DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 349: Test of importance of rotation in QH-mode using the I-coil for rotation and density control | ||
| Name: | Tom Osborne ( |
Affiliation: | General Atomics |
| Research Area: | ELM Control & Pedestal Physics | Presentation time: | Not requested | Co-Author(s): | K. Burrell, M. Fenstermacher, T. Evans, P. Snyder |
| Description: | The goal of this experiment is three fold: 1) The I-coil is used to vary the plasma rotation and thereby test the importance of rotational shear in QH-mode independent of the CO/CNTR beam (and therefore fast ion orbit) mix 2) The I-Coil is used to eliminate the density rise which occured in previous attempts to increase the CO beam fraction in QH-mode separating the effect of the density rise from the CO/CNTR beam fraction in loss of QH-mode at increased CO/CNTR fraction. 3) Develop the RMP as a pedestal density control method to extend QH-mode operation to less favorable discharge shapes which could impact the possibility of QH-mode operation in ITER. | ||
| Experimental Approach/Plan: | 1) Use I-Coil field (perhaps fully non-resonant odd parity) to reduce rotation in a QH-mode discharge and look for loss of QH-mode or changes in EHO character. 2) Apply resonant or near resonant RMP field to maintain density at fixed level during CO/CNTR beam fraction scan. 3) Use resonant RMP to reduce pedestal density while maintaioning central density to extend QH-mode operation to 'unfavorably' shaped (ITER shape) discharge otherwise poor access to low n peeling instabilites. | ||
| Background: | In a model proposed by Phil Snyder, QH-mode requires a combination of high rotational shear and access to the low n peeling/ballooning regime. In previous results QH-mode was lost and the discharge began to ELM when the CO/CNTR beam fraction reached 20%. As CO/CNTR fraction increased however there was also an increase in pedestal density as well as a change in fast ion orbits (and associated change in fast ion population in the pedestal) which made it difficult to separate the rotational effects. In these experiments the RMP coil will be used to control the plasma rotation. Braking of the plasma rotation may be achievable with only non resonant fields (odd parity I-coil connection). Density control with the I-coil has been shown to be effective over a wider range of q than required for ELM suppression and for the density control experiment then even parity will be used but q will not likely have to at 3.6. | ||
| Resource Requirements: | I-coil with possible flips from odd to even parity. Reverse Ip for primary CNTR injection. | ||
| Diagnostic Requirements: | Any QH-mode iexperiments in the future, particularly where ELMs and EHO will be mixed, should the have the possibility of getting BES and fast UCSD camera data to try to understand the EHO structure and its relationship to the ELM precurson. CER and TS are required | ||
| Analysis Requirements: | Profiles including rotation, kinetic EFIT, ELITE stability, etc. | ||
| Other Requirements: | Low recycling machine conditions (not after disruption mitigation or Ar puff experiments for example). | ||
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