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Edge Ion Temperature Measurement in the STOR-M Tokamak

Date

2012-07-26

Journal Title

Journal ISSN

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Type

Degree Level

Masters

Abstract

A newly developed bidirectional Retarding Field Energy Analyzer, RFEA, which measures ion temperatures from both sides (downstream and upstream), was commissioned in the STOR-M tokamak. Its entrance slit width follows one of the design criteria, < 2 lambda_{De}. The dimension of the RFEA is small enough to avoid creating a shadow effect. The probe is the replacement of previous RFEA which measures ion temperature, T_i, from one side only. An external cable used as an antenna parallel to the cables, connected to the collector, is used to suppress noise picked up by the cable. A similar technique was used in the previous RFEA. By operating the probe in standard ramping mode, T_i in the scrape-off layer (SOL) region between 15.5cm and 12cm from the chamber center is measured (minor radius). The probe performs T_i measurement campaign twice with different entrance slits. The entrance slit 1 provides higher collector current than the entrance slit 2, but the entrance slit 1 on the downstream side did not survive during the fi rst T_i campaign. T_i measured by the entrance slit 2 in the SOL region of the STOR-M is between 19eV and 34eV. The probe operation is validated by T_e values simultaneously measured by the Triple probe. T_i/T_e is between 1.8 and 2.8 in the STOR-M SOL. RFEA in DC mode operation demands higher ion current to estimate T_i fluctuation. The 2011 Ti campaign shows that the direction of magnetic fi eld largely affects the current RFEA operation both in conventional ramping mode and in DC mode.

Description

Keywords

Retarding Field Energy Analyzer, RFEA, RFA, ion temperature, T_i, Ti, 2 lambda_{De}, electron temperature, T_e, Te

Citation

Degree

Master of Science (M.Sc.)

Department

Physics and Engineering Physics

Program

Physics

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