Speaker
Jeremy M. Hanson
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1110.pdf
Understanding and controlling the ITER baseline plasma response
J.M. Hanson1 , N. C. Logan2 , T. C. Luce3 , F. Turco1 , G. A. Navratil1 , and E. J. Strait3
1 Columbia University, New York, NY 10027-6900, USA.
2 Princeton Plasma Physics Laboratory, Princeton, NJ 08543-0451, USA.
3 General Atomics, San Diego, California 92186-5608, USA.
DIII-D experiments with low-torque ITER baseline demonstration discharges show that the
plasma’s magnetic response to applied low-frequency, non-axisymmetric field perturbations is
correlated with the onset of plasma disruptions.
Measurements of the low-frequency RWM growth rate
DIII-D ITER baseline demonstration discharges
plasma response have previously been Measurements Measurements
-0.4 Ideal MHD (DCON) Ideal MHD (DCON)
linked to proximity to the resistive wall 0.925 < ℓi < 0.975
-0.6 3.0 < q 95 < 3.4
γτw
mode (RWM) stability boundary [1].
-0.8
However, understanding the response in 1.5 < βN < 1.8
-1.0 3.0 < q95 < 3.4 (a) (b)
plasma regimes, such as the ITER base- 0.7 0.8 0.9 1.0 1.0 1.5 2.0 2.5
ℓi βN
line, that are well below the RWM pres-
sure limit and subject to resistive tear- Figure 1: Comparisons of the (a) `i and (b) βN dependen-
ing instabilities remains an active area cies of the normalized RWM growth rate γτw inferred from
of research. The growth rate γ of the plasma response measurements (squares) with predictions
driven, stable RWM is calculated from of the linearized, ideal MHD, resistive wall dispersion re-
lation (diamonds).
n = 1 response measurements using a
single mode model [1], normalized to the wall eddy current decay timescale τw = 2.5 ms, and
compared with the linearized, ideal MHD, resistive wall dispersion relation [2]. Figure 1 shows
that the dependencies of γτw on the plasma normalized internal inductance `i and normalized
beta βN are consistent with ideal MHD predictions. The βN dependence was exploited to demon-
strate closed-loop control of the response via feedback modulation of the neutral beam injected
power in the low-torque baseline regime. Using heating power to directly control a plasma
stability-related parameter, such as the response, may help facilitate the optimization of fusion
output while simultaneously avoiding stability limits.
This work was supported in part by the US Department of Energy under DE-FG02-04ER54761,
DE-AC02-09CH11466, and DE-FC02-04ER54698.
References
[1] H. Reimerdes et al., Physical Review Letters 93, 135002 (2004).
[2] S. W. Haney and J. P. Freidberg, Physics of Fluids B: Plasma Physics 1, 1637 (1989).
