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Abstract

THE USE OF DIFFUSIVE OPERATORS TO MODEL PHYSICAL PROCESSES IS WIDESPREAD. IN PARTICULAR, IN NUMERICAL CODES WHICH MODEL THE EFFECTS OF RADIO-FREQUENCY HEATING ON PARTICLE DISTRIBUTION FUNCTIONS IN MAGNETICALLY CONFINED PLASMAS, THE HEATING IS REPRESENTED BY AN OPERATOR WHICH IS DIFFUSIVE IN VELOCITY SPACE. THE VALIDITY OF THE DIFFUSIVE APPROACH RESTS ON TWO ASSUMPTIONS : FIRSTLY, THAT THE PARTICLE MOTION IN THE WAVE FIELDS IS REPRESENTED ADEQUATELY BY UNPERTURBED ORBIT THEORY, AND SECONDLY THAT CHANGES IN PARTICLE SPEED RESULTING FROM INTERACTION WITH THE WAVES ARE SMALL COMPARED TO THE SCALE LENGTH OF THE DISTRIBUTION FUNCTION F IN VELOCITY SPACE. IN THIS PAPER THE OPERATOR APPROPRIATE WHEN THESE CONDITIONS ARE VIOLATED IS DISCUSSED, AND THE RESULTING EQUATION FOR F IS SOLVED NUMERICALLY FOR CASES IN WHICH THE FIRST APPROXIMATION IS VALID BUT THE SECOND IS NOT, THUS ALLOWING INVESTIGATION OF THE VALIDITY OF DIFFUSIVE THEORY. ELECTRON CYCLOTRON RESONANCE HEATING (ECRH) IS DISCUSSED HERE, ALTHOUGH THE THEORY IS READILY GENERALISED TO LANDAU DAMPING, ICRH, AND OTHER PROCESSES USUALLY MODELLED WITH DIFFUSIVE OPERATORS.

Additional information

Authors: O'BRIEN M R CULHAM LABORATORY, ABINGDON, UK, CULHAM LABORATORY, ABINGDON, UK
Bibliographic Reference: AVAILABILITY: WRITE TO THE LIBRARIAN, UKAEA, CULHAM LABORATORY, ABINGDON OXON, OX14 3DB (UK), MENTIONING REPORT DLM-P841, 1988.
Record Number: 1989126227900 / Last updated on: 1989-04-01
Category: PUBLICATION
Available languages: en
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