Tritium depth profiling by neutron time-of-flight

A method has been developed to measure the depth profile of tritium implanted or absorbed in materials. The sample is bombarded with a pulsed proton beam. Neutron energies from T(p,n) reactions occurring in the target are measured by time-of-flight over a 10.8-m flight path. From the neutron energy the proton energy and, thus, the tritium depth in the target may be inferred. The measurements were initiated to determine the depletion of tritium absorbed in titanium layers. These layers had served as targets on a 400-keV T(d,n) neutron generator. A depth resolution of 0.4 mg/cm2 of titanium (0.9 μ) was obtained. Unlike proton backscattering methods, the technique can be used with thick samples. It is estimated that a sensitivity of 0.1 at. percent tritium in host materials can be obtained. Extension of the method to deuterium depth profiling is possible with the use of the D(d,n) reaction. (U.S.)