Ge Detector System Research Articles

Developments of a new data acquisition system at ANNRI

A new data acquisition system (DAQ system) has been developed at the Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) facility in the Japan Proton Accelerator Research Complex, Materials and Life Science Experimental Facility (J-PARC/MLF). DAQ systems for both the Ge detector system and the Li-glass detector system were tested by using a gold sample. The applicability of the time-of-flight method was checked. System performance was evaluated on the basis of digital conversion nonlinearity, energy resolution, multi-channel coincidence and dead time.

Nuclear data study at J-PARC BL04

A project on nuclear data is being executed in Japan, and a beam line for nuclear data measurement is being developed at the materials and life science facility in J-PARC as a part of the project. Radiation shields, collimators, choppers, filters, etc. have been designed, and most of them have been made and installed at the beam line. A Ge detector system covering a large solid angle is being developed to measure neutron capture cross-sections of Cm isotopes and long-lived fission products in a neutron energy region from thermal to 100 keV. Most of the capture samples have been prepared. After testing the beam line, detector systems, etc. with the J-PARC neutron beam, the capture cross-section measurement will be started in 2009.

Development of multiple prompt gamma-ray analysis

In order to improve the limits of quantification for trace elements, we applied the multiple gamma-ray detection method in the prompt gamma-ray analysis (PGA). The Clover Ge detector system was constructed for multiple prompt gamma-ray analysis (MPGA) at the neutron guide hall of the JRR-3M reactor of the Japan Atomic Energy Agency (JAEA). The MPGA system consists of three Clover detectors and a BGO Compton suppressor. The instrumentation of the MPGA beam line and the detector system were developed. The estimated limit of quantification of cadmium in the plastic sample is approximately 0.1 ppm. The capability of the MPGA system could be improved by modification of the detector system, shield arrangement, software algorithm, etc.

Analysis of toxic elements by MPGA

In order to improve the sensitivity for the quantification of trace elements, we propose the combination of prompt gamma-ray analysis (PGA) and a multiple gamma-ray detection method. A new Ge detector system for multiple prompt gamma-ray analysis (MPGA) was constructed at the neutron guide-hall of the JRR-3M reactor of the Japan Atomic Energy Agency (JAEA). The first demonstration of this system was given with a plastic sample containing traces of cadmium. The quantification limit of cadmium in a plastic sample was found to be about 0.1 ppm.

Performance of a whole-body counter with five high-purity germanium detectors

A germanium (Ge) detector system has been installed in a whole-body counting facility at NIRS (Japan). The system employs five detectors that have relative efficiencies of more than 80%. A basic performance of the Ge detectors was tested and compared with that of the former NaI(Tl) detector system. Although the Ge detector system has advantages of improved radionuclide identification capability and MDA values, it also has disadvantages of high operation costs and demanding maintenance such as supply of liquid nitrogen.

Study of Radionuclides Induced in Low-activation Concrete Using the 12-GeV Proton Synchrotron Accelerator at KEK

Low-activation concrete made of limestone aggregates was irradiated by secondary particles in the beam-line tunnel of the 12-GeV proton synchrotron accelerator at KEK (12GeV-PS), and the radioactive concentrations induced in the concrete were measured using a Ge detector system. Although various radionuclides, such as 22Na, 24Na, 54Mn, 56Mn, 60Co and l52Eu, were induced in the low-activation concrete, those concentrations were below those induced in ordinary concrete made of non-limestone aggregates. Among the induced radionuclides, reducing the 24Na concentration is especially important for preventing the radiation exposures of radiation workers during the maintenance of an accelerator. In order to estimate the 24Na concentration induced in shielding concrete, chemical reagents such as NaHC03, MgO, A1203, Si02 and CaC03 were irradiated at several locations in the beam-line tunnel of the 12GeV-PS, and the 24Na concentrations induced in those chemical reagents were measured. Although the MgO concentration in limestone varies widely from 0.4% to 10% in each mine, the experimental results concluded that low-activation concrete made of limestone aggregates is useful for preventing the radiation exposure of workers as shielding concrete in a particle accelerator facility because the 24Na concentration induced in Mg is below that in Na. It was also confirmed that concentrations of long-lived radionuclides, such as 60Co and 152Eu, induced in the low-activation concrete were lower than those induced in ordinary concrete.

Deblurring of x-ray spectra acquired with a Nal-photomultiplier detector by constrained least-squares deconvolution.

A constrained least-squares technique to correct diagnostic x-ray tube energy spectra for inherent blurring by scintillation detectors was developed. The measured detector response function to monoenergetic sources was used to construct a matrix that modeled the energy broadening in the crystal. This blurring operator, along with an estimate of statistical noise in the count data, comprised the a priori system knowledge required for application of the method. Tungsten anode spectra up to 90 kVp were acquired with a Nal-photomultiplier detector system at a source-to-detector distance of 30 cm. X-ray tube output was collimated at the detector by a 0.5 mm diameter pinhole collimator. Measured Nal spectra were compared to both published reference data and to spectra acquired in our laboratory with a Ge detector system. Application of the constrained least-squares technique involved first defining a criterion function that combined an assessment of the goodness of fit with a weighted measure of the smoothness of the solution. Minimization of this function resulted in the corrected spectrum. While it is not possible to recover the characteristic tungsten peaks, the success of our method in deconvolving the measured spectra was demonstrated by a significant improvement in agreement with reference data. To provide a measure of this agreement, a histogram of the differences between the two curves was generated. The full width at half maximum (FWHM) of the Gaussian distribution fit to the histogram was used to quantify the similarity between the spectra and the reference data, both before and after correction. As spectral agreement improves, the FWHM becomes smaller. We show that application of the constrained least-squares technique improved spectral matching by 20%-60%.

K shell fluorescence yields for elements with 33⩽ Z⩽53 using 59.5 keV photons

K shell fluorescence yields for As, Se, Br, Rb, Sr, Zr, Nb, Mo Ru, Pd, Ag, Cd, In, Sn, Sb, Te and I are reported. The experimental values of the fluorescence yields were determined by measuring K X-ray fluorescence and incoherent scattered γ-ray spectrum induced by 59.5 keV photons employing a Ge(Li) detector system in a reflection geometry set-up. For measuring the K shell fluorescence yield, the intensity ratio of K X-rays to incoherently scattered γ-rays was used. For this reason, carbon was used as a scattering target. The experimental results are compared with literature experimental values, theoretical predictions, and semiempirical fits.

High-resolution gamma-ray spectroscopy of Λ7Li

We report on the first observation of hypernuclear γ transitions using germanium detectors. Using a large-acceptance Ge detector system, we observed two γ transitions in Λ 7Li, the spin-flip M1( 3 2 +→ 1 2 +) transition at 689±4keV and the E2( 5 2 +→ 1 2 +) transition at 2050±2 keV (preliminary). The strength of the ΛN spin-spin interaction is derived from the energy of the former transition. As for the latter transition, B( E2) was measured to be 3.9±0.6±0.4 e 2fm 4 (preliminary), which indicates a shrinkage of the nuclear size of Λ 7Li from 6Li and confirms “glue-like role” of Λ.

Search for evidence of nuclear involvement in the fatal explosion of a “cold fusion” experiment

Forensic analyses of debris from the fatal explosion of an electrochemical “cold fusion” cell at SRI International were conducted at LLNL at the request of Cal-OSHA. One investigation focused on the possibility of conventional nuclear reaction mechanisms contributing to the total energy inventory of the incident. Selected metal components of the electrolysis apparatus were subjected to nondestructive γ-ray spectrometry with high-sensitivity, low-background Ge detector systems. The anticipated analytes in these studies were radioactivation products potentially induced in the explosion residue by either fast or thermal neutrons. The results of this investigation were negative within the temporal constraints of the incident and the analytical sensitivities of the instrumentation.

Measurement of low-level radioactivity in the Modane underground laboratory

A coaxial high-purity n-type Ge detector system has been installed in the Modane underground laboratory for low-level monitoring of environmental samples. This laboratory is located near the mid-point of the thirteen-kilometer Fréjus road tunnel at the French-Italian border. The facility is shielded from cosmic radiation by 1700 m of rock (equivalent to 4400 m of water), thus cutting the background level by a factor of approximately 70 compared with the operating conditions of an equivalent system in a low-background counting room of the usual type. A high-purity germanium detector is used with a sensitive volume of 207 cm 3, 52% relative efficiency and FWHM resolution of 2.1 keV at 1332 keV. The detector is shielded by 15 cm of old lead and the detector hood and sample (up to 500 cm 3 in volume) are protected by an electrolytic copper shield to eliminate the influence of radon; the integrated count rate within the 20–2000 keV energy interval is 1.7 × 10 −2 s −1. The detector system has been used to monitor atmospheric gamma radioactivity, especially 137Cs and 134Cs. Radioactive aerosol particles are collected from the surface atmosphere onto cellulose filters, and these samples are stored in batches corresponding to a six-month period, before being calcined and dissolved in acid. The filtered air volume is approximately 450 000 m 3. Very low annual 137Cs concentrations between 1.5 × 10 −7 and 2.0 × 10 −7 Bq/m 3 were measured, while no 134Cs was detected in 1991 at Tahiti or Mururoa (less than 4 × 10 −8 Bq/m 3). A 134Cs concentration of 7 × 10 −8 Bq/m 3 was measured at Montlhéry, near Paris, in 1991.

RNAA of trace iridium in Precambrian-Cambrian boundary samples by thiourea type chelate resin separation

A RNAA procedure is described for the determination of trace Ir in Precambrian-Cambrian boundary samples. After irradiation, the powdered sample is transferred to a graphite crucible to expel the massive silicon with mixed acid (HF−HCl−HNO3) by heating. The residue is then fused with mixed fusion (Na2O2−NaOH) in a muffle furnace at 700°C for 15 minutes. After cooling, the fused mixture is leached with hot water. The final solution is adjusted to pH 1.5–2.0 and then passed through a column filled with thiourea type chelate resin. The resin absorbed with192Ir is measured for 4000–10 000 s by means of SCORPIO-3000 multi-channel computer — Ge(Li) detector system. Experiments with radioactive tracer are carried aout for checking radiochemical separation yield. The accuracy and precision of the method are evaluated by the analysis of U.S. geological SRMs DTS-1 and AG-Bohor-1. The method is used for the determination of trace Ir in several sets of Precambrian-Cambrian boundary samples collected from Yunnan province in China and the Ir anomaly is observed.

LIII subshell intensity ratios of Pb, Th and U

AbstractA study of LIII intensity ratios by using characteristic x‐rays as the exciting radiation is described. Only the LIII subshells of Pb, Th and U were excited by the characteristic x‐rays of the elements used as the secondary sources. A Ge(Li) detector system coupled to a programmable multi‐channel analyser was used in the measurements. Lα1, 2/L1, Lα1, 2/Lβ6 and Lα1, 2/Lβ2, 15 intensity ratios of Pb, Th and U were determined by spectral analysis and were compared with recent theoretical and experimental results.

A method for quick estimation of129I by low energy photon spectrometry

Methods have been developed for the routine analysis of129I in effluents of fuel reprocessing plants using 29.4 keV xenon X-rays. Direct counting methods have been standardized in liquid medium as well as in ion-exchange resin medium. A low energy photon spectrometry Ge detector system and a well-type NaI/Tl/ detector are used for direct counting. Attenuation of xenon X-rays in liquid medium as well as in ion-exchange resin medium have been studied. Sample size is optimized by studying the self attenuation of xenon X-rays in the sample. Activity as low as 1 Bq could be detected with an accuracy of 11% and 30% using LEPS and NaI/Tl/counting systems, respectively.

Performance of a high purity Ge gamma detection system cooled by a cryogenic refrigerator

The energy resolution and thermal performance of a high purity Ge-detector system cooled by a cryogenic refrigerator is described. The mechanical vibrations of the cryomachine are damped effectively leading to a degradation in energy resolution of 200 eV only. Cool-down time is two hours and output pulse height stability is excellent between 82 and 94 K. For data display and spectrum analysis an economic personal computer-based system is used.

Low background study of the neutrinoless double beta decay of 76-GE and upper limit for neutrino mass

A Ge detector system was built possessing significnt reduced background, from natural radioactivities, notably 208-TI (2.6 MeV line). After a 2600 h measuring period a lower limit for the half life of the neutrinoless double beta decay in 76- Ge of T( 1 2 oν) > 1.7 × 10 22 yr (1σ) was obtained, corresponding to a neutrino mass upper limit of 22 eV.

PIXE analysis of tumors and localization behavior of a lanthanide in nude mice

We have used particle induced X-ray emission (PIXE) to analyze the elemental compositions and uptakes of a lanthanide, yttrium in this report, in tumors and normal tissues of nude mice. A small amount of yttrium nitrate was injected into nude mice with tumors. Samples of normal and malignant tissues taken from these mice were bombarded by the 2 MeV proton beam from a 3 MeV Van de Graaff accelerator with a Ge detector system to determine the relative elemental compositions of tissues and the relative concentrations of yttrium taken up by these tissues. We found that the uptakes of yttrium by tumors were at least five times more than those by normal tissues. Substantial differences were often observed between the trace element weight (or concentration) pattern of the cancerous and normal tissues. The present result is compared with human tissues.

Gamma-Ray Production Due to Neutron Interactions with Copper for Neutron Energies between 0.7 and 10.5 MeV

Differential cross sections for 22 gamma rays produced by neutron interactions with elemental copper having energies E..gamma.. between 0.36 and 2.5 MeV have been measured for neutron energies E /SUB n/ between 0.7 and 10.5 MeV for theta..gamma.. = 90 deg using a Ge(Li) detector system. The data are compared with previously reported measurements: agreement with earlier reported data is generally good for E /SUB n/ 4 MeV.

Levels inPo84204from the decay ofAt85204

The electron-capture decay of $_{85}^{204}\mathrm{At}$ (9 min) has been studied by means of $\ensuremath{\gamma}$ and ${e}^{\ensuremath{-}}$ multiscaled singles and $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence measurements with Ge(Li) and Si(Li) detector systems. The samples were produced by $\mathrm{Ir}(^{16}\mathrm{O}, xn)$ reactions and on-line isotope separation. About 50 $\ensuremath{\gamma}$-ray transitions have been assigned to the $^{204}\mathrm{At}$ decay, \ensuremath{\sim}35 of which have been placed in a proposed level scheme for $_{84}^{204}\mathrm{Po}$. The energy of the ${8}^{+}$\ensuremath{\rightarrow}${6}^{+}$ isomeric transition has been deduced to be 12.1 keV, and the half-life of the ${8}^{+}$ isomer has been measured to be 150\ifmmode\pm\else\textpm\fi{}10 ns. From these data, the $B(E2)$ value of this isomeric transition is found to be 3.7 Weisskopf units. The $^{204}\mathrm{At}$ ground state is assigned an ${I}^{\ensuremath{\pi}}$ value of ${7}^{+}$, which eliminates the need for some low-energy levels in $^{204}\mathrm{At}$ and $^{200}\mathrm{Bi}$ that were tentatively proposed in recent data evaluations, where a ${5}^{+}$ assignment was made.RADIOACTIVITY $^{204}\mathrm{At}$ from $\mathrm{Ir}(^{16}\mathrm{O}, xn)$; measured ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$, ICC, $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}\ensuremath{-}t$, isomeric lifetime in $^{204}\mathrm{Po}$; $^{204}\mathrm{Po}$ deduced levels, $J$, $\ensuremath{\pi}$; $^{204}\mathrm{At}$ ground state deduced $J$, $\ensuremath{\pi}$; Ge(Li) and Si(Li) detectors; on-line isotope-separated sources.

Correlation of environmental sample radioactivity determination with sample pretreatment.

Abstract This report describes a calculation equation for radioactivity determination, and sample pretreatment based on the fundamental design mentioned in previous report (Na79), which satisfied the guide for dose assessment objectives for a light-water-cooled nuclear power reactor (AECJ75). The effect of the sample pretreatment on the determination of half the level of needed determination limit (NDL} (Na79) was evaluated using a commercially available Ge(Li) detector system. It was clarified that pretreatment should be carried out for environmental samples up to 8301. of the initial sample amount. The most suitable radioactivity determination method with a commercially available Ge(Li) detector system far dose assessment is presented herein.