DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2013 EXPERIMENTAL CAMPAIGN Review | Direct submission with log-in | Request submission without log-in
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Title	185: Measure Plasma Response to RMPs
Name:	Xi Chen chenxi@fusion.gat.com	Affiliation:	General Atomics
Research Area:	ELM Control	Presentation time:	Requested
Co-Author(s):	Bill Heidbrink, Gerrit Kramer, Raffi Nazikian, Mike Van Zeeland, Jeremy Hanson and the EP group	ITPA Joint Experiment :	No
Description:	Use fast ion transport/loss to probe the plasma response to RMPs in three regimes: strong kink response, strong plasma screening and weak plasma response. Quantify fast ion loss (and transport) with the magnitude of kink response; Search for islands (location, size, strength); test/validate plasma response model/code,e.g. use the case where some islands are not screened when Vperp_e ~0 as screening model predicts.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Using plasma current and beam settings favorable for fast ion first orbit loss detection: * Apply n=1 rotating RMP: 1. In strong kink response regime, quantify loss/FIDA data with plasma kink response: - Beta-scan, collect data with different magnitude of kink response - scan the relative phase between upper and lower coils, collect data at all phase related to the mode - change from even parity to odd parity, collect data with different mode coupling (resonant vs. non-resonant) - vary I-coil currents 2. In strong plasma screening regime, search for islands, test screening model/code: - at a beta value when plasma kink is strong in co-rotating from #1, flip plasma rotation direction, i.e. ctr-rotating now, collect data (not screened vs. screened) - very slowly? rotating RMPs, collect data(the X- and O- point travel by) 3. Collect data in the regime where neither kink response nor screening is important for comparison with #1 and #2 4. If ELM suppression is achieved, slightly vary q95 near the marginal value, collect loss for case with magnetic island sitting on top of pedestal as predict by theory (ELM suppression) and without. * Apply n=3 RMP: - Scan plasma rotation, high co-rotating to high ctr-rotating, collect loss (without screening and with screening) - With ctr-rotating, vary plasma screening by + varying the toroidal phase of applied n=3 RMP + varying q95 - Flip polarity of RMP coils in one shot - Vary I-coils current * Use PCS, no RMPs: - Reproduce the plasma "movement"(variation in gapout, axis, x-point) caused by RMPs, collect loss/FIDA (only due to plasma "movement")
Background:	First orbit loss of fast ions is very sensitive to the plasma fluctuating field. Alfvn eigenmodes induced first orbit loss of beam ions have been observed where the mode amplitude B_tw/B, is on the order of 10E-3. The perturbations caused by RMPs have similar amplitude. Therefore, fast ion loss/transport measurement can contribute to the study of plasma response, field penetration/plasma screening. * Quantify the fast ion loss/transport due to plasma kink response How much does plasma kink response affect fast ions during RMP? Will we find a connection between these two and use fast ion measurement to study the kink response? * Search for islands: We can use fast ions first orbit loss to search for magnetic islands due to RMPs. The particle orbits are different and the losses might be different: - with and without magnetic islands - when the ion travels through the x-point and the o-point of the island. * Test/Validate/Contribute to the development of plasma screening model --- "at certain plasma parameters and due to the non-linear evolution of the redial electric field produced by RMPs, the ExB rotation can be compensated by electron diamagnetic rotation locally. In this case, RMPs can penetrate and form magnetic islands." M. Becoulet et al. NF 52(2012) - Does the simulated fast ion loss with vacuum field or with plasma screening match the experimental fast loss signal better? - How does the fast ion loss vary with RMP strength/q95/rotation as the plasma screening changes with those parameters predicted by the modeling/theory? - To validate the case of island not screened (when the Vperp_e ~ 0)
Resource Requirements:	normal BT and Ip direction, n=1 rotating RMP, n=3 RMP, 30L, 150L&R, 330L, 210L&R
Diagnostic Requirements:	FILD1&2, CER, BES, ECEI, UCSD fast camera, FIDA, LIBEAM, MIR (if available), Thomson Scattering,...
Analysis Requirements:	Kinetic EFIT, TRANSP, NOVA-K, SPIRAL, M3D-c1, IPEC,...
Other Requirements:	--