Preparation and analysis of carbon foils implanted with 100 μCi cm-2 of tritium

摘要

The approaching use of tritium in tokamaks necessitates precursory studies to assess safety and handling, to ready diagnostics of T in plasmas, and to study T–H exchange, loss of T from solids, and T transport. To aid these efforts, eight carbon foils 12.7×1.25 cm were implanted in a linear plasma device with ions from hydrogen plasma containing 10-3 fraction of T. These foils will be used in future PLT plasma experiments. Experimental guidelines are: low activity, high safety, and sufficient T for detection. Incident ion energies and total fluxes yielded deposits of ∼100 μCi cm-2 (2×1015 cm-2) of tritium. Using autoradiography, we find that variations of ≲20% of an average concentration of 100 μCi cm-2 of T can be detected. Areas of ≪1 mm2 can be examined by the use of densitometry, thus providing a nondestructive method of analyzing surface distribution. Absolute calibrations were made by the measurement of tritium in one of the foils using carbon dissolution and scintillation counting techniques, while relative tritium concentrations were measured using an electron multiplier. Enhanced tritium deposition, attributed to plasma arcs, was observed on one of the foils.