Description
Nonlinear wave-particle interactions play a crucial role in determining the heating and transport properties of magnetically confined, low collisional plasmas. Experimental detection of persistent non-Maxwellian velocity-space distributions with real-space structures is still extremely challenging, and validation of the theoretical concept has not been extensively performed. Assuming that the plasma emission spectrum is a good proxy for the velocity distribution function, the detection of wave-particle coupling structures is within reach [1]. Recent hardware [2,3,4] and software [5] developments in phase-space structure detection have made it possible to find a bifurcation in the phase-space structures observed in the LHD, potentially affecting the resonant plasma heating [6].
Recently, the Bayesian approach is used to systematically analyze the velocity distribution function from the charge exchange recombination spectrum. Not only the charge exchange recombination emission spectrum but also the neutral beam injection profile are modeled as a function of plasma parameters and operation parameters, and inverse problems are solved using the Bayesian approach. The estimation uncertainties are determined based on its statistical properties. This approach is expected to accelerate experimental work on nonlinear wave-particle interaction.
[1] T. Kobayashi, Plasma and Fusion Research 18, 2402059 (2023)
[2] K. Ida, T. Kobayashi, M. Yoshinuma, et al., Communications Physics 5, 228 (2022)
[3] M. Yoshinuma, K. Ida, and T. Kobayashi, Plasma and Fusion Research 19, 1402037 (2024)
[4] T. Kobayashi, M. Yoshinuma, W. Hu, and K. Ida, Physics of Plasmas 30, 052303 (2023)
[5] T. Kobayashi, M. Yoshinuma, W. Hu, and K. Ida, PNAS 121, e2408112121 (2024)
[6] T. Kobayashi, M. Yoshinuma, and K. Ida, Review of Scientific Instruments 96, 033502 (2025)