APPLICATION OF A DELTA-E-E TELESCOPE FOR SENSITIVE ERDA MEASUREMENT OF HYDROGEN

A Delta E-E telescope was used in coincidence to separate the isotopes of hydrogen and to improve the sensitivity of hydrogen detection when recoiled with 3.8 MeV He+. This was achieved by recording coincident events in both detectors (corresponding to the recoil of H, D or T fro m the target) thereby excluding any contribution from D (or T) beam co ntamination to the ERDA spectrum for hydrogen and also eliminating ele ctronic noise from the background. The analysis of standard hydrogen-b earing silicates (6-189 wt ppm H) suggested that the concentrations at the lower part of this range were resolvable. The lowest counts were accumulated on two fragments of colourless diamond and were <20% of th e counts obtained for the standard bearing 6 wt ppm H. We suggest sens itivities of better than 0.0056 wt% H2O (or 75 at. ppm H in carbon-ric h matrices) are achievable with relative precisions <20% in the range 0-400 at. ppm H. (C) 1998 Elsevier Science B.V.