Ge Li Detector Research Articles

Using the gamma spectrometry method to determine the concentration of radon in samples of mineral radon water

The results of a study on the choice of the optimal measurement geometry, measuring capacity and method of sealing the measuring capacity for determining the concentration of radon-222 in samples of mineral radon water are presented. Studies of radon water samples were carried out in laboratory conditions on a stationary gamma spectrometer based on a semiconductor Ge(Li) detector. The concentration measurements in the samples were carried out in accordance with MVI. MN 3421-2010 “Methodology for measuring the volumetric and concentration of gamma-emitting radionuclides on gamma spectrometers with semiconductor detectors” for standard plastic vessels “Denta, 0.1 l” and “Marinelli, 1 l”, and glass containers with a volume of 0.5 l with lids for twisting and seaming. The results of the research showed that the leakage of radon from a glass container with a metal lid for sealing is minimal. This method of sampling and sealing the measuring vessel makes it possible to increase the accuracy of the presented measurement results by reducing the corrections for sample preparation when calculating the expanded measurement uncertainty. A glass container with a volume of 0.5 l with a metal cap for seaming was used to measure the concentration of radon in samples of mineral radon water taken from wells and a drinking fountain of the Radon sanatorium of Belagrozdravnitsa JSC (Dyatlovo District, Grodno Region). The concentration range was 760–2100 Bq/kg. The selected measuring container, the method of its sealing and the measurement geometry can be used for future measurements of the radon concentration in samples of mineral radon water taken in the sanatoriums of the Republic of Belarus.

Activity Concentrations Of Environmental Samples Collected In Samarkand Region Of Uzbekistan

The results of the investigations of the activity concentration of natural radionuclides in certain building materials and foodstuff samples obtained from the Nurabad district of the Samarkand region of Uzbekistan are presented. The gamma radiation spectra of the samples were measured in Marinelli beaker geometry on γ- spectrometer with a Ge(Li) detector and energy resolution 6% on the 1332 keV line of 60Co. A personal computer and standard computer programs were used to accumulate and process the spectra. The characteristic density of the samples ranged from 140 to 1810 g/l. The activity concentration of 40K was observed to be comparatively higher than that of both 226Ra and 232Th in all the studied samples. The results reveal that the low activity of 137Cs in the samples is attributed due to its half-life decay period.

Decay properties of 2.05-h [formula omitted]Am

Gamma rays following the β− decay of the 245Am radionuclide (T1/2 = 2.05 h) were measured in early 1970s with a co-axial Ge(Li) detector using a chemically and isotopically pure, mass-separated 245Am source. These data were analyzed in the present work where several weak γ rays in 245Cm were identified. The 245Am decay scheme was deduced and extended when compared to the previously known one.

Apparatus complex based on liquid xenon detector for gamma spectrometry in the intervals between pulses of intense radiation

To investigate the effects of intense radiation on the operation of the liquid xenon spectrometer we have created apparatus complex on the basis of the liquid xenon detector. The experimental setup consists of a multifunctional chamber, gas system, cooling system, temperature control system, X-ray generator, a special preamp, passive protection, scintillation monitor of the accelerator beam, thermoluminescent dosimeters, copper monitor bremsstrahlung, Ge(Li) detector. Multifunctional chamber includes a detecting unit (flat or cylindrical ionization chamber), the cleaning unit of the xenon, control unit of the purity of liquid xenon. The liquid xenon detector was irradiated by bremsstrahlung pulses of the microtron. The frequency of irradiation pulses was 400 Hz. The absorbed dose was varied from 10-7 to 0.1 Gy per pulse. The electronic and ionic processes in liquid xenon at different radiation doses were investigated. The recovery time of the spectrometric mode of operation of the liquid xenon detector after intense pulse irradiation has been studied. Stable operation of the liquid xenon spectrometer in the intervals between the pulses of the accelerator shown for a long time.

Tungsten anode spectral model using interpolating cubic splines: Unfiltered x‐ray spectra from 20 kV to 640 kV

Monte Carlo methods were used to generate lightly filtered high resolution x-ray spectra spanning from 20 kV to 640 kV. X-ray spectra were simulated for a conventional tungsten anode. The Monte Carlo N-Particle eXtended radiation transport code (MCNPX 2.6.0) was used to produce 35 spectra over the tube potential range from 20 kV to 640 kV, and cubic spline interpolation procedures were used to create piecewise polynomials characterizing the photon fluence per energy bin as a function of x-ray tube potential. Using these basis spectra and the cubic spline interpolation, 621 spectra were generated at 1 kV intervals from 20 to 640 kV. The tungsten anode spectral model using interpolating cubic splines (TASMICS) produces minimally filtered (0.8 mm Be) x-ray spectra with 1 keV energy resolution. The TASMICS spectra were compared mathematically with other, previously reported spectra. Using pairedt-test analyses, no statistically significant difference (i.e., p > 0.05) was observed between compared spectra over energy bins above 1% of peak bremsstrahlung fluence. For all energy bins, the correlation of determination (R(2)) demonstrated good correlation for all spectral comparisons. The mean overall difference (MOD) and mean absolute difference (MAD) were computed over energy bins (above 1% of peak bremsstrahlung fluence) and over all the kV permutations compared. MOD and MAD comparisons with previously reported spectra were 2.7% and 9.7%, respectively (TASMIP), 0.1% and 12.0%, respectively [R. Birch and M. Marshall, "Computation of bremsstrahlung x-ray spectra and comparison with spectra measured with a Ge(Li) detector," Phys. Med. Biol. 24, 505-517 (1979)], 0.4% and 8.1%, respectively (Poludniowski), and 0.4% and 8.1%, respectively (AAPM TG 195). The effective energy of TASMICS spectra with 2.5 mm of added Al filtration ranged from 17 keV (at 20 kV) to 138 keV (at 640 kV); with 0.2 mm of added Cu filtration the effective energy was 9 keV at 20 kV and 169 keV at 640 kV. Ranging from 20 kV to 640 kV, 621 x-ray spectra were produced and are available at 1 kV tube potential intervals. The spectra are tabulated at 1 keV intervals. TASMICS spectra were shown to be largely equivalent to published spectral models and are available in spreadsheet format for interested users by emailing the corresponding author (JMB).

Revisiting the decay scheme and half-life of 139Ba

The decay of 139Ba to levels of 139La has been studied employing singles and \( \gamma\) -\( \gamma\) coincidence spectroscopy techniques, using four Compton suppressed Clover detectors. The \( \gamma\) -\( \gamma\) coincidence data obtained in the present work has been more conclusive as compared to the coincidence data obtained using NaI(Tl)-Ge(Li) detectors in the earlier investigations. The relative intensities of twenty-seven \( \gamma\) -ray transitions have been determined. The \( \gamma\) -ray transitions with energies 1044 and 1525keV, attributed to the decay of 139Ba in the previous works, have been found to be due to long-lived impurities. The 1691keV transition, previously assigned to the decay of 139Ba , is found to be mainly associated with an impurity with only a small fraction belonging to 139Ba decay. The half-life of 139Ba has been measured. The present work attempts to resolve some of the discrepancies in the previous investigations, which will be helpful in the precise determination of \( \beta\) -decay scheme of 139Ba.

Application of in-situ measurement to determine 137Cs in the Swiss Alps

Establishment of 137Cs inventories is often used to gain information on soil stability. The latter is crucial in mountain systems, where ecosystem stability is tightly connected to soil stability. In-situ measurements of 137Cs in steep alpine environments are scarce. Most studies have been carried out in arable lands and with Germanium (Ge) detectors. Sodium Iodide (NaI) detector system is an inexpensive and easy to handle field instrument, but its validity on steep alpine environments has not been tested yet. In this study, a comparison of laboratory measurements with GeLi detector and in-situ measurements with NaI detector of 137Cs gamma soil radiation has been done in an alpine catchment with high 137Cs concentration (Urseren Valley, Switzerland). The aim of this study was to calibrate the in-situ NaI detector system for application on steep alpine slopes. Replicate samples from an altitudinal transect through the Urseren Valley, measured in the laboratory with a GeLi detector, showed a large variability in 137Cs activities at a meter scale. This small-scale heterogeneity determined with the GeLi detector is smoothed out by uncollimated in-situ measurements with the NaI detector, which provides integrated estimates of 137Cs within the field of view (3.1 m 2) of each measurement. There was no dependency of 137Cs on pH, clay content and carbon content, but a close relationship was determined between measured 137Cs activities and soil moisture. Thus, in-situ data must be corrected for soil moisture. Close correlation ( R 2 = 0.86, p < 0.0001) was found for 137Cs activities (in Bq kg −1) estimated with in-situ (NaI detector) and laboratory (GeLi detector) methods. We thus concluded that the NaI detector system is a suitable tool for in-situ measurements in alpine environments. This paper describes the calibration of the NaI detector system for field application under elevated 137Cs activities originating from Chernobyl fallout.

Nondestructive analysis of the gold quarter liras

In this study, we have prepared seven Au-Cu standards in the concentration range of 18–24 (as carat) for nondestructive control of gold quarter liras. Some calibration curves for quantitative analysis of Au in the gold quarter liras that commercially present in Turkey have been plotted using these standard samples. The characteristic X-rays of Au and Cu emitted from these standard samples and the test sample with known composition are recorded by using a Ge(Li) detector. These calibration curves provide a nondestructive analysis of gold quarter liras with the uncertainties about 1.18%.

Components of the background of Ge(Li) and Ge detectors in passive shielding

The components of the background of a Ge(Li) detector and an ultrapure Ge detector in gamma spectrometers in passive shielding with a special design were studied in a ground-surface laboratory in 1996–2006. The measurement time varied from 45 to 240 h. The background for the detectors is due to radionuclides in the shielding material and cavities in the shielding and the detector materials themselves. Special attention is devoted to the study of the time dependence found for the background of the daughter of products of 222Rn decay, including the 46.5 keV peak of 210Pb.

Evaluation of Radon in Soil Gas and Natural Radioactivity in Surface Soil of Kinki District, Japan

Radon and its progeny are an important part of natural environmental exposure to radiation. However, little information is available about the radon contents of soil gas. We carried out a survey of radioactivity, focusing on 222Rn-concentrations in soil gas in parts of western Japan. Fifty nine samples in soil gas from 4 Prefectures of the Kinki district were analyzed with a liquid scintillation counter after the trapping of radon in soil gas into a toluene based-scintillation cocktail, together with 19 samples of interest from karst and uranium mining sites in another two Prefectures for comparison. The cumulative frequency of the 222Rn-concentrations in soil gas of the Kinki district showed a log-normal distribution. The average content was found to be 11.9kBqm−3 (arithmetic mean) and 7.5kBqm−3 (geometric mean). A maximum concentration of radon in soil gas, 2.1 MBqm−3 was found at the marker of the Ningyo uranium mining site. Surveys of natural radioactivity in soil were also carried out with a Ge(Li) detector to determine the concentrations in soil, mainly focusing on uranium and thorium series. The radon concentrations in soil gas were weakly correlated with those of uranium series in soils. There were no great differences vertically in the natural radioactivity in soils within 1 m, but a difference by one order of magnitude was found in soils horizontally even in the residence area of the Kinki district.

Evaluation of Radon in Soil Gas and Natural Radioactivity in Surface Soil of Kinki District, Japan

Radon and its progeny are an important part of natural environmental exposure to radiation. However, little information is available about the radon contents of soil gas. We carried out a survey of radioactivity, focusing on 222Rn-concentrations in soil gas in parts of western Japan. Fifty nine samples in soil gas from 4 Prefectures of the Kinki district were analyzed with a liquid scintillation counter after the trapping of radon in soil gas into a toluene based-scintillation cocktail, together with 19 samples of interest from karst and uranium mining sites in another two Prefectures for comparison. The cumulative frequency of the 222Rn-concentrations in soil gas of the Kinki district showed a log-normal distribution. The average content was found to be 11.9kBqm−3 (arithmetic mean) and 7.5kBqm−3 (geometric mean). A maximum concentration of radon in soil gas, 2.1 MBqm−3 was found at the marker of the Ningyo uranium mining site. Surveys of natural radioactivity in soil were also carried out with a Ge(Li) detector to determine the concentrations in soil, mainly focusing on uranium and thorium series. The radon concentrations in soil gas were weakly correlated with those of uranium series in soils. There were no great differences vertically in the natural radioactivity in soils within 1 m, but a difference by one order of magnitude was found in soils horizontally even in the residence area of the Kinki district.

Virtual point detector: On the interpolation and extrapolation of scintillation detectors counting efficiencies

The concept of transforming the detector volume to a virtual point detector, in order to facilitate efficiency evaluations for different source locations, was proposed in the past for HPGe and Ge(Li) detectors. The validity of this model for NaI(Tl) and BGO scintillation detectors was studied in the present work. It was found that for both scintillation detectors, the point detector model does not seem to fit too well to the experimental data, for the whole range of source-to-detector distances; however, for source-to-detector cap distances larger than 4 cm, the accuracy was found to be high. A two-parameter polynomial expression describing the dependence of the normalized count rate versus the source-to-detector distance was fitted to the experimental data. For this fit, the maximum deviations are up to about 12%. These deviations are much smaller than the values obtained by applying the virtual point concept, even for distances greater than 4 cm, thus the polynomial fitting is to be preferred for scintillation detectors.

SU‐FF‐I‐83: Derivation of Diagnostic X‐Ray Spectra Using An Interpolation Program with Calculated and Measured Input Parameters

Purpose: To determine diagnostic x‐ray photon spectra using simple transmission measurements. Method and Materials: A database of measured and calculated x‐ray photon spectra values from the Catalogue of Spectral Data for Diagnostic X‐rays, R. Birch, M. Marshall and G.M. Ardran, Diagnostic Topic Group of the Hospital Physicists' Association, England, 1979 was collected and used to form a multidimensional interpolation matrix. These researchers measured x‐ray spectra using a Ge(Li) detector for various x‐ray systems in the diagnostic energy range and derived a calculation method to calculate x‐ray spectra which agreed closely with measured spectra for different conditions. X‐ray spectra for tungsten targets and different inherent filtration in Al and Cu were coded in relative number of photons per mm2 per keV for kVps ranging from 30 to 140 kVp at 10 kVp intervals. Other parameters were given such as mean photon energy in keV, photon flux at 0.75 m in photons‐mA−1‐s−1‐mm−2, output in micro Gy‐mA−1‐s−1 and exposure in mR‐mA−1‐s−1 and 1st, 2nd, and 3rd half‐value layer (HVL) in mm Al. Most spectra were derived for constant potential units but some with ripple were also derived. Target angles included 10, 17, 20 and 22 degrees. Results: From this input, interpolation curves were derived which enables one to interpolate between the 10 kVp intervals and to derive the inherent filtration for a particular unit in Al equivalent from simple transmission measurements in Al and mR/mAs at a particular distance. The kVp of the unit was also derived from the transmission measurements by comparison with the calculated curves. Conclusion: With some additional data, this method could be used to derive the x‐ray spectra for any unit in this energy range, 30 to 140 kVp for different parameters.

DECOMMISSIONING PROCEDURES FOR AN 11 MEV SELF-SHIELDED MEDICAL CYCLOTRON AFTER 16 YEARS OF WORKING TIME

The present article describes the decommissioning of a compact, self-shielded, 11 MeV medical cyclotron. A Monte Carlo simulation of the possible nuclear reactions was performed in order to plan the decommissioning activities. In the course of the cyclotron dismantling, cyclotron components, shields, and floor concrete samples were measured. Residual activities were analyzed with a Ge(Li) detector and compared with simulation data. Doses to staff involved in the decommissioning procedure were monitored by individual TL dosimeters. The simulations identified five radioactive nuclides in shields and floor concrete: 55Fe and 45Ca (beta emitters, total specific activity: 2.29 x 10(4) Bq kg) and 152Eu, 154Eu, 60Co (gamma emitters, total specific activity: 1.62 x 10(3) Bq kg-1). Gamma-ray spectrometry confirmed the presence of gamma emitters, corresponding to a total specific activity of 3.40 x 10(2) Bq kg-1. The presence of the radioisotope 124Sb in the lead contained in the shield structure, corresponding to a simulated specific activity of 9.38 x 10(3) Bq kg-1, was experimentally confirmed. The measured dose from external exposure of the involved staff was <20 muSv, in accordance with the expected range of values between 10 and 20 muSv. The measured dose from intake was negligible. Finally, the decommissioning of the 11 MeV cyclotron does not represent a risk for the involved staff, but due to the presence of long-lived radioisotopes, the cyclotron components are to be treated as low level radioactive waste and stored in an authorized storage area.

Contribution of pair production process in full-energy peak efficiency calculation of semiconductor detectors for axial point sources with high-energy γ-rays

Study has been made of the contribution of the pair production process in calculation of detector efficiency. Particular attention has been paid to positron annihilation in flight and subsequent scattering of the annihilation quanta in the detector material. A mathematical formula has been derived to directly calculate the liner attenuation coefficient of the full-energy peak (μp) for a Ge (Li) detector using an axial point source. The calculated values of the photopeak efficiency are found to be in a good agreement with published experimental data.

Development of a 3-D convolution / superposition algorithm for precise dose calculation in the skull

In this paper an algorithm for calculating 3-D dose distributions within the brain is introduced and adapted to the demands of modem radiosurgery. The dose calculation with this model is based on a 3-D distribution of the primary photon intensity which is calculated with a ray casting algorithm. A prelocated matrix takes into account field sizes as well as modifying elements as collimator positions (MLC), blocks, wedges and compensators. Monte Carlo precalculated monoenergetic kernels from 0.1 MeV to 50 MeV were at our disposal. The components of the spectrum were either determined by deconvoluting depth dose curves measured in water or analyzed with a Ge-Li detector system in the case of 60Co. The calculated fluence distribution has to be superposed to the complete kernel containing the spatial energy deposition. Inhomogeneities and tissue interface phenomena (rhoe, Z) have been investigated. The divergence of the rays and the curved surface of the patient are taken into account. Assuming homogenous media, it is possible to shorten the computation time by using the Fast Fourier Transformation (FFT) delivering a first overview within seconds. The algorithm was evaluated and verified under specific conditions of small fields as used in radiosurgery and compared to dose measurements and Monte Carlo calculations. In using both the fast algorithm (FFT) for mainly homogenous conditions on one hand and the very precise superposition for inhomogeneous cases on the other, this algorithm can be a very helpful instrument especially for critical locations in the skull.

Measurement and Analysis of Alpha Particle Induced Reactions on Praseodymium

Excitation functions (EFs) for the reaction 141 Pr(α, n ) 144 Pm and 141 Pr(α,2 n ) 143 Pm have been measured using 141 Pr as a target up to 50 MeV α-particle energy. Stacked foil activation technique and γ-ray spectroscopy using 100 cm 3 Ge (Li) detector, has been used. Excitation functions are also calculated theoretically using Blann's geometry dependent hybrid (GDH) model code ALICE-91, with and without inclusion of pre-equilibrium particle emission. It has been observed that high-energy tails of the EFs are dominated by pre-equilibrium reaction mechanism. With the accepted set of input parameter, initial exciton number n 0 =4 (2 p +2 n +0 h ), a good qualitative agreement is found. However, quantitative agreement for this magic nucleus 141 Pr is also good when theoretical calculations are normalized by a multiple factor of 0.5.

Incoherent scattering cross-sections for elements with 23 ≤ Z ≤ 51 at 59.5 keV photon energy

With the help of a Ge(Li) detector, the incoherent scattering differential cross-sections by 59.54 keV γ-rays from the 10 elements in the atomic region 23 ≤ Z ≤ 51 were measured through angles from 30° to 140°. The background correction and detection efficiency are also included in this study. The present results constitute the first measurements for this combination of energy and angle. The present experimental results have been compared with those estimated on the basis of the nonrelativistic Hartree-Fock wave functions. The present results were in good agreement with those of [J.H. Hubbell, W.J. Veigele, E.A. Briggs, R.T. Brown, D.T. Cromer, R.J. Howerton, J. Phys. Chem. Ref. Data 4 (1975) 471].

Low-level gamma spectrometry using beta coincidence and Compton suppression

A low-level gamma-ray spectrometry system was developed using a Ge(Li) detector with 6% relative efficiency coupled to a 2π beta plastic detector for coincidence selection and a massive NaI(Tl) detector for Compton suppression. The integral background count rate for (50–1500) keV was 0.5 s −1 kg −1 (Ge), using only beta coincidences. With Compton suppression, a value of 0.25 s −1 kg −1 (Ge) was obtained. Spectra with and without Compton suppression were studied for 60Co, 137Cs and 152Eu point sources. Considerations are made concerning the Compton suppression advantages in different situations.

Rapid determination of gold in Romanian auriferous alluvial sands, concentrates and rocks by 14 MeV NAA

The nuclear and spectral interferences in the 14 MeV neutron activation analysis (NAA) of gold from Romanian auriferous alluvial sands, concentrates and rocks have been studied and the optimum of activation, cooling and measuring times was determined for a maximum peak-to-background ratio for gold. The contribution of the nuclear interfering elements in the samples, Hg and Pt, to the concentration of gold has been calculated and, concluded that the nuclear reactions 197Au(n,2n)196Au, 197Au(n,2n)196mAu and 197Au(n,n')197mAu can be used for gold determination, with minimal errors. Using the nuclear reactions 197Au(n,n')197mAu and 197Au(n,2n)196Au the spectral interferences are minimal and are due to Rb, Ti and V for a short irradiation and to Se for a long one. Two methods of fast gold determination were proposed for auriferous alluvial sands and rocks in the range of 20-2500 ppm, under the optimum conditions established so that the systematic errors of analysis due to the gold accompanying elements can be considerably diminished. For measuring the induced gamma-radioactivity in the samples either a short irradiation (25 seconds) with a NaI(Tl) detector or a long irradiation (3000 seconds) with a Ge(Li) detector were used.