Fast reciprocating Langmuir probe for the DIII-D divertor
- Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)
- University of California at San Diego, San Diego, California 92093 (United States)
- Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
- General Atomics, San Diego, California 92286 (United States)
A new reciprocating Langmuir probe was used to measure density and temperature profiles, ion flow, and potential fluctuation levels from the lower divertor floor up to the X point on the DIII-D Tokamak. This probe is designed to make fast (2 kHz swept, 20 kHz Mach, 500 kHz Vfloat) measurements with 2 mm spatial resolution in the region where the largest gradients on the plasma open flux tubes are found and therefore provide the best benchmarks for scrap-off layer and divertor numerical models. Profiles are constructed using the 300 ms time history of the probe measurements during the 25 cm reciprocating stroke. Both single and double null plasmas can be measured and compared with a 20 Hz divertor Thomson scattering system. The probe head is constructed of four different kinds of graphite to optimize the electrical and thermal characteristics. Electrically insulated pyrolytic graphite rings act as a heat shield to absorb the plasma heat flux on the probe shaft and are mounted on a carbon/carbon composite core for mechanical strength. The Langmuir probe sampling tips are made of a linear carbon fiber composite. The mechanical, electrical, data acquisition, and power supply systems will be described. Initial measurements will also be presented. {copyright} {ital 1997 American Institute of Physics.}
- Research Organization:
- General Atomics
- DOE Contract Number:
- AC03-89ER51114; AC04-94AL85000
- OSTI ID:
- 451752
- Report Number(s):
- CONF-960543--
- Journal Information:
- Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 1 Vol. 68; ISSN RSINAK; ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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