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Gas jet disruption mitigation of locked mode plasmas using DPCS real-time detection and response. R. Granetz, D. Whyte, S. Angelini, S. Wolfe. DPCS real-time detection of VDEs and subsequent firing of the gas jet worked well. DPCS: no false positives, no misses, fast response
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Gas jet disruption mitigation of locked mode plasmas using DPCS real-time detection and response R. Granetz, D. Whyte, S. Angelini, S. Wolfe • DPCS real-time detection of VDEs and subsequent firing of the gas jet worked well. • DPCS: no false positives, no misses, fast response • Mitigation: good, but not quite as good as with stable plasmas on the midplane. Not surprising, given the short VDE timescale on C-Mod • We want to use DPCS to detect and mitigate other kinds of disruptions as well (locked mode, density limit, β-limit, …) Alcator C-Mod Ideas Forum, Dec 2006
Digital Plasma Control System (DPCS) monitors vertical position, fires gas jet
Some details • Two options for DPCS: • Continuously calculate 2/1 error field from Wolfe’s model[1] and compare to locked mode threshold scaling[2,3]. Trigger when getting ‘close’. • Or, use a central ECE channel and look for the cessation of sawteeth (perhaps with some use of the predictive model). • Must develop an algorithm and software to get DPCS to recognize ‘cessation of sawteeth’. Neural net? • Time response of DPCS and gas system should not be as critical as with VDEs • Requires 1 dedicated run, plus piggybacking to test out the DPCS locked mode prediction software. Alcator C-Mod Ideas Forum, Dec 2006