""Ion cyclotron harmonic waves in the boundary of magnetized toroidal plasma," by Gunsu S. Yun (Pohang University of Science and Technology, Korea)

Date: 
Wednesday, March 14, 2018 - 2:00pm to 3:00pm
Series: 
Plasma Seminars

Plasma Seminar

Physics & Astronomy Building (PAB) Room 4-330
Wednesday, March 14, 2018
2:00PM

Guest Speaker: Professor Gunsu S. Yun (Pohang University of Science and Technology, Korea)

Talk Title: "Ion cyclotron harmonic waves in the boundary of magnetized toroidal plasma"

Abstract:

A high-speed radio frequency (RF) spectroscopy system integrated with a mm-wave imaging system has been developed on the Korea Superconducting Tokamak Research (KSTAR) device to study electromagnetic waves associated with fast relaxation of MHD instabilities and energetic particles [1]. Intense RF emissions (0.1 – 1 GHz) are observed within several hundreds of microsecond before and at the relaxation of the edge confinement barrier region called pedestal [2]. The RF emissions occur in several distinct stages in strong correlation with the evolution of fluid instabilities [3,4] from eigenmode-like filamentary perturbation structure to non-modal solitary perturbation (SP) and its burst: (1) appearance of high-harmonics of deuterium ion cyclotron frequency (fcD ~ 11 MHz), (2) intensification of the harmonic ion cyclotron emissions at the emergence of the solitary structure, (3) broadband RF emission toward high frequency (< 500 MHz) at the burst of the SP, and (4) rapid chirping up/down in step of fcD in the subsequent relaxation of the pedestal. Possible mechanisms for the RF emissions are discussed including magneto-acoustic cyclotron instability driven by fast ions with orbits of large radial excursion [5], drift–Alfven instabilities driven by parallel shear flows [6], and electrostatic Bernstein-like waves modified by E×B velocity shear in the pedestal [7].

 

References:

  1. G.S. Yun et al., Rev. Sci. Instrum. 85 (2015) 11D820
  2. S.G. Thatipamula et al, Plasma Phys. Control. Fusion 58 (2016) 065003.
  3. G.S. Yun et al., Phys. Rev. Lett. 107 (2011) 045004
  4. J.E. Lee et al., Sci. Report 7 (2017) 45075
  5. B. Chapman et al, Nucl. Fusion 57 (2017) 124004
  6. V.V. Mikhailenko, V.S. Mikhailenko, and H.J. Lee, Phys. Plasmas 24 (2017) 092112
  7. M.U. Lee et al., KSTAR Conference (2018)
Event Attachments: 
Location: 
PAB 4-330