Interpretation and implementation of an ion sensitive probe as a plasma potential diagnostic on Alcator C-Mod

TY - JOUR

T1 - Interpretation and implementation of an ion sensitive probe as a plasma potential diagnostic on Alcator C-Mod

AU - Ochoukov, R.

AU - Whyte, D.G.

AU - Lipschultz, B.

AU - Labombard, B.

AU - Wukitch, S.

PY - 2011/8/1

Y1 - 2011/8/1

N2 - An ion sensitive probe (ISP) is developed as a robust diagnostic for measuring plasma potentials (Φ ) in magnetized plasmas of Alcator C-Mod. The ISP relies on the large difference between the ion and electron gyro-radii (ρ /ρ ∼ 60) to reduce electron collection at a collector recessed at a distance ∼ρ behind a separately biased wall. We develop a new ISP method based on voltage sweeping to measure Φ that is independent of the precise position and shape of the collector: Φ is found to be the wall voltage when net current to the collector vanishes during an increasing voltage sweep. We have designed and installed an ISP to study Φ and radio frequency (RF) sheath rectification on Alcator C-Mod. Preliminary results show that the ISP is a viable plasma potential diagnostic in Alcator C-Mod plasmas and Φ measurements are in good agreement with independent results obtained with an emissive probe.

AB - An ion sensitive probe (ISP) is developed as a robust diagnostic for measuring plasma potentials (Φ ) in magnetized plasmas of Alcator C-Mod. The ISP relies on the large difference between the ion and electron gyro-radii (ρ /ρ ∼ 60) to reduce electron collection at a collector recessed at a distance ∼ρ behind a separately biased wall. We develop a new ISP method based on voltage sweeping to measure Φ that is independent of the precise position and shape of the collector: Φ is found to be the wall voltage when net current to the collector vanishes during an increasing voltage sweep. We have designed and installed an ISP to study Φ and radio frequency (RF) sheath rectification on Alcator C-Mod. Preliminary results show that the ISP is a viable plasma potential diagnostic in Alcator C-Mod plasmas and Φ measurements are in good agreement with independent results obtained with an emissive probe.

UR - http://www.scopus.com/inward/record.url?scp=80054844721&partnerID=8YFLogxK

U2 - 10.1016/j.jnucmat.2010.10.053

DO - 10.1016/j.jnucmat.2010.10.053

M3 - Article

AN - SCOPUS:80054844721

SN - 0022-3115

VL - 415

JO - Journal of Nuclear Materials

JF - Journal of Nuclear Materials

IS - 1 SUPPL

ER -