Fusion Science and Technology / Volume 48 / Number 1 / July 2005 / Pages 349-353
Technical Paper / Tritium Science and Technology - Tritium Measurement, Monitoring, and Accountancy
A bi-layer device was fabricated and tested for the direct collection of electrons emitted by tritium beta decay. The sensor functions at high pressures and concentrations where previously no simple and cost effective direct measurement technique existed for tritium. A polished KOVARTM (Fe-Ni-Co alloy) rod was coated with a 1-m thick insulating layer of alumina using electron-beam evaporation, physical vapor deposition (PVD) of alumina with oxygen dosing. The alumina deposition process was optimized to minimize pinholes and obtain a stable coating with high resistivity. The detector exhibited a nanoampere electrical response over a few decades of tritium concentration, up to pure tritium at 200 kPa. The sensor has been in service for several months now without showing signs of degradation and no discernible physical damage or change in efficiency has been observed.