Study of structural effects of Langmuir probe array on edge fluctuation measurement in the compact helical system heliotron/torsatron

Ohkuni, K.; Toi, K.
January 2001
Review of Scientific Instruments;Jan2001, Vol. 72 Issue 1, p446
Academic Journal
A new type of Langmuir probe array is installed on the compact helical system heliotron/torsatron for the study of edge plasma turbulence. The probe array consists of four sets of the standard triple probes which are composed by four electrodes. Each triple probe set is slightly displaced both in the toroidal and poloidal directions to minimize the shadow effects among these probe sets. In order to investigate the structural effects of Langmuir probe arrays, the results obtained by this new probe array are compared with the results previously obtained by the old probe array where the triple probe sets were displaced only in the poloidal direction from each other. Stationary plasma parameters near the plasma edge such as electron temperature, density, and plasma potential were consistently obtained by two probe arrays. However, the new probe array displaced toroidally is more reliable to measure the particle flux induced by fluctuations where accurate measurement of the poloidal electric field fluctuations is required, compared with the old probe array. © 2001 American Institute of Physics.


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