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	17: 3-D Fields and ECH Density Pumpout
Name:	John deGrassie degrassie@fusion.gat.com	Affiliation:	General Atomics
Research Area:	Turbulence & Transport	Presentation time:	Not requested
Co-Author(s):	Andrea Garofalo	ITPA Joint Experiment :	No
Description:	The purpose of the experiment is to see if applied 3-D fields, or error fields in non-specific 3-D field experiments, play a role in the density pumpout when ECH is applied to a NBI target H-mode discharge. ECH density pumpout will be parameterized as a function of target discharge toroidal rotation, varying beam mix, at varying levels of applied 3-D field, or error field if there is an effect for small levels of perturbation.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	The target discharge will be an ELMing H-mode with variable toroidal velocity set by co/counter NBI. Off-axis ECH will be applied to cause some density pumpout. We will try to avoid huge density pumpouts, rather looking for conditions that allow somewhat controlled experimental conditions. The effect of rotation on pumpout will be measured. Then, 3-D fields will be applied, first by compromising the error correction and then applying stronger external 3-D fields. If there is a clear 3-D effect on the ECH density pumpout, in 'break in slope' or depth of the drop, etc, then a comprehensive 3-D spectrum study should be undertaken, i.e. n=1,2.3.
Background:	* In doing DIII-D intrinsic rotation experiments in recent years the effect of large ECH density pumpout has been observed. Anecdotally, the two somewhat different conditions that were applied were 1) low toroidal rotation plasmas using balanced NBI and 2) off-axis ECH. Both were used in order to have conditions to better identify intrinsic rotation with the higher beta resulting from NBI heating in addition to ECH. * Pumpout associated with ECH has been seen in many tokamaks, over decades. There are also cases of "pump-in". I don't know of a focussed experimental parameterization of the effect. * Theories have emerged in which the electron heating reduces the anomalous density pinch (e.g. Angioni). There are also experimental observations of ECH pumpout being associated with non-axisymmetric internal magnetic fields, due to MHD activity. * Pumpout is also seen in the RMP ELM control experiments. There it is clear that pumpout is caused by the 3-D fields applied. * In the ECH pumpout phenomenon, in DIII-D H-mode targets, as the density drops the ELM frequency typically increases, and the density decrement seems due to a reduction in the pedestal density. This increases the number of possible effects. Is it the ELMs that are reducing the density and the ECH is affecting ELMing? Even if this is the case, then it also may indicate a tie-in to the RMP ELM suppression experiments.
Resource Requirements:	1 day experiment. 2 days if compelling results obtained. Standard DIII-D. Minimally: All beams, All gyrotrons, I-coils,C-coils.
Diagnostic Requirements:	detailed kinetic profiles, reflectometry profiles, rotation profiles, main ion rotation valuable
Analysis Requirements:
Other Requirements: