Speaker
Description
See the full abstract here:
http://ocs.ciemat.es/EPS2019ABS/pdf/P1.1091.pdf
Existing methods for diagnostics and control are still insufficient to deal with the various kinds of instabilities and collective dynamics that occur in magnetically confined fusion plasmas, which may impact the missions of the ITER and DEMO projects. Using small-scale laser experiments on the J-KAREN-P laser at KPSI, numerical simulations on the JFRS-1 supercomputer at IFERC-CSC, and theoretical analyses, we are investigating whether short pulses (ps-fs) of a high power laser (TW-PW) may be used to address some of these issues. The object of interest is the electron-free positively charged plasma wake channel that is carved out by a laser pulse with relativistic intensity (normalized amplitude a0 1) [1]. Using the relativistic PIC codes EPOCH [2] and REMP [3], we simulate the long-time evolution of such wake channels in the presence of a strong magnetic field ( 2 T) as is typical for present-day tokamaks.
We demonstrate that there exists a parameter window where the after-glow dynamics of the magnetized wake channels are effectively independent of the laser wavelength under tokamak conditions; namely, for highly subcritical electron density n_e/n_crit w_pe^2/W_laser^2<<1. This justifies scaled simulations with artificially increased wavelengths, which reduces the computational expenses (memory and time) to the point where long-time 3D simulations become feasible.
We compare the results of recently performed 2D and 3D simulations and examine the effects of the plasma density and magnetic field strength via parameter scans. In particular, we will report our observations regarding particle acceleration, charge separation and the generation of magnetic vortices. First insights concerning the role of thermal motion will be discussed along with possible implications for tokamak plasma control and diagnostics [4].
This research is supported by QST Director Fund for Creative Scientific Research (No. 16).
References
[1] G.A. Mourou, T. Tajima and S.V. Bulanov, Rev. Mod. Phys. 78 309 (2006)
[2] T.D. Arber et al., Plasma Phys. Control. Fusion 57 113001 (2015)
[3] T.Zh. Esirkepov, Comp. Phys. Comm. 135 144 (2001)
[4] A. Bierwage et al, 2nd QST Intl. Symp.: "Frontier of Quantum Beam Science with High Power Lasers", Nara, Japan, Nov. 2018, invited.
