DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 34: Cross-machine comparison of n=2 (non-resonant) magnetic braking | ||
| Name: | Holger Reimerdes ( |
Affiliation: | Columbia University |
| Research Area: | Rotation Physics | Presentation time: | Requested | Co-Author(s): | J. Callen, A. Cole, A. Garofalo, C. Hegna, T. Hender, D. Howell, S. Wolfe |
| Description: | Test theory models such as neoclassical theory of toroidal viscosity against measurements in C-Mod, DIII-D and JET. Carrying out n=2 braking experiments in DIII-D will allow to compare the observed torque to observations in previous (and planned) n=2 braking experiments in C-Mod and JET and previous as well as proposed n=3 braking experiments in DIII-D. | ||
| Experimental Approach/Plan: | We plan to apply n=2 magnetic field pulses with the C-coil in NBI heated, fast rotating plasmas and measure deceleration and new equilibrium rotation. Both measurements should give independent estimates of the torque resulting from the externally applied non-axisymmetric magnetic fields. The C-coil currents are optimized to match the toroidal spectrum (n = 0, 2 and 4) in C-Mod and JET and the toroidal phase is chosen to minimize the interference with the plasma shape control. Alternatively, rotating n=2 fields could be applied. The experiment is repeated in similar plasmas with varying NBI-torque in an attempt to connect the observations in C-Mod plasmas without momentum input to the braking in JET plasmas with uni-directional NBI torque and gather further information on a possible rotation offset as predicted by neoclassical theory. The experiment should benefit form the results of ROF proposal 308 by A.M. Garofalo, which aims at separating resonant and non-resonant braking effects. | ||
| Background: | NTV theory has been successfully applied to explain n=3 magnetic braking experiments on NSTX [Zhu , Sabbagh, et al, Phys. Rev. Lett. 96 (2006) 225002]. The model has since been used to evaluate proposed non-axisymmetric coils for ITER. There is an extensive database of n=3 braking experiments in DIII-D. Further n=2 braking experiments were recently carried out on C-Mod (using the A-coil) and JET (using the error field correction coils (EFCCs) as part of an ITPA experiment on non-resonant braking. While the NBI heated JET experiments showed significant braking, the (intrinsic) rotation in ICRH heated C-Mod plasmas was not affected by the externally applied fields of comparable magnitude (i.e. same delta B(n=2)/B_0). | ||
| Resource Requirements: | C-coil in n=2 configuration. | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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