Effects of Nanoparticle Plasma Jet Injection on Runaway Electron Dynamics in Tokamaks

Numerical simulations indicate that runaway electron (RE) current generation can be suppressed by injecting a few km/s velocity nanoparticle plasma jet (NPPJ) from a plasma accelerator [1,2] into tokamak plasma at the beginning of current quench. RE dynamics is based on the model [3], which includes Dreicer and “avalanche” mechanisms and has a strong non-linear dependence on Z_eff. The model was extended with self-consistent Z_eff calculations using the atomic code FLYCHK [4]. Injection of carbon, boron nitride (BN) or other impurities into plasma can increase Z_eff to 4~5 and even higher. Essential influence of larger than one Z_eff on the RE dynamics was shown. Penetration of C₆₀ and BN NPPJ through increasing B-field was studied with the HEM-2D code [5], which was equipped with two new models/modules for the fragmentation (C₆₀) and the sublimation (BN). Simulations were made with both DIII-D and ITER parameters.

[1-2] I.N. Bogatu, S.A. Galkin, J.S. Kim: [1] J. Fusion Energy 27, 6, 2008, [2] J. Fusion Energy 28, 144, 2009; [3] H. Smith et al., Phys. Plasmas 13, 102502, 2006; [4] H.-K. Chung, et al. High Energy Density Physics 1, 3, (2005); [5] S.A. Galkin, Bull. APS DPP 2008, BO5.005, https://www.researchgate.net/publication/252593039