Many scintillator materials are used as a single crystal with high transparency, and their production and research have been driven by the development of crystal growth techniques. Therefore, we have developed various advanced crystal growth techniques for material research of novel scintillator materials and implementation of scintillators. In this presentation, I will talk about developments of novel scintillators with advanced crystal growth techniques including shape-controlled scintillators, halide scintillators with hygroscopicity and high melting point scintillators.

Currently, NONE of the existing alpha detection methods can be tested directly in water or in real-time due mainly to the limitation of the detector material itself as well as associated device design. These existing detector technologies all require some form of evaporation, sample preparation as well as laboratories test procedures in the lab, which is not practical for time-critical situations as in war-fare environment or future threads. In this work, we report the development of a novel scintillation detector material and its associated device design, the SiPM-based Hg2Br2 scintillation detector that can directly detect gross alpha in drinking water in the field, and in real-time while being wearable as needed. This novel detector does not require test sample preparation, environmental and health safe, and can be practically used in low radioactivity scenarios. It is also simultaneously capable of detecting other forms of nuclear radiation and having excellent radiation hardness

The characterization of elpasolite (Cs,Tl)2LiLaBr6:Ce (CTLLB) scintillator performance before and after sequential gamma irradiation exposure studies was performed. The crystal was subjected to irradiation four times at dose rates of 1, 10, 100 and 1000 Gy of absorbed dose in a 60Co irradiation, for a cumulative dose rates of 1, 11, 111 and 1,111 Gy. Initial results show a decreased measured light yield after each radiation exposure. Other measurement results and possible factors affecting these results will be presented.

We grow the Cs3Cu2I5:Tl and Cs3Cu2I5:Ag crystals with the Bridgman crystal growth method and studied luminescence and scintillation properties.

This study explores Cs3Cu2I5 perovskite crystals for gamma-ray detection, grown via inverse temperature crystallization. Formic acid inhibits ion oxidation, ensuring optimal sample sizes. Cleaning with dimethyl sulfoxide and dimethylformamide enhances conditions. A 10 × 10 × 6 mm3 crystal, covered with an ESR cap, couples to a photomultiplier tube for energy spectrum measurement. Scintillation light, digitized and analyzed, yields 15.1% and 12.5% energy resolutions for 22Na and 137Cs sources. UV-Vis-NIR spectrometer measurements reveal superior optical performance at 85.1%, surpassing other scintillators. This study presents a promising outcome, offering valuable insights for future research in various fields.

The Lunar Vulkan Imaging and Spectroscopy Explorer (Lunar-VISE) mission consists of a suite of instruments to explore the Gruithuisen Domes located in the northern lunar hemisphere. One of instruments to be mounted on a rover is a gamma ray and neutron spectrometer. The spectrometer uses a Li-6 enriched Cs26LiYCl6 (CLYC) scintillator to detect both gamma rays and neutrons. The design of the instrument balances mass, power and performance to obtain high-quality gamma ray spectroscopy with a 6.4-cm diameter, CLYC crystal encased in a gadolinium shell to veto thermal neutrons. To obtain a measure of the thermal neutron albedo to assess the concentration of local neutron moderating materials, a 5.0-cm diameter CLYC without a gadolinium shell is used to measure the full spectral, neutron flux. To minimize power, the system design utilizes a multi-channel configuration to provide pulse shape analysis and spectroscopy using a single, readout channel.

We report on the on-orbit performance of the Glowbug instrument, which operated on the International Space Station from March 2023 to April 2024. Glowbug is a NASA APRA funded instrument built by NRL, and is the pathfinder instrument for the upcoming NASA StarBurst Multi-messenger Pioneers mission. Glowbug was launched to the ISS on the 27th Commercial Resupply Services mission operated by SpaceX (SpX-27) as part of the Department of Defense Space Test Program H9 pallet. Glowbug’s primary science objective is the detection and localization of short GRBs, which are the result of mergers of stellar binaries involving a neutron star with either another neutron star or a black hole. Detection is enabled by 12 large area CsI scintillator panels, arrayed on the surface of a half cube. Each panel is read out on one edge by a 1x21 array of onsemi J-series 6mm x 6mm SiPMs. Additionally, within the half cube, resides two inorganic scintillators, CLLB, and a small plastic scintillator on the exterior used as an SAA entry and exit detector. We discuss the Glowbug on-orbit results for one year’s worth of data, in terms of on-orbit operations, SiPM performance in LEO and GRB detections.

The operation of nuclear instruments in high-radiation environments is critical for a myriad of applications, which include intense particle beams for future science experiments, in-situ measurements for emerging and advanced nuclear fuel cycles, or operation in a diverse range of environmental and harsh radiation conditions for military applications. A common tool used to measure ionizing radiation is scintillation materials, which produce a light pulse with an intensity proportional to the energy deposited, where a photodetector is used to measure the light pulse. A photodetector sensitive enough for scintillator readout is the photomultiplier tube, yet these devices are typically bulky. Though SiPMs, formed from an array of single photon avalanche photodiodes, or Geiger photodiodes (GPD), are replacing photomultiplier tubes, they are susceptible to radiation damage. This work discusses new technologies of GPDs consisting of GaAs and AlGaAsSb for operation in intense radiation and environmental conditions.

The Remote Sensing Laboratory – Andrews (RSLA) initiated an advanced robotic systems feasibility study project under the Site Directed Research and Development (SDRD) in 2023. Two prototype systems with radiation detection sensors were developed and tested for use in the forensics investigation of debris produced from explosively dispersed radioactive materials. To automate the robots, an Arduino microcontroller was added, and instead of reading signals directly from the radio control receiver, the system takes signals from the motor controller. The robots can be programmed to drive various search and survey patterns. Mapping results obtained by deploying this robotic system will be presented.

Explosive devices typically consist of several common materials, most of which have differing densities. When these materials are imaged through x-ray imaging, the resultant image displays differing contrast intensities within due to the scattering effects of these materials. These intensities provide shape and definition to the operator conducting the imaging, informing their decision making as to parts and components within the suspected device. A power source the size of a battery, or a piece of shrapnel, such a ball bearing, would have a noticeably different appearance than that of plastic explosives. The purpose of this research is to enhance single sided Compton Backscatter Imaging (CBI) of suspected explosive devices to support operators investigating a suspected device. Previous research by the team at UF in material discrepancy utilized Modulation Transfer Functions (MTF) derived from bar patterns of decreasing size to characterize a linear detector array and determine the maximum resolution in a CBI configuration.

The Nuclear Imaging System at the National Ignition Facility (NIF) collects primary and downscattered neutron, x-ray, and gamma-ray images of inertial confinement fusion implosions. Penumbral and pinhole-projection images are recorded using scintillators coupled to fast-gated intensified cameras. Successful reconstruction relies on accurate characterization of the imaging system sensitivity, which can vary by up to a factor of 2 across the field of view. Historically, this has been accomplished by using NIF shots without the aperture to uniformly illuminate the detector, or to project onto it a grid pattern from a fiducial plate to correct for detector sensitivity and optical system aberrations, respectively. However, frequent changes to the imaging system due to equipment failures or vibrations within the building have increased the need for calibrations, which are limited in availability to approximately once per year because they require sacrificing imaging data on a neutron-producing shot. We present development work on an optical calibration system that will enable the collection of this data without that requirement promptly, easily, and at regular intervals.

Micro-channel plate (MCP) detectors have long been a workhorse for space-based x-ray research and are advantageous over other imaging detectors because of their low size, weight and power. The Lunar Environment heliospheric x-ray Imager (LEXI), will utilize a MCP to image Earth’s magnetosphere in soft x-rays from the lunar surface. A critical element for interpreting on-orbit data is to understand the quantum detection efficiency (QDE) of the MCP. LEXI’s MCP is coated with potassium bromide (KBr) to increase the soft x-ray QDE. Historically, few measurements of QDE exist in the soft x-ray band for KBr detectors. This paper reviews the performance of LEXI’s detector, and the QDE experiment procedure conducted at and results from the Advanced Light Source synchrotron soft x-ray beam line. A unique beam line setup was required to limit the photon flux as to not saturate the pores of the MCP or detector signal chain. The experimental results are similar to previous literature, with some caveats unique to this MCP and experimental setup.

Semiconductor radiation detectors with high sensitivity at high energies have been mainly developed, but there is a need for semiconductor detectors with sensitivity at low energies, such as 30 keV or lower. We have been developing semiconductor detectors using CdTe, but CdTe has low sensitivity at low energies due to its K-absorption edge. We propose gallium nitride (GaN) as a new semiconductor detector material, which has higher sensitivity than CdTe in the low-energy region of about 10 to 26 keV used in mammography, etc. GaN has a large band gap, which enables room-temperature operation with low thermal noise. GaN has been shown to have excellent charge transfer characteristics, which has been demonstrated in LEDs and power devices, and its excellent properties as a semiconductor detector material can be used in low energy applications such as mammography. In this study, we fabricated a GaN semiconductor radiation detector with a vertical structure, evaluated its basic characteristics, and discussed future detection design guidelines.

Silicon carbide (SiC), particularly the 4H-SiC polytype, is a maturing wide bandgap semiconductor that has been shown to be an optimal material for high performance electronics in extreme environments. Conventional semiconductor radiation detectors have been shown to have limited performance above room temperature, with loss of sensitivity and degradation of detector resolution due to increase in electronic noise. The wide bandgap (3.27 eV) of 4H-SiC and the variable active region of Schottky barrier diodes produce a device capable of maintaining a lower-level of electronic noise, even at elevated temperature. We fabricated 4H-SiC Schottky barrier diodes and evaluated their electrical parameters using current-voltage (I-V) and capacitance-voltage (C-V) measurements. The I-V and C-V measurements were performed at elevated temperatures up to 500 °C at 100 °C increments. Electrical performance was also measured at room temperature following each thermal cycle. Energy spectroscopy performance of the devices was also measured following each thermal cycle. Detector characteristics such as resolution and peak channel were compared following thermal cycles.

While defects are known to inhibit device level performance, research shows specific spin defects resulting from silicon vacancy, carbon vacancy, or divacancy in SiC are alternative platforms to NV center in diamond for quantum sensing. Multiple 4H-SiC Schottky barrier diodes (SBD) were in-house fabricated and irradiated with 241Am alpha particles to a total accumulated fluence between 1×1013-1×1014 cm-2 over about 2-years low dose irradiation at room temperature. These irradiated devices, after annealing, were electrically characterized using I/V and C-V measurements and electron paramagnetic resonance (EPR) spectroscopy for the concentration of electronic active traps, atomic and electronic structure. The EPR spectroscopy shows that alpha irradiation induces changes in the properties of paramagnetic sites in 4H-SiC. Differences include increased line width and distorted line shape in irradiated samples, suggesting changes in relaxation behavior. Slight differences in g-values suggest possible changes in the paramagnetic sites due to irradiation.

Quantum sensing utilizes the inherent sensitivity of a quantum system to external stimuli. Our goal is to leverage this sensitivity to develop a quantum sensor designed for the detection of ionizing radiation. Here we report on the design, fabrication, and measurement of a new quantum device for hard x-ray and gamma-ray detection. Our quantum device is based on a superconducting quantum bit (qubit) with superconducting tunnel junctions as the core device elements. We describe our experimental investigation directed toward the detection metrics of energy resolution, dynamic range, and active area. In contrast to existing superconducting detectors, the active area per qubit may be much larger than the physical area of the tunnel junctions or the physical area of the qubit device, due to the sensitivity of quantum coherence to ionizing radiation deposition within a radius on the millimeter or centimeter scale. Our experimental design enables an ionizing radiation source at room temperature to be detected by our quantum sensor at low temperature.

Simulations and surgical aids using mixed reality are attracting attention in the medical field. Data captured by such as x-ray CT and MRA in advance is often rendered in 3D and displayed on HMD devices, but due to differences in rendering thresholds and the information displayed being different from the MPR images, it is difficult to grasp the internal structure of the body with only rendered data. In this study, the representation method that uses the camera see-through function of the HMD to generate a two-dimensional MPR image in real time according to the bed position and viewpoint direction was proposed. This enables the practitioner to check the MPR image from the same viewpoint from which they view the patient and comprehend the body's internal structure.

X-ray fluorescence imaging (XFI) is a non-invasive technique enabling key applications such as pharmacokinetic studies and immune cell tracking. Labeling with medium to heavy elements enables detection by excitation with hard X-rays and subsequent measurement of emitted characteristic radiation. XFI provides high spatial resolution, high sensitivity and provides quantitative data. Special requirements need to be fulfilled by the X-ray detectors to reach a high sensitivity. These include high energy resolution, detection efficiency, large active area, and throughput, while minimizing noise from internal detectors effects. Here we discuss recent XFI applications in preclinical imaging and experiences with various detector types.

A comparative analysis of the ¹³⁷Cs isotope spectra measured both by single and series-connected Cr/CdTe/Au diodetype X/γ-ray detectors has been conducted. Rectifying (Cr) and ohmic (Au) contacts were respectively formed on the Band A-faces of detector-grade CdTe(111) crystals after Ar plasma surface processing. The diode sandwiches (stacks) were created by staking and connecting in series two Cr/CdTe/Au Schottky diodes with similar parameters. A key feature of the ¹³⁷Cs isotope spectra obtained from these sandwiches was the presence of two peaks with maxima and energy positions (channel numbers) depending on the CdTe crystal thickness and relative positions of the diodes in the sandwich. The sum of channel numbers corresponding to these peaks equaled the channel number of the peak in the spectrum obtained by a single diode. Even when Cr/CdTe/Au diodes of different thicknesses were used in the sandwich, the sum of the channel numbers corresponding to two peaks in the ¹³⁷Cs spectra remained constant. The heights (maxima) of the two peaks were much higher than the peak height the spectrum measured by a single diode. The series-connected Cr/CdTe/Au Schottky diodes detected X/γ-rays much more effectively than a single detector at a bias voltage equal to half that applied to the sandwich. Another advantage of the diode sandwiches was the time stability of their characteristics. The ¹³⁷Cs isotope spectrum degraded during 8 hours of measurement by a single detector, while no noticeable changes were found in detection efficiency and energy resolution when the sandwich detectors were used.

Room temperature semiconductor detectors provide high energy resolution in gamma-ray spectroscopic applications, such as radioisotope identification. Materials such as TlBr and CsPbBr3, which provide ~2% FWHM, or better, energy resolution for 662-keV photopeak from Cs-137 irradiation at room temperature and high stopping power, nevertheless exhibit mixed electronic and ionic conduction that can lead to undesirable performance degradation. While the charge pulses generated by the gamma-ray interaction and a component of the leakage current are composed of a dominant electronic signal, the ionic component contributes to the current. It affects device stability via the migration of ionic species under applied bias and polarization at the semiconductor-electrode interface, interfering with charge collection. In this work, we characterize electronic and ionic conduction in single-crystal devices of TlBr and CsPbBr3 (CLB) using ionically blocking electrodes. The ionic contribution to the leakage current is evaluated from the devices' impedance spectra. In contrast, the electronic contribution is extracted from the asymptotic limit of the devices' current-voltage-time (iVt) plots for different bias values. The response to illumination with a 375-nm LED is also measured in the iVt plots. This work presents expressions for the temperature dependence of the conductivity, referencing previous work for TlBr. It also presents the gamma-ray spectra's bias dependence and evaluates ionic conduction's role in device burn-in, conditioning, and aging processes. Comparing the impedance spectra with and without LED illumination confirms that ions represent the majority charge carrier at room temperature for TlBr and CLB, which is consistent with previous work.

The electro-physical properties of Cd_0.96Mn_0.04Te_0.96Se_0.04 n-type conductivity single crystals with relatively low resistivity were studied. The determined resistivity of semiconductor single crystals Cd_0.96Mn_0.04Te_0.96Se_0.04 n-type conductivity is equal to ρ≈2 Ω-cm at 293K. The activation energy of dark conductivity, measured from the temperature dependence of the resistivity of the In/Cd_0.96Mn_0.04Te_0.96Se_0.04/In structure, is equal to ΔE≈0.11eV. From optical measurements of the absorption coefficient from the energy of photons in the region of large α, the band-gap width of the single crystal was found, which is equal to E_g=1.53eV. Diode structures of Ni/Cd_0.96Mn_0.04Te_0.96Se_0.04/In obtained by vacuum sputtering of Ni on the surface of a single crystal n-Cd_0.96Mn_0.04Te_0.96Se_0.04 were manufactured and studied. The rectification coefficient at a voltage of U=1V is equal to 10⁸. Within the framework of the Sah-Noys-Shockley carrier generation-recombination model, a quantitative match of the experimental measurements of the volt-ampere characteristics with the calculation was achieved.

The melting behavior of CsPbBr₃ perovskite was studied by differential thermal analysis (DTA). It was found that melting of CsPbBr₃ occurs non-isothermally in the temperature range of 561 to 570 °C. From the temperature dependence of the solid-phase melting rate, it was established that at 567±1 °C the change in the mechanism of the solid-phase melting goes from fragmentation to dissolution at the surface. The obtained values of the activation energy of the melting of the solid phase in CsPbBr₃ show that the activation energy of the dissolution of the solid-phase fragments is 4 times greater than the energy of the fragmentation of the solid phase.