On the determination of bismuth concentration in specimens by an alpha-activation technique

The alpha-activation technique for high-sensitivity Bi exploration in common rock minerals and alloys is developed. The technique based on bombardment of smooth surfaces of specimens being investigated with high fluxes of accelerated deuterium ions, E(d) greater-than-or-equal-to 6 MeV/n total fluence empty-set = 10(13) - 10(14) cm-2. The alpha-active polonium isotopes then are produced in nuclear reaction Bi-209(d,n)Po-210. After deuterium beam exposure the induced activity of Po-210 alpha-emitter is measured with alpha-sensitive plastic track detector - poly(allil)diglycolcarbone (CR-39) placed in close contact with the specimen surface for few hours or days. The control experiment with deuterium exposed Pb foils provides no alpha-particle track at all. The sensitivity obtained under these conditions corresponds to Bi concentrations at the level less-than-or-equal-to 10(-6) g/g, the space resolution of Bi inclusions is +/- 20-25 mum. Our technique allows one to determine minor Bi concentrations in specimens which posess much higher content of Pb, Th and U.