GAMMA-RAY DETECTION WITH A 4-PI NAI SPECTROMETER FOR MATERIAL ANALYSIS

A gamma-ray detection system with nearly 4 pi geometry for application s in materials science is described. The energy resolution of the NaI( Tl)-bore hole detector was found to be about 2% for 10 MeV gamma-rays. The total detection efficiency has been determined to be above 80% fo r gamma-energies between 0.5 and 20 MeV. A precision of the efficiency calibration of about 2% has been obtained for a wide range of gamma-e nergies. The experimental results were found to be in excellent agreem ent with computer simulations using the GEANT computer code. The high efficiency of the system combined with its relatively high energy reso lution opened a wide range of applications. Examples are the simultane ous detection of light isotopes in thin films by (d,p gamma) nuclear r eactions, high depth resolution profiling of isotopes by narrow, low-e nergy resonances in (p,gamma) reactions, and hydrogen profiling using the 6.4 MeV resonance in the H-1(N-15,alpha gamma)C-12 reaction. (C) 1 997 Elsevier Science B.V.