DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 66: Separating Rotational Shear and rho* Scaling Effects on Transport | ||
| Name: | C. Craig Petty ( |
Affiliation: | General Atomics |
| Research Area: | Transport Model Validation | Presentation time: | Not requested | Co-Author(s): | T. C. Luce, R. E. Waltz |
| Description: | Measure the rho* scaling of transport and fluctuations for both L-mode and H-mode plasmas as a function of the toroidal Mach number to ascertain the importance of the rotational shear on question of Bohm vs. gyro-Bohm scaling. | ||
| Experimental Approach/Plan: | Study both limiter L-mode and divertor H-mode plasmas on separate days. (1) Start at BT=2 T and q95=4. Scan the beams from all co to all counter in 5 steps (including a balanced case). (2) Go to BT=1 T at the same q95 and same plasma shape. Reduce density by factor of 2.5. NBI power should be adjusted to match beta values of first step. (3) Repeat scan of beams from all co to all counter in 5 steps. (4) Fine tune the mix of co and counter NBI to precisely match the Mach numbers between the low and high rho* cases. | ||
| Background: | Transport modeling of rho* scaling experiments, using either theory based modeling or turbulence simulation codes, have predicted that changing rotational shear during a rho* scan can make intrinsic gyro-Bohm transport appear to be Bohm-like. Experiments were begun (but not finished) on TFTR to separate the two effects by measuring the rho* scaling at different toroidal Mach numbers. It is proposed to use the balanced NBI capabilities on DIII-D to measure the rho* scaling of transport and turbulent fluctuations for both L-mode and H-mode plasmas as the Mach number is scanned for co-rotating to counter-rotating. This should allow multiple pairs of rho* scans at fixed rotational shear to be obtained. | ||
| Resource Requirements: | NBI: All seven sources required (not simultaneously). | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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