Detection of fusion alphas from D2-T2 gas targets

Detectors for recording alphas from fusions in D2–T2 gas targets require protection against diffusion of tritium into the detector medium. Tests have been carried out on surface barrier detectors to determine the feasibility of using thin coatings of oxide and metal for this purpose. The results show that a layer of 0.5 μm aluminium oxide plus 0.2 μm gold provides effective protection for at least 280 h, without impairing the transmission of 2 MeV alphas into the detector. Tests of an alternative detector, a phoswich of thin film plastic and lithium-glass scintillators, are also described.