Efficiency and directional effects in the detection of low-energy recoil nuclei in a NaI(Tl) single crystal

The pulse shape for low-energy I-127 recoils in a NaI(Tl) single crystal was investigated as a function of the crystal orientation, using elastic neutron scattering. For comparison, the pulse shape was also studied for Compton-scattered electrons at small pulse heights. In addition, relative and absolute yields were measured for the elastic scattering of neutrons from Na-23 and I-127. Large deficits were observed in the count rates, indicating detection efficiencies for the recoiling nuclei which are much smaller than 100%. (C) 2001 Elsevier Science B.V. All rights reserved.