MONTE CARLO MODELLING OF IMPURITY ION TRANSPORT FOR A LIMITER SOURCE SINK
In relating the impurity influx Phi"0"-"rm I" (atoms per sec) into a plasma from the edge and the central impurity ion density n-"rm I"(0), it is necessary to know the value of tau"rm SOL"-"rm I", the average dwell time of impurity ions in the scrape-off layer. It is usually assumed that tau"rm SOL"-"rm I" = L-"rm c"/c-"rm s", the hydrogenic dwell time, where L-"rm c" is the limiter connection length and c-"rm s" is the hydrogenic ion acoustic speed. Monte Carlo ion transport results are reported here which show that for a wall (uniform) influx tau"rm SOL"-"rm I" is no longer than L-"rm c"/c-"rm s" while for a limiter influx it is shorter. Thus for a limiter influx n-"rm I"(0) is predicted to be smaller than the reference value while for a wall flux it is larger than the reference value. Impurities released from the limiter form ever larger clouds'' of successively higher ionization stages. These are reproduced by the Monte Carlo code as are the cloud shapes for a localized impurity injection far from the limiter.
Bibliographic Reference: WRITE TO THE PUBLICATIONS OFFICER, JET JOINT UNDERTAKING, ABINGDON, OXON, OX14 3EA, MENTIONING REPORT UJET-P(87)61, 1987
Record Number: 1989126117800 / Last updated on: 1989-06-01
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