DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 62: Measurement of Inductive Poloidal Current | ||
| Name: | C. Craig Petty ( |
Affiliation: | General Atomics |
| Research Area: | Heating & Current Drive | Presentation time: | Not requested | Co-Author(s): | P. A. Politzer |
| Description: | Measure the poloidal current density profile induced by ramping the toroidal field coil. Compare with the poloidal current expected from the parallel Ohm's law to determine if the perpendicular conductivity is large enough to give a significant contribution. | ||
| Experimental Approach/Plan: | Study H-mode plasmas with beta_pol near unity so that the "natural" poloidal current is negligible. Compare discharges with positive and negative ramps of the toroidal field to cases with no BT ramping. Keep the plasma current, density, and temperature constant during these ramps. Study two cases, a low electron temperature plasma with NBI heating only, and a high electron temperature plasma using ECH in addition to the diagnostic beams. | ||
| Background: | The magnitude of the perpendicular conductivity has not been measured to my knowledge in tokamaks. In this experiment, ramping the toroidal field will induce a poloidal electric field that can be exactly computed using Faraday's law. Multiplying this E_pol by the parallel conductivity gives the parallel contribution to Ohm's law, while multiplying E_pol by the perpendicular conductivity gives the perpendicular Ohmic current density. Using the MSE data (although not necessarily equilibrium reconstruction), both the poloidal current density and the parallel current density can be measured. By comparing plasmas with and without a BT ramp, it will be possible to determine if the measured change in the parallel current density is enough to explain the total measured poloidal current (i.e., the perpendicular conductivity is negligible). | ||
| Resource Requirements: | NBI: Co and counter MSE beams, and at least 2 other sources.
EC: Minimum 5 gyrotrons. | ||
| Diagnostic Requirements: | MSE is critical. | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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