DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
Login | Review | Submit | Logout | Help
Questions about this website? Contact Andrew LeBlanc Questions about ROF? Contact Chuck Greenfield
| Title | 288: Measurement of internal structure of RFA | ||
| Name: | Andrea M. Garofalo ( |
Affiliation: | Columbia University |
| Research Area: | RWM Physics | Presentation time: | Not requested | Co-Author(s): | M. Lanctot, H. Reimerdes |
| Description: | Measure the internal structure of the RFA during application of a slowly rotating n=1 I-coil field at beta above the n=1 no-wall limit. Compare to the predicted structure of the stable RWM. | ||
| Experimental Approach/Plan: | We propose to calculate the radial profile of the n=1 plasma displacement due to a slowly rotating n=1 field, from the ECE measurement of the Te fluctuations at two opposite toroidal locations. Yes, you read that right: two opposite toroidal locations of measurements of the entire Te profile. We have that unique capability right here at DIII-D. It cannot be used for rapidly rotating tearing modes, but it will work just fine for a 10 Hz rotating RWM. The idea is to use the standard ECE radiometer, located at the 81° port, in combination with the Michelson interferometer (HECE), located at the 270° port: almost exactly 180° apart!
The limitation is that the fastest that the HECE can measure the profile is every 25 ms. For a 10 Hz rotating field, that gives 4 measurements every period. To increase the sampling, we propose to add data from repeat discharges with time-shifted start of the measurements. With just a handful of good repeat discharges we can collect high quality profile information on the amplitude and toroidal phase of the n=1 RFA, to compare with codes like GATO and MARS. In particular, comparing the toroidal phase profile with MARS will give us information on the dissipation physics. | ||
| Background: | The internal structure of the RFA excited by a rotating I-coil field has never been measured. It is a necessary step to conclude that the RFA is due to the stable RWM. | ||
| Resource Requirements: | -- | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
Print this page