Ge Detector Efficiency Research Articles

Robustness of LabSOCS calculating Ge detector efficiency for the measurement of radionuclides

The LabSOCS software is one of the main simulation codes employed to calculate the full-energy peak efficiency (FEPE) for the measurements of radionuclides by gamma-ray spectrometry. The validity of LabSOCS has not previously been evaluated for a large variety of matrixes, geometry types, and energies. This study aims to analyze in depth the LabSOCS FEPE robustness comparing the LabSOCS and experimental FEPEs by using three coaxial Ge detectors for a wide range of samples, varying the matrix composition, counting geometry (thickness (h) for cylindrical geometry), gamma emission energy (Eγ), and bulk density (ρ). The FEPE averages and variances calculated for numerous matrix types prepared using gamma cocktails were statistically comparable for a wide Eγ range (from 46 keV (210Pb) to 1836 keV (88Y)). To test the accuracy of the LabSOCS FEPEs varying h (6–50 mm), four certified samples containing only natural radionuclides were used. The 234, 228Th, 228, 226Ra, 210Pb and 40K activities were determined for each h, obtaining |zscore| < 2 in general. This also proves the good reproducibility of LabSOCS calculating activity concentrations. The LabSOCS FEPE robustness was also tested for a wide ρ range (1.3–2.8 g cm−3) mixing a sediment sample with Pb(NO3)2 for h = 50 mm. The 210Pb and 234Th contained in each mixture were determined, achieving all |zscore| < 2. Furthermore, the ability of LabSOCS to correct self-attenuation effects was checked to be wider than when other correction models are applied.

An estimation of EDXRF spectrometer properties, based on a two‐layer composite Si‐Ge detector

A mathematical model for the two‐layer composite Si‐Ge energy dispersive X‐ray detector is proposed, based on analyses of radiation and electron transport in the detector, and a mathematical model of an energy dispersive X‐ray fluorescent spectrometer with the detector is considered. The Monte Carlo method is applied to calculate probabilities of photon detection in different parts of the detector's response function. The composite detector with the time anti‐coincidence scheme is proposed; its first layer is Si detector, and the second layer is Ge detector. It is shown that this composite detector has some advantages, such as reduced Ge photo escape peaks intensities and efficiency of detection of high energy photons similar to efficiency of Ge detector. Applying the X‐ray detector for the energy dispersive X‐ray fluorescent spectrometer provides for a lower background level. Copyright © 2012 John Wiley &amp; Sons, Ltd.

The use of Monte Carlo calculations in the determination of a Ge detector efficiency curve

Precise measured data and an extensive set of Monte Carlo calculations have been combined to optimize the parameters for a 280 cm 3 n-type Ge semiconductor photon detector, with the outcome that the Monte Carlo calculations now provide a very precise detector efficiency curve. The detector position and its length were determined from a set of measurements that included an axial scan. Measurements of the relative efficiencies based on radionuclides with accurately known relative photon emission rates were combined with efficiencies calculated by a Monte Carlo photon and electron transport code to adjust the detector diameter, internal deadlayer thickness, and the effective external deadlayer thickness. Our results show that, in a well-studied situation, it is possible to use Monte Carlo calculations to aid in the determination of a Ge detector's efficiency with an accuracy of about 0.2% from 50 to 1400 keV.

66Ga: a standard for high-energy calibration of Ge detectors

Two independent measurements of the relative emission probabilities for the strongest transitions in 66Ga electron capture decay are reported here. The results of these measurements are in excellent agreement with each other and with those from another recent measurement. Consequently, 66Ga emission probabilities for 18 strong lines, from 834 to 4806 keV, are now known to better than 1% accuracy. Thus, 66Ga can now be considered a suitable radionuclide for Ge detector efficiency calibration up to an energy of 4806 keV, the highest energy attainable with radioactive calibration sources. We have also provided an empirical function for correcting earlier incorrect emission probability results for E γ greater than about 3 MeV which were produced using an inappropriate efficiency curve extrapolation.

Ge detector efficiency calculations for determination of three-dimensional radioactivity distributions

For the analysis of large inhomogeneous radioactive samples the 3D detection efficiency of the measurement system is required. In this paper we present a method to determine the detection efficiency of a HPGe detector as a function of the spatial position of the source. This method is based on the Monte Carlo simulation of gamma-ray pencil beams, incident on different positions on the detector crystal. Integration of the efficiency of the pencil beams renders the detector efficiency. This allows for determination of the efficiency in more complicated systems, like collimated detectors. The result of the method is compared to the measured efficiency of two detectors.

A detector setup to study the decay properties of exotic nuclei

General features of a detector setup for decay studies at on-line mass-separators are discussed. The detection system was used for measurements of β-decay properties of exotic nuclei with A≈70. Results of GEANT Monte-Carlo simulations of the detector setup generally confirm the measurements. Both measurements and simulations show that even in case of low multiplicity events the Ge detector efficiency and peak to total ratio of γ-lines are reduced by large factor due to summing. Steps to improve the detection system are discussed.

容積線源に対するGe検出器のピーク効率の計算

ゲルマニウム検出器内のγ線通過距離から計算されるピーク効率を数値積分することによって, 容積試料に対するピーク効率を決定する計算方法を開発した。この計算では, Ge結晶のサイズや不感層など検出器に関するいくつかのパラメータ, 容積試料のサイズと媒体の元素組成, および, 基準化のため1ないし2個の実測ピーク効率が必要である。この方法によって, いかなる媒体の容積試料に対しても自己吸収の補正を含むピーク効率を決定することができる。

Radioactivity concentration in soil in Jeddah area, Saudi Arabia

Abstract The level of radioactivity in soil was measured in Jeddah area. 137Cs concentration was determined as an indication of the degree of contamination from Chernobyl accident. Natural uranium and thorium radioactive series, as well as 40K concentration levels have been determined. These radioisotopes contribute to the background exposure both indoor and outdoor. The concentration of 214Bi a member of 238U Series and that of 228Ac from 232Th series were measured. For the gamma spectroscopy method 10% efficiency high purity vertifical Ge detector of 2 KeV resolution at 1.332 Mcv was utilized. Standard soil sources were made using 152Eu and 137Cs of known activities. The concentration of 137Cs, 214Bi, 228Ac and 40K in Bq/Kg were 0.32, 9,25, 7.4 and 369 respectively. The energy dependent Ge detector efficiency for measuring radioactivity in soil was further determined.

Computer interactive graphics fitting of efficiency curves for Ge detectors

A method of fitting the experimental data for a Ge detector efficiency curve using interactive computer graphics is described that allows the user to adjust the analytical fit to correct the undesired structure in the fitted curve sometimes introduced by the method of least squares. Special types of plots of the efficiency data are described that enhance the visual resolution and allow correction of distortions in the fitted efficiency curve that are not possible from the traditional log/log graph of the efficiency vs energy.

Absorption edge technique for determination of intrinsic Ge detector parameters

A systematic study of the intrinsic Ge detector efficiency in the energy region 2–20 keV is presented. The definition of the efficiency is discussed and auxiliary quantities introduced. The most influential construction parameters of the detector — the dead layer width and the thickness of the gold contact — are determined in separate measurements employing the differential counting technique in the vicinity of respective absorption edges. A simple analytical aproximation to the efficiency is proposed.

Calculation of Ge detector responses as a function of photon starting point and energy

Expressions for the absorption coefficients of photons in Ge are presented, which are particularly simple and fast for calculations. The Monte Carlo MES code, using these analytical expressions, is exploited to calculate many values of the total efficiency of planar Ge detectors for pointlike sources, placed even out of their symmetry axis. An analytical expression which gives the Ge detector efficiency as a function of the photon starting point and energy is then derived. It is verified that this expression can be easily integrated to obtain efficiency values in the case of extended sources.

Variation of Ge-detector efficiency with source diameter and radial source position

For two Ge detectors, the γ-ray efficiency obtained with a disk source was determined relative to that for a point source. These ratios were measured by two methods and calculated by a third method and are compared.