Active MHD Spectroscopy of Alfvn Eigenmodes

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Active MHD Spectroscopyof Alfvén Eigenmodes
J. A. Snipes, A. Fasoli, R. S. Granetz, R. R.
Parker, D. A. Schmittdiel, S. M. Wolfe

• MIT Plasma Science and Fusion Center
• Cambridge, MA USA

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C-Mod Active MHD antennas
Welded stainless steel Bitter plate design
with boron nitride protection tiles,
5 turns/antenna, 4 antennas on the
outboard wall at 2 poloidal and 2 toroidal
locations 72 apart provide sin ? and cos ?
0.4 kW from 80 kHz 1 MHz, existing amplifier
2 kW 1 kHz 1 MHz amplifier being
designed
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Active MHD Spectroscopy of Alfvén Eigenmodes
Motivation Stable TAE modes driven on JET with
active MHD antennas measure the frequency, mode
structure, and damping rate of the modes and
effects of fast particles from NBI, ICRH, and DT
operation. Even without ? particles C-Mod can
help predict ? stability in reactor relevant
regimes with Ti ? Te Goals
measure growth rate of induced stable eigenmodes
with 100 kHz lt fTAE lt 900 kHz and
proximity to marginal stability Survey modes
potentially driven by ?s at high BT, ne, TiTe
Information on q profile (from fTAE vA/4?qR)
ICRH at low ne to drive
stable modes with a fast ion tail Plan of
execution sweep frequency to look for plasma
resonances ICRH in D(H) at 5.4 T, ne ? 0.5 ?
1020 m-3 to drive fast ion tail Vary H/(HD)
and ne to look for effects on fast particles and
stability ICRH in current rise with slow Ip
ramp to sweep q and fTAE at low ne steady ICRF
EDA H-mode at low H/(HD) to fix fTAE with an ion
tail