Calculations of WHAM2 Mirror Neutron Rates and FI Transport using the GENRAY-C/ CQL3D-M and MCGO-M codes

The GENRAY-C ray tracing, and CQL3D zero-orbit-width neutral beam/RF/collisional Fokker-Planck code are applied for calculation of D distribution functions in the WHAM2 mirror configuration, obtaining DD neutron rates, similar to [1]. We compare calculated neutron rates from available 25 keV NB and RF fast wave (FW) power. For 0.5 MW second harmonic FW heating at 26 MHz, we obtain 5e13 neutrons per sec, compared to 2e12 n/s with 1 MW NB power. Electron density is 6e13/cm**-3; Te is 2 keV. The much higher D-energies obtained with FW are very effective for DD neutron production.

There has been concern that full gyro-orbit orbits may be subject to large pitch angle scattering in the sharply varying magnetic fields such as in WHAM[2], and this could cause fast ion loss into the mirror loss cone. Using the MCGO Monte Carlo orbit code, the full deuterium orbits were following for collisional slowing down times. Orbits appear to be in the QLM Quantum-Like-Mode, falling in to discrete states, and at least for the examined orbits the resulting diffusion is limited and does not appear large.

[1] R. W. Harvey, Y. V. Petrov, and C. B. Forest, AIP Conf. Proc.1771, 040002 (2016). https://doi.org/10.1063/1.4964187.

[2] Ronald H. Cohen et al., Phys. Fluids 21, 6127 (1978)

[3]A. Ambastha and R.K. Varma, PPCF 30, 1279 (1988).