CRF physics studies using the Large Plasma Device

Troy Carter

UCLA

Friday, September 14, 2018

3:00pm

NW17-218

PSFC Seminars

Abstract: 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].    Evidence of rectified RF sheaths is seen in large increases (~ 10 Te) in the plasma potential on field lines connected to the antenna, and in copper deposition on plasma facing components due to sputtering at the antenna. The rectified potential scales linearly with antenna current. The rectified RF sheaths set up convective cells of local E x B flows, measured indirectly by potential measurements, and measured directly with Mach probes. 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.  Surprisingly,  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)

Bio: 

Troy Carter is a Professor of Physics at the University of California, Los Angeles. Prof. Carter is the Director of the Basic Plasma Science Facility (BaPSF), a national user facility for plasma science supported by DOE and NSF. He is also the Director of the Plasma Science at Technology Institute (PSTI), and organized research unit at UCLA. His research focuses on experimental studies of fundamental processes in magnetized plasmas and is motivated by current issues in magnetic confinement fusion energy research and in space and astrophysical plasmas including magnetic reconnection, turbulence and transport in magnetized plasmas, and the nonlinear physics of Alfvén waves. He was a co-recipient of the 2002 APS DPP Excellence in Plasma Physics Research Award and is a Fellow of the APS. Prof. Carter received BS degrees in Physics and Nuclear Engineering from North Carolina State University in 1995 and a PhD in Astrophysical Sciences from Princeton University in 2001.