Fast scanning probe for the NSTX spherical tokamak
- Department of Mechanical and Aerospace Engineering, Energy Research Center, University of California, San Diego, La Jolla, California 92093-0417 (United States)
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
We describe a fast reciprocating Langmuir probe and drive system, which has four main new features: (1) use of high-temperature, vacuum, circuit boards instead of cables to reduce weight and increase to 21 the number of possible connections, (2) rotatable and removable shaft, (3) 10 tip construction with designed hardware bandwidth up to 10 MHz, and (4) a detachable and modular tip assembly for easy maintenance. The probe is mounted in a fast pneumatic drive capable of speeds {approx}7 m/s and {approx}20g's acceleration in order to reach the scrape-off layer (SOL) and pedestal regions and remain inserted long enough to obtain good statistics while minimizing the heat deposition to the tips and head in a power density environment of 1-10 MW/m{sup 2}. The National Spherical Torus Experiment SOL features electron temperature, T{sub e}{approx}10-30 eV, and electron density, n{sub e}{approx}0.1-5x10{sup 12} cm{sup -3} while the pedestal features n{sub e}{approx}0.5-1.5x10{sup 13} cm{sup -3} and T{sub e}{approx}30-150 eV. The probe described here has ten tips which obtain a wide spectrum of plasma parameters: electron temperature profile T{sub e}(r), electron density profile n{sub e}(r) and Mach number profile M(r), floating potential V{sub f}(r), poloidal and radial electric field profiles E{sub {theta}}(r) and E{sub {rho}}(r), saturation current profile I{sub sat}(r), and their fluctuations up to 3 MHz. We describe the probe and show representative radial profiles of various parameters.
- OSTI ID:
- 22051118
- Journal Information:
- Review of Scientific Instruments, Vol. 80, Issue 12; Other Information: (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
Similar Records
Fast scanning probe for tokamak plasmas
Lower hybrid current drive in a high density diverted tokamak