AVS 49th International Symposium
    Vacuum Technology Tuesday Sessions
       Session VT-TuA

Invited Paper VT-TuA3
Ultra-sensitive Detection of Helium Release from Metal Tritides

Tuesday, November 5, 2002, 2:40 pm, Room C-104

Session: Vacuum System Architecture and Specialized Analytical Techniques
Presenter: J. Poths, Los Alamos National Laboratory
Authors: J. Poths, Los Alamos National Laboratory
T.J. Venhaus, Los Alamos National Laboratory
F.J. Steinkruger, Los Alamos National Laboratory
Correspondent: Click to Email
Static noble gas mass spectrometry has been in use for ultra-sensitive analysis of samples in the geological community for almost 5 decades. We have been using a magnetic sector instrument created by Al Nier at the University of Minnesota in both geological and nuclear research. In static mode of operation, the sample is equilibrated into the volume of the instrument with no pumping, rather than flowing through the source and into a pump as in a standard dynamic mass spectrometry. Thus, static operation provides a factor of 10,000 increase in sensitivity. We have recently applied this technique to analyzing the release of helium-3 from erbium ditritide films. The increased sensitivity has allowed us to compare helium release on timescales ranging from 5 minutes to 100 days. We confirm that helium release is highest at the beginning of an erbium ditritide film's lifetime, then decreases after a few months to a steady rate. Interestingly, during this period of steady-state release, the helium release rate seems to be independent of the buildup of helium-3 levels in the film. This observation suggests that at the moment of tritium decay a helium-3 atom is either immediately released or is trapped and no longer accessible for release. At steady-state, the ratio of helium released to helium decayed during storage is about 0.008.