Collisions with new_trap_int = T

When not using the Radau-Gauss pitch angle grid it is possible to get significantly reduced velocity integration errors by setting new_trap_int = T. Unfortunately this appears to be incompatible with the pitch angle collision operator.

‌

I believe this is because the pitch angle scattering operator uses the integration weights and assumes that these are exactly the spacing of the pitch angle grid points (or the volume around the point?). This is true for new_trap_int = F but not for new_trap_int = T (where the weights now represent the weights of Lagrange interpolating polynomials).

The simplest solution is to simply always calculate the new_trap_int = F weights and store these in a different array for use in the collision operator. This then allows the choice of either approach to the integration weights whilst ensuring the collision operator is unchanged.

Comments (2)