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Manuscript Title: FIFPC: a fast ion Fokker-Planck code.
Authors: R.H. Fowler, J. Smith, J.A. Rome
Program title: FIFPC
Catalogue identifier: ABSD_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 13(1977)323
Programming language: Fortran.
Computer: IBM 360/91.
Operating system: IBM SYSTEM/360.
RAM: 270K words
Word size: 8
Peripherals: graph plotter, disc.
Keywords: Plasma physics, Tokamak plasma, Fokker-planck equation, Kinetic model, Distribution, Fast ion, Neutral beam injection.
Classification: 19.8.

Nature of problem:
The distribution function of fast ions resulting from neutral beam injection into a Tokamak plasma is calculated. The Fast Ion Fokker- Planck Code (FIFPC) also computes the momentum and power delivered to the electrons and ions in the background plasma, the power lost through charge exchange, the particle input to the plasma, and other quantities of interest.

Solution method:
FIFPC solves the Fokker-Planck equation that describes the slowing down process of fast ions in a Tokamak plasma. This two-dimensional velocity space equation is transformed into sets of implicit finite difference equations to obtain the time-dependent solution or to obtain the steady- state solution directly. Two methods of solution are employed for the time-dependent problem. One method uses the Crank-Nicolson scheme. The resulting set of finite difference equations is solved by using the strongly implicit procedure (SIP) developed by Stone. The other method is based upon the alternating direction implicit (ADI) scheme which results in equations with tridiagonal coefficient matrices that are solved using a standard technique. The steady-state finite difference equations are solved by the SIP technique.

FIFPC has been used over a large physical domain and has produced valid results for all cases with resonable Tokamak parameters. The velocity space grid is limited to 40 points in each direction; however, this limit can be altered by changing the appropriate dimensions. The fast ions are assumed to stay on a flux surface and the pitch angle scattering operator for very untrapped ions is used. Thus, the code is most accurate for tangential injection and when the poloidal gyroradius is much less than the minor radius of the Tokamak.