NUCLEAR-REACTION ANALYSIS OF HYDROGEN AT LEVELS BELOW 10 AT PPM

A setup for sensitive hydrogen analysis with the H(N-15,alphagamma)C-1 2 reaction has been developed. The detector for the reaction gamma-ray s is a bore-hole BGO scintillation counter with an efficiency of 27%. The natural-radiation background count rate is reduced by lead and ant icoincidence shielding to 25 counts/h. This detector system is used in combination with a specially designed UHV chamber which enables measu rements under vacuum in the 10(-10) mbar region. Various kinds of back ground arising from interaction of the ion beam with parts of the beam line and with contaminations on the sample surface (H, D, C) as well as possibilities for background quantification and reduction have been investigated for N-15 ion energies up to 12 MeV. Profiling examples d emonstrating a detection sensitivity of better than 10 at.ppm are pres ented.