Exp__5_Nuc_E_450_Sp11

Exp__5_Nuc_E_450_Sp11 - 5 -1 Gamma Ray Spectroscopy Using a...

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5-1 Gamma Ray Spectroscopy Using a Single Channel Analyzer and a NaI (Tl) Detector (Experiment 5) Objective The primary objective of this experiment is to investigate the use of a thallium activated sodium iodide detector (NaI (Tl) ) and a single channel analyzer. Gamma spectra of 137 Cs and 60 Co isotopes will be investigated. Introduction A. Gamma Ray Spectroscopy The radiation spectroscopy process under study is usually called gamma ray spectroscopy. This technique actually can monitor ionizing photons from four different sources. Gamma rays which originate in the nucleus of atoms and have discrete energies between 10 keV and 10 MeV X-rays which originate in the orbital electron shell of atoms and have discrete energies in the range of 0.01 to 100 keV Annihilation photons which occur upon the annihilation of a positive electron (positron) with a negative electron and have an energy of exactly 0.511 MeV Bremsstrahlung photons which are produced by the slowing down of electrons in the neighborhood of a nucleus and have a continuum of photons from near zero to the maximum beta ray energy. Most of the detection systems utilized today for gamma ray spectroscopy employ either scintillation detectors, usually thallium activated sodium iodide detector (NaI(Tl)) or semiconductor detectors, lithium drifted silicon detectors (Si(Li) or high purity germanium detectors (HPGe). B. Components of a Gamma Ray Spectra Because of the various types of attenuation processes taking place in the detector, not all the energy of all the photons striking a detector will be completely absorbed. This results variations in detector efficiency. Some of the photons will pass through the detector with no measurable interaction, and thus will not contribute to the spectrum. Some others may be partially absorbed with a portion of the photon energy escaping from the detector. Other photons will interact with materials exterior to the detector, producing lower energy photons that can then enter and be absorbed by the detector and be recorded in the spectrum. It is, therefore, important to be able to distinguish between those peaks in a spectrum which are representative of the total absorption of the primary gamma rays from the source and those peaks and other structures which result from other partial absorption processes. The major features that may appear in a gamma spectrum are illustrated in Figure 1. Figure 1 is a NaI(Tl) spectrum of the 28 Al radionuclide. It should be noted that 28 Al emits only a single 1.779 MeV gamma ray. For further information on these features see your text and class notes. Reading Assignment Read from Knoll, all of Chapters 8, 9, and 10.
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5-2 Figure 1 - 28 Al Spectrum Obtained Using a NaI(Tl) Detector EQUIPMENT The equipment used in this experiment is listed in Table-1 and setup is shown in Figure-2. Table 1 - List of equipment to be used
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Exp__5_Nuc_E_450_Sp11 - 5 -1 Gamma Ray Spectroscopy Using a...

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