90 ro Y | RELATIVE COUNTER PHOTON EFFICIENCY (PER CENT) 80 €@ T r [ « T —_ = \ | | | T T _ \ ‘0 t NS 30 —-— 20 —- po ape ——] nn whe ee ff —= . | L OP Pope ap fee ap! mei nee nen pafy 3 i00 200 300 | i aoc 500 600 700 800 900 INCIDENT PHOTON ENERGY (KEV) Fig. 2.1 Relative Photon Efficiency for Scintillation Counters, Using 1-1/2 by 1-1/2 in. Nal Crystal and 1600 ng/sq cm Aluminum Absorber 1000 HOC 1200