DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 130: High BetaN, f_BS, ITB plasmas | ||
| Name: | Chris Holcomb ( |
Affiliation: | Lawrence Livermore National Laboratory |
| Research Area: | Fully Noninductive High Beta Operation | Presentation time: | Requested | Co-Author(s): | Andrea Garofalo |
| Description: | Demonstrate BetaN>4, f_BS~90%, scenario with ITB, qmin>2, rhoqmin>0.6 and moderate pressure peaking in reverse Ip using counter NBI and ECCD | ||
| Experimental Approach/Plan: | In reverse Ip, start-up with counter NBI sources to i) reduce on-axis NBCD and ii) maintain sufficient rotation to avoid locked modes. Scan the starting Bt down from 2.1 T to obtain high Beta with fewer beams, lower density, and higher ECCD efficiency. Use early ECH/ctr-ECCD to compensate for the expected lower temperature and faster current evolution. Ramp Bt and Ip to obtain broad current profiles. In the high Beta phase, apply 2 co-beams (210r,l) as needed for feedback and diagnostics, and apply ctr-ECCD near rhoqmin to compensate for bootstrap current overdrive that otherwise would decrease qmin. Scan the deposition location to find where it has the greatest effect sustaining high qmin. | ||
| Background: | Steady state high BetaN with f_BS > 90% requires qmin>2, rhoqmin ~ 0.7, and moderate pressure peaking. (Turnbull, NF, 1998). BetaN ~ 4 with qmin ~2 with an ITB has been achieved transiently (Garofalo, PoP 2006). However, the rhoqmin was smaller than desired due to too much on axis beam current drive, and non-inductive current overdrive near rhoqmin lead to current profile evolution and a smaller n=1 ideal wall limit. In 2006 an experiment was conducted that used reverse Ip and up to 5 counter NB sources to try to expand rhoqmin. Ip and Bt ramps (starting at 2.1 T) were used to broaden the current profile. Start-up with co-rotation and a transition to counter-rotation caused a locked mode that disrupted these shots. Various important components, such as the MSE diagnostic and the RWM control, were not optimized correctly in the control room, and density control was a problem. The above experimental approach takes advantage of what was learned in the 2006 run day. | ||
| Resource Requirements: | All seven NBI sources. Five or more gyrotrons. | ||
| Diagnostic Requirements: | |||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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