Scanning retarding field analyzer for plasma profile measurements in the boundary of the Alcator C-Mod tokamak

Brunner, D.; LaBombard, B.; Ochoukov, R.; Whyte, D.
March 2013
Review of Scientific Instruments;Mar2013, Vol. 84 Issue 3, p033502
Academic Journal
A new Retarding Field Analyzer (RFA) head has been created for the outer-midplane scanning probe system on the Alcator C-Mod tokamak. The new probe head contains back-to-back retarding field analyzers aligned with the local magnetic field. One faces 'upstream' into the field-aligned plasma flow and the other faces 'downstream' away from the flow. The RFA was created primarily to benchmark ion temperature measurements of an ion sensitive probe; it may also be used to interrogate electrons. However, its construction is robust enough to be used to measure ion and electron temperatures up to the last-closed flux surface in C-Mod. A RFA probe of identical design has been attached to the side of a limiter to explore direct changes to the boundary plasma due to lower hybrid heating and current drive. Design of the high heat flux (>100 MW/m2) handling probe and initial results are presented.


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