Suren Kandasamy Dissertation.pdf - University of Surrey

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