Active probing of plasma edge turbulence and feedback studies on the Texas Experimental Tokamak (TEXT)
- Oak Ridge National Lab., TN (United States)
- Texas Univ., Austin, TX (United States). Fusion Research Center; and others
A novel experiment is under way on the Texas Experimental Tokamak (TEXT) to actively modify the turbulence at the plasma edge by launching waves using electrostatic probes in the shadow of the limiter. The experiments are carried out with a wave launching system consisting of two Langmuir probes, which are about 1.8 cm apart in the poloidal direction, with respect to the magnetic field. These probes are operated in the electron side of the (I,V) characteristic. The probe tips are fed separately by independent ac power supplies. Measurements indicate that the wave, launched with a typical frequency image of 15--50 kHz from the edge of the machine top, is received by sensing probes located halfway around the torus. The detected signal strength depends on the frequency of the wave, the plasma current, and the phasing of the applied ac signal between the launching probes. Modifications to the spectra of the density and potential fluctuations are observed. These experiments have been extended to control of the edge plasma fluctuation level using feedback to explore its effects on confinement. When the launcher is driven by the floating potential of the fluctuating plasma at the location of the launching probes, then the fluctuations are suppressed or excited, depending on the phasing between the probe tips, both locally and at the downstream sensing probes. The fluctuation-induced particle flux also varies with the feedback phasing.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 10184498
- Report Number(s):
- ORNL/TM-12424; ON: DE94001017; TRN: 93:024035
- Resource Relation:
- Other Information: PBD: Aug 1993
- Country of Publication:
- United States
- Language:
- English
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