Simulation study of electron beam optics for a distributed X-ray source toward stationary CT architecture

Nuclear Technology

Prompt gamma-ray polarization is a practical method for detecting highly enriched uranium (HEU) in concealed sources. It also provides information on their geometry, magnetic fields, and radiation mechanisms. However, prompt gamma-ray polarization measurements have rarely been applied in nuclear nonproliferation areas to detect HEU. In this study, the feasibility of detecting the characteristic energy peak of 186 keV, which is associated with the asymmetry of the activation mechanism and the detection of energy-dependent polarization from concealed HEU sources, was evaluated using the Compton scattering approach. A Monte Carlo N-particle transport code simulation was used to realize the activation mechanism of HEU via two 1.4-mm strips of converter material [i.e., cesium lead tribromide (CsPbBr3)], transported by secondary scattered gamma rays during the three-stage process of Compton scattering …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Testing and qualification of advanced nuclear fuels involve an iterative process of prototyping, in-pile irradiation testing, and in/ex situ examination. Fuel restructuring and fission product migration during burnup are among the most important aspects of fuel evolution and affect several important performance characteristics (e.g., heat removal, accident tolerance, and fission product retention). Poolside nondestructive characterization techniques provide fuel developers with tools to understand fuel evolution at different time points of burnup. A design for a compact, submersible, and multi-modal (transmission and emission) gamma-ray tomography system for imaging irradiated nuclear fuel is presented herein. Detector selection, collimator geometry and fabrication, mechanical design, imaging protocol, and acquisition protocol are discussed. Modeling calculations showed that sub-millimeter resolution could be …

In the last few decades, uncertainty quantification (UQ) methods have been used widely to ensure the robustness of engineering designs. This chapter aims to detail recent advances in popular uncertainty quantification methods used in engineering applications. This chapter describes the two most popular meta-modeling methods for uncertainty quantification suitable for engineering applications: polynomial chaos method and Gaussian process. Furthermore, the UQ methods are applied to an engineering test problem under multiple uncertainties. The test problem considered here is a supersonic nozzle under operational uncertainties. For the deterministic solution, an open-source computational fluid dynamics (CFD) solver SU2 is used. The UQ methods are developed in Matlab® and are further combined with SU2 for the uncertainty and sensitivity estimates. The results are presented in terms of the mean and …

The Gaussian Process (GP)-based surrogate model will not be very accurate when we have limited high-fidelity (experimental) data. In addition, it is challenging to apply higher-dimensional functions (>20-dimensional function) to approximate predictions with the GP. Furthermore, noisy data or data-containing erroneous observations and outliers are major challenges for advanced accident-tolerant fuel (ATF) concepts. This challenge can be aggravated by a lack of data, missing data, and inconsistencies in data, which require techniques to identify missing data in a dataset before the dataset is used in a predictive algorithm. Also, the governing differential equation is empirical for longer-term ATF candidates, and data availability is an issue. Physics-informed Multi-fidelity Kriging (MFK) can be useful for identifying and predicting the required material properties. MFK is particularly useful with low-fidelity physics …

In Positron Emission Tomography (PET), the positron-emitting radiotracer is administered to the patient’s body, and the annihilation photons are used to create an image map of the spatial distribution of the radiotracer uptake. However, a positron can also combine with an electron in the surrounding lattice, forming para-positronium (p-Ps) or ortho-positronium (o-Ps). The decay of positronium, as compared to "pick-off" from the tissue can potentially provide additional information about the material and improve image contrast. In this study, we experimentally demonstrated the dependence of positronium lifetime on the tissue type using the positron annihilation lifetime spectroscopy (PALS) technique. We extracted the three components of positron lifetime corresponding to the positron free annihilation lifetime, p-PS lifetime, and o-Ps lifetime for three types of bovine, non-fixated soft tissues: adipose, hepatic, and muscle …

Artificial Intelligence continues to undergo rapid advancements in the modern age. This technology is becoming more commonplace in society, and it carries the potential for a significant impact on how people carry out their activities. As more applications of Artificial Intelligence are explored, it becomes pertinent to identify areas in which caution and reluctant adoption of this technology are necessary. Artificial Intelligence has existed alongside nuclear strategy and nonproliferation endeavors since the 1960s and as the technology develops it is inevitable that expansions or upgrades to existing systems will be proposed. This chapter attempt to address the feasibility of implementing an advanced system in current aspects of nuclear security, safeguard, and nonproliferation. The aspects under consideration are early-warning systems, autonomous defense systems, and integrated decision support for the adoption of …

This conference presentation was prepared for the Medical Imaging 2023: Physics of Medical Imaging conference at SPIE Medical Imaging 2023.

Processes

Utilization of nuclear research reactors is of high importance for education and training, research and development, and many other applications. However, less effective utilization encountered in research reactors is mainly due to limitations in power levels and related experimental facilities. Such limitations, however, have led different global owners of research reactors to consider upgrading the power levels of their reactors to accommodate the increase in utilization demands. To consider upgrading the power levels of research reactors without replacing major components, a pair of essential analyses must be performed, namely the neutronic evaluation of nuclear fission and thermal-hydraulic evaluation for heat removal from the reactor core. In this work, a conceptual upgrade to the core design and configuration of MSTR, or Missouri University of Science and Technology Reactor (200 kilowatts (kW)), is demonstrated. The conceptual design of the MSTR high-power configuration (MSTR-HPC) aims to achieve high neutron flux and demonstrate the power level and core configuration with greater flexibility and adaptability while not exceeding safety limits. The conceptual design of the MSTR-HPC involves uprating the power level to 2 megawatts (MW), reconfiguring the core, changing the fuel meat type, inclusion of a flux trap (FT) facility, and others. In addition, the conceptual design of MSTR-HPC includes three in-core irradiation facilities, namely FT, bare rabbit tube (BRT), and cadmium rabbit tube (CRT). The neutronic evaluation of the MSTR-HPC was carried out using the Monte Carlo N-particle Code (MCNP), version 6. In addition, the thermal …

CONCLUSION• Quantitative phase retrieval (QPR) is a challenging problem in propagation-based x-ray phase contrast (PB-XPC) imaging under benchtop conditions, particularly for objects that are structurally complicated and heterogenous.

It is important to accurately model materials’ properties at lower length scales (micro-level) while translating the effects to the components and/or system level (macro-level) can significantly reduce the amount of experimentation required to develop new technologies. Robustness analysis of fuel and structural performance for harsh environments (such as power uprated reactor systems or aerospace applications) using machine learning-based multiscale modeling and robust optimization under uncertainties are required. The fiber and matrix material characteristics are potential sources of uncertainty at the microscale. The stacking sequence (angles of stacking and thickness of layers) of composite layers causes mesoscale uncertainties. It is also possible for macroscale uncertainties to arise from system properties, like the load or the initial conditions. This chapter demonstrates advanced data-driven methods and …

Deep Learning using Neural Networks (DNNs) has emerged as a viable alternative to standard physical modeling in nuclear systems and engineering. This paper seeks to develop a multi-stage predictive model consisting of 2 feed-forward DNNs to determine the final steady state power of a reactor transient in the real research reactor facility (Missouri University of Science and Technology Reactor (MSTR)). Physical information is collected from the initial and final steady states of the transient to create a single trial. A dataset is generated by using the generalized prompt jump equation to expand upon the data collected from MSTR. Noise is added to the simulated data to reduce the likelihood of memorization. 6 classifier models are developed, tested, and compared for the first stage of the model, with an output representing a large band power output resolution. 4 regression models are developed and tested with input from the first stage model to predict a single value representing the reactor power output. The combined model yields 96% classification accuracy for the first stage and 92% absolute prediction accuracy for the second stage. The development procedure is discussed so that the method can be applied generally to similar systems.

Physics in Medicine & Biology

Objective Quantitative phase retrieval (QPR) in propagation-based x-ray phase contrast imaging of heterogeneous and structurally complicated objects is challenging under laboratory conditions due to partial spatial coherence and polychromaticity. A deep learning-based method (DLBM) provides a nonlinear approach to this problem while not being constrained by restrictive assumptions about object properties and beam coherence. The objective of this work is to assess a DLBM for its applicability under practical scenarios by evaluating its robustness and generalizability under typical experimental variations. Approach Towards this end, an end-to-end DLBM was employed for QPR under laboratory conditions and its robustness was investigated across various system and object conditions. The robustness of the method was tested via varying propagation distances and its generalizability with respect to object …

Machine learning tools are becoming more popular for engineering problem solving, including those in nuclear systems. Nuclear reactor systems are complex, and cannot necessarily be analytically solved or simulated without a significant amount of resources. However, high reliability models with low computational resources are desired. A new type of model, Multi-Stage Deep Neural Network (MSDNN), is proposed to create a high-reliability machine learning model by using probabilistic classification information to generate more accurate continuous predictions. Multiple MSDNN architectures are designed and compared for predicting the final steady state power of a research nuclear reactor after a power changes. Results show that MSDNN models tend to perform better than standard feedforward neural networks in terms of both accuracy and generalization. This type of model is expected to be utilized and extrapolated for future nuclear problem solving using machine learning techniques.

Many criticality experiments performed to aid in nuclear data evaluation are designed to maximize the sensitivity of the system’s effective neutron multiplication factor to a certain nuclide reaction pair over an energy region of interest. This is typically done by evaluating possible designs in a transport code such as MCNP and selecting the one with the highest desired sensitivity. A designer has many tools to try to maximize this sensitivity such as different moderators, reflectors, fuels, and geometries. This balancing act of identifying a critical and maximally sensitive system become very computationally expensive as more variables are added and higher precisions are desired. In order to identify these optimal configurations more efficiently a Particle Swarm Optimization (PSO) algorithm coupled with MCNP has been developed by Los Alamos National Laboratory (LANL). This algorithm has been used to design two upcoming criticality experiments that will be performed at the National Criticality Experiments Research Center (NCERC), located at the Nevada National Security Site, and operated by LANL, the only general-purpose critical experiments laboratory in the United States. PSO uses a population (swarm) of candidate solutions (particles) on a search space of dimensions such as moderator and reflector thicknesses or enrichments and concentrations. These particles move around the search space from generation to generation according to simple rules. Eventually, the swarm converges on the configuration that is both critical and maximally sensitive to a piece of nuclear data. PSO is well suited for criticality experiments as the algorithm is …

Rigorous peer-reviews are the basis of high-quality academic publishing. Thanks to the great efforts of our reviewers, JNE was able to maintain its standards for the high quality of its published papers. Thanks to the contribution of our reviewers, in 2021, the median time to first decision was 107 days and the median time to publication was 143 days. The editors would like to extend their gratitude and recognition to the following reviewers for their precious time and dedication, regardless of whether the papers they reviewed were finally published:

Physics in Medicine & Biology

Objective Quantitative phase retrieval (QPR) in propagation-based x-ray phase contrast imaging of heterogeneous and structurally complicated objects is challenging under laboratory conditions due to partial spatial coherence and polychromaticity. A deep learning-based method (DLBM) provides a nonlinear approach to this problem while not being constrained by restrictive assumptions about object properties and beam coherence. The objective of this work is to assess a DLBM for its applicability under practical scenarios by evaluating its robustness and generalizability under typical experimental variations. Approach Towards this end, an end-to-end DLBM was employed for QPR under laboratory conditions and its robustness was investigated across various system and object conditions. The robustness of the method was tested via varying propagation distances and its generalizability with respect to object …

Accident-tolerant fuels and their licensing are one of the top priority strategic areas under “US Nuclear Regulation Committee (NRC) Systems Analysis Research Activities.” In addition, United States Department of Energy (DOE) has given significant attention for the advanced novel fuel, which can increase the burnup while exhibiting superior accident tolerance under “DOE Accident Tolerant Fuel Program” (under Fuel Cycle Research R&D). Therefore, this chapter focuses on the advanced composite accident-tolerant fuel systems. This chapter explains the integration of experiments with computational research efforts and data availability for the challenging qualification effort for accident-tolerant fuel concepts leveraging existing US DOE Accident-Tolerant Fuel Program’s industrial information. An overview of conventional empirical modeling reliance and its limitations in nuclear fuel development is also explained …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Monte Carlo radiation transport modeling studies were performed for a compact, and high-resolution gamma-ray computed tomography system designed for imaging irradiated nuclear fuel. The system comprises a 60Co source – chosen for its highly penetrating 1173 keV and 1332 keV gamma rays – a pair of high-aspect-ratio pencil beam collimators, and an inorganic scintillator detector. Two acceleration methods are proposed to rapidly model a transmission type gamma-ray tomography system. The first, a variance reduction technique, is based on performing Monte Carlo simulations with a monodirectionally-biased source, sampled from a characteristic sub-volume of the full source volume. The second acceleration method is based on the deterministic calculations using the Beer–Lambert law and detector response characteristics. Comparison of simulations using acceleration approaches with analog …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

This work presents a systematic study of the properties (Light Output Non-Uniformity (LONU) and energy resolution) of two CsI (Tl) scintillation units over a span of almost three years, under adverse conditions of humidity and temperature. These two crystals are part of the CALIFA detector, a highly segmented calorimeter and spectrometer for γ rays and light-charged particles, that is placed surrounding the reaction target at Cave C, the experimental cave of the R 3 B (Reactions with Radioactive Relativistic Beams) collaboration at the GSI-FAIR facilities in Darmstadt, Germany. The findings obtained after the experiment indicate that there was no significant impact on the performance in terms of resolution and LONU. This suggests that the employed wrapping for light collection effectively serves as an excellent barrier against humidity. As a result, the crystal is preserved in a far better condition than initially anticipated.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Studies based on imaging the annihilation of the electron (e−) and its antiparticle positron (e+) open up several interesting applications in nuclear medicine and fundamental research. The annihilation process involves both the direct conversion of e+ e− into photons and the formation of their atomically bound state, the positronium atom (Ps), which can be used as a probe for fundamental studies. With the ability to produce large quantities of Ps, manipulate them in a long-lived Ps states, and image their annihilations after a free fall or after passing through atomic interferometers, this purely leptonic antimatter system can be used to perform inertial sensing studies in view of a direct test of Einstein’s equivalence principle. It is envisioned that modular multi-strip detectors can be exploited as potential detection units for this kind of studies. In this work, we report the results of the first feasibility study performed on a e …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Abstract Over the years, Maxwellian Averaged Cross Sections (MACS) have been measured by neutron activation, providing a neutron energy spectrum resembling the one found inside the stars. Recently, a new method has been proposed to produce stellar spectra at different stellar temperatures (a Maxwell–Boltzmann neutron energy distribution), employing the 7 Li (p, n) 7 Be reaction. The method is based on the idea of shaping the proton beam energy to shape the neutron beam spectrum. This method was applied to obtain a well-reproduced Maxwell–Boltzmann neutron spectrum (MBNS) at k T= 28 keV. An initial proton energy of 3170 keV and an aluminum foil as a proton energy shaper were employed. Differential angular neutron energy distributions from 0 to 90 degrees in 10∘ steps were measured to obtain the 0∘–90∘ integrated neutron spectrum over a neutron flight path of 50 cm. This manuscript …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

We report on a highly selective experimental setup for particle-γ coincidence experiments at the Super-Enge Split-Pole Spectrograph (SE-SPS) of the John D. Fox Superconducting Linear Accelerator Laboratory at Florida State University (FSU) using fast CeBr 3 scintillators for γ-ray detection. Specifically, we report on the results of characterization tests for the first five CeBr 3 scintillation detectors of the CeBr 3 Array (CeBrA) with respect to energy resolution and timing characteristics. We also present results from the first particle-γ coincidence experiments successfully performed with the CeBrA demonstrator and the FSU SE-SPS. We show that with the new setup, γ-decay branching ratios and particle-γ angular correlations can be measured very selectively using narrow excitation energy gates, which are possible thanks to the excellent particle energy resolution of the SE-SPS. In addition, we highlight that nuclear …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

In deep-underground experiments, intrinsic detector background can exceed the external one, limiting the detection sensitivity. Intrinsic background in liquid scintillator neutron detectors consists of α particles emitted from radioactive impurities in the detector housing (and possibly in the liquid). We present the results of long background measurements of 12 EJ-309 liquid organic scintillators detectors in the deep-underground Gran Sasso National Laboratory of the Italian Institute of Nuclear Physics. These detectors are a part of the detection array for the SHADES ERC project that aims to measure the very low cross section (down to picobarn) of the astrophysically important reaction 22 Ne (α, n) 25 Mg. With an exposure of∼ 35 days we identify an actinide concentration in the detector housing of 8. 4 (1. 8) sta (1. 4) sys× 1 0− 2 ppm and 1. 62 (0. 57) sta (0. 03) sys× 1 0− 1 ppm of 238 U and 232 Th, resulting in 64 α …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

The nozzle geometry has a significant impact on the nozzle internal flow, which affects the fuel spray atomization and combustion of internal combustion engine. In this study, the internal geometry and flow characteristics of the nozzle was studied visually by using X-ray phase contrast imaging technique. The results indicate that the angle between the orifice wall and sac significantly influences the formation and development of cavitation in the orifice. A numerical model including the nozzle internal flow and the spray near-field characteristics was established to provide a more detailed description of how the inlet included angle affects the orifice's internal flow. It has been found that the hydraulic flip width increases with the decrease of the inlet included angle. The symmetry of cavitation distribution is greater when the inlet included angles on the left and right sides of the orifice are equal. When the inlet included …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

An aerodynamic lens injector was developed specifically for the needs of single-particle diffractive imaging experiments at free-electron lasers. Its design allows for quick changes of injector geometries and focusing properties in order to optimize injection for specific individual samples. Here, we present results of its first use at the FLASH free-electron-laser facility. Recorded diffraction patterns of polystyrene spheres are modeled using Mie scattering, which allowed for the characterization of the particle beam under diffractive-imaging conditions and yielded good agreement with particle-trajectory simulations. The complex refractive index of polystyrene at λ= 4. 5 nm was determined as m= 0. 976− 0. 001 i.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

We report on a highly selective experimental setup for particle-γ coincidence experiments at the Super-Enge Split-Pole Spectrograph (SE-SPS) of the John D. Fox Superconducting Linear Accelerator Laboratory at Florida State University (FSU) using fast CeBr 3 scintillators for γ-ray detection. Specifically, we report on the results of characterization tests for the first five CeBr 3 scintillation detectors of the CeBr 3 Array (CeBrA) with respect to energy resolution and timing characteristics. We also present results from the first particle-γ coincidence experiments successfully performed with the CeBrA demonstrator and the FSU SE-SPS. We show that with the new setup, γ-decay branching ratios and particle-γ angular correlations can be measured very selectively using narrow excitation energy gates, which are possible thanks to the excellent particle energy resolution of the SE-SPS. In addition, we highlight that nuclear …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

The measurement of shower muons on an event-by-event basis offers a potent tool for conducting ground-based experiments on gamma rays and cosmic rays due to its sensitivity to primary mass and interaction models. In recent years, underground water Cherenkov detectors as large-area muon counters provide the most powerful way of rejecting cosmic ray background when searching for TeV–PeV gamma rays and cosmic ray electrons, an unprecedented rejection power of 1 0 4–1 0 5 is achieved. Unburied water Cherenkov detectors are widely used in ground-based gamma astronomy experiments, eg, Milagro, HAWC, LHAASO-WCDA, etc. However, due to the presence of electromagnetic components, their deployment as event-by-event muon counters has encountered considerable challenges. All the experiments mentioned above reconstruct lateral-distribution-function related parameters to tell a gamma …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

The measurement of shower muons on an event-by-event basis offers a potent tool for conducting ground-based experiments on gamma rays and cosmic rays due to its sensitivity to primary mass and interaction models. In recent years, underground water Cherenkov detectors as large-area muon counters provide the most powerful way of rejecting cosmic ray background when searching for TeV–PeV gamma rays and cosmic ray electrons, an unprecedented rejection power of 1 0 4–1 0 5 is achieved. Unburied water Cherenkov detectors are widely used in ground-based gamma astronomy experiments, eg, Milagro, HAWC, LHAASO-WCDA, etc. However, due to the presence of electromagnetic components, their deployment as event-by-event muon counters has encountered considerable challenges. All the experiments mentioned above reconstruct lateral-distribution-function related parameters to tell a gamma …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Abstract The improved Resistive Plate Chambers (iRPC) are designed using thin low resistivity High-Pressure Laminate (HPL) gaps. They are proposed to equip the very forward region of the Compact Muon Solenoid (CMS) detector, as they can stand rates∼ 2 kHz/cm 2. To withstand 3 times higher rates than the installed CMS RPC chambers, the HPL electrode thickness was reduced from 2 mm to 1.4 mm. The gas gain of the detector is dependent on the gas pressure and temperature which requires correcting for the applied voltage to keep detector operational characteristics such as efficiency, cluster size and noise rate constant. Herein, we study the pressure correction at constant temperature for CMS iRPC and compare its correction coefficient with the one for the 2 mm RPC gap technology. Pressure correction parameters for both technologies are found compatible.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

The ANDROMeDa project, recently funded by the Italian ministry of research with a 1M€ grant, aims to develop a novel light dark matter (DM) detector sensitive to DM-electron recoil in a target of vertically-aligned carbon nanotubes: the “dark-PMT”. Thanks to their vanishing density in the direction of the tube axis, carbon nanotubes allow a scattered electron to leave the target without being re-absorbed only if it travels parallel to the tubes. Therefore the detector is expected to have directional sensitivity, a key feature in DM searches. With only 1 g of exposure per year and a careful suppression of the backgrounds, such detector might achieve world-leading sensitivity for DM masses below 30 MeV.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

For computed tomography (CT) imaging to be considered “real time”, one set of tomographic projections are to be acquired in less than 30 ms. Current conventional CT systems are limited to approximately 300 ms because of mechanical and material limitations. To bypass the mechanical limitations of a conventional gantry system, there is an open design challenge to develop a distributed X-ray source that is tightly packed and bright. The work presented here reports a design for a distributed X-ray source based on a rotating cylindrical anode. In particular, this work focuses on designing the electron beam optics for said X-ray source and refining these optics via multi-physics simulation studies. We designed these studies to investigate the electron beam behavior for switching, steering, and focusing. We demonstrated that the high-energy electron beam could be turned off and on via the grid-switching technique …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Studies based on imaging the annihilation of the electron (e−) and its antiparticle positron (e+) open up several interesting applications in nuclear medicine and fundamental research. The annihilation process involves both the direct conversion of e+ e− into photons and the formation of their atomically bound state, the positronium atom (Ps), which can be used as a probe for fundamental studies. With the ability to produce large quantities of Ps, manipulate them in a long-lived Ps states, and image their annihilations after a free fall or after passing through atomic interferometers, this purely leptonic antimatter system can be used to perform inertial sensing studies in view of a direct test of Einstein’s equivalence principle. It is envisioned that modular multi-strip detectors can be exploited as potential detection units for this kind of studies. In this work, we report the results of the first feasibility study performed on a e …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Neutron and gamma-ray imaging systems are deployed within the field of nuclear safeguards for the detection and localization of special nuclear materials and other materials of interest. 237Np is one of these materials of interest due its presence in spent nuclear fuel and potential for use in nuclear weapons when purified. Here, for the first time, a 6 kg neptunium sphere (98.8 wt% 237Np) was measured using a dual-particle imager, from the University of Michigan, consisting of organic glass and inorganic scintillators. The novel composition of organic glass scintillator was recently developed at Sandia National Labs and has been used in particle imaging systems due to its time resolution and particle discrimination capabilities. Gamma-ray energy spectra from single and coincident events were extracted and the sequencing of Compton scatter and photoelectric absorption gamma-ray events was used to generate …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Abstract The Cherenkov Telescope Array Observatory (CTAO) will be the major global observatory for gamma-ray astronomy over the next decade and beyond. It will consist of two arrays of telescopes of different sizes, one for each hemisphere, and will be sensitive to gamma rays in the energy range from a few tens of GeV to hundreds of TeV. The Small-Sized Telescopes (SSTs) are a crucial component of the southern array, as they will extend the sensitivity of the observatory to the highest energies. Their focal plane will be equipped with 2048 Silicon Photomultiplier (SiPM) pixels, each one read independently by a state-of-the-art full waveform sampling readout. These solid-state sensors offer advantages over the traditional photomultiplier tubes, such as lower operating voltage, higher photon detection efficiency, and tolerance to bright illumination. In particular, they are the best choice for a small and compact …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Abstract The HERMES (High Energy Rapid Modular Ensemble of Satellites) Pathfinder mission aims to develop a constellation of nanosatellites to study astronomical transient sources, such as gamma-ray bursts, in the X and soft γ energy range, exploiting a novel inorganic scintillator. This study presents the results obtained describing, with an empirical model, the unusually intense and long-lasting residual emission of the GAGG: Ce scintillating crystal after irradiating it with high energy protons (70 MeV) and ultraviolet light (∼ 300 nm). From the model so derived, the consequences of this residual luminescence for the detector performance in operational conditions has been analysed. The suitability of this detector for the HERMES Pathfinder nanosatellites was demonstrated by the low contribution of the afterglow, 1–2 pA at peak, to the input current of the front-end electronics.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

The development of advanced, high gradient accelerating structures is one of the leading activity of the particle accelerator community. In the technological research of new construction methods for these devices, high-power testing is a critical step for the verification of their viability. Recent experiments showed that accelerating cavities made out of hard copper, fabricated without high-temperature processes, can achieve better performance as compared with soft copper ones. Recently, we have built cavities using Tungsten Inert Gas welding and the high-power experiments confirmed that this joining process is a robust and low-cost alternative to brazing or diffusion bonding. This is a good solution for high-gradient operation, with a gradient of about 150 MV/m in X-band, at a breakdown rate of 1 0− 3/pulse/meter using a shaped RF pulse with a 150 ns flat part. We continue the design, construction and high power …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

We have been developing silicon-on-insulator (SOI) pixel detectors with a pinned depleted diode (PDD) structure, named “XRPIX”, for X-ray astronomy. The PDD structure is formed in a thick p-type substrate, to which high negative voltage is applied to make it fully depleted. A pinned p-well is introduced at the backside of the insulator layer to reduce a dark current generation at the Si-SiO2 interface and to fix the back-gate voltage of the SOI transistors. An n-well is further introduced between the p-well and the substrate to make a potential barrier between them and suppress a leakage current. An optimization study on the n-well dopant concentration is necessary because a higher dopant concentration could result in a higher potential barrier but also in a larger sense-node capacitance leading to a lower spectroscopic performance, and vice versa. Based on a device simulation, we fabricated five candidate chips …

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

In view of the High Luminosity LHC, the CMS Muon system will be upgraded to sustain its efficient muon triggering and reconstruction performance. Resistive Plate Chambers (RPC) are dedicated detectors for muon triggering due to their excellent timing resolution. The RPC system will be extended up to 2.4 in pseudorapidity. Before the LHC Long Shutdown 3, new RE3/1 and RE4/1 stations of the forward Muon system will be equipped with improved Resistive Plate Chambers (iRPC) having, compared to the present RPC system, a different design and geometry and 2D strip readout. This advanced iRPC geometry configuration allows the rate capability to improve and hence survive the harsh background conditions during the HL-LHC phase. Several iRPC demonstrator chambers were installed in CMS during the recently completed 2nd Long Shutdown to study the detector behaviour under real LHC conditions …