Thermal Release Behavior of Tritium from Tungsten After Implantation by Glow Discharge

Tritium release behavior in a tungsten sample after exposing to tritium ions with energy about 200 eV created by glow discharge has been studied by both β-ray–induced X-ray spectrometry (BIXS) and imaging plate (IP). The tungsten sample was heated stepwise in a vacuum vessel at temperatures from 400 to 1000 K in experiments, and results obtained from both BIXS and IP measurements showed that the amount of tritium absorbed on the sample surface decreased more than 97% after heating at 800 K. Both intensity and shape of the measured X-ray spectrum have been specified to estimate the change of the tritium depth profile after each heat treatment. Besides, the Monte Carlo Stopping and Range of Ions in Matter (SRIM) code has been introduced to calculate the initial tritium depth profile just after being irradiated by glow discharge. Analysis shows that tritium atoms locate around 3 nm in depth before annealing, and tritium distribution becomes uniform in the near-surface layers (around several nanometers) gradually after heat treatment. At about 800 K, the relative tritium concentration in the near-surface layers reaches its maximum value compared with tritium in the deeper part of the tungsten sample. Then more and more tritium diffuses deeper into the sample as the temperature increases.