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	47: Quantifying the TBM torque, both in magnitude and radial location
Name:	Tuomas Tala Tuomas.Tala@vtt.fi	Affiliation:	VTT Technical Research Centre
Research Area:	Plasma Rotation	Presentation time:	Not requested
Co-Author(s):	W. Solomon, H. Reimerdes, A. Salmi, J. Snipes	ITPA Joint Experiment :	No
Description:	Understand the physics of TBM induced rotation changes and the origin (magnitude, radial location, beta dependence) of the TBM torque (NTV torque).	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Based on the single shot where the TBM modulation at 5Hz was applied in the 2011 TBM experiments on DIII-D, this method turned out to be a very good one to study the rotation changes induced by the TBM. The analysis of the single shot shows that the effect of the TBM on rotation originates from the edge, as published in H. Reimerdes et al., IAEA FEC 2012 paper. In order to be able to calculate quantitatively the TBM torque, a few more pulses with TBM modulation would be needed combined with good measurements of momentum transport within the same shots. What is needed for this is a scan of TBM perturbation amplitude (either by coil current, plasma movement, I-coil error field correction) so that the amplitude of the rotation change varies, and simultaneously apply NBI modulation to measure the momentum transport coefficients within each shot. So, each of the shot in this scan should have a phase with TBM modulation and a phase with NBI modulation. Another important parameter to be scanned is beta. At high beta, larger changes in rotation were observed. There, the effect of TBM on rotation could be different (possibly a combination of edge and core contributions), and using the TBM modulation technique, this difference could be studied, in particular where the TBM torque sources/sinks are radially located. A beta scan with TBM modulation and NBI modulation within a shot to nail down the reason why at higher beta the TBM influences more rotation is proposed.
Background:	A series of experiments was performed on DIII-D to mock-up the field that will be induced in a pair of ferromagnetic Test Blanket Modules (TBMs) in ITER to determine the effects of such error fields on plasma operation and performance. The largest effect was slowed plasma toroidal rotation v across the entire radial profile by as much as ~50% decrease due to TBM. A decrease in global density, beta and confinement were typically ~3 times smaller. Further experiments to pin down the physical mechanism how the TBM affects rotation, by inducing a torque source/sink and/or changes in momentum transport and edge rotation. Using the TBM modulation at 5Hz frequency, the evidence point out towards the fact that TBM is inducing a counter edge torque and this decrease is then further propagated to the core. To quantify the TBM torque, a TBM perturbation scan with TBM modulation combined with a separate beta is needed for ITER extrapolation.
Resource Requirements:	TBM mock-up active, Co and counter NBI
Diagnostic Requirements:	Full profile diagnostics, especially CER, plus FIDA and main ion CER.
Analysis Requirements:	TRANSP, intrinsic torque + modulated transport analysis
Other Requirements: