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Title 28: Small-sized LSN to test off axis NBCD
Name:John Degrassie () Affiliation:General Atomics
Research Area:Heating & Current Drive Presentation time: Not requested
Co-Author(s): M. Murakami, W. Heidbrink
Description:
Experimental Approach/Plan: *Run this shape with NBI comparing left and right co-souces, and counter-sources, with, at minimum, blips from 30L (or 21R if validated) for MSE. L- or H-mode, beam modulation, using ECH to raise Te and lengthen the beam slowing down time will all be details to be determined in an actual run plan should time be allocated.
*After day 1 (with normal BT) selected discharges will be matched on day 2 in reversed BT. NBCD from detailed analyses will be compared.
*Reversing Ip instead of BT and using the 210 sources for co-NBCD is an option that will be considered also. This will keep BxGradB downward if it is deemed necessary to match H-mode characteristics in the same shape.
*With 3 days allocated for this important experiment, both reversed BT and reversed Ip can be used.
Background: DIII-D is proposing to modify a beam-line to shoot off of the midplane in order to obtain off-axis NBCD. Off-axis NBCD in ASDEX-U has produced a result that falls below theory. Modeling by Murakami et al indicates that the problem may be the alignment of the prompt NBI orbit and the total B field, leading to more trapped fast ions in the misaligned situation. We can experimentally test this for ourselves before spending the megabucks to tilt the beamline.
Resource Requirements: All beams
ECH: Possibly at least 2 gyrotrons if Te control becomes part of the plan.
Diagnostic Requirements: standard. MSE.
Analysis Requirements: "NVLoop" (or the modern equivalent) with MSE for toroidal current density.
Other Requirements: --