Tritium profiling in solids using the T(d, 4He)n reaction

The T(d, 4He)n reaction provides a quantitative, non destructive technique for measuring the depth distribution of tritium in prospective first wall materials over depths to ∼ 1 μm. Calculations have been undertaken to show how the depth resolution and detection sensitivity vary with experimental conditions. The best depth resolution is attained at an angle of incidence between 40 degrees and 60 degrees to the surface normal and an exit angle of 80 degrees to the surface normal. Results of calculations on the deuterium depth profiling technique using the D(3He, 4He)p reaction are shown for comparison. Assuming typical experimental conditions, for a silicon target a surface resolution of 0.03 μm is predicted, degrading to approximately 0.3 μm at a 1 μm depth. For a gold target, a resolution of 0.015 μm at the surface and 0.5 μm at a 0.5 μm depth is predicted. Experimental depth resolution curves have been obtained from a tritiated Ti thin film overlaid with gold films of various thicknesses. Misalignment of the deuteron beam with the target resulted in a systematic uncertainty in the profiling geometry. Accounting for this effect in the experimental calculations resulted in good agreement between theory and experiment. Also depth profiles have been obtained for a tritated Ti thin film and tritium implanted Si and graphite samples. Evidence suggests that sensitivities of 0.001 at.% can be attained