Experimental set-up for gas balance measurement at JET
The JET experiment using tritium needs to address the problem of tritium retention in the vessel walls. Measurements to assess the first wall behaviour in respect to gas retention and gas release during and after tokamak pulses are made in the deuterium phase of JET. A pumping system parallel to the standard forevacuum system of JET has been installed to pump and store the discharged gas after each plasma shot. Using a timing sequence to operate the valves, the normal mechanical forevacuum pumps are disconnected and a special cryogenic pumping set is used to collect the gas discharged by the torus turbomolecular pumps for a given time after each shot. A storage tank takes the collected gas from the cryogenic pump after a period of operation, from which gas samples can be taken for analysis. The paper describes the set-up, the type of cryo-pump and also the various modes of operation of the experimental set-up. The results obtained show that the torus walls have a very strong retention capability. Depending on wall surfaces and plasma conditions, release rates between 10% and 80% of injected gas have been measured.
Bibliographic Reference: Report: JET-P(89)51 EN (1989)
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199010654 / Last updated on: 1994-12-01
Original language: en
Available languages: en