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Abstract

For the Plasma Boundary Probe System and the Fast Transfer System at JET the design of a Time Resolving Collector Probe was performed. Special attention was given to the collector material and its implication to the analysis technique used to detect the deposited fluxes of hydrogen and impurities after plasma exposure. The investigations on the collector material showed that widely used Payex is inadequate due to high level bulk impurities (some 100 ppm). Instead, well purified graphite, even in the dimensions needed is available and can be obtained with a rather smooth surface (roughness < 2 um). Routine analysis of collector probe surfaces with regard to impurity fluxes after having been exposed to the plasma can be performed most conveniently by means of Proton Induced X-Ray Analysis (PIXE) or Rutherford Backscattering Spectrometry (RBS). PIXE has the advantage of discriminating the elements in question better than RBS (stainless steel components for instance) whereas RBS gives some depth discrimination. The value of this, however, is in doubt because of possible metal droplet formation on the collector surface. The mechanical layout of the probe enables a fast exchange of single components without changing others. This allows the use of different collector materials later on (for instance silicon) and assures a more flexible use of the probe for different purposes (H trapping and depth profiling).

Additional information

Authors: EHRENBERG J, MAX-PLANCK-INSTITUT FUER PLASMAPHYSIK, GARCHING BEI MUENCHEN (GERMANY);BOERGESEN P, MAX-PLANCK-INSTITUT FUER PLASMAPHYSIK, GARCHING BEI MUENCHEN (GERMANY);DORN C MAX-PLANCK-INSTITUT FUER PLASMAPHYSIK, GARCHING BEI MUENCHEN (GERMANY), MAX-PLANCK-INSTITUT FUER PLASMAPHYSIK, GARCHING BEI MUENCHEN (GERMANY)
Bibliographic Reference: WRITE TO MAX-PLANCK-INSTITUT FUER PLASMAPHYSIK, 8046 GARCHING BEI MUENCHEN (GERMANY), MENTIONING REPORT IPP 9/49, 1984
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