Suren Kandasamy Dissertation.pdf - University of Surrey
Suren Kandasamy Dissertation.pdf - University of Surrey
Suren Kandasamy Dissertation.pdf - University of Surrey
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Energy Resolution (%)M.Sc <strong>Dissertation</strong>4.604.404.204.003.803.600 2 4 6 8 10Shaping time (us)Figure 4.2 Variation <strong>of</strong> the Energy resolution <strong>of</strong> a LaCl 3 :Ce detector systems asthe amplifier shaping time is changedThe energy resolution (% FWHM) <strong>of</strong> the 662 keV ( 137 Cs) photopeak was studiedwith <strong>of</strong> LaCl 3 :Ce(10%) with the size <strong>of</strong> 44.450.8mmscintillator detector, atdifferent shaping time <strong>of</strong> amplifier. Figure 4.2 shows the value <strong>of</strong> energy resolution wasdecreased and increased as the shaping time increases. This gives good characteristic toselect optimum shaping time.Of all elements in pulse height analysis system, the linear amplifier presents theuser with the greatest variety <strong>of</strong> operational characteristics and, as result, the mostdifficult choices. One <strong>of</strong> the major „trade-<strong>of</strong>fs‟ in using a linear amplifier is betweenevent rate and energy resolution. The best energy resolution is <strong>of</strong>ten with a long shapingtime (reduced noise), but high rates require short shaping time [1]. On manycommercial linear amplifiers, the shaping time is adjustable. Then the choice may beoptimized for a given application by measuring the pulse height resolution <strong>of</strong> thesystems as the shaping times are varied. This optimization is given in Fig. 4.2. Note theoptimum shaping time in case, where the energy resolution is a minimum. From theFig. 4.2 the optimum shaping time was selected as 1.0 s. This shaping time constant <strong>of</strong>the amplifier was kept for other studies.K. <strong>Suren</strong> 20
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