Re-cycling experiments in the DITE tokamak

Abstract

Re-cycling is studied in the DITE tokamak by changing the working gas from hydrogen to deuterium and back to hydrogen. The change in the composition of the plasma is followed both during the discharge and from shot to shot by using a scanning Fabry-Perot interferometer, a mass spectrometer and a carbon thermal desorption probe. The results of the three techniques are consistent and show that the gas trapped and desorbed from the wall plays a major part in the re-cycling process. A detailed analytical modelof the principal re-cycling mechanisms is proposed.