Monte Carlo collision operators for use with exact trajectory integrators

Classical transport theory in a spherical torus differs from that in a standard tokamak because in the spherical torus the gyroradius has a width comparable to that of a drift orbit, the banana width. In addition, the operating spherical torus experiments have gradient scales that are comparable to the gyroradius of the ions. Transport theories should use the full kinetic equation, which can be solved numerically using Monte Carlo methods. Such a code for the spherical torus could be based on Alan Glasser's unpublished ORBIT code, which solves the full orbit equations, plus a Monte Carlo equivalent of the collision operator. This paper derives an appropriate Monte Carlo collision operator for use in such a code. (C) 2002 American Institute of Physics.