The dependence of Ge detectors efficiency on the density of the samples in gamma-ray spectrometry (original) (raw)
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This research investigates the basic properties of γ-rays using a high-resolution Germanium (Ge) detector, a Sodium Iodide (NaI(Tl)) Scintillation detector and Multi-Channel Analyser (MCA). These detectors are kept cold in operation and once the detector is switched on neither power supply nor the electronics setup are altered. In this experiment, we also determine linear attenuation coefficient for two different materials (Aluminium and Steel) by taking spectra and recording the count rate with varying thicknesses of these materials between the source and detector. Starting with five plates of our chosen materials, we took a spectrum until the 511.0 keV and 1274.6 keV photopeaks were clearly identified for a set time interval. We recorded the net number of counts (including the error) in each of these two peaks using the software which takes account of the large background under the peak. Also, recorded are the live time, real time and dead time. Dead time is the amount of time spent by the detector in a state where it could be missing events. Any detection system has a limit to the rate at which events can be registered and processed. In the case of a scintillation detector, if pulses from different photon interactions overlap significantly, only one light pulse will be measured by the photomultiplier tubes (pulse pileup). The electronics also have a maximum rate at which they can process data, typically around 1 MHz. __________________________________________________________________________________________ I. Introduction Gamma rays interact with matter by three main processes, the photo-electric effect, Compton scattering and pair production[6]. For the range of γ-ray sources used, Compton scattering is the most dominant process, since this process involves γ-rays scattering from electrons, the amount of scattering or attenuation strongly depend on the number of electrons in the material. Heavier materials, such as lead, are often used to shield γ-rays because they have a large atomic number and therefore, a greater density of electrons. II. Aim & Objective This work looks at the manner at which γ-rays interact with matter. The setup uses a high-resolution Germanium (Ge) detector, a Sodium Iodide (NaI(Tl)) Scintillation detector and a Multi-Channel Analyser (MCA). This research is an important tool in health physics and is effectively used to shield oneself from a radiation source. The work also investigates the attenuation of γ-rays in matter. The first part of this work focus on the radiation emitted from a 137 Cs source. The understanding of this work was made easy by studying the schematic nuclear decay charts to help understand the decays of the radioactive sources used. III. Methodology & Result A. The 137 Cs source Place the 137 Cs source on the holder a few centimetres above the detector face and take a γ-ray decay spectrum of this source for approximately five minutes.
Gamma-Ray Spectrometry and the Investigation of Environmental and Food Samples
2017
Gamma radiation consists of high‐energy photons and penetrates matter. This is an advantage for the detection of gamma rays, as gamma spectrometry does not need the elimination of the matrix. The disadvantage is the need of shielding to protect against this radiation. Gamma rays are everywhere: in the atmosphere; gamma nuclides are produced by radiation of the sun; in the Earth, the primordial radioactive nuclides thorium and uranium are sources for gamma and other radiation. The technical enrichment and use of radioisotopes led to the unscrupulously use of radioactive material and to the Cold War, with over 900 bomb tests from 1945 to 1990, combined with global fallout over the northern hemisphere. The friendly use of radiation in medicine and for the production of energy at nuclear power plants (NPPs) has caused further expositions with ionising radiation. This chapter describes in a practical manner the instrumentation for the detection of gamma radiation and some results of the ...
IOSR Journals , 2019
The utilization and prolonged working of two gamma spectrometry (GS1 and GS2) in nuclear laboratories, UTM, causing one to questioning its performance. To achievethe higher quality outcomes of gamma spectrometry system. Itsperformance specifications should verify against the warranted values offered by the manufacturer. High purity germanium (HPGe) detectors is the most distinguished radiation measurement instrument that produced excellent energy resolution. The aims of this studyis to determine the working condition and compare the performances of two gamma spectrometry systems. The GS1 consist of n-type closed end coaxial HPGe detector GC 2018 model and GS2 consist of p-type closed end coaxial HPGe detector of GEM25-76-LB-C model. The test performance specifications such as resolution, peak shapes, peak-to-Compton ratio, figure of merit, and dead time for both spectrometry systems are measured using American ANSI/IEEE 325-1996 standard procedure.Four (4) standard source 60 Co, 152 Eu, 133 Ba, and 137 Cs were used. It covered energies range from (4.3 keV-3194.9) keV. The source-to-detector distance is set 25 cm to avoid the summing coincident gamma ray. The relative efficiency measured improve by 0.2% and 4% for GS1 and GS2 respectively. Peak-to-Compton ratio of both detectors improved by factor of 4.Dead time found to be less than 1% at 25 cm compared to 12 cm. From the results, GS1 has higher resolution compared to GS2 detector. Based on the results obtained, it can be concluded that the performance of two coaxial HPGe detectors in nuclear laboratories, (UTM) are in good working condition.Thisrevealed propercontrol and maintenance of the two detectors.