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This study introduces an X-ray imager that uses TlBr detectors and demonstrates its potential for X-ray imaging applications. Although TlBr detectors are suitable for X-ray imaging applications because of the associated large attenuation coefficients and direct conversion behavior, realizing a flat-panel detector with TlBr involves developing processes. The proposed imager is constructed utilizing a combination of existing technologies; it comprises a plate electrode containing thallium metal to suppress the polarization phenomenon, pixelated silver electrodes with $80~\mu \text{m}$ pitch, and a photon-counting-type readout integrated circuit (ROIC) that can work in the hole as well as electron collection modes. The modulation transfer function (MTF) of the imager is calculated based on the imaging results of an X-ray test chart, and the result corresponds to $180~\mu \text{m}$ sampling. Even though the imager is not designed specifically for TlBr detectors, the measured high-MTF shows the immense potential of TlBr detectors for X-ray imaging applications. In addition, the polarization phenomenon and its recovery effect through bias switching are confirmed to be similar to conventional detectors with large electrodes. The results of this study can motivate the development of flat-panel-detector processes optimized for TlBr detectors.

The site characterization around the Fukushima Daiichi nuclear power plant (FDNPP) was conducted to measure the dose rate of radioactive cesium using mobile gamma-ray spectrometry through a backpack survey based on a LaBr3(Ce) detector. Four sites were selected in the Fukushima prefecture with diverse dose rate levels in residence and non-residence areas. One reference site in Sendai city was also designated with a low dose rate in comparison with sites in the Fukushima prefecture. The ambient dose rate was distributed from several tens of dose rate to above 1 μGy h due to the radioactive cesium distributed on the ground of the Fukushima prefecture. To assess the dose rates of Cs and Cs using the backpack survey with a short acquisition time, a good correlation was identified between the dose rate of radioactive cesium and the gross count rate in specific regions of interest (ROIs) with gamma rays from radioactive cesium. The dose rates of Cs and Cs accounted for more than 25% of the ambient dose rate during the survey period. The ratio of the Cs dose rate to the Cs dose rate was shown to be about 30% for all survey sites.

This study demonstrates a result of polarization effect of an X-ray imager that uses TlBr detectors with silver small electrodes. Although TlBr detectors are suitable for X-ray imaging applications because of the associated large attenuation coefficients and direct conversion behavior, realizing a flat-panel detector with TlBr involves developing processes. The demonstrated imager is constructed utilizing a combination of existing technologies; it comprises a plate electrode containing thallium metal to suppress the polarization phenomenon, pixelated silver electrodes with 80 µm pitch, and a photon-counting-type readout integrated circuit that can work in the hole as well as electron collection modes. As a result, it was reconfirmed that the polarization phenomenon is a serious problem for small electrodes as well as for large electrodes. In addition, the polarization could have accelerated by high X-rays flux. This result can motivate the development of polarization-tolerant small electrodes for TlBr detectors.

Semiconductor detectors for PIXE applications were fabricated using TlBr crystals. The TlBr detectors had a multiple-electrode detector design to minimize the pulse-height loss due to hole trapping. Electrodes containing thallium metal were employed for the TlBr detectors to suppress the polarization phenomena. Energy resolutions of 2.4, 3.3, and 3.8 keV FWHM for 5.9, 22.1, and 59.5 keV photons, respectively, were obtained for a TlBr detector operating at −50 °C.

Ground-based gamma-ray spectrometry using a LaBr3(Ce) detector was conducted to assess radioactive cesium deposition in soil contaminated by the accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in Japan. Five sites, including a reference site with relatively low contamination, were selected as having different levels of ambient dose rate due to significant effects of radioactive fallout of 134Cs and 137Cs. According to ICRU Report 53, the radioactivity in the ground and dose rate at 1 m above the ground were determined from the measured net count rates of gamma-rays induced from radioactive cesium. Because the radioactivity and dose rate depended on the depth profile of radioactive cesium in the ground, a database of possible radioactivity and dose rate could be established according to several depth distributions. A new approach to estimate the depth profile was then developed by directly calculating dose rates of 134Cs and 137Cs at the same geometry through dose rate spectroscopy and comparing them with the database of possible dose rates of radioactive cesium. Once the depth profile was determined, radioactivity was estimated from the database depending on the depth profile in the ground. The activity ratio between two radioactive cesium was shown to average about 0.112, in December 2017. It was in good agreement with the originally same released amount of 134Cs and 137Cs at the time of the FDNPP accident, when physical decay correction was applied to the results of the radioactivity assessment.

We developed a 20[Formula: see text]MeV particle-induced X-ray emission (PIXE) analysis method using a medical cyclotron, which is conventionally used for positron emission tomography analysis performed in vacuo, during which the target sample is damaged. For non-destructive analysis and ease of switching between target samples, we developed a technique allowing 20[Formula: see text]MeV proton PIXE analysis to be performed at the atmospheric pressure. We filled the PIXE analysis chamber with helium and checked that the continuous background of the Compton tails of nuclear reaction [Formula: see text]-rays increased only minimally, and that the quasi-free electron bremsstrahlung (QFEB) did not increase at all, in the X-ray energy spectrum.

For the first time, particle-induced X-ray emission (PIXE) spectra were obtained using TlBr detectors. The TlBr detector was fabricated from a crystal grown with material purified by the zone purification. Its active volume was 1.5 mm × 1.5 mm × 3.1 mm, and it exhibited an energy resolution of a 6.2 keV full-width at half-maximum (FWHM) for 59.5 keV at room temperature. The detector was installed into a PIXE system at Aomori Prefecture Quantum Science Center. A Pb plate target in the PIXE chamber was irradiated with a 20 MeV proton beam, and X-ray peaks for Pb K[Formula: see text] and K[Formula: see text] were successfully detected by the TlBr detector at room temperature.

An optical fiber-based neutron detector can be used as a real-time neutron monitor for an intense neutron field. In this study, optical fiber-based neutron detectors were fabricated using Li-glass scintillator. The thermal neutron sensitivity, upper limit of the output linearity, and response to gamma rays from 60Co and Cd were evaluated. The thermal neutron sensitivity was proportional to the mass of the Li-glass scintillator, and the calibration factor was 2.06 × 10^-6 and 3.18 × 10^-6 cps/(n/cm 2/s)/g for the lower-level discrimination of the peak and valley channel, respectively. The detector output linearity was confirmed to be up to nearly 2 Mcps. While evaluating the response to gamma rays, for both 60Co and Cd, the gamma-ray counting rate was found to be smaller than the uncertainty associated with counting statistics in most expected applications where the neutron counting rate was >1 kcps.

Compound semiconductor detectors such as CdTe, CdZnTe, HgI2 and TlBr are known to exhibit large variations in their charge collection times. This paper considers the effect of such variations on the measurement of induced charge pulses by using resistive feedback charge-sensitive preamplifiers. It is shown that, due to the finite decaytime constant of the preamplifiers, the capacitive decay during the signal readout leads to a variable deficit in the measurement of ballistic signals and a digital pulse processing method is employed to correct for it. The method is experimentally examined by using sampled pulses from a TlBr detector coupled to a charge-sensitive preamplifier with 150 μs of decay-time constant and 20 % improvement in the energy resolution of the detector at 662 keV is achieved. The implications of the capacitive decay on the correction of charge-trapping effect by using depth-sensing technique are also considered.

We explored whether medical positron emission tomography (PET) cyclotron proton beams could be used for proton-induced X-ray emission (PIXE) analysis. The beam current of the medical PET cyclotron is high, as required for radioisotope production, and is not commonly used for PIXE analysis. We successfully extracted stable proton beams of low intensity by using the ion source of a medical cyclotron to exploit proton impurities in deuteron gas. We performed 20-MeV PIXE analysis of a biological sample (used tea leaves). Elements lighter than Sr could be detected with high sensitivity ([Formula: see text]14 ppm) using a silicon drift detector. We thus showed that a medical cyclotron widely used for PET diagnosis could be employed for PIXE analysis of biological samples.

To estimate the applicability of thiodiglycolamide-type extractant-impregnated adsorbents to separation of the platinum group metals (PGMs) from high-level liquid waste, radiation effects on the adsorption behavior of PGMs onto a macroporous silica-based (Crea-TOA)/SiO 2 -P absorbent and on the stability of the adsorbent were investigated by using γ-rays emitted from 60 Co, and the results were compared with those obtained using (MOTDGA-TOA)/SiO 2 -P. A difference in adsorption behaviors of PGMs onto the two adsorbents was not observed with or without irradiation up to 100 kGy of the absorbed dose. Decomposition of the impregnated extractants and degradation of the adsorption capability increased with increasing absorbed dose, but the distribution coefficient of Pd remained >10 2 up to approximately 250 kGy. The retention ratio of loaded PGMs gradually decreased with increasing absorbed dose. From these results, the adsorbents were considered to be useful for the adsorption of PGMs irrespective of whether the adsorption system was irradiated, except for when the adsorbent was irradiated by a very large dose.

TlBr based photon-counting imaging device has been developed by using our photon-charge counting ASIC. TlBr of 0.8mm-thick wafer was used for detector, and it was pixelized as 80um pitch pixel. Tl based electrode was deposited on TlBr surface as common electrode and Ag electrodes were used as pixelized electrode. The ASIC has 32 x 32 pixels with 80um pitch, 16 thresholds, upto 250kcps of count rate by fully digital processing. This ASIC treat generated charge by detector directly, it can be applied CdTe, TlBr and so on. We detected X-ray / gamma-ray signals. We demonstrate X-ray / gamma-ray images taken by this device and discuss with energy discrimination property and so on.

Ground-based gamma-ray spectrometry using a LaBr

We fabricated Tb3+-doped Li2O–Al2O3–B2O3 glasses using 6Li or n Li and 10B or 11B (6Li–10B glass, 6Li–11B glass, nLi–10B glass, and nLi–11B glass) to develop a new thermoluminescent (TL) material for neutron detection and investigated the TL properties of these glasses after X-ray, He ion, and neutron irradiation. TL glow peaks were observed at 350 and 550 K after X-ray irradiation, at 390 and 550 K after He ion irradiation, and at 400 and 600 K after neutron irradiation. The TL intensities around 400 K for 6Li–10B glass, 6Li–11B glass, and n Li–10B glass after neutron irradiation were higher than that of n Li–11B glass, suggesting that the particles generated in 6Li(n, t)4He and 10B(n, α)7Li reactions efficiently induce TL. We observed neutron-induced TL in the range 1 × 107–5 × 108 neutrons cm−2, and the detectable minimum thermal neutron fluence of this glass was estimated to be approximately 4 × 106 neutrons cm−2.

Double-sided strip detectors were fabricated from thallium bromide (TlBr) crystals grown by the traveling-molten zone method using zone-purified materials. The detectors had three 3.4-mm-long strips with 1-mm widths and a surrounding electrode placed orthogonally on opposite surfaces of the crystals at approximately 6.5×6.5 mm2 in area and 5 mm in thickness. Excellent charge transport properties for both electrons and holes were observed from the TlBr crystals. The mobility-lifetime products for electrons and holes in the detector were measured to be ~3×10−3 cm2/V and ~1×10−3 cm2/V, respectively. The 137Cs spectra corresponding to the gamma-ray interaction position were obtained from the detector. An energy resolution of 3.4% of full width at half maximum for 662-keV gamma rays was obtained from one “pixel” (an intersection of the strips) of the detector at room temperature.

The oxidation behavior of chromium and the corrosion behavior of austenitic stainless steel in boiling nitric acid solution containing highly concentrated nitrates were investigated using UV-visible spectroscopic measurements, Raman spectral measurements, immersion tests, and potentiodynamic polarization measurements. The oxidation rate measurement of chromium from Cr(III) to Cr(VI) was performed by 1 M boiling nitric acid solution containing each highly concentrated nitrates: Al(NO3)3, Nd(NO3)3, Ca(NO3)2, Mg(NO3)2, and NaNO3 as a simulant of uranium nitrate in uranium concentrator in reprocessing plants. As a result, the rate of chromium oxidation was different depending on the added nitrates even at the same nitric acid concentration. In addition, the oxidation rate of chromium was increased with increasing the calculated partial pressure of nitric acid in consideration of the hydration of cation of nitrates. Furthermore, the corrosion rate of type 310 stainless steel was accelerated by the solu...

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.

The average ionization energy required to excite an electron-hole pair in TlBr was estimated to be $5.50 \pm 0.05~\hbox{eV}$ by comparing the peak position of 59.5-keV gamma rays obtained from four pixels of a pixelated TlBr detector to the peak position obtained from a Si PIN photodiode at room temperature.

Basic properties of a silica-based macroporous N’,N’-di-n-hexyl-thiodiglycolamide (Crea) extraction resin, (Crea+Dodec)/SiO2-P were examined. This extraction resin was synthesized by impregnating Crea and its modifier, n-Dodecyl alcohol (Dodec) into the macroporous SiO2-P support with a mean diameter of 50 μm. Adsorption behavior of platinum group metals (PGMs) and some fission product elements from simulated high level liquid waste onto the resin was investigated by batch experiment. It was found that (Crea+Dodec)/SiO2-P extraction resin exhibited good adsorption selectivity for PGMs over other tested elements in 0.1-5.0 M HNO3 solution. This resin showed strong affinity to Pd(II) especially in a short contact time but almost no adsorption for rare earth elements. Adsorption behavior of PGMs in experiment could be expressed by the Langmuir monomolecular layer adsorption mode. Meanwhile, adsorption results were fitted well with the pseudo-second order model and the rate-controlling step of this adsorption...

We investigated the relationship between the corrosion of austenitic stainless steel (R-SUS304ULC) and the redox behavior of chromium in nitric acid solution under three conditions – boiling at atmospheric pressure, boiling at reduced pressure, and non-boiling – to evaluate the effects of the boiling phenomenon. In the Cr(III) oxidation rate measurement, about 20% of the Cr(III) was oxidized to Cr(VI) under atmospheric-pressure boiling at 384 K after 168 h. Under non-boiling conditions at 373 K, Cr(VI) was not observed. However, about 3% of Cr(III) oxidation was observed at 373 K with reduced-pressure boiling. Thermodynamic calculations showed that the abundance of Cr(VI) in boiling nitric acid was increased over that in non-boiling nitric acid, even at the same temperature. These results show that Cr(III) is more likely to oxidize under boiling conditions than non-boiling conditions. On the other hand, in the corrosion tests, we found that the apparent reduction rate of Cr(VI) as a result of corrosion of...

A 4.36-mm-thick pixelated thallium bromide (TlBr) detector with Tl electrodes was fabricated from a crystal grown by the traveling molten zone method using zone-purified material. The detector had four 1×1 mm2 pixelated anodes. The detector performance was characterized at room temperature. The mobility-lifetime products of electrons for each pixel of the TlBr detector were measured to be >2.8×10−3 cm2/V. The four pixelated anodes of the detector exhibited energy resolutions of 1.5–1.8% full width at half maximum (FWHM) for 662-keV gamma rays for single-pixel events with the depth correction method. An energy resolution of 4.5% FWHM for 662-keV gamma rays was obtained from a reconstructed energy spectrum using two-pixel events from the two pixelated anodes on the detector.

Thallium-bromide (TlBr) is a viable alternative to CZT for room-temperature gamma ray spectroscopy because of its high atomic number, high density, and wide band-gap. Sub-1% FWHM energy resolution at 662 keV has been achieved on 5 mm thick pixelated devices, however, these results are mostly limited to stable operation at −20°C. During room-temperature operation, the devices degrade and fail, a phenomenon known as polarization. Polarization is likely caused by bulk-to-contact interactions facilitated by ionic conduction. In 2008, Hitomi et al. found that room-temperature lifetime could be extended by applying Tl electrodes. In this work we verify stable room-temperature performance of a 4.1 mm thick pixelated TlBr detector with Tl electrodes. Energy resolution, mobility-lifetime product, and resistivity are characterized and presented. Resolutions of 1.6% and 1.2% FWHM are achieved for all depths and cathode-side events only, respectively. A very high electron mobility-lifetime product is calculated: 3.1±0.2 ·10-2 cm2/V.

As fundamental research for separation of platinum group metals (PGMs) from high level liquid waste (HLLW) by macroporous silica-based adsorbent, (MOTDGA-TOA)/SiO2-P adsorbent was prepared by impregnation of N,N′-dimethyl-N,N′-di-n-octyl-thiodiglycolamide (MOTDGA) and Tri-n-octylamine (TOA) into silica/polymer composite support (SiO2-P). The adsorption behavior of Ru(III), Rh(III), and Pd(II) in simulated HLLW onto the adsorbent were investigated by the batch method to obtain their corresponding equilibrium and kinetic data. The adsorbent showed strong adsorption for Pd(II) and the adsorption reached equilibrium within 2 hr. High distribution coefficient (K d) values for Pd(II) were obtained in 0.1–1 M HNO3 concentration. In addition, the use of both MOTDGA and TOA improved adsorption of Ru(III) and Rh(III) better than individual use of them. Especially, the K d value for Ru(III) towards (MOTDGA-TOA)/SiO2-P adsorbent was three times larger than that in the adsorption using only with MOTDGA or TOA as extra...

Thallium bromide (TlBr) has been regarded as candidate detector materials for the gamma-ray spectrometers operating at room temperature. In this study, a simple and rapid method, the filter method, was performed to purify a raw TlBr material used for fabrication of TlBr detectors. The material was loaded on shards of crashed quartz and installed in a Pyrex tube, and was melted using a furnace. A purified material passing through interspaces of the shards of quartz was collected in a quartz ampoule located at the outlet of the Pyrex tube. After the purification, impurities colored black extracted from the raw material remained. TlBr crystals were then grown by the travelling molten zone method both from the raw material and the purified material. TlBr detectors were fabricated from the grown crystals, and were characterized by measuring mobility-lifetime products (μτ) for carriers and gamma-ray spectra ( 137Cs) at room temperature. μτ for electrons of a TlBr detector fabricated from the purified material was around 5 times higher than that of a detector fabricated from the raw material.

To separate minor actinides from high level liquid waste (HLLW) of PUREX reprocessing, a silica-based macroporous isobutyl-BTP/SiO2-P adsorbent was synthesized by impregnating isobutyl-BTP (2,6-di(5,6-diisobutyl-1,2,4-triazin-3-yl)pyridine) extractant into the macroporous SiO2-P support with a mean diameter of 60 μm. A partitioning process using extraction chromatography for the treatment of HLLW was designed consisting five separation columns. As a partly work focused on isobutyl-BTP/SiO2-P separation column, adsorption behavior of 241Am and trivalent rare earth (RE) from simulated HLLW onto silica-based isobutyl-BTP/SiO2-P adsorbent was investigated by batch method. Meanwhile, the chemical and radiolytic stabilities of isobutyl-BTP/SiO2-P adsorbent against 0.01 M HNO3 solution and γ-ray irradiation were studied. It was found that isobutyl-BTP/SiO2-P adsorbent exhibited good adsorption selectivity for 241Am over RE(III) in 0.01 M HNO3 solution and showed weak or no adsorption affinity to light and middle RE(III) groups. In addition, in stability experiments, isobutyl-BTP adsorbent showed excellent stability against 0.01 M HNO3 solution and γ-ray irradiation over 4 months contact time.

Thallium bromide (TlBr) is a promising compound semiconductor for fabrication of gamma-ray detectors. The attractive physical properties of TlBr lie in its high photon stopping power, high resistivity and good charge transport properties. Gamma-ray detectors fabricated from TlBr crystals have exhibited excellent spectroscopic performance. In this paper, advances in TlBr radiation detector development are reviewed with emphasis on crystal growth, detector fabrication, physical properties and detector performance.

The timing performance of TlBr detectors was evaluated at room temperature (22 °C). 0.5-mm-thick planar TlBr detectors with Tl circular electrodes with a diameter of 3 mm were fabricated from TlBr crystals grown by the traveling molten zone method using a zone-purified material. The pulse rise time of the TlBr detector was measured using a digital oscilloscope as the cathode surface of the device was irradiated with a 22Na gamma-ray source. Coincidence timing spectra were obtained between the TlBr detector and a BaF2 scintillation detector when both detectors were irradiated with 511 keV positron annihilation gamma-rays. The timing resolution of the TlBr detector was found to be inversely proportional to the applied bias voltage. The TlBr detector, in coincidence with the BaF2 detector, exhibited timing resolutions characterized by a 6.5 ns full width at half maximum (FWHM) and an 8.5 ns FWHM with and without an energy window of 350 keV-560 keV, respectively.

Capacitive Frisch grid detectors with the dimensions of 2 mm × 2 mm × 4.4 mm were fabricated from TlBr crystals grown by the travelling molten zone method using zone-purified materials. Spectroscopic performance of the detectors was evaluated at room temperature (24°C), - 5°C and - 20°C. The TlBr detector exhibited an energy resolution of 1.6% FWHM at 662 keV with a peak-to-Compton ratio of 8.7 with the depth correction at room temperature. Improvement of the detector performance was achieved by cooling the detector-preamplifier system. The energy resolutions of 3.4%, 1.5%, 1.0% and 0.9% FWHM at 122 keV, 356 keV, 662 keV and 1332 keV, respectively, were recorded with the TlBr detector without the depth correction at - 5°C. An energy resolution of 0.9% FWHM at 662 keV with a peak-to-Compton ratio of 18.2 was obtained from the TlBr detector with the depth correction at -20°C. An upper limit for the Fano factor of TlBr was estimated to be 0.43 at -20°C.

To separate (90)Y from the fission product (90)Sr-(90)Y group, a silica-based TODGA/SiO(2)-P adsorbent was prepared by impregnating N,N,N',N'-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) extractant into the macroporous SiO(2)-P support with a mean diameter of 60 μm. The adsorption behavior of Sr(II) and Y(III) onto TODGA/SiO(2)-P adsorbent from HNO(3) solution and their mutual separation were investigated. Under the experimental conditions, this adsorbent showed high adsorption affinity to Y(III) and weak adsorption to Sr(II). It was found that the adsorption process of Y(III) could be expressed by both of Langmuir monomolecular layer adsorption mode and the pseudo-second order model. From the results of stability experiments, it became clear that TODGA/SiO(2)-P adsorbent is stable in 3M HNO(3) solution for 1 month contact time at 298 K. Using a column packed with TODGA/SiO(2)-P adsorbent, Sr(II) and Y(III) were eluted by distilled water and diethylenetriamine pentaacetic acid (DTPA) solution, respectively. The separation of Y(III) from Sr(II)-Y(III) group was achieved successfully.