Ge Semiconductor Detector Research Articles

Through-Plane Cerium Ion Migration and Diffusion Analysis on Plymer Electrolyte Membrane by Operando X-Ray Fluorescence Spectroscopy

High durability is a critical requirement for expanding the use of polymer electrolyte fuel cells (PEFCs). One degradation factor of PEFCs under typical operating conditions is electrolyte membrane degradation. Radical species formed from the reaction between hydrogen peroxide and impurities during fuel cell operation cause significant degradation of the PEM. To scavenge the radicals, cerium species are added to the PEM, which react with the radicals by redoxing the cerium ion [1]. To maintain the effectiveness of the cerium radical quencher in the PEM, the concentration of cerium in the PEM must be maintained during the long-term operation of the PEFC. However, cerium species easily diffuse and migrate out of the PEM [2]. If the cerium ion is depleted, the PEM will be severely attacked by radicals. To prevent such cerium depletion, it is important to understand the cerium migration phenomena. Experimental detection of cerium distribution phenomena through PEM by operando X-ray fluorescence spectroscopy with resolution of several micrometers has been reported [3]. We have also developed operando XRF using focused micron X-ray with submicrometer resolution [4]. In this study, we further develop the analysis method for cerium diffusion through planar PEM with sub-second time resolution. This method is used to estimate the apparent diffusion coefficient of cerium in PEM.MEAs were prepared by a conventional method using a Pt/C catalyst and a cerium-containing polymer electrolyte with a thickness of 12 μm(GORE-SELECT® MEMBRANEM788.12). The active electrode area was 1.0 cm2. Single cells were assembled using custom end plates with an X-ray permeation window. Operando X-ray fluorescence spectroscopy measurements were performed on BL37XU at SPring-8 (Japan). The monochromated X-ray at an energy of 45 keV was focused to less than 500 nm by a Kirkpatrick-Baez mirror. To detect the cerium distribution in MEA, the fluorescence intensity of Ce-Kα was counted with a Ge semiconductor detector by scanning the position of the cell.In the open circuit condition, most of the cerium is present in the PEM, but during cell loading, the cerium moves to the cathode layer. Immediately after the start of 2.0 A cm-2 loading, the intensity of cerium in the cathode layer increases in a few seconds. Simultaneously, a cerium concentration gradient is observed through the MEA. The cerium concentration gradient shows the current density dependence. When the current load is stopped, the concentrated cerium in the catalyst layer diffuses into the PEM. The diffusion coefficient of cerium ion is estimated from the time dependence of cerium concentration in PEM.Acknowledgments: This work is based on results obtained from the project commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan. E. Endoh et al, ECS Electrochem. Lett., 2, F73 (2013).S. M. Stewart et al, ECS Electrochem. Lett., 3, F19 (2014).A. M. Baker et al, ECS Trans., 92, 107 (2019).Y. Orikasa et al, ECS Trans., 109 109 (2022).

Non‐destructive elemental analysis of lunar meteorites using a negative muon beam

AbstractWe report the result of a non‐destructive elemental analysis of lunar meteorites using a negative muon beam at J‐PARC. An experimental system of six Ge semiconductor detectors and a newly designed He analysis chamber (to enable quantitative analysis of Al) was used to provide a high signal‐to‐noise ratio for the detection of major elements from lunar rocks (Mg, Si, Fe, O, Ca, and Al). We performed a Monte Carlo simulation to determine the chemical compositions at two sides and the center of a sample (at depths of 0.33 and 0.96 mm below the sample surface, respectively) of the lunar meteorite DEW 12007. These results indicate that the three interior regions of DEW 12007 are likely to be 55.8:44.2, 51.4:48.6, and 54.4:45.6 wt% mixtures of anorthositic and basaltic clasts, respectively. This study is the first quantitative analysis of a heterogeneous meteorite interior using a negative muon beam. As elemental analysis using a muon beam is non‐destructive and highly sensitive to light elements, including C, N, and O, the protocols established in this study are applicable to initial characterization of returned samples from the South Pole of the Moon.

Development of Nondestructive Elemental Analysis System for Hayabusa2 Samples Using Muonic X-rays

The concentrations of carbon and other major elements in asteroid samples provide very important information on the birth of life on the Earth and the solar-system evolution. Elemental analysis using muonic X-rays is one of the best analytical methods to determine the elemental composition of solid materials and, notably, is the only method to determine the concentration of light elements in bulk samples in a nondestructive manner. We developed a new analysis system using muonic X-rays to measure the concentrations of carbon and other major elements in precious and expectedly tiny samples recovered from the asteroid Ryugu by spacecraft Hayabusa2. Here we report the development process of the system in 4 stages and their system configurations, The analysis system is composed of a stainless-steel analysis chamber, an acrylic glovebox for manipulating asteroid samples in a clean environment, and Ge semiconductor detectors arranged to surround the analysis chamber. The performance of the analysis system, including the background level, which is crucial for the measurement, was greatly improved from the first stage to the later ones. Our feasibility study showed that the latest model of our muonic X-ray analysis system is capable of determining the carbon concentration in Hayabusa2’s sample model with an uncertainty of less than 10% in a 6 day measurement.

Operando X-Ray Fluorescence Measurement Method of Cerium Radical Quencher Distribution in through-Plane MEA

Hydroxyl and hydroperoxyl radicals produced by reacting impurities with hydrogen peroxide is one of the degradation factors of polymer electrolyte [1]. A method to suppress this degradation is the addition of cerium into the polymer electrolyte membrane (PEM), which serves as radical quencher [2,3]. However, cerium ion in PEM migrates from the initial state by fuel cell operation [4]. The lack of cerium ion in PEM causes degradation from radical species. Information on cerium migration in PEM is necessary to design the membrane electrode assembly (MEA) for long-term operation. Although the observation of cerium ion diffusion with in-plane direction of PEM has been reported [5], it is difficult to detect the distribution in through-plane of MEA under fuel cell operating condition due to the quite narrow thickness of PEM. This study reports an operando X-ray fluorescence analysis technique to detect cerium distribution in through-plane direction of MEA using high-energy X-ray nanobeam.MEAs were prepared by a conventional method using Pt/C catalyst and polymer electrolyte with the thickness of 12 mm. The active electrode area was 1 cm2. Single cells were assembled using custom-made end-plates that have an X-ray permeation window. Operando X-ray fluorescence spectroscopy measurements were performed at SPring-8, BL37XU (Japan). The monochromatized X-ray at an energy of 45 keV was focused to less than 200 nm by Kirkpatrick-Baez mirror. To detect the cerium distribution in MEA, Ce-Ka fluorescence intensity was counted using a Ge semiconductor detector with scanning the position of the cell. The cell temperature was 80 ℃. O2 and H2 gases with relative humidity of 100% were flew to cathode and anode, respectively.Figure 1 shows line-scan profile of Ce-Kα fluorescence X-ray intensity from the as-prepared MEA. The x-axis represents the through-plain position, where the positive and negative sides corresponds to cathode and anode sides, respectively. The two peaks are observed at 678 and 685 mm and the peak width is approximately 13 mm. This peak shows PEM containing cerium ion. During the fuel cell operation, the line-scan is repeated and cerium ion distribution can be analyzed. Acknowledgment Part of this work is based on results obtained from the project commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.[1] R. Borup et al., Chem. Rev., 107 3904-3951 (2007).[2] E. Endoh et al., ECS Electrochem. Lett. 2 F73-F75 (2013).[3] P. Trogadas et al., Electrochem. Solid-State Lett. 11 B113-B116 (2008).[4] S.M. Stewart et al., ECS Electrochem. Lett. 3 F19-F22 (2014).[5] A.M. Baker et al., J. Electrochem. Soc. 164 F1272-F1278 (2017). Figure 1

Use of Clay Minerals to Control Radioactive Cesium Leaching from Municipal Solid Waste Incineration Ash in Fukushima Prefecture in Summer and Winter

Radioactive cesium (r-Cs) released from the 2011 Fukushima Daiichi Nuclear Power Plant attaches to vegetation/soil and is collected as municipal solid waste (MSW) for incineration, being concentrated in incineration ash (bottom ash [BA], fly ash [FA], and chelate-treated FA [TFA]). r-Cs in FA and TFA can easily leach upon contact with moisture. It is important to prevent further contamination, as r-Cs has negative effects on ecosystems and the human body. Naturally available clay minerals, considered effective for capturing r-Cs, are a good alternative. Here, we sampled ash from MSW incineration facilities in Fukushima in August 2016 and February 2017. We used energy dispersive X-ray fluorescence spectroscopy and Ge semiconductor detector to determine elemental composition and r-Cs concentration in the samples and conducted leaching tests. We also determined the extent of leaching suppression by zeolite, acidic clay, and vermiculite. Chloride contents and r-Cs leaching rates were higher in FA and TFA than in BA, regardless of the season. Prior direct addition and mixing of clay minerals (5 to 20 wt.%) effectively prevented r-Cs leaching. This study is the first to examine r-Cs leaching inhibition by clay mineral direct addition and mixing to MSW incineration ash.

Neutrinoless Double Beta Decay with Germanium Detectors: 1026 yr and Beyond

In the global landscape of neutrinoless double beta (0νββ) decay search, the use of semiconductor germanium detectors provides many advantages. The excellent energy resolution, the negligible intrinsic radioactive contamination, the possibility of enriching the crystals up to 88% in the 76Ge isotope as well as the high detection efficiency, are all key ingredients for highly sensitive 0νββ decay search. The Majorana and Gerda experiments successfully implemented the use of germanium (Ge) semiconductor detectors, reaching an energy resolution of 2.53 ± 0.08 keV at the Qββ and an unprecedented low background level of 5.2×10−4 cts/(keV·kg·yr), respectively. In this paper, we will review the path of 0νββ decay search with Ge detectors from the original idea of E. Fiorini et al. in 1967, to the final recent results of the Gerda experiment setting a limit on the half-life of 76Ge 0νββ decay at T1/2>1.8×1026 yr (90% C.L.). We will then present the LEGEND project designed to reach a sensitivity to the half-life up to 1028 yr and beyond, opening the way to the exploration of the normal ordering region.

In-situ determination of residual specific activity in activated concrete walls of a PET-cyclotron room

In the decommissioning work for concrete walls of PET-cyclotron rooms, an in-situ measurement is expected to be useful for obtaining a contour map of the specific activity on the walls without destroying the structure. In this study, specific activities of γ-ray-emitting radionuclides in concrete walls were determined by using an in-situ measurement method employing a portable Ge semiconductor detector, and compared with the specific activity obtained using the sampling measurement method, at the Medical and Pharmacological Research Center Foundation in Hakui, Ishikawa, Japan. Accordingly, the specific activity could be determined by the in-situ determination method. Since there is a clear correlation between the total specific activity of γ-ray-emitting radionuclides and contact dose rate, the specific activity can be determined approximately by contact dose-rate measurement using a NaI scintillation survey meter. The specific activity of each γ-ray-emitting radionuclide can also be estimated from the contact dose rate using a NaI scintillation survey meter. The in-situ measurement method is a powerful tool for the decommissioning of the PET cyclotron room.

Measurement of the activity and spectrum of internal bremsstrahlung of a 51Cr source

The activity of the 51Cr source in the BEST experiment searching for sterile neutrinos is planned to be determined by measuring the spectrum of internal bremsstrahlung. The measurements of activity and the spectrum of internal bremsstrahlung of point low-activity 51Cr sources with Ge semiconductor detectors are discussed. The accuracy and errors of this measurement method are examined.

High Energy Gamma-Ray Spectroscopy Using Transition-Edge Sensor With a Superconducting Bulk Tantalum Absorber

We are developing transition edge sensor with a superconducting high-Z metal bulk absorber for high energy resolution spectroscopy of hard X-ray and gamma-ray within 100 keV ~ 1 MeV. We applied a bulk tantalum absorber for it has low heat capacity and high absorption efficiency to high energy photons. As a result of an experiment using gamma-ray from 137 Cs, an energy resolution that is better than that of Ge semiconductor detector was achieved at 662 keV. In addition, we demonstrated more than three times higher absorption efficiency to 662 keV photons compared to Sn absorber TES as previously reported elsewhere. From our rough calculation, it is estimated that the heat capacity of tantalum is increased than theory and that may be the limit factor of the energy resolution.

Isomeric and ground state energy level measurements of natural tellurium isotopes via (γ,n) reaction

We have planned to measure isomeric and ground state energy levels in 120Te(γ,n)119m,gTe, 122Te(γ,n)121m,gTe, 128Te(γ,n)127m,gTe, 130Te(γ,n)129m,gTe photonuclear reactions of natural tellurium induced by bremsstrahlung photons with end-point energy at 18 MeV. The sample was irradiated in the clinical linear electron accelerator (Philips SLi-25) at Akdeniz University Hospital. The gamma spectrum of the tellurium sample was measured using HP(Ge) semiconductor detector (ORTEC) and multi channel analyzer. We used both MAESTRO (ORTEC) and home made root based gui program (Theia) for data analyzing. The obtained experimental data values are compared with NUDAT energy values.

Russia and the US in the Cold War arms race

The perspectives Frank von Hippel gives on the end of the Cold War are illuminating, but I was surprised to learn (page 45) of an experiment conducted to detect “gamma rays from a warhead by means of a liquid-nitrogen-cooled high-purity germanium scintillation counter.” As is common knowledge in radiation detection and nuclear physics, high-purity germanium (HPGe) detectors are not scintillators, they are semiconductors. If one examines von Hippel’s reference 10, it’s clear the confusion may have arisen because, in addition to the use of both HPGe and lithium-drifted Ge, thallium-doped sodium iodide scintillators were also employed for gamma-ray detection. However, the principal analyses were based on measurements made with the Ge semiconductor detectors.© 2014 American Institute of Physics.

A study on the measurement and analysis of radioactivity concentration and the ambient dose rate in soil on the playgrounds of elementary schools in the Gwangju area

The aim of this study was to obtain nationwide basic data on the distribution of environmental radiation in normal times and to compare the characteristics and distribution in many areas. The data obtained can contribute to improve the radioactivity analysis technology, public health, and the environment in the future. Ten elementary schools in the Gwangju area were selected and soil samples were taken from the playgrounds of the selected schools for analysis. A high-purity Ge (HPGe) semiconductor detector, a multi-channel analyzer (MCA), and a FH40G dose rate detector were used to measure the radioactivity concentration of K-40 and Cs-137, and the ambient gamma dose rate. According to the measured radioactivity concentrations of 40K and 137Cs, the K-40 concentration (Bq/kg dry) was measured at 723.61 ± 162.72, which was higher than the minimum detection limit (MDL). The Cs-137 concentration (Bq/kg dry) measured was 0.203 ± 0.023, which was lower than the MDL. FH40G was used to measure the ambient gamma dose rate (nSv/h) in different areas. According to the measurement results, the ambient gamma dose rate was 176.73 ± 4.91. With regard to the correlation between the ambient gamma dose rate and radioactivity concentrations of 40K and 137Cs, 40K showed a correlation coefficient with Cs-137 and the ambient gamma dose rate of −0.36 and 0.124, respectively. 137Cs revealed a correlation coefficient of 0.293 with an ambient gamma dose rate of −0.210. In conclusion, the low correlation coefficient (<0.5) indicates no significant correlation between the ambient dose rate measurements of K-40 and 137Cs.

Study of the isomeric ratios in photonuclear reactions of natural indium induced by bremsstrahlungs with end-point energies in the giant dipole resonance region

We have determined the isomeric ratios in 113In(γ, n)112m,g In and 113In(γ, 2n)111m,g In photonuclear reactions of natural indium induced by bremsstrahlungs with end-point energies in the giant dipole resonance (GDR) region. The investigated samples were irradiated at the electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, Dubna. The gamma spectra of the samples irradiated were measured with a spectroscopic system consisting of an 8192-channel analyzer and a high-energy resolution (180 keV at gamma ray 1332 keV of 60Co) HP(Ge) semiconductor detector Canberra. The GENIE2000 (Canberra) computer program was used for data processing. The results were discussed and compared with those of other authors. For both the mentioned reactions, the isomeric ratios in the bremsstrahlung energy range from 19 to 24 MeV in this work are new measurements.

The Kaguya gamma-ray spectrometer: instrumentation and in-flight performances

A Gamma-Ray Spectrometer (GRS) had been developed as a part of the science payload for the first Japanese lunar explorer, Kaguya. The Kaguya was successfully launched from Tanegashima Space Center on September 14, 2007 and was injected into an orbit around the Moon and the mission ended on June 11, 2009. The Kaguya GRS (hereafter KGRS) has a large-volume Ge semiconductor detector of 252 cc as the main detector and bismuth-germanate and plastic scintillators as an active shielding. The Ge detector achieved an energy resolution of 3.0 keV (FWHM) for 1332 keV gamma ray in ground test despite the use of a mechanical cryocooler and observed gamma rays in energies ranging 0.2 to 12 MeV in lunar orbit. It was the first use of a Ge detector for lunar exploration. During the mission, KGRS participated in geochemical survey and investigated the elemental compositions of subsurface materials of the Moon. In this paper, we summarize the overview of the KGRS describing the design and in-flight performance of the instrument. This paper provides basic information required for reading science articles regarding the KGRS's observation data.

Searches for neutrinoless resonant double electron captures at LNGS

Several experiments were performed during last years at underground (3600 m w.e.) Laboratori Nazionali del Gran Sasso (LNGS) of the INFN, Italy; to search for resonant 2ε0ν captures in 96Ru, 106Cd, 136Ce, 156Dy, 158Dy, 180W, 184Os, 190Pt with the help of HP Ge semiconductor detectors, and ZnWO4 and 106CdWO4 crystal scintillators. No evidence for r-2ε0ν decays was found, and only T1/2 limits were established in the range of 1014 - 1021 yr.

Deposition of fission and activation products after the Fukushima Dai-ichi nuclear power plant accident

The Great Eastern Japan Earthquake on March 11, 2011, damaged reactor cooling systems at Fukushima Dai-ichi nuclear power plant. The subsequent venting operation and hydrogen explosion resulted in a large radioactive nuclide emission from reactor containers into the environment. Here, we collected environmental samples such as soil, plant species, and water on April 10, 2011, in front of the power plant main gate as well as 35 km away in Iitate village, and observed gamma-rays with a Ge(Li) semiconductor detector. We observed activation products (239Np and 59Fe) and fission products (131I, 134Cs (133Cs), 137Cs, 110mAg (109Ag), 132Te, 132I, 140Ba, 140La, 91Sr, 91Y, 95Zr, and 95Nb). 239Np is the parent nuclide of 239Pu; 59Fe are presumably activation products of 58Fe obtained by corrosion of cooling pipes. The results show that these activation and fission products, diffused within a month of the accident.

Early-Stage Bioassay for Monitoring Radioactive Contamination in Living Livestock

Soil samples from the ground surface and feces and blood from a mixed-breed male pig were collected on April 10, 2011 at a farm within 20 km of the Fukushima Daiichi nuclear power plant. The radioactivity of each sample was measured using a Ge semiconductor detector. Despite the fact that the pig had been fed non-contaminated imported feed, (131)I, (134)Cs and (137)Cs were detected in the feces, and (134)Cs and (137)Cs were detected in the blood clots. Because it is considerably difficult to measure radioactive contamination in the edible muscle of living livestock, bioassays are an option for the screening of radioactive contamination in living livestock to ensure food safety.

The isomeric ratios in photonuclear reactions of natural barium induced by bremsstrahlungs with endpoint energies in the giant dipole resonance region

We have determined the isomeric ratios in 113In(γ, n)112m,g In and 113In(γ, 2n)111m,g In photonuclear reactions of natural indium induced by bremsstrahlungs with end-point energies in the giant dipole resonance (GDR) region. The investigated samples were irradiated at the electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, Dubna. The gamma spectra of the samples irradiated were measured with a spectroscopic system consisting of an 8192-channel analyzer and a high-energy resolution (180 keV at gamma ray 1332 keV of 60Co) HP(Ge) semiconductor detector Canberra. The GENIE2000 (Canberra) computer program was used for data processing. The results were discussed and compared with those of other authors. For both the mentioned reactions, the isomeric ratios in the bremsstrahlung energy range from 19 to 24 MeV in this work are new measurements.

Study of the isomeric ratios in photonuclear reactions of natural holmium and lutetium induced by bremsstrahlungs with endpoint energies in the giant dipole resonance region

We have determined the isomeric ratios in 165Ho(γ, n)164m,gHo and 175Lu(γ, n)174m,gLu photonuclear reactions of natural holmium and lutetium induced by bremsstrahlungs with end-point energies in the giant dipole resonance (GDR) region. The investigated samples were irradiated at electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The gamma spectra of the samples irradiated were measured with spectroscopic system consisting of 8192 channel analyzer and high-energy resolution (180 keV at gamma ray 1332 keV of 60Co) HP(Ge) semiconductor detector Canberra. The GENIE2000 (Canberra) computer program was used for data processing. The results were discussed and compared with those of other authors.

The isomeric ratios in photonuclear reactions of natural tellurium induced by bremsstrahlungs with endpoint energies in the giant dipole resonance region

We have determined the isomeric ratios in 120Te(γ, n)119m,gTe, 122Te(γ, n)121m,gTe, 128Te(γ, n)127m,gTe and 130Te(γ, n)129m,gTe photonuclear reactions of natural tellurium induced by bremsstrahlungs with end-point energies in the giant dipole resonance (GDR) region. The investigated samples were irradiated at electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The gamma spectra of the samples irradiated were measured with spectroscopic system consisting of 8192 channel analyzer and high-energy resolution (180 keV at gamma ray 1,332 keV of 60Co) HP(Ge) semiconductor detector Canberra. The GENIE2000 (Canberra) computer program was used for data processing. The results were discussed and compared with those of other authors.