Langmuir probe measurements in the TEXTOR tokamak during ALT-I pump limiter experiments
Langmuir probes have been used to characterize the edge plasma of the TEXTOR tokamak and measure the parameters of the plasma incident on the ALT-I pump limiter during ohmic and ICRH heating. Probes mounted directly on the ALT limiter, and a scanning probe located 90/sup 0/ toroidally from the limiter, provide data for the evaluation of pump limiter performance and its effect on the edge plasma. The edge plasma is characterized by density and flux e-folding lengths of about 1.8cm when ALT is the main limiter. These scrape-off lengths do not vary significantly as ALT is moved between the normal 42-46cm minor radii, but increase to over 2.2cm when ALT is inserted to 40cm. The flux to probes at a fixed position in the limiter shadow varies by less than 25% for core density changes of a factor of five. This suggests that the global particle confinement time tau/sub p/, scales as the core density. Estimates from the probes indicate that tau/sub p/ is on the order of the energy confinement time, tau/sub E/. The edge electron temperature, T/sub e/, typically decreases by a factor of two when the core density is raised from 1 to 4 x 10/sup 13/ cm/sup -3/. The T/sub e/ profile is essentially flat in the limiter shadow, with values of 10-25 eV depending on the core plasma density and ICRH power. ICRH heating increases the electron temperature and flux in proportion to the coupled power. With ALT as the primary limiter and no direct shadowing, the ion side receives 2 to 3 times the flux of the electron side during both ohmic and ICRH heating. The edge plasma is not directly modified by pump limiter operation, but changes with the core plasma density as particle removal lowers the recycling of neutrals in the boundary.
- Research Organization:
- Univ. of California, Los Angeles, CA (United States); Kernforschungsanlage Juelich G.m.b.H. (Germany, F.R.). Inst. fuer Plasmaphysik; Sandia National Lab. (SNL-CA), Livermore, CA (United States)
- DOE Contract Number:
- FG03-85ER51069
- OSTI ID:
- 5224011
- Report Number(s):
- UCLA/PPG-945; ON: DE86015878
- Country of Publication:
- United States
- Language:
- English
Similar Records
ALT-I pump limiter experiments with ICRF heating on TEXTOR
ALT-I pump limiter experiments with ICRF heating on TEXTOR. Revision
Related Subjects
PLASMA DIAGNOSTICS
LANGMUIR PROBE
TEXTOR TOKAMAK
ICR HEATING
JOULE HEATING
LIMITERS
PLASMA CONFINEMENT
PLASMA SCRAPE-OFF LAYER
BOUNDARY LAYERS
CLOSED PLASMA DEVICES
CONFINEMENT
ELECTRIC HEATING
ELECTRIC PROBES
HEATING
HIGH-FREQUENCY HEATING
LAYERS
PLASMA HEATING
PROBES
RESISTANCE HEATING
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
700102* - Fusion Energy- Plasma Research- Diagnostics