Quantitative Measurement of Surface Tritium by β-Ray-Induced X-Ray Spectrometry (BIXS)

To make a nondestructive measurement of tritium retained on/in materials surfaces, conversion efficiency of β-rays to characteristic X-rays in an argon atmosphere has been examined. For this purpose, various tritium-containing graphite plates were prepared at first by ion implantation. After the tritium implantation, measurements of an X-ray spectrum from the graphite plates were carried out in the argon atmosphere. A good linear relation was observed between the intensity of Ar(Kα) characteristic X-rays and the total amount of tritium deter-mined by full-combustion. The apparent conversion efficiency was determined as 4.15x10⁻⁶ counts/s/Bq. To determine the intrinsic conversion efficiency for argon atoms, relevant correction factors such as geometrical efficiency, absorption of X-rays, effects of a tritium depth profile and a photoelectric effect were experimentally evaluated through numerical calculations. Taking into account these correction factors, the intrinsic conversion efficiency was determined to be 3.1x10⁻⁴ photons/β-particle.