4月2日 Studies of ICRF Physics using the Basic Plasma Science Facility

　　题目：Studies of ICRF Physics using the Basic Plasma Science Facility

　　报告人：Troy Carter

　　时间：2019年4月2日（周二）上午9:30-11:00

　　地点： 四号楼六楼中间会议室

　　报告摘要：

　　The Basic Plasma Science Facility (BaPSF) at UCLA is a US national user facility for studies of fundamental processes in magnetized plasmas. The centerpiece of the facility is the Large Plasma Device (LAPD), a 20m long, magnetized linear plasma device [1]. This LAPD has been utilized to study a number of fundamental processes, including: collisionless shocks, dispersion and damping of kinetic and inertial Alfvén waves, flux ropes and magnetic reconnection, three-wave interactions and parametric  instabilities of Alfvén waves, turbulence and transport and interactions of energetic ions and electrons with plasma waves. An overview of research using the facility will be given, followed by a more detailed discussion of studies of high power ICRF waves 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 fci, depending on plasma parameters. Recent work has focused on the structure and scaling of RF sheaths and convection cells near the antenna [2]. 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 frequency 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.  A new four strap ICRF antenna, built by ASIPP in collaboration with TAE Technologies, has recently been installed on LAPD and will enable future work on ICRF physics; these plans will be discussed.

　　[1] W. Gekelman, et al., Review of Scientific Instruments 87, 025105 (2016).

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

　　报告人介绍：

　　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.

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