Page 13 - Electrostatic quasi-neutral formulation of global cross-separatrix particle simulation in field-reversed configuration geometry

Physics of Plasmas ARTICLE
In Fig. 11, the results of these comparison tests are shown: (a) poloidal plane R-Z trajectories of electrons near or at the turning point of the FRC core; (b) velocity space, parallel and perpendicular relative to the magnetic field, which shows that the electrons have not changed in energy much during this time (magnitude stays almost constant here); (c) toroidal phase space, which shows a slight toroidal drift; and (d) the delta-f weight evolution over time. The grid cells are also plotted in the corresponding color for context (not shown for the direct calculation case since it does not matter), and “ip” is the tracking label of the particle. Only a subset of the electrons tracked are shown to avoid confusion.
With respect to interpolation from field-aligned mesh to par- ticles, note that position updates are indirectly affected via velocity, the velocity updates are directly affected, and the delta-f weight updates are both directly affected and indirectly affected via position and velocity. The R-Z trajectory, the azimuthal phase space, and the velocity space are all indistinguishable (10􏰁6%–10􏰁5 % difference for positions and 10􏰁4%–10􏰁3 % difference for velocities, when compared to the direct calculation). On the other hand, the delta-f weight has some noticeable differences (0:1% 􏰁 1% difference, when compared to the direct calculation) since it is more sensitive to the velocity and position differences. In all aspects, these differences decrease as the grid resolution is increased as expected. For this particular case of this test function, no significant change is seen when increasing the num- ber of w cells in the core from 60 to 90.
DATA AVAILABILITY
The data that support the findings of this study are available from the corresponding author upon reasonable request.
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Phys. Plasmas 27, 082504 (2020); doi: 10.1063/5.0012439 Published under license by AIP Publishing
27, 082504-13