Prospects for Edge Current Density Determination Using Li beam on DIII-D
The specific size and structure of the edge current profile has important effects on the MHD stability and ultimate performance of many advanced tokamak (AT) operating modes. This is true for both bootstrap and externally driven currents that may be used to tailor the edge shear. Absent a direct local measurement of j(r), the best alternative is a determination of the poloidal field. Measurements of the precision (0.1-0.01{sup o} in magnetic pitch angle and 1-10 ms) necessary to address issues of stability and control and provide constraints for EFIT are difficult to do in the region of interest ({rho} = 0.9-1.1). Using Zeeman polarization spectroscopy of the 2S-2P lithium resonance line emission from the DIII-D LIBEAM, measurements of the various field components may be made to the necessary precision in exactly the region of interest to these studies. Because of the negligible Stark mixing of the relevant atomic levels, this method of determining j(r) is insensitive to the large local electric fields typically found in enhanced confinement (H-mode) edges, and thus avoids an ambiguity common to Motional Stark Effect (MSE) measurements of B. Key issues for utilizing this technique include good beam quality, an optimum viewing geometry, and a suitable optical pre-filter to isolate the polarized emission line. A prospective diagnostic system for the DIII-D AT program will be described.
- Research Organization:
- General Atomics, San Diego, CA (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC03-99ER54463; W-7405-ENG-48
- OSTI ID:
- 766700
- Report Number(s):
- GA-A23426; TRN: US0109258
- Resource Relation:
- Conference: 13th Topical Conference on High-Temperature Plasma Diagnostics, Tucson, AZ (US), 06/18/2000--06/22/2000; Other Information: PBD: 1 Aug 2000
- Country of Publication:
- United States
- Language:
- English
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