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Analysis of Fast Ion Loss and Current Profile Modifications Due to BAAE/EPM Bursts

This study investigates the impact of BAAE/EPM bursts on ion loss and current redistribution in plasmas. Observations indicate that such bursts, primarily occurring during Ip ramp-up and flattop, influence neutron emission and the behavior of fast ions. The experimental plan involves examining specific shots with bursts, documenting their effects on current density and fast ion loss, and assessing mode structures through advanced diagnostics. Key objectives include quantifying current transport related to operational modes and comparing experimental results with theoretical models.

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Analysis of Fast Ion Loss and Current Profile Modifications Due to BAAE/EPM Bursts

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  1. Current Profile Modifications and Fast Ion Loss from BAAEs/EPMs D. Darrow, et al. January 15, 2009

  2. EPMs 119624 BAAE/EPM bursts expel NB ions & may redistribute current • Bursts are often seen during Ip ramp up, causing neutron drops and possibly contributing to rapid j(r) redistribution • Important for NHTX, VNS, & ITER to quantify j(r) transport due to modes

  3. Bursts also seen during Ip flattop—simplest situation to study

  4. Experimental plan • Reload shot with bursts during flattop (127383, 127393, or 127397) from 2008 • Check for presence of bursts • Reduce Ip or alter density if no bursts • Document effects of bursts on j(r), fast ion loss • Focus on effect of repeated bursts as a single burst appears to have indistinguishable effect on MSE • Document mode numbers, profiles & amplitudes • Repeat shots with n=3 braking to get data on mode structure near wrot=0

  5. Key diagnostics • MSE: j(r, t) • Mirnov coils: mode n, freq, & amplitude • FIDA: fNB(E, r, t) • NPA: fNB(E, r, t) • CHERS:wrot(R, t) (for fast ion loss torque) • Neutron detectors: Sn(t) • sFLIP: Gloss(E, c, t) • SXR array: mode structure • FIReTIP: mode structure • Reflectometer: mode structure? (H-mode) • High-k scattering: mode structure info

  6. Analysis emphases • MSE: Focus on cumulative effect of multiple bursts as bursts occur too frequently to separate in MSE data; identify amount of current transported to or from each flux surface • Mode profile diagnostics: fit best mode radial profiles and compare with NOVA predictions for BAAE under those conditions; compare also at lowest attainable toroidal rotation: how well do modes match BAAE theory?

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