DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 124: Optimize the 6 gyrotron, q_min near 1.5, high noninductive fraction scenario | ||
| Name: | John Ferron ( |
Affiliation: | General Atomics |
| Research Area: | Fully Noninductive High Beta Operation | Presentation time: | Requested | Co-Author(s): | -- |
| Description: | Apply several changes to the way the standard high noninductive fraction scenario has been operated to improve its performance. These would be in addition to the big change that is needed which is additional gyrotron power. The assumption here is that a total of 6 gyrotrons will become available, motivating an additional attempt at optimizing the q_min near 1.5 scenario. | ||
| Experimental Approach/Plan: | Several changes to the operating method for these discharges are suggested. 1) Use of feedback control of the q evolution, NTM stabilization with ECCD and use of counter beams and gyrotrons for heating during the discharge formation (these are described in separate proposals). 2) The start of the high-performance phase should be moved earlier in the discharge. To keep to the target q_min the same, q feedback should be used. This would allow an increase in the duration of the high-performance phase by using less beam energy during the formation. 3) Even without moving the high-performance phase earlier, there were adjustments in the beam usage that could have been made in the 2007 shots to give a few hundred milliseconds longer high-performance duration. 4) According to the ELM experts, if the double null shape is biased away from the grad-B direction, the ELM frequency is increased. This would help keep the density low. 5) More effort is probably needed on the optimization of the shape and achievable beta versus the pumping capability. Density still is rather high when the shape is double null. | ||
| Background: | The high noninductive fraction scenario which has received a lot of experiment time has q_min near 1.5 and has been successful in approaching 100% noninductive current. However, the duration of the high-performance phase has been short (about two seconds) and to achieve 100% noninductive current reproducibly, additional gyrotron power is what is really needed. | ||
| Resource Requirements: | -- | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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