the non-ionizing radiation environment was shown to be adequate for low Earth orbits.

Small-scale (sub-organ and cellular level) alpha-particle dosimetry methods using an iQID digital autoradiography imaging system

Targeted radiopharmaceutical therapy with alpha-particle emitters (αRPT) is advantageous in cancer treatment because the short range and high local energy deposition of alpha particles enable precise radiation delivery and efficient tumor cell killing. However, these properties create sub-organ dose deposition effects that are not easily characterized by direct gamma-ray imaging (PET or SPECT). We present a computational procedure to determine the spatial distribution of absorbed dose from alpha-emitting radionuclides in tissues using digital autoradiography activity images from an ionizing-radiation quantum imaging detector (iQID). Data from 211At-radioimmunotherapy studies for allogeneic hematopoietic cell transplantation in a canine model were used to develop these methods. Nine healthy canines were treated with 16.9–30.9 MBq 211At/mg monoclonal antibodies (mAb). Lymph node biopsies from early (2–5 h) and late (19–20 h) time points (16 total) were obtained, with 10–20 consecutive 12-µm cryosections extracted from each and imaged with an iQID device. iQID spatial activity images were registered within a 3D volume for dose-point-kernel convolution, producing dose-rate maps. The accumulated absorbed doses for high- and low-rate regions were 9 ± 4 Gy and 1.2 ± 0.8 Gy from separate dose-rate curves, respectively. We further assess uptake uniformity, co-registration with histological pathology, and requisite slice numbers to improve microscale characterization of absorbed dose inhomogeneities in αRPT.

Monte Carlo modelling of pixel clusters in Timepix detectors using the MCNP code

The track structure of the signal measured by the semiconductor pixel detector Timepix3 was modelled in the Monte Carlo MCNP® code. A detailed model at the pixel-level (256 × 256 pixels, 55 × 55 µm2 pixel size) was developed and used to generate and store clusters of adjacent hit pixels observed in the measured data because of particle energy deposition path, charge sharing, and drift processes. An analytical model of charge sharing effect and the detector energy resolution was applied to the simulated data. The method will help the user sort the measured clusters and distinguish radiation components of mixed fields by determining the response of Timepix3 detector to particular particle types, energies, and incidence angles that cannot be measured separately.

Heavy-ion beam test of a monolithic silicon pixel sensor with a new 130 nm High-Resistivity CMOS process

The Topmetal-M is a newly designed monolithic silicon pixel sensor for charged particle tracking based on a novel detector structure and implemented in a new 130 nm High-Resistivity (>1 kΩ cm) CMOS process. This sensor integrates the functionality of the Monolithic Active Pixel Sensor (MAPS) and the Topmetal sensor. It has a matrix of 512 × 400 pixels with the pitch of 40μm×40μm. Heavy-ion campaigns with a 181Ta35+ beam have been performed to study the performance of this Topmetal-M sensor. The test results demonstrate it has an excellent response to particle energy deposition. Furthermore,this sensor is still fully functional after exposure to ∼14.1 krad, and no Single Event Latch-up (SEL) occurred. In addition, the baseline, the Equivalent Noise Charge (ENC), and the number of bad pixels show relatively good performance.

Modification of the fusion energy gain factor in magnetic confinement fusion due to plasma temperature anisotropy

In magnetic confinement fusion (MCF), the plasma always exhibits an anisotropic temperature distribution, which may impact not only the plasma dynamics but also the nuclear reaction process. Here, through theoretical derivations and self-consistent particle-in-cell simulations with the newly-developed nuclear reaction and alpha particle energy deposition calculation modules, we find that, if considering the plasma has an anisotropic temperature distribution, the fusion energy gain factor (Q) of MCF is significantly modified, where both the deuteron–triton nuclear reactivity and the alpha particle energy deposition fraction are heavily influenced. The simulation results show that, under the International Thermonuclear Experimental Reactor (ITER) condition, if the plasma temperature anisotropy ratio can reach 0.1, i.e., the plasma perpendicular temperature component is one-tenth of its parallel component corresponding to the ambient magnetic field direction, the Q-value of ITER can be increased from the originally-designed 5 to about 10, with doubled enhancement.

An ultra-low background alpha detection system with a Micromegas-based time projection chamber.

In this paper, a time projection chamber (TPC) system for α radiation detection with ultra-low background is presented, which is based on Micromegas, a type of micro-pattern gaseous detector. Based on multi-dimensional information acquired by the TPC, such as the features of particle energy deposition and 3D track, the system can achieve the purpose of α identification with ultra-low background. A prototype TPC with the volume of 15 × 15 × 6.5cm3 was developed. It was filled with a gas mixture of 95% neon and 5% isobutene at about 1bar, and no additional shielding or control of alpha-emitting materials was employed. A low-noise high-integration electronic system based on multi-channel waveform sampling techniques was adopted to read out the anode strip signals. A test with a 241Am α source (5.5MeV), a 49-h background test, and several other tests with weak radioactive samples in the laboratory environment were conducted. A feature selection method was designed to maximize the suppression of background events while retaining the events of interest. Test results showed that within an assumed 5 × 5cm2 effective area in the center region of the TPC window, the background count rate of this system was lower than 1.6 × 10-3 counts per minute at 95% confidence level, while retaining the acceptance rate of about 96% for 241Am α particles.

Realistic energy deposition and temperature heating in molecular clouds due to cosmic rays: a computation simulation with the GEANT4 code employing light particles and medium-mass and heavy ions

ABSTRACT In the interstellar medium, Galactic and extragalactic cosmic rays (CRs) penetrate deeper in the molecular clouds (MCs) and promote inside several physical and physicochemical changes due to the energy deposition, including gas and grain heating, and triggering also molecular destruction and formation. In this work, in an attempt to simulate, in a more realistic way, the energy delivered by CRs in a typical MC (mass ∼5400 M☉ and size ∼106 au; mainly composed of H atoms), we combine the energy deposition of light particles and heavy ions, with the new calculations considering the medium-mass ions (3 ≤ Z ≤ 11). To execute the calculation, the Monte Carlo toolkit GEANT4 was applied to get the energy deposition rate per mass from many kinds of secondary particles, used in nuclear and hadron physics. The energy deposition by its induced cascade shower within the MC was characterized, as well as the relative energy deposition for all members of the medium-mass group. The results show that the incoming protons are the dominant source in the energy deposition and heating of the cloud, followed by alphas and electrons, with the medium-mass-ion and heavy-ion groups each contributing roughly 8 per cent. The current model also shows a temperature enhancement of up to 10 per cent in the external layers of the cloud (reaching 22.5 K) with respect to the previous calculations where only light particles were considered. However, neither heavy nor medium-mass ions contribute to the temperature enhancement in the deep core of the cloud.

Monte Carlo simulation for predicting neutron-induced single-event upset in ferroelectric random access memory

The influence of the single event effects (SEE) induced by neutron up to 14 MeV on ferroelectric random access memory (FRAM) is simulated by the Monte Carlo method. Simulation results show that single-event upset (SEU) occurs in FRAM when the neutron energy is greater than 6 MeV, and the average energy deposition of neutrons in the sensitive volume increases with increasing neutron energy. Neutron SEU in FRAM occurs when the energy deposition of a single secondary particles generated by a nuclear reaction in the sensitive region exceeds the critical energy. The neutron SEU cross-section of FRAM increases exponentially with increasing energy in the range of 6–14 MeV, and the SEU cross-section is about 1.39 × 10−14 cm2 at 14 MeV. These findings are due to concomitant increases in the variety and numbers of secondary particles whose energy deposition in the sensitive region exceeds the critical energy.

A Preliminary Study of Magnetosphere-Ionosphere-Thermosphere Coupling at Jupiter: Juno Multi-Instrument Measurements and Modeling Tools.

The dynamics of the Jovian magnetosphere are controlled by the interplay of the planet's fast rotation, its main iogenic plasma source and its interaction with the solar wind. Magnetosphere‐Ionosphere‐Thermosphere (MIT) coupling processes controlling this interplay are significantly different from their Earth and Saturn counterparts. At the ionospheric level, they can be characterized by a set of key parameters: ionospheric conductances, electric currents and fields, exchanges of particles along field lines, Joule heating and particle energy deposition. From these parameters, one can determine (a) how magnetospheric currents close into the ionosphere, and (b) the net deposition/extraction of energy into/out of the upper atmosphere associated to MIT coupling. We present a new method combining Juno multi‐instrument data (MAG, JADE, JEDI, UVS, JIRAM and Waves) and modeling tools to estimate these key parameters along Juno's trajectories. We first apply this method to two southern hemisphere main auroral oval crossings to illustrate how the coupling parameters are derived. We then present a preliminary statistical analysis of the morphology and amplitudes of these key parameters for eight among the first nine southern perijoves. We aim to extend our method to more Juno orbits to progressively build a comprehensive view of Jovian MIT coupling at the level of the main auroral oval.

Neutron-induced single event upset simulation in Geant4 for three-dimensional die-stacked SRAM* *Project supported by the National Natural Science Foundation of China (Grant Nos. 12035019, 111690041, and 11675233) and the Project of Science and Technology on Analog Integrated Circuit Laboratory, China ((Grant No. 6142802WD201801).

Three-dimensional integrated circuits (3D ICs) have entered into the mainstream due to their high performance, high integration, and low power consumption. When used in atmospheric environments, 3D ICs are irradiated inevitably by neutrons. In this paper, a 3D die-stacked SRAM device is constructed based on a real planar SRAM device. Then, the single event upsets (SEUs) caused by neutrons with different energies are studied by the Monte Carlo method. The SEU cross-sections for each die and for the whole three-layer die-stacked SRAM device is obtained for neutrons with energy ranging from 1 MeV to 1000 MeV. The results indicate that the variation trend of the SEU cross-section for every single die and for the entire die-stacked device is consistent, but the specific values are different. The SEU cross-section is shown to be dependent on the threshold of linear energy transfer (LETth) and thickness of the sensitive volume (Tsv). The secondary particle distribution and energy deposition are analyzed, and the internal mechanism that is responsible for this difference is illustrated. Besides, the ratio and patterns of multiple bit upset (MBU) caused by neutrons with different energies are also presented. This work is helpful for the aerospace IC designers to understand the SEU mechanism of 3D ICs caused by neutrons irradiation.

A High-Granularity Digital Tracking Calorimeter Optimized for Proton CT

A typical proton CT (pCT) detector comprises a tracking system, used to measure the proton position before and after the imaged object, and an energy/range detector to measure the residual proton range after crossing the object. The Bergen pCT collaboration was established to design and build a prototype pCT scanner with a high granularity digital tracking calorimeter (DTC) used as both tracking and energy/range detector. In this work the conceptual design and the layout of the mechanical and electronics implementation, along with a Monte Carlo (MC) simulation of the new pCT system are reported. The DTC is a multilayer structure with a lateral aperture of 27 cm × 15 cm, made of 41 detector/absorber sandwich layers (calorimeter), with aluminum (3.5 mm) used both as absorber and carrier, and 2 additional layers used as tracking system (rear trackers) positioned downstream of the imaged object; no tracking upstream the object is included. The rear tracker’s structure only differs from the calorimeter layers for the carrier made of ~200 μm carbon fleece and carbon paper (carbon-Epoxy sandwich), to minimize scattering. Each sensitive layer consists of 108 ALPIDE chip sensors (developed for ALICE, CERN) bonded on a polyimide flex and subsequently bonded to a larger flexible printed circuit board. Beam tests tailored to the pCT operation have been performed using high-energetic (50–220 MeV/u) proton and ion beams at the Heidelberg Ion-Beam Therapy Center (HIT) in Germany. These tests proved the ALPIDE response independent of occupancy and proportional to the particle energy deposition, making the distinction of different ion tracks possible. The read-out electronics is able to handle enough data to acquire a single 2D image in few seconds making the system fast enough to be used in a clinical environment. For the reconstructed images in the modeled MC simulation, the water equivalent path length error is lower than 2 mm, and the relative stopping power accuracy is better than 0.4%. Thanks to its ability to detect different types of radiation and its specific design, the pCT scanner can be employed for additional online applications during the treatment, such as in-situ proton range verification.

Defining the performance envelope of reactivity-initiated accidents in a high-temperature gas-cooled reactor

The purpose of this study is to define an envelope of possible transient conditions during two reactivity-initiated accidents (RIAs) in a modular high-temperature gas-cooled reactor (mHTGR). The accident scenarios studied were a group control rod withdrawal (CRW), a design basis accident, and a control rod ejection (CRE), a beyond design basis accident. Variance-based sensitivity analysis methods were employed to obtain realistic bounds on the reactor power and maximum temperature, energy deposition, and heating rate in the fuel during these accidents. Key reactor kinetic parameters and the heat transfer properties of the fuel and moderator were varied in a RELAP computer model of a 350-megawatt mHTGR to obtain these bounds. Sobol sensitivity indices were calculated to highlight which inputs account for the most variance in the outputs. Results showed that the kinetic properties and reactivity temperature coefficients were the most dominant inputs, while thermal properties had little impact on the outputs. Compared to previous experimental work, the fuel particle energy deposition from the simulated RIAs would not be expected to cause fuel failure in any design basis or beyond design basis reactivity accident we investigated. The predicted energy deposition in fuel kernels ranged from 98 to 331 J/g-fuel, significantly less than the expected failure threshold of approximately 1500 J/g-fuel. However, the power pulse widths and heating rates used in previous fuel safety experiments were different from the values predicted in this study for both accident scenarios. Regardless of these differences, this analysis shows that the safety margins in graphite-moderated mHTGRs for reactivity accidents are very large, and additional fuel safety tests are not expected to be necessary for this application.

Simulated X-Ray Radiographic Performance of a Bismuth-Loaded PVT Array

Recent material advancements in organic plastic scintillators enable marked increases in material detection efficiency, light yield, and pulse shape discrimination properties. These advances may resolve significant capability gaps for low-cost, portable, and durable dual-particle imaging (DPI) systems for nuclear safety, security, and safeguard purposes. One such material, a 21% bismuth-loaded polyvinyl toluene (BiPVT), is computationally evaluated as a small, pixelated radiographic array using Monte Carlo N-Particle (MCNP) and Zemax OpticStudio, and it is compared to identical evaluations of EJ-200 and EJ-256 arrays. MCNP software enables estimates of particle interaction and energy deposition, while OpticStudio computes optical light transport within each material. Computational estimates of spatial resolution and relative light collection at 370 kVp are found to agree with experimental results for both EJ-200 and EJ-256 arrays, thereby validating predictions of the same for the BiPVT array. As such, for equivalent exposures at 370 kVp, a BiPVT array may provide $\sim 20\times $ the light collection expected from EJ-200 and $\sim 10\times $ that expected from EJ-256. Similar comparisons of estimated light collection are also computed at 150 and 270 kVp, and these results suggest that BiPVT will provide significantly improved performance over EJ-200 and EJ-256 across all energies practical for portable X-ray radiography.