Interaction between high-power ICRF waves and drift-wave turbulence in LAPD

An experimental campaign on the physics of ICRF waves has recently begun using the Large
Plasma Device (LAPD) at UCLA. A new high-power (∼150 kW) RF system and antenna have been developed for excitation of large amplitude fast waves in LAPD. The source runs at a
frequency of 1-5 MHz, corresponding to ∼ 1-10 f_ci, depending on plasma parameters. Recent work has focused on the structure and scaling of RF sheaths and convection cells near the antenna [1]. In these same experiments, strong low-frequency modulation of coupled fast wave power is observed via direct measurement of the magnetic signals associated with the fast waves in the core plasma. This modulation is well correlated with low-frequency edge
density fluctuations associated with drift waves. Suprisingly, the amplitude of the RF modulation and the amplitude of edge density fluctuations in the drift wave frenquency range both grow with increasing RF power, suggesting some nonlinear coupling between the edge drift waves and large amplitude fast waves in the core region.

[1] Martin, et al., PRL 119, 205002 (2017)