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Effect of Space Radiation on TES Detectors Performance

The Athena mission and its X-IFU instrument (X-ray Integral Field Unit) will be positioned at the Sun-Earth Lagrangian point L1, where it will be subject to solar wind (low flux plasma of 95% protons and 5% alpha particles) with energy below 0.1 MeV, and to galactic cosmic rays and solar flares (energetic protons, alpha particles, and electrons) with energies up to hundreds of MeV for protons and the GeV for heavier ions. Some of these particles will go through the satellite and hit the focal plane assembly and hence the detectors. These detectors will be TES (Transition-edge sensor) microcalorimeters, flown for the first time in such an environment. In order to ensure the performance of this type of detectors throughout the duration of such mission, it is critical to study the impact of the radiation on their behavior. Indeed, although a lot of reference material exist for semiconductor detectors such as CCDs, little is currently known about the impact of radiation on TES detectors. These energetic events could cause local heating or damage to the detectors and affect their performance. In this work, we describe how we designed a test campaign to assess the impact of L1 radiation on TES detectors for Athena/X-IFU-like missions and present the results of the tests. Analyses includes assessing changes in the pulse shapes and energy resolution of the detectors measured at 55 mK after several radiation dose steps performed at 4 K.

Sophie Beaumont↗
DOE OSTI2021

Uranium Holdup Monitoring with Compton Imaging as Function of Depth and Mass

Material Control and Accountability (MC&A) programs track masses of materials flowing through production processes, where some material remains in process equipment as holdup. Quantification of these masses using gamma emissions typically involves usage of a well characterized radiation detector and assumptions of geometric configuration to constrain detection efficiencies, where the Generalized Geometry Holdup (GGH) method is often used. Uncertainties on the order of ±50% are observed, where the difficulties arise based on the asymmetric and gradient distributions of material that do not fall within the bounds of GGH. Gamma imagers provide a possible means to improve this geometric knowledge. This work describes the process used in creating a series of mass standards to aid the development of imaging algorithms for quantification.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

A Simple Search for Sterile Neutrino Dark Matter

We have tested the feasibility of an experiment to search for keV sterile neutrino dark matter with superconducting radiation detectors. For this, we have implanted radioactive 7 Be nuclei into our detectors, which decay by electron capture with a half-life of 53 days. The electron neutrino produced in this decay escapes from the detector, and we can measure the recoil energy of the 7 Li daughter nucleus with high accuracy. The recoil spectrum consists of four peaks, two due to capture of a 1s electron (“K-capture”) and two due to capture of a 2s electron (“L-capture”) for decay into the 7 Li ground state and the 7 Li* excited state. If the electron neutrino contains some admixture of a keV sterile neutrino, the 7 Li recoil energy will be shifted and produce an additional peak in the spectrum whose energy depends on the sterile neutrino mass and whose amplitude depends on the neutrino admixture.

42 ENGINEERING↗
DOE OSTI2017

Organic Scintillator for Real-Time Neutron Dosimetry

We have developed a radiation detector based on an organic scintillator for spectrometry and dosimetry of out-of-field secondary neutrons from clinical proton beams. The detector consists of an EJ-299-34 crystalline organic scintillator, coupled by fiber optic cable to a silicon photomultiplier (SiPM). Proof of concept measurements were taken with 137 Cs and 252 Cf, and corresponding simulations were performed in MCNPX-PoliMi. Despite its small size, the detector is able to discriminate between neutron and gamma-rays via pulse shape discrimination. We simulated the response function of the detector to monoenergetic neutrons in the 100 keV–0 MeV range using MCNPX-PoliMi. The measured unfolded 252 Cf neutron spectrum is in good agreement with the theoretical Watt fission spectrum. We determined the ambient dose equivalent by folding the spectrum with the fluence-to-ambient dose conversion coefficient, with a 1.4% deviation from theory. Some preliminary proton beam experiments were preformed at the Bronowice Cyclotron Center patient treatment facility using a clinically relevant proton pencil beam for brain tumor and craino-spinal treatment directed at a child phantom.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Contributions to the BeEST sterile neutrino search

Sterile neutrinos are hypothetical right-handed leptons that have been postulated as extensions to the Standard Model to help explain the origin of neutrino masses and the matter-antimatter asymmetry in the Universe. Sterile neutrinos with keV-scale masses are also a promising candidate for dark matter. LLNL and the Colorado School of Mines are developing an experiment to search for sterile neutrinos by measuring the \Beryllium-7 Electron capture in Superconducting Tunnel junctions (STJs)" (the \BeEST" Experiment). When 7 Be implanted into STJ radiation detectors decays by electron capture, the neutrino escapes and the energy of the recoiling 7 Li nucleus can be measured with high accuracy. Using conservation of energy and momentum, the mass of the emitted neutrino can then be found. Sterile keV neutrinos would generate additional peaks in the spectrum, and the experiment uses high-resolution STJs to observe such a potential signal. During my internship, I contributed to different aspects of the BeEST experiment. I designed a UHV setup for X-ray spectroscopy analysis with STJs. It will allow high-resolution X-ray spectroscopy of different materials to examine the broadening in the BeEST spectra, the origins of which are unknown but may be related to material effects inside the STJ detectors. The design accounts for the specific demands of the BeEST project, but provides a degree of flexibility that makes it useful for other potential STJ projects. Additionally, to test the accuracy of the electronics and data analysis routine, an arbitrary waveform generator (AWG) will be used to generate simulated spectra that contain sterile neutrino signals of a specified mass and admixture. For this I programmed an AWG to output random STJ signals whose amplitudes follow the appropriate user-de ned probability distribution. The AWG signals can be input into the 32-channel preamplifier to simulate any spectrum of interest and test the uniformity of the amplifier chain, as well as the sensitivity of the data analysis.

42 ENGINEERING↗
DOE OSTI2018

Zero-dimensional Cs 4 EuX 6 (X = Br, I) all-inorganic perovskite single crystals for gamma-ray spectroscopy

Organic–inorganic and all-inorganic halide perovskites have become leading candidates toward high-performance optoelectronic devices and radiation detectors. In this work, we report novel zero-dimensional Cs 4 EuX 6 (X = Br, I) perovskite single crystals as self-activated scintillators with superior performance for gamma-ray spectroscopy. Both Cs 4 EuBr 6 and Cs 4 EuI 6 single crystals grown by the Bridgman method were determined to have the trigonal crystal structure with the R$\bar{3}$c space group, and have a melting point of approximately 540°C. Cs 4 EuBr 6 and Cs4EuI 6 exhibit blue emission under UV excitation and high light yields of 78,000 ± 4000 photons/MeV and 53,000 ± 3000 photons/MeV under 137 Cs gamma-ray irradiation, respectively. In particular, the former represents the best result achieved for self-activated scintillators thus far. Thermally stimulated luminescence studies and density functional theory calculations elucidate the correlation between halogen vacancies and long-lived emission (afterglow) at room temperature in Cs4EuX 6 (X=Br, I) single crystals. In conclusion, our findings not only demonstrate the high gamma-ray detection efficiency in Cs 4 EuX 6 (X=Br, I), but will further promote the development of 0D metal halide-based novel luminescent and radiation detection materials.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Adding ($\mathcal{α}$,n) Emission to an Existing Subcritical Benchmark Statistical Uncertainty Method

Subcritical measurements often use radiation detectors to infer parameters related to the physics of a measured system. One type of subcritical measurements typically performed are called neutron noise measurements. These types of measurements utilize the fact that prompt neutrons are produced from fission immediately after a fission event and are therefore correlated in time. Subcritical benchmarks require evaluation of the statistical and systematic uncertainties of a measurement. Previous work established methods for determining statistical and systematic uncertainties in subcritical benchmarks. The data were analyzed using the Hage-Cifarelli formalism of the Feynman Variance-to-Mean method. The previous work made an assumption that the ($\mathcal{α}$,n) emission rate was negligible. This assumption was used because the previous work focused on systems with metal Plutonium. This work extends the existing statistical uncertainty method to include ($\mathcal{α}$,n) emissions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Study on thermal annealing of cadmium zinc telluride (CZT) crystals

Cadmium Zinc Telluride (CZT) has attracted increasing interest with its promising potential as a room-temperature nuclear-radiation-detector material. However, different defects in CZT crystals, especially Te inclusions and dislocations, can degrade the performance of CZT detectors. Post-growth annealing is a good approach potentially to eliminate the deleterious influence of these defects. At Brookhaven National Laboratory (BNL), we built up different facilities for investigating post-growth annealing of CZT. Here, we report our latest experimental results. Cd-vapor annealing reduces the density of Te inclusions, while large temperature gradient promotes the migration of small-size Te inclusions. Simultaneously, the annealing lowers the density of dislocations. However, only-Cd-vapor annealing decreases the resistivity, possibly reflecting the introduction of extra Cd in the lattice. Subsequent Te-vapor annealing is needed to ensure the recovery of the resistivity after removing the Te inclusions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Sensor Placement Optimization Study for the Built Environment: Operational Use Cases

Systems of fixed-position radiation sensors can provide information that assists emergency responders following nuclear and radiological incidents. State, local, tribal, and territorial (SLTT) government agencies that implement systems of fixed-position sensors are faced with numerous decisions regarding sensor selection, quantity, and placement. To develop guidance on implementation of radiation detection systems, we simulated the release of radioactive material in an urban environment using a combination of three models: the Weather Research Forecasting (WRF), Quick Urban and Industrial Complex (QUIC), and Monte Carlo N-Particle (MCNP) models. We then evaluated the performance of several hypothetical sensor systems. The small number of simulations we conducted are not sufficient to generate definitive design guidance for radiation sensor systems, but we did identify trends that would be of interest to emergency planners. For a scenario that releases 1000 curies of Cs-137, radiation detectors were needed at 500-meter intervals to have a high likelihood of event detection and to estimate source location and plume detection. We also noted that optimal detector altitude varied with distance to the source. We recommend additional research in this area be conducted to support developing sensor placement guidelines that expand on a range of locations, isotopes, activity levels, and different weather conditions. Original simulation strategies included a range of environments, additional radioisotopes (Am241 and AmBe), and a larger selection of sensor types. These types of expansions would support SLTT guidance on sensor system recommendations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Matrix-Assisted Ionization of Molecular Uranium Species

Matrix-assisted ionization (MAI) demonstrates high sensitivity for a variety of organic compounds; however, few studies have reported the application of MAI for the detection and characterization of inorganic analytes. Trace-level uranium analysis is important in the realms of nuclear forensics, nuclear safeguards, and environmental monitoring. Traditional mass spectrometry methods employed in these fields require combinations of extensive laboratory chemistry sample preparation and destructive ionization methods. There has been recent interest in exploring ambient mass spectrometry methods that enable timely sample analysis and higher sensitivity than what is attainable by field-portable radiation detectors. Rapid characterization of uranium at nanogram levels is demonstrated in this study using MAI techniques. Mass spectra were collected on an atmospheric pressure mass spectrometer for solutions of uranyl nitrate, uranyl chloride, uranyl acetate, and uranyl oxalate utilizing 3-nibrobenzonitrile as the ionization matrix. The uranyl complexes investigated were detectable, and the chemical speciation was preserved. Sample analysis was accomplished in a matter of seconds, and limits of detection of 5 ng of uranyl nitrate, 10 ng of uranyl oxalate, 100 ng of uranyl chloride, and 200 ng of uranyl acetate were achieved. The observed gas-phase speciation was similar to negative-ion electrospray ionization of uranyl compounds with notable differences. Six matrix-derived ions were detected in all negative-ion mass spectra, and some of these ions formed adducts with the uranyl analyte. Subsequent analysis of the matrix suggests that these molecules are not matrix contaminants and are instead created during the ionization process.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

$β$-delayed-neutron studies of 135,136 Sb and 140 I performed with trapped ions

In this work, Beta-delayed-neutron $(βn)$ spectroscopy was performed using the Beta-decay Paul Trap and an array of radiation detectors. The $βn$ branching ratios and energy spectra for 135,136 Sb and 140 I were obtained by measuring the time of flight of recoil ions emerging from the trapped ion cloud. These nuclei are located at the edge of an isotopic region identified as having $βn$ branching ratios that impact the $r$-process abundance pattern around the A ≈ 130 peak. For 135,136 Sb and 140 I, $βn$ branching ratios of 14.6(13)%, 17.6(29)%, and 7.6(28)% were determined, respectively. The $βn$ energy spectra obtained for 135 Sb and 140 I are compared with results from direct neutron measurements, and the $βn$ energy spectrum for 136 Sb has been measured for the first time.

42 ENGINEERING↗
DOE OSTI2019

Front-end ASIC for spectroscopic readout of virtual Frisch-grid CZT bar sensors

Compact multi-channel radiation detectors rely on low noise front-end application specific integrated circuits (ASICs) to achieve high spectral resolution. Here, a new ASIC developed to readout virtual Frisch-grid cadmium zinc telluride (VFG CZT) detectors for gamma ray spectroscopy is presented. Corresponding to each ionizing event in the detector, the ASIC measures the amplitude and timing at the anode, the cathode and four pad sense electrodes associated with each sensor in a detector array. The ASIC is comprised of 52 channels of which there are 4 cathode channels and 48 channels which can be configured as either anode channels with a baseline of 250 mV or pad sense channels to process induced signals with a baseline of 1.2 V. With a static power dissipation of 3 mW, each channel performs low-noise charge amplification, high-order shaping, peak and timing detection along with analog storage and multiplexing. The overall channel linearity was better than ± 1% with timing resolution down to 700 ps for charges greater than 8 fC in the 3 MeV range. With a 4 × 4 array of 6 mm × 6 mm × 20 mm virtual Frisch-grid bar sensors connected and biased, an electronic resolution of ≈270 e - rms for charges up to 100 fC in the 3.2 MeV range was measured. Spectral measurements obtained with the 3D correction technique demonstrated resolutions of 1.8% FWHM at 238 keV and 0.9% FWHM at 662 keV.

3D↗
DOE OSTI2026

Study on Application of Distributed Network of Sensors with List Mode for NMAC Literature Review

Nuclear material accounting and control (NMAC) for nuclear security detects, deters, and resolves questions related to unauthorized removal (i.e. theft) or misuse of nuclear material. NMAC also serves as a key insider threat mitigation measure and aids in recovery of nuclear material that is missing. Effective nuclear security depends on NMAC for timely and accurate information about nuclear material types, quantities, and locations. Bulk nuclear material processing facilities, however, present unique challenges for effective NMAC due to the presence of large quantities of material in-process and the accumulation of residual material holdup within process equipment. These holdup accumulations can obscure accurate physical inventory taking and complicate efforts to resolve NMAC irregularities at the facility level. Bulk material monitoring systems often rely on material balance calculations and indirect measurement techniques, which may mask protracted theft of smaller amounts of nuclear material. These monitoring limitations have generated increased interest in continuous monitoring technologies, including distributed non-destructive assay (NDA) sensor networks capable of providing real-time or near-real-time measurement of material movement and accumulation within bulk processing environments. Recent advancements in distributed networks of NDA radiation detectors and sensing technologies provide an opportunity to address these limitations. Although such distributed sensor networks have been implemented in select facilities for IAEA Safeguards applications, their potential for supporting NMAC functions specifically tailored to nuclear security objectives remains largely unexplored. Furthermore, emerging list-mode data acquisition technologies have reached high technology readiness levels, enabling time-correlated detection of nuclear events across multiple temporal scales. These capabilities provide enhanced opportunities for accurate holdup measurement, continuous process monitoring, and improved detection of material theft or misuse over time. The increasing global expansion of civil nuclear power and development of related bulk material processing facilities, including those supporting high-assay low-enriched uranium (HALEU) and other advanced reactor fuel fabrication, further increases the need for advanced measurement and monitoring strategies for NMAC.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Application of Fireworks Algorithm in Gamma-Ray Spectrum Fitting for Radioisotope Identification

We present that identification of radioisotopic signature patterns in gamma-ray spectra is of paramount importance in various applications of gamma spectroscopy. Therefore, there are several active research efforts to develop accurate and precise methods to perform automated spectroscopic analysis and subsequently recognize gamma-ray signatures. In this work, the authors present a new method for radioisotope identification in gamma-ray spectra obtained with a low resolution radiation detector. The method fits the obtained spectrum with a linear combina-tion of known template signature patterns. Coefficients of the linear combination are evaluated by computing the solution of a single objective optimization problem, whose objective is the Theil-1 inequality coefficient. Optimization of the problem is performed by the Fireworks Algorithm, which identifies a set of coefficients that minimize the Theil-1 value. The computed coefficients are statistically tested for being significantly different than zero or not, and if at least one is found to be zero then the Fireworks Algorithm is used to reiterate fitting using the non-zero templates. Fitting iterations are continued up to the point that no linear coefficients are found to be zero. The output of the method is a list that contains the radioisotopes that have been identified in the measured spectrum. The method is tested on a set of both simulated and real experimental gamma-ray spectra comprised of a variety of isotopes, and compared to a multiple linear regression fitting, and genetic algorithm Theil-1 based fitting. Finally, results demonstrate the potentiality of the Fireworks Algorithm based method, expressed as higher accuracy and similar precision over the other two tested methodologies for radioisotope signature pattern identification in the framework of gamma-ray spectrum fitting.

Theil Coefficient↗
DOE OSTI2026

Enhanced sensitivity to trace 238 U impurity of sapphire via coincidence neutron activation analysis

Sapphire has mechanical and electrical properties that are advantageous for the construction of internal components of radiation detectors such as time projection chambers and bolometers. However, it has proved difficult to assess its 232 Th and 238 U content down to the picogram per gram level. Here, this work reports an experimental verification of a computational study that demonstrates 𝛾⁢𝛾 coincidence counting, coupled with neutron activation analysis (NAA), can reach ppt sensitivities. Combining results from 𝛾⁢𝛾 coincidence counting with those of earlier single-𝛾 counting based NAA shows that a sample of Saint Gobain sapphire has 232 Th and 238 U concentrations of <0.26 ppt and <2.3 ppt, respectively; the best constraints on the radiopurity of sapphire.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Enhanced Neutron and γ-Ray Detection via 6 Li Substitution in Undoped and Tl-Doped Zero-Dimensional Perovskite Cs 3 Cu 2 I 5 Scintillators

Radiation detectors are crucial in a wide variety of research and commercial applications, such as oil and gas exploration, medical imaging, nuclear nonproliferation, and homeland security. Neutron and gamma-ray detectors are fundamental components in portal monitors at ports and border crossings, bolstering national security against radiological threats. This study presents a dual-mode scintillator, undoped and Tl-doped 6 Li-Cs 3 Cu 2 I 5 , and demonstrates its potential as a promising material for simultaneous thermal neutron and gamma-ray detection. We explore the Bridgman growth of both undoped and thallium doped Li → Cu and Li → Cs substitutional systems with various Li doping levels and assess their impact on scintillation properties. Under 662 keV gamma-ray excitation, the undoped crystals had light yields up to 35,900 ph/MeV, with energy resolutions down to 4.5%. The Tl-doped crystals performed better than the undoped crystals with light yields peaking at 65,900 ph/MeV and energy resolutions as low as 3.5%. When exposed to a moderated 252 Cf excitation source, our crystals had light yields between 102,900 and 167,200 photons per thermal neutron capture, with a full energy thermal neutron peak reaching 3 MeV in gamma equivalent energy. Pulse shape discrimination studies reveal well-separated gamma and neutron events, resulting in Figure-Of-Merit (FOM) as high as 3.7. Furthermore, these findings highlight the potential of Li-doped Cs 3 Cu 2 I 5 as a viable candidate for next-generation dual-mode scintillators.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1972

Infrared response measurements on radiation-damaged Si/Li/ detectors.

The improved infrared response (IRR) technique has been used to qualitatively compare radiation effects on Si(Li) detectors with energy levels reported for silicon in the literature. Measurements have been made on five commercial silicon detectors and one fabricated in-house, both before and after irradiation with fast neutrons, 1.9-MeV protons, and 1.6-MeV electrons. Effects dependent upon the extent of radiation damage have been observed. It seems likely that the photo-EMF, or photo-voltage, effect is the basic mechanism for the observation of IRR in p-i-n diodes with a wide i-region. Experimental characteristics of the IRR measurement are in agreement with those of the photovoltage effect.

Sher, A. H.↗
DOE OSTI2012

Dose homogeneity specification for reference dosimetry of nonstandard fields

Purpose: To investigate the sensitivity of the plan-class specific correction factor to dose distributions in composite nonstandard field dosimetry. Methods: A cylindrical water-filled PMMA phantom was constructed at the center of which reference absorbed dose could be measured. Ten different TomoTherapy-based IMRT fields were created on the CT images of the phantom. The dose distribution for each IMRT field was estimated at the position of a radiation detector or ionization chamber. The dose in each IMRT field normalized to that in a reference 10 x 10 cm{sup 2} field was measured using a PTW micro liquid ion chamber. Based on the new dosimetry formalism, a plan-class specific correction factor k{sub Q{sub p{sub c{sub s{sub r,Q}{sup f{sub p}{sub c}{sub s}{sub r},f{sub r}{sub e}{sub f}}}}}} for each field was measured for two Farmer-type chambers, Exradin A12 and NE2571, as well as for a smaller Exradin A1SL chamber. The dependence of the measured correction factor on parameters characterizing dose distribution was analyzed. Results: Uncertainty on the plan-class specific correction factor measurement was in the range of 0.3%-0.5% and 0.3%-0.8% for the Farmer-type chambers and the Exradin A1SL, respectively. When the heterogeneity of the central region of the target volume was less than 5%, the correction factor did not differ from unity by more than 0.7% for the three air-filled ionization chambers. For more heterogeneous dose deliveries, the correction factor differed from unity by up to 2.4% for the Farmer-type chambers. For the Exradin A1SL, the correction factor was closer to unity due to the reduced effect of dose gradients, while it was highly variable in different IMRT fields because of a more significant impact of positioning uncertainties on the response of this chamber. Conclusions: The authors have shown that a plan-class specific correction factor can be specified as a function of plan evaluation parameters especially for Farmer-type chambers. This work provides a recipe based on quantifying dose distribution to accurately select air-filled ionization chamber correction factors for nonstandard fields.

62 RADIOLOGY AND NUCLEAR MEDICINE↗