Speaker
Dr
R.W. (Bob) Harvey
(CompX)
Description
The CQL3D bounce-averaged Fokker-Planck (FP) code [1] has been widely applied within the tokamak modeling community. For the reported work, it has been augmented to include axisymmetric open-field-line geometry, suitable for calculation of energetic ion and electron distributions in the low collisionality, tau_bounce << tau_collision, regime of energetic particles in mirrors. Our target application is calculation of energetic ion and electron distributions in GDT-like devices [2]. A time-dependent, particle-conserving, finite difference solution of the bounce-averaged collisional FP equation is obtained for particle distribution f(u,theta,rho,t), where u is momentum per mass, theta is pitch angle with respect to the magnetic field vector, and rho is a normalized function of magnetic flux function. A neutral beam source is provided by the NFREYA Monte Carlo beam deposition code, which has been benchmarked against the NUBEAM deposition code. The effects of radiofrequency wave heating are obtained based on the general Stix quasilinear wave-particle diffusion coefficients [3], using ray tracing data. GENRAY-C, a new general magnetic geometry variant of the all-frequency plasma-wave ray tracing code GENRAY[4] adapted to mirror machines, provides ray data ; iteration between CQL3D and ray quasilinear absorption is used to obtain self-consistency with the nonthermal distributions. Applications are made for fast and ion cyclotron wave heating of ions, and electron cyclotron heating of electrons.
The bounce-averaged code calculates the nonthermal distributions of trapped particles; the untrapped particles are lost in a particle transit time. Except that for near- and sub-thermal approximately Maxwellian particles , we do not apply the loss operator. A set of synthetic diagnostics based on the nonthermal distributions is available, for example for xray spectra, electron cyclotron emission, neutral particle spectra, and neutron rates.
CQL3D is well-benchmarked against experiments such as lower hybrid current drive in C-Mod [5], and neutral beam/high harmonic fast wave in NSTX[6].
Preliminary results with 4 MW of 25 keV D neutral beam at 45 deg pitch angle injection into a 3e13 /cm**3, T=1 keV GDT-like D-plasma[7] give a neutron rate of 6.6e11 n/sec. Shine through of the neutral beam is 22%. An additional 0.27MW of absorbed fast wave RF power increases the neutron rate to 2.2e12 n/sec.
References:
[1] R.W. Harvey, M.G. McCoy, "The CQL3D Fokker-Planck Code", www.compxco.com/cql3d.html
[2] V.V. Mirnov, D.D. Ryutov, Sov. Tech Phys. Lett. 5, 279 (1979).
[3] T.H. Stix, Waves in Plasmas, AIP (1992).
[4] A.P. Smirnov, R.W. Harvey, “The GENRAY Ray Tracing Code”, www.compxco.com/genray.html
[5] G.M. Wallace, et al., Phys. of Plasmas 19, 062505 (2012); http://dx.doi.org/10.1063/1.4729734
[6] R.W. Harvey, Yu.V. Petrov, D. Liu, et al., 20th Top. Mtg. RF Power in Plasmas, Sorrento, It. (2013).
[7] A.A. Ivanov, V.V. Prikhodko, Plasma Phys. Control. Fusion 55, 063001 (2013).
Primary author
Dr
R.W. (Bob) Harvey
(CompX)
Co-authors
Prof.
Cary Forest
(University of Wisconsin, Madison)
Dr
Yu.V. Petrov
(CompX)
