Wave propagation near cyclotron resonance in the presence of large Larmor radius particlesFunded under: EAEC-FUSION 12C
Absorption of waves propagating across an inhomogeneous magnetic field is of crucial importance for cyclotron resonance heating. In a fusion plasma there may be a significant number of hot ions for which the Larmor radius is comparable to or larger than the perpendicular wavelength. In this case the system is described by integro-differential equations, the structure of which is essentially determined by the fact that the response at a given position is determined by the wave amplitude over a region whose width is of the order of a Larmor radius. Two simplifications of the full integral response are given. The first uses the WKB approximation to obtain a local dispersion relation which retains some of the information contained in the non-local response. The second makes use of the fast wave approximation, Kay et al. and Lashmore-Davies et al., which is equivalent to the Born approximation, to reduce the integro-differential equations to a second order differential equation. Clearly, this offers considerable savings in computational time for numerical modelling of ion cyclotron heating in tokamaks. The latter approach is illustrated by giving the equations for a minority ion cyclotron resonance. Finally the results obtained with the aid of these equations are compared with other approximations.
Bibliographic Reference: Report: UKAEA FUS 283 EN (1995) 18 pp.
Availability: Available from the Librarian, UKAEA, Culham Laboratory, Abingdon, Oxon. OX14 3DB (GB)
Record Number: 199510568 / Last updated on: 1995-04-21
Original language: en
Available languages: en