DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 184: Test of neoclassical toroidal viscosity (NTV) theory for magnetic braking | ||
| Name: | Ted Strait ( |
Affiliation: | General Atomics |
| Research Area: | Rotation Physics | Presentation time: | Requested | Co-Author(s): | J. Callen, C. Hegna, A. Cole |
| Description: | The goal of this experiment is to test the hypothesis that non-resonant magnetic braking is predicted by neoclassical toroidal viscosity theory (NTV). Several key predictions can be tested:
(1) The strong scaling of torque with ion temperature: Ti^(5/2), leading to a deceleration that scales as Ti^(7/2) at constant beta (2) The scaling of torque with toroidal mode number: n^2 (3) The "offset frequency" to which rotation saturates with strong braking Agreement with the theory in all of these features would constitute strong evidence of the validity of NTV theory. | ||
| Experimental Approach/Plan: | A square pulse of magnetic braking with n>1 is applied using the I-coil. (The C-coil provides optimized n=1 error field correction.) The transient response of the plasma to the braking pulse (initial dv/dt) yields the torque at the initial value of beta and rotation. The three features of the theory described above will be tested by:
(1) Density scan at fixed beta. Due to the strong scaling, only a small range of density is needed (20% change in density should yield a factor of 2 change in deceleration). (2) Comparison of n=2 and n=3 braking. (3) Variation of the initial rotation value using co/counter NBI. Determine whether the torque is proportional to V or (V-V0). | ||
| Background: | NTV theory is widely quoted as predicting the torque due to non-resonant braking. It was used as one figure of merit in assessing options for ELM control coils in ITER. However, a systematic experimental test of the theory has apparently not been performed.
This experiment should include a contribution to an ongoing joint experiment between JET and C-Mod on n=2 braking. | ||
| Resource Requirements: | I-coils and audio amps. | ||
| Diagnostic Requirements: | CER rotation profiles | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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