Development of a prompt gamma activation analysis facility using diffracted polychromatic neutron beam

A prompt gamma activation analysis facility has recently been developed at Hanaro, the 24MW research reactor in the Korea Atomic Energy Research Institute. Polychromatic thermal neutrons are extracted by setting pyrolytic graphite crystals at a Bragg angle of 45°. The detection system comprises a large single n-type HPGe detector, signal electronics and a fast ADC. Neutron beam characterization was performed both theoretically and experimentally. The neutron flux was measured to be 7.9×107n/cm2s in a 1×1cm2 beam area at the sample position with a uniformity of 12%. The corresponding Cd-ratio for gold was found to be 266. The beam quality was compared with other representative thermal neutron prompt gamma activation analysis. The detection efficiency was calibrated up to 11MeV using a set of radionuclides and the (n,γ) reactions of N and Cl. Finally, the sensitivities and the detection limits were obtained for several elements.