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This publication presents a review of hydrogen and helium recycling phenomena in tokamaks with limiters and walls largely made of carbon (graphite, a-C:H layers). Points of interest are plasma fuelling efficiency, wall pumping phenomena as observed in JET, TFTR, TEXTOR and other machines under various fuelling schemes (gas, neutral beams, pellets), the release of hydrogen/helium from material surfaces during and after plasma discharges and the long term retention (total particle inventory) of hydrogen in graphite or carbonised structures in tokamaks. The effect of recycling in a combined hydrogen/helium plasma is also discussed. It is shown that only part of the above phenomena can be understood in terms of processes between hydrogen/helium and carbon as known from simulation experiments (ion beams, gas discharge facilities) and that others (in particular the JET wall pumping phenomenon) have still to be explained. Possible mechanisms are outlined and discussed by means of global models.

Additional information

Authors: EHRENBERG J, JET Joint Undertaking, Abingdon (GB)
Bibliographic Reference: Report: JET-P(88)57 EN (1988)
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 198910060 / Last updated on: 1994-12-01
Original language: en
Available languages: en
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