DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 139: Direct Measurement of Momentum Drag from Error Fields | ||
| Name: | C. Craig Petty ( |
Affiliation: | General Atomics |
| Research Area: | Rotation Physics | Presentation time: | Not requested | Co-Author(s): | T. C. Luce |
| Description: | By modulating the error fields, and two comparing discharges where the phase of the error field has been changed by 180 deg, the profile of the error field drag can be determined. The toroidal rotation speed as measured by CER with ~5 ms resolution can be fit to a linearized (perturbative) momentum transport equation with two unknown profiles: the momentum diffusivity and the error field drag. Making a consisent fit of the data for both signs of error field perturbation helps to distinguish between the transport effect and the drag effect.
This modulation measurement can be used to determine the following effects: (1) the interaction between the error fields and magnetic islands, (2) resonant vs. non-resonant error field drag, and (3) rotational screening of the error field drag. | ||
| Experimental Approach/Plan: | (1) Establish stationary target plasma with high toroidal rotation rate. We should compare plasmas with and without tearing modes to document the interaction between magnetic islands and error fields. (2) Modulate the error field between 25-100 Hz. The stronger the plasma response, the higher the modulation frequency can be. Repeat with a 180 deg phase shift. (3) Vary q95 from <3 to >4 to help distinguish between resonant and non-resonant effects. (4) Repeat at lowest possible toroidal rotation rate. | ||
| Background: | This method is analogous to measuring the heating profile or the current drive profile by modulating the source, both of which have been done on DIII-D. | ||
| Resource Requirements: | -- | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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