A model for bootstrap current calculations with bounce averaged Fokker-Planck codes

A model is presented that allows the calculation of the neoclassical bootstrap current originating from the radial electron density and pressure gradients in standard (2+1)D bounce averaged Fokker-Planck codes. The model leads to an electron momentum source located almost exclusively at the trapped-passing boundary. It is easily implemented in existing codes at virtually no additional cost in computing. Good agreement is obtained with known analytical expressions.