241Am Alpha Particles Research Articles

Modeling and simulation of a high power InGaP/GaAs heterojunction alphavoltaic battery irradiated by americium-241

The design of semiconductor-based heterojunction structures can be turned useful to raise the efficiency of nuclear micro-batteries. In this study, we have investigated a micro-power alphavoltaic battery by using a lab-made software. The nuclear battery consists of an In0.49Ga0.51P/GaAs heterostructure irradiated by americium-241 (Am241) alpha particles with an average kinetic energy of 5.485 MeV. The alphavoltaic battery exhibits an overall active area of 1 cm2. Based on a comprehensive analytical model, the device current density-voltage J(V) and output electric power P(V) characteristics are simulated extracting the energy conversion efficiency. The model takes into account the reflection of the incident alpha particles, the ohmic losses, the effect of the boundary between the two layers, and the depletion region borders. Different values of the radioisotope apparent activity density, the emitter and base dopant concentrations, and the surface recombination velocities in both the front and back layers are considered during the simulations to optimize the battery performance. The present study reports that by irradiating by a 2.4 mCi/cm2 Am241 source, the obtained energy conversion efficiency of the battery can reach 10.31% with a maximum output power density of 16.07 µW/cm2. Therefore, In0.49Ga0.51P/GaAs heterostructure coupled with Am241 seems a promising design for long-term energy supply in harsh environments.

Influence of high fluence heavy ion irradiation on the performance of single crystal diamond detectors

Radiation detectors based on diamond are highly favored for particle physics research due to their superior radiation hardness. In this work, the performance of single crystal diamond detectors under high fluence heavy ion radiation has been investigated. After irradiation by Fe13+ and Xe20+ ion beams with a high particle fluence of 1.2 × 1015 cm-2, the properties of unirradiated and irradiated intrinsic single crystal chemical vapor deposition (CVD) diamond detectors are compared by means of the spectroscopic energy resolution, charge collection efficiency (CCE), mobility-lifetime (μτ) product and time response using a 241Am alpha (α) particle source. The experimental results of the unirradiated sample with respect to I-V dark current levels, showed an ohmic behaviour of the Al and Cr/Au contact, CCE of 100%, fast response with a rise time of 750 ps and a fall time of 600 ps as well as drift velocities of 6.67 × 104 m/s and 4.72 × 104 m/s for holes and electrons respectively. In the case of the irradiated samples, the CCE, μτ product and time response pulse amplitude of holes and electrons were all degraded, indicating that high density trappings for both kinds of carriers were created under the diamond crystal surface and the trapping probability of holes and electrons was equal, which was different from the previous reports in the literature where only higher trapping probability of holes were observed under heavy ions irradiation. In particular, the spectroscopic performance as well as μτ product of holes and electrons in Fe13+ irradiated sample decreased more than those in Xe20+ irradiated sample, which implied that the recombination of electrons and holes increased in Fe13+ irradiated sample with greater penetration depth than that in Xe20+ irradiated sample when radiation fluence was up to 1015 cm-2, despite the lower density of lattice vacancies in Fe13+ irradiated sample. Moreover, the rise time of holes was slightly different, but the drift velocity was basically the same as that of the unirradiated sample, and so was that of the electrons. Anyway, the presented results showed that the diamond detectors irradiated by heavy ions at a high fluence of 1015 cm-2 still retained their good spectroscopic and very fast time response properties.

A diamond double-sided strip detector for alpha-tagging in associated particle imaging

- In associated particle imaging, neutrons from deuterium-tritium fusion are used to interrogate objects of interest. The associated particle imaging technique utilizes an alpha-tagging sensor in the neutron generator to detect the alpha particle that is emitted antiparallel to the neutron, providing neutron birth time and direction. This technique of neutron imaging and induced fission imaging can provide higher contrast image reconstructions and better estimations of fissile material mass than passive measurement techniques. The performance goals of an alpha-tagging sensor in associated particle imaging are a 700-ps timing resolution, a 0.5 mm spatial resolution, high level of radiation hardness, low sensitivity to X-rays, high signal-to-noise ratio, and survivability in the high temperature bake out of the neutron generator. Currently employed YAP scintillators are overwhelmed by the intense X-ray field in the neutron generator, requiring a new alpha tagging sensor design to be developed. We have developed and tested a diamond double-sided strip detector as a proposed sensor for associated particle imaging. Diamond is radiation hard, has a low sensitivity to X-rays, fast timing capabilities, high signal-to-noise ratio, and can withstand the temperatures of bake-out. The spatial resolution can be accomplished with a charge division readout and double-sided strip design. We measured the timing resolution of a single crystal chemical vapor deposition (CVD) diamond with a Cividec C6 charge amplifier readout by measuring the time-of-flight of 241Am alpha particles between a thin plastic scintillator and the diamond. We also fabricated a polycrystalline CVD diamond double-sided strip detector with charge division readout to test the spatial resolution of the design. We found that the detector met both the 700-ps timing resolution and the 0.5 mm spatial resolution goals (both reported as FWHM resolution).

Correlated ionisations in two spatially separated nanometric volumes within the track structure of 241Am alpha particles: comparison with Monte Carlo simulations

The production of two double strand breaks in spatially separated locations on the DNA molecule can cause the loss of a whole DNA loop. This loss, which can be of substantial length depending on the geometrical position of the two damaged sites, depends on the degree of correlation between ionisation clusters formed in sites of several nanometres in size. The first part of this paper reported on nanodosimetric measurements of alpha particle tracks in 1.2 mbar H2O, 1.2 mbar C3H8 and 1.2 mbar C4H8O with the PTB ion counter nanodosimeter. In this second part, the focus is on the geometrical characterisation of the two sites simulated with the nanodosimeter in the three target gases and on the comparison of the measurement results with Monte Carlo simulations. The measurements in 1.2 mbar C3H8 were simulated with PTra, a track structure code dedicated to modelling the PTB ion counter nanodosimeter. Further simulations were performed with Geant4-DNA for 241Am alpha particle tracks in liquid water. Simulations of the experiment were found to be in good agreement with the measurements for the investigated irradiation geometries.

Preliminary benchmarks and analysis of boundary conditions in a trenched microstructured silicon radiation detector

Microstructured neutron detectors have the benefit of enhanced neutron detection efficiency as compared to planar devices, achieved by etching 6LiF-filled trenches on the top surface of a silicon PIN diode. This sensor geometry results in a complex electric field distribution and depletion characteristics within the diode under reverse bias. For the first time on record, the effects of a fixed oxide charge on the microstructured device depletion characteristics and mobile carrier transport is investigated. Prototype detectors were fabricated with non-conformal surface doping. Capacitance voltage and current voltage measurements were performed for these prototypes and compared with COMSOL Multiphysics simulations. A spectral response from an 241Am alpha particle source was acquired and analyzed. It was found that monoenergetic alpha particles produce three prominent peaks in the pulse height spectrum output by the device. The peaks were confirmed by simulations to correlate with dead layers and incident trajectories into the microstructure. It was also found that significant differences in pulse rise time result, corresponding with events arriving in a low-field region in the fins and a high-field region in the bulk. Geant4 was utilized for radiation transport, interaction modeling, and benchmarking the spectral data. The results of this simulation work provide confidence in the ability to attain and benchmark electrical characteristics and spectral data for semiconductor radiation detectors employing complex microstructures.

SILICON CARBIDE NEUTRON DETECTOR PROTOTYPE TESTING AT THE JSI TRIGA REACTOR FOR ENHANCED BORDER AND PORTS SECURITY

In 2016, the “E-SiCure” project (standing for “Engineering Silicon Carbide for Border and Port Security”), funded by the NATO Science for Peace and Security Programme was launched. The main objective is to combine theoretical, experimental and applied research towards the development of radiation-hard SiC-based detectors of special nuclear materials (SNM), with the end goal to enhance border and port security barriers. Prototype neutron detectors, configured as 4H-SiC-based Schottky barrier diodes, were developed for the detection of secondary charged particles (tritons, alphas and lithium atoms) which are the result of thermal neutron reactions on 10B and 6LiF layers above the surface of the 4H-SiC diodes. We designed a stand-alone prototype detection system, consisting of a preamplifier, shaping amplifier and a multichannel analyser operated by a laptop computer, for testing of neutron detector prototypes at the Jožef Stefan Institute (JSI) TRIGA reactor using a broad beam of reactor neutrons. The reverse bias for the detector diode and the power to electronic system were provided by a standalone battery-powered voltage source. The detector functionality was established through measurements using an 241Am alpha particle source. Two dedicated experimental campaigns were performed at the JSI TRIGA reactor. The registered pulse height spectra from the detectors, using both 10B and 6LiF neutron converting layers, clearly demonstrated the neutron detection abilities of the SiC detector prototypes. The computed neutron detection sensitivity of the single prototype detectors demonstrates that scaling SiC detectors into larger arrays, of dimensions relevant for border and port radiation detectors, could enable neutron sensitivity levels matching gas-based detector technology.

Comparison of light outputs, decay times, and imaging performance of a ZnS(Ag) scintillator for alpha particles, beta particles, and gamma photons

ZnS(Ag) is a scintillator mainly used for alpha particle detection because of the high light output for alpha particles. However, the light output and decay times of ZnS(Ag) for beta particles or gamma photons are not obvious. We therefore measured and compared the light outputs and decay times of ZnS(Ag) for beta particles or gamma photons with that for alpha particles. We measured the pulse height distribution and decay times of ZnS(Ag) for Am-241 alpha particles (5.5 MeV), St-Y-90 beta particles (2.28-MeV maximum energy), and Cs-137 gamma photons (0.66 MeV). The relative light output/MeV for the beta particles and gamma photons was ~2%–~5% of that for alpha particles. Decay time for the beta particles and gamma photons was 2.7 ns–2.8 ns, while that for alpha particles was 61 ns. With the different decay times, pulse shape discrimination of the alpha and beta particles was possible for the ZnS(Ag) radiation-imaging detector. We confirmed that ZnS(Ag) is a suitable scintillator for the detection of alpha particles using energy discrimination as well as pulse shape discrimination.

Correlated ionisations in two spatially separated nanometric volumes in the track structure of 241Am alpha particles: Measurements with the PTB ion counter

The simultaneous occurrence of two double-strand breaks in spatially separated locations on the DNA molecule can cause the loss of a whole DNA loop. The length of the lost DNA loop depends on the geometrical position of the two damaged sites and on the degree of damage in sites of several nanometres in size. As they are more prone to produce complex ionisation clusters in such sites, densely ionising charged particles are expected to produce more spatially correlated ionisation clusters than electrons and photons. In this work, correlations in the production of ionisation clusters in two spatially separated sites were investigated for the first time in detail by nanodosimetric measurements in 1.2 mbar H2O, 1.2 mbar C3H8 and 1.2 mbar C4H8O using alpha particles from a 241Am source. The results show that there are irradiation geometries where only weak correlation exists between the probabilities for ionisation clusters in the two spatially separated sites, e. g. when the primary beam passes one site centrally. In general, however, the two probability distributions are not statistically independent, for instance if both sites are irradiated in a broad beam.

Energy straggling and an experimental investigation of Bragg's rule for 241Am alpha particles in air and its constituents

We present here energy straggling data for alpha particles from 241Am in air and its constituents, and an experimental investigation of Bragg’s rule. High resolution alpha spectroscopy system from ORTEC with an ultra-thin source, an ion implanted thin entrance window detector of small diameter, and state of the art counting electronics with a 4096 MCA is used. In the controlled experimental environment gases of 5N purity are used to measure energy straggling. Measured values are compared with the theoretical predictions of Bohr, Bethe-Livingston, Titeica and Yang et. al. An experimental investigation on using Bragg’s rule to estimate the energy straggling in air from the experimental obtained data of constituents is presented.

Scintillation and ionization yields of helium–xenon gas mixture for application in neutron detectors

The scintillation and ionization yields of helium–xenon gas mixture were measured using a gridded ionization chamber with 241Am alpha particles to study the potential of the mixture to be applied in neutron detectors. The ionization yields for various ratios of the mixture gases were obtained with gas pressures of 1.0, 0.657, and 0.100 MPa. The yield data were explained well using the ratio of the number of excited atoms to that of ionized atoms in helium, i.e. The scintillation yield increased with xenon partial pressure and saturated at 10% of the total pressure, while the ionization yield increased up to 1.59 times of the initial value for pure helium at 1% of the total pressure then gradually increased to 1.8 times. The helium gas with added xenon at 10% of its pressure was suggested as a medium of a neutron detector with signal readouts from both scintillation and ionization, since it increases the scintillation yield to more than 1.1 times of pure xenon and increases the ionization yield to more than increases 1.8 times of pure helium.

E-SiCure Collaboration Project: Silicon Carbide Material Studies and Detector Prototype Testing at the JSI TRIGA Reactor

In 2016, the ”E-SiCure” project (standing for Engineering Silicon Carbide for Border and Port Security), funded by the NATO Science for Peace and Security Programme, was launched. The main objective is to combine theoretical, experimental and applied research towards the development of radiation-hard SiC-based detectors of special nuclear materials (SNM), and by that way, to enhance border and port security barriers. Along the plan, material modification processes are employed firstly to study, and secondly to manipulate the most severe electrically active defects (which trap or annihilate free charge carriers), by specific ion implantation and defect engineering. This paper gives an overview of the experimental activities performed at the JSI TRIGA reactor in the framework of the E-SiCure project. Initial activities were aimed at obtaining information on the radiation hardness of SiC and at the study of the energy levels of the defects induced by neutron irradiation. Several Schottky barrier diodes were fabricated out of nitrogen-doped epitaxial grown 4H-SiC, and irradiated under Cd filters in the PT irradiation channel in the JSI TRIGA reactor with varying neutron fluence levels. Neutron-induced defects in the material were studied using temperature dependent current-voltage (I-V), capacitance-voltage (C-V) and Deep-Level Transient Spectroscopy (DLTS) measurements. Our prototype neutron detectors are configured as 4H-SiC-based Schottky barrier diodes for detection of secondary charged particles (tritons, alphas and lithium atoms) which are result of thermal neutron conversion process in 10B and 6LiF layers above the surface of the 4H-SiC diodes. For field testing of neutron detectors using a broad beam of reactor neutrons we designed a standalone prototype detection system consisting of a preamplifier, shaping amplifier and a multichannel analyser operated by a laptop computer. The reverse bias for the detector diode and the power to electronic system are provided by a standalone battery-powered voltage source. The detector functionality was established through measurements using an 241Am alpha particle source. Two dedicated experimental campaigns were performed at the JSI TRIGA reactor. The registered pulse height spectra from the detectors, using both 10B and 6LiF neutron converting layers, clearly demonstrated the neutron detection abilities of the SiC detector prototypes.

SiC based charged particle strip sensor spectrometer with neutron detection capability

Silicon carbide (SiC) devices have gained much attention owing to their superior characteristics that make them high-temperature and radiation-hard. The advantage of the SiC arises from its unique combination of electronic and physical properties such as a wide band-gap, high breakdown electric field strength, high saturated electron velocity, and high thermal conductivity. The wide band-gap results in a low intrinsic charge carrier concentration and a radiation hardness. The low intrinsic charge carrier concentration leads to low device leakages at high temperature. The high breakdown strength allows SiC devices to operate at much higher voltages. The aim of this publication is to present current status of a charged particle spectrometer based on a SiC strip detector. The sensor is made of a 4H-SiC (α-SiC) hexagonal crystalline structure material which manifests good spectroscopic characteristics for charged particle detection similar to a standard silicon diode (20 keV FWHM with 5,4857 MeV 241Am alpha particle). To obtain sensors for the charged particle detection out of the SiC bulk material we created Schottky contacts on the top and the Ohmic contact on the bottom. Preparation of the contacts will be discussed alongside the electric characterization of the sensor material. Results of the charged particle and the gamma detection and detection of thermal neutron detection (after a neutron converter deposition) will be presented. There will be also a discussion regarding fast neutron detection. The SiC sensor material was attached to a VATA GP8 based 128 strip readout to form the handheld spectrometer which will be demonstrated.

Primary and secondary bystander effect and genomic instability in cells exposed to high and low linear energy transfer radiations

Purpose: Non-Targeted effects (NTE), such as bystander effect (BE) and genomic instability (GI) challenge central dogma of radiation biology. Moreover, there is a need to understand its universality in different type of cells and radiation quality.Materials and method: To study BE (primary and secondary) and GI Human adult dermal fibroblast (HADF) and peripheral blood lymphocytes (PBL) were exposed to low fluence of 241Am alpha (α) particle and 6 MV X-ray. The BE was carried out by means of co-culture methodology after exposing the cells to both types of radiation and damage was measured using micronucleus assay (MN) and chromosomal aberration assay (CA) in the p1 cells while the GI was followed up in their progeny.Results: A dose-dependent increase in DNA damages (MN and CA) was observed in directly irradiated and bystander cells. The magnitude of BE was higher (6 fold) in cells co-cultured with the α-irradiated cells than that of with X-irradiated cells. Cross exposure of both cell types confirms that radiation induced BE is cell type dependent. In addition, induced DNA damage persisted for a longer population doubling in α-particle irradiated cells.Conclusion: This work adds evidence to secondary bystander response generated from primary bystander normal cells and its dependence to radiation quality.

The performance of 4H–SiC detector at high temperature after gamma irradiation

A 4H–SiC detector based on the Schottky diode was fabricated and the combined influence of high temperature and gamma irradiation on 4H–SiC detector has been investigated. We tested the detector's performance at high temperature before gamma irradiation. I–V characteristics and the alpha energy spectra were measured with the 4H–SiC detector before gamma irradiation at high temperature up to 200 °C. The leakage current of the 4H–SiC detector was only 98.7 nA at 200 °C and with a operating voltage of 70 V. The detector showed an energy resolution of 2.36% at 200 °C in detection of 241Am alpha-particles. Then the detector was irradiated by 60Co gamma-ray up to a dose of 1 MGy. I–V characteristics measurements and α energy spectrum measurements were also performed at 200 °C after each irradiation. Both the forward current and the reverse current increased after gamma irradiation. The Schottky barrier height was extracted from the forward I–V curves and it decreased by 0.17 V at a dose of 1 MGy. The response for 241Am source showed that the charge collection efficiency of the detector reduced by only 1.6% and the FWHM can be regarded as unchanged. It has been proved that 4H–SiC detector can work well at 200 °C after exposure to 60Co gamma-ray of 1 MGy.

Light particle spectroscopy using CR-39 detectors: An experimental and simulation study

CR-39 detectors have been irradiated with both 241Am alpha particles and protons in the energy range of 1.0–5.5 MeV and 0.8–2.8 MeV, respectively. The proton irradiation has been achieved through two different techniques: Rutherford Backscattering (RB) and Nuclear Reaction (NR). The detectors were chemically etched in a hot KOH solution for periods ranging from 0.5 h to 3 h for alpha particles and 2.5 to 5.5 h for protons. The track diameter variation as a function of particles energies and etching time has been studied. A new predictive model based on experimental track parameters has been developed for the studied particles and for variable bulk track etching velocities. This predictive model is based on a single parameter β determined by fitting our experimental data.

Direct and bystander effects in human blood lymphocytes exposed to 241Am alpha particles and the relative biological effectiveness using chromosomal aberration and micronucleus assay

Purpose: It is important to understand the significance of alpha (α) radiation-induced bystander effects (RIBE) and its relative biological effectiveness (RBE); this is because the phenomenon is not universal and the mechanism is unclear and because the RBE is widely varying and projected to be very high.Materials and methods: Isolated lymphocytes from healthy volunteers (n = 10) were exposed to either low fluence α-particles (241Am), γ-rays (60Co), or X-rays (225 kVp and 6 MV). Co-culture methodology was employed to investigate bystander effects (BEs). Chromosomal aberrations (CA) and micronucleus (MN) formation were used to study the BE and calculated RBE.Results: Lymphocytes directly exposed to the types of radiation used showed a dose-dependent increase in the frequency of CA and MN; dose independent increases in the frequency of these chromosomal damages in co-cultured bystander cells, implies that all three types of radiation-induced a BE. The calculated RBE at the level of 5% induced aberrations varied between 9 and 20.Conclusion: The magnitude of low fluence α-particle induced RIBE is higher than in low LET (linear energy transfer) radiation. The RBE also varies depending upon the endpoints used and adds up to targeted effects. Since the endpoint of CA is considered as an important and early marker of risk prediction, the RIBE and RBE using CA as a marker are relevant for radiation protection purposes.

A high resolution radiation imaging detector using a ceramic YGAG scintillator plate

Ce doped (YGd)3(GaAl)5O12:Ce (YGAG) is a ceramic scintillator originally developed for X-ray computed tomography (CT). It has high light output and is also a promising candidate for high resolution event-by-event radiation imaging detectors. Thus we developed a radiation imaging detector using a YGAG plate combined with a position sensitive photomultiplier tube (PSPMT) and evaluated the performance. The spatial resolution for Am-241 alpha particles (5.5 MeV) was ∼0.4 mm FWHM and the energy resolution was 12 % FWHM. The spatial resolution for Sr-Y-90 beta particles, Am-241 gammas (60 keV) and Cs-137 X-ray (∼35 keV) was 0.8 mm FWHM, 1.6 mm FWHM and 2.0 mm FWHM, respectively. The decay time difference of YGAG between 5.5 MeV alpha particles and 662 keV Cs-137 gammas was 37 ns and the pulse shape spectra for 5.5 MeV alpha particles and 662 keV Cs-137 gammas were separated without overlap with the figure of merit (FOM) of 1.14. It was possible to separate the alpha particle and gamma photon images using pulse shape discrimination. Using pulse shape discrimination, it was also possible to separate the alpha particles and gamma photons in the electrostatically collected radon daughters on the imaging detector. We conclude that the developed YGAG imaging detector is useful for high resolution radiation detector with pulse shape discrimination capability to discriminate the different types of radiations.

An ultrahigh spatial resolution radiation-imaging detector using 0.1 mm × 0.1 mm pixelated GAGG plate combined with 1 mm channel size Si-PM array

Spatial resolution of a pixelated scintillator-based radiation-imaging detector is sometimes limited by the pixel size of the scintillators. We developed a small-size pixelated GAGG scintillator using a dicing method and combined it with a small channel-size Si-PM array for the development of an ultrahigh resolution radiation-imaging detector. The developed pixelated GAGG scintillator had a pixel size of 0.1 mm × 0.1 mm arranged in 0.15-mm separations. It was combined with a Si-PM array made of 1 mm × 1 mm channels to form a radiation-imaging detector. With the developed radiation imaging detectors, the 0.1 mm × 0.1 mm pixels could be resolved for Am-241 alpha particles (5.5 MeV). The spatial resolutions of this imaging detector were better than 0.31-mm FWHM for Am-241 alpha particles and Ca-45 (maximum energy: 0.257 MeV) beta particles. The spatial resolutions for Am-241 gamma photons (60 keV) and Cs-137 X-ray (∼32 keV) were better than 0.6-mm FWHM. Separation of the images of alpha particles and gamma photons was possible using the scintillation decay time difference of GAGG between alpha particles and gamma photons. The developed ultrahigh spatial resolution pixelated GAGG radiation-imaging detector is promising for the imaging of alpha particles, beta particles, low-energy gamma photons and X-ray.

Evaluation of gamma-ray disturbing effect on readout of charged particle tracks using fluorescent nuclear track detectors (FNTDs)

In this study, we aimed to identify the reasons for track misrecognition caused by gamma-rays in the FNTD (fluorescent nuclear track detector) system. FNTDs were irradiated with fluence-controlled 241Am alpha-particles at 0°. The irradiated FNTDs were scanned by a commercial reader to obtain fluorescence images of uniform shape tracks and a reader-counted track density per unit area [mm−2]. The track density was good agreement with manually eye-counted track density. Then, the FNTDs irradiated with alpha-particles were additionally irradiated with 137Cs gamma-rays and scanned by the reader in order to monitor transition of the reader-counted track density with gamma dose. Track counting efficiency, which is defined as the reader-counted density divided by the eye-counted density, was reliable with until 33 mSv of gamma dose with ± 30% accuracy. However, with the higher dose of gamma-rays at 95 and 242 mSv, the efficiency fluctuated over the accuracy because of track misrecognition. To clarify the reasons for the track misrecognition, fluorescence track images were compared before and after gamma irradiations. On the fluorescence images with gamma-rays, the non-uniform signal caused by secondary electrons were observed (Sykora et al., 2010a). Especially with 242 mSv of gamma dose, the non-uniform signal formed “track-like” spots. To analyze the characteristics of the non-uniform signal, fluorescence intensity (FI) per pixel was analyzed for track and background (BG) areas separately. The FIs at both track and BG areas showed linearity to gamma dose. In the analysis of FI distributions, the fluctuation of FIs at BG area increased with gamma doses while the fluctuation of FIs at track areas did not change significantly. As a result, the difference of FI values between track and BG areas was smaller with the higher dose of gamma-rays. This phenomenon caused the difficulty of detecting tracks under gamma-ray exposure.

Evaluation of Antimony Tri-Iodide Crystals for Radiation Detectors

This study was carried out to examine the potential of antimony tri-iodide (SbI3) as a material for radiation detectors that operate at room temperature. SbI3 is a compound semiconductor with an AsI3-type crystal structure, high atomic number (Sb: 51, I: 53), high density (4.92 g/cm3), and a wide band-gap energy (2.2 eV). In addition, crystalline SbI3 is easy to grow by conventional crystal growth techniques from melting phase because the material exhibits a low melting point (171°C) and undergoes no phase transition in the range of its solid phase. In this study, SbI3 crystals were grown by the Bridgman method after synthesis of SbI3 from 99.9999% pure Sb and 99.999% pure I2. The grown crystals consisted of several large grains with red color and were confirmed to be single-phase crystals by X-ray diffraction analysis. SbI3 detectors with a simple planar structure were fabricated using the cleavage plates of the grown crystals, and the pulse-height spectra were recorded at room temperature using an 241Am alpha-particle (5.48 MeV) source. The detector showed response to the alpha-particle radiation.