Suren Kandasamy Dissertation.pdf - University of Surrey

M.Sc Dissertationenergies (approximately below 200 keV). This could be due to the fact thatLaCl 3 :Ce(10%) crystal has a significantly low light output approximately below 200keV. That means at low energies, the contribution of the intrinsic resolution is larger [8].4.5 Detection EfficiencyThe absolute efficiency ( ABS) of the detector can be calculated using Eq. 2.4, andare dependent not only on detector properties but also on the details of the countinggeometry (distance. between the source and detector). But in the case of intrinsicefficiency ( int) no longer includes the solid angle sustained by the detector as animplicit factor. These two efficiencies are simply related for isotropic sourcesby 4int ABS, where, is the solid angle of the detector seen from the actualsource position [1].The distance between the source and detector is 5.0 cm, and this was kept for allsources, and the diameter of the LaCl 3 :Ce detector is 51 mm. Table 4.5 shows theAbsolute total efficiency ABSand the Intrinsic efficiency INTcalculated for LaCl 3 :Cedetector.Table 4.5 Detection efficiency for LaCl 3 :Ce detectorSourceActivityD(s)BqI E ) N( N CtcpsC tABSN%100 100N137 Cs 259845 0.85 220868.25 12055.47 5092 2.31 42.24INTC t%60 Co 39928 2.00 79855.60 4358.69 1510 1.89 34.6422 Na 20045 2.80 56126.00 3063.48 366 0.98 17.93152 Eu 152911 1.24 189609.64 10349.31 5016 1.77 32.36The intrinsic photopeak efficiency was calculated using Eq. 2.8. The net countsunder the each peak are measured automatically by using maestro for windowssoftware.K. Suren 26