DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 370: ECRH/ECCD Control of ELMs | ||
| Name: | Francesco Volpe ( |
Affiliation: | ORAU |
| Research Area: | ELM Control & Pedestal Physics | Presentation time: | Requested | Co-Author(s): | J. Lohr, R. Groebner, R. Moyer, R. Prater |
| Description: | Modify the edge pressure gradient and/or edge current by means of ECRH/ECCD to affect ELM frequency and size and possibly suppress them. | ||
| Experimental Approach/Plan: | Heat the very edge of the plasma (pure ECRH), comparing deposition slightly inside/outside the separatrix. Repeat for oblique launch (both co- and ctr-ECCD). | ||
| Background: | A similar experiment was carried out with success at DIII-D by J.Lohr et al. in the late 80's and early 90's (Stambaugh et al., PPCF 1988; T.Luce et al., IAEA 1990): 1.2MW of ECRH at 60GHz deposited inside/outside the separatix, on the high field side, was observed to halve/double the ELM period; no ECCD was attempted at that time. The idea would be to repeat the experiment on the low-field side with the new 110GHz system and with the improved edge diagnostics (improved TS, to measure the edge pressure, and MSE, to measure the edge current) and codes (ELITE) that became available in the meantime. These offer the perspective of a deeper physical understanding in terms of peeling-ballooning limit.
From the point of view of MHD control, the minimum goal would be to reproduce the effect on the ELM period, and possibly improve it, thanks to the increased ECRH power, the improved focusing and the fact that the experiment would be repeated on the low field side, i.e. with the target closer to the launcher, and thus reduced broadening of the gyrotron beams. Furthermore, ECRH tests on marginally ballooning-stable plasmas and ECCD tests on marginally peelng-stable plasmas have the potential for complete ELM (de)stabilization. Note that for extreme off-axis deposition, ECRH is known to affect n_e more than T_e, for not well understood reasons. It is still a valuable knob to control the product of the two, i.e. the edge pressure, but extensive tests would help to clarify why the effect on n_e is dominant. | ||
| Resource Requirements: | Up to 6 gyrotrons | ||
| Diagnostic Requirements: | Good TS and MSE at plasma edge | ||
| Analysis Requirements: | ELITE | ||
| Other Requirements: | -- | ||
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