Gyrokinetic calculations of the neoclassical radial electric field in stellarator plasmas

A novel method to calculate the neoclassical radial electric field in stell arator plasmas is described. The method, which does not have the inconvenie nce of large statistical fluctuations (noise) of the standard Monte Carlo t echnique, is based on the variation of the combined parallel and perpendicu lar pressures on a magnetic surface. Using a three-dimensional gyro-kinetic deltaf code, the calculation of the radial electric field (E-r) in the Nat ional Compact Stellarator Experiment [G. H. Neilson , Phys. Plasmas 7, 1911 (2000)] has been carried out. It is shown that a direct evaluation of E-r based on a direct calculation of the radial particle flux is not tractable due to the considerable noise. (C) 2001 American Institute of Physics.