PROMPT GAMMA-ACTIVATION ANALYSIS ENHANCED BY A NEUTRON FOCUSING CAPILLARY LENS

A focusing neutron lens using glass polycapillary fibers has been intr oduced successfully into a prompt gamma activation analysis (PGAA) ins trument placed at the exit of a cold neutron guide. The neutron curren t density gain of the lens is 80, averaged over the focused beam size of 0.53 mm diameter. PGAA measurements have been made on submillimeter particles of gadolinium and cadmium. The results indicate that elemen tal sensitivities of measurements are increased by similar to 60, and that particles of sizes smaller than 0.5 mm can be discerned using the focusing lens. The measured gain in prompt gamma signals for these pa rticles is less than anticipated, probably due to alignment difficulti es. Gamma ray background associated with the lens is discussed and imp rovements are suggested.