# 2016-Feb-15 Computational Physics Biweekly Report

He Zhang:

1. Finished and submitted a proposal to NSF, in which a methodology is proposed to simulate space charge effect with arbitrary boundary using boundary element method (BEM) and fast multipole method (FMM).

2. Identified and corrected an error in the FMM code for arbitrary kernel function. The formula for the local expansion calculation using source particles works for Coulomb potential (1/r), thanks to the symmetry of the potential. But it could give wrong results for other kernel functions, such as a function has a term of x/r. The correct formula has been derived and codes are revised.

3. Revised the kernel-independent FMM code to calculate multiple kernel functions simultaneously. This is useful when the kernel function has multiple components. For example the kernel function could be a vector potential. The old code can calculate only one kernel function, so that one has to call the FMM three times to calculate a vector potential kernel. But many calculations are exactly the same for the three calls. The new code can finish the calculation of multiple kernel functions in one run to avoid redundant calculations.

(2 and 3 are useful for dipole radiation field calculation, which will be implemented in the field emission simulation.)

River Huang:

4. River has finished a preliminary simulation code for the field emission simulation. In this version, the Coulomb field is calculated between all the particles, but the dipole radiation field is only calculated on the emitter. (Later we will add the dipole radiation field between particles.) We have got some simulation results and we are analyzing them. I helped in debugging the code and analyzing the data.

Yves Roblin:

+worked on machine configuration and setup for CEBAF, providing Optics support and Hall A APEL support +Attended NET2025 workshop. A call for proposal is being written by the DOE (Richard carlsen) with input from the participants +Attended a meeting with Richard York regarding the path forward for the JLEIC simulations +Preparing a talk for the APEX review

Collaborators:

Together with ODU collaborators, we are submitting a publication on long term GHOST tracking simulations.