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The influence of trapping effects on neutron production in NBI-heated tokamak plasmas

Published online by Cambridge University Press:  01 June 1997

B. WOLLE
Affiliation:
Institut für Angewandte Physik, Universität Heidelberg, D-69120 Heidelberg, Germany
Z. JAUCH
Affiliation:
Institut für Theoretische Astrophysik, Universität Heidelberg, D-69120 Heidelberg, Germany
L.-G. ERIKSSON
Affiliation:
JET Joint Undertaking, Abingdon, Oxfordshire OX14 3EA, UK

Abstract

Fast computer codes for evaluating non-thermal velocity distributions are needed in order to carry out routine analysis of neutron signals in plasmas heated by neutral-beam injection (NBI). By neglecting the magnetic field inhomogeneity along a field line, i.e. neglecting trapped-particle effects, calculations of the velocity distribution can be made relatively rapidly. In this paper, we investigate under which circumstances such an approximation is justified. We solve the bounce-averaged Fokker–Planck equation, which includes particle trapping, by expressing the solution in terms of a series of appropriate eigenfunctions of the pitch-angle scattering operator. The eigenfunctions, eigenvalues and time-dependent coefficient functions are calculated numerically. We use the solution for calculating the effect of particle trapping on neutron production for beam-heated deuterium plasmas.

Type
Research Article
Copyright
1997 Cambridge University Press

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