Suren Kandasamy Dissertation.pdf - University of Surrey

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M.Sc DissertationFigure 2.2 A graph depicting the various regions where the different gamma-rayinteractions are dominant [1].2.4 Detector CharacterisationThe performance of a γ-ray spectroscopy system is generally characterised bythree properties. They are energy calibration, energy resolution and detectionefficiency. These quantities are dependent on the energy of the incident radiation andshould therefore be measured using several sources with different γ-ray energies [7]. .2.4.1 Energy CalibrationThe multichannel analyzer collects the voltage output from the amplifier anddivides in to a number of channels of the same width. The number of channel of ananalyzer gives an estimation of its sensitivity, which is increased with the numberchannel.The sensitivity of the analyzer Sandefined asVoutSan 2.1NchWhere, Voutoutput signal from the amplifier, Nchnumber channel of the analyzer.K. Suren 7
M.Sc DissertationA desirable feature of any γ-ray detector is linearity of energy response. That is,direct proportionality between the quantity of energy deposited in the detector by theincident radiation event and the height of the analogue output pulse. A detector energycalibration may be obtained by plotting incident photon energy versus the centralchannel number of the corresponding full energy peak. Using each of the sourcescollect an energy spectrum and determine the central channel of the full energy peak.Plot a graph of channel number versus energy, making sure to indicate all errors [7].Energy calibration is one of the most important factors that should be consideredbefore making any analysis. The gain of the system is given by the slope of thecalibration plot. The units are energy per channel (eg. keV per channel). Changing theamplifier gain is the most immediate way of altering the calibration of the system.2.4.2 Energy ResolutionOne important property of a detector in radiation spectroscopy can be examinedby noting its response to a monoenergetic source of that radiation. Statistical factors andelectronic noise affects the shape of the spectra obtained by a radiation detector. Sharplines and sharp edges would be the ideal spectrum, but in practice the lines are boardpeaks, and the edges are rounded. The energy resolution of a detector is a measure of itsability to resolve small differences in the energy of incident γ-rays, varies with theenergy and type of detector. Scintillator detectors tend to have lower energy resolutionin comparison with the solid state detectors at room temperature.An ideal photopeak will be close to Gaussian shape, because the total number ofcharge carriers N is typically a large number. In this case, the Gaussian function can bewritten with analytical parameter :A C exp 2 H H22022.2Where C is the number of count, H 0 is centroid channel number and A is peak area. Thewidth parameter determines the full width at half maximum (FWHM) of anyGaussian through the relation FWHM=2.35.K. Suren 8
Page 1 and 2: Characterisation of novel detector:
Page 3 and 4: M.Sc DissertationTable of ContentsC
Page 5 and 6: M.Sc DissertationAbstractDelft and
Page 7 and 8: M.Sc DissertationThe most commonly
Page 9 and 10: M.Sc DissertationGas-filled Detecto
Page 11: M.Sc Dissertation(A)(B)Figure 2.1 S
Page 15 and 16: M.Sc DissertationAbsolute total eff
Page 17 and 18: Counts per channelM.Sc Dissertation
Page 19 and 20: M.Sc Dissertation3.2 To get the opt
Page 21 and 22: M.Sc Dissertationoperated at - 1800
Page 23 and 24: Total number of net countsM.Sc Diss
Page 25 and 26: Energy Resolution (%)M.Sc Dissertat
Page 27 and 28: Number of countsM.Sc DissertationFr
Page 29 and 30: Number of counts128.78 keV244.70 ke
Page 31 and 32: M.Sc Dissertationenergies (approxim
Page 33 and 34: Photo-fraction %M.Sc Dissertation4.
Page 35 and 36: M.Sc DissertationFigure 4.10 shows
Page 38 and 39: M.Sc DissertationChapter 5Conclusio
Page 40 and 41: M.Sc Dissertation[10] Alan Owens, A
Page 42 and 43: M.Sc DissertationAppendix BDetector
Page 44 and 45: M.Sc DissertationAppendix CDecay ch
Page 46: No of CountsNumber of counts1274.5

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