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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-9327
DTSTART:20250722T180000Z
DTEND:20250722T200000Z
DTSTAMP:20260413T151504Z
LAST-MODIFIED:20250701T175145Z
LOCATION:ERB 106 or https://uwmadison.zoom.us/j/95862209630
SUMMARY:Design and Operation of a Novel Spectrometer Diagnostic at DII
 I-D for the Measurement of Magnetic Pitch and Toroidal Rotation at ELM
 -Relevant Timescales\, Thesis Defense\, Ryan Albosta\, Physics PhD Gra
 duate Student
DESCRIPTION:Two novel single-channel Czerny-Turner spectrometers [1&2]
  have been deployed at the DIII-D tokamak for simultaneous and co-loca
 ted measurements of the full spectrally-resolved Motional Stark Effect
  (MSE) Split Deuterium Beam Emission and the Carbon CVI charge exchang
 e emission at high spectral (∆λ=0.13 nm) and temporal resolution (1
 -5 kHz). High throughput optics (f/#=2.8) allow for good signal-to-noi
 se at high time resolution using fast EMCCD detectors. Initial results
  from a 2024 DIII-D ITER-similar H-mode experiment at DIII-D show clea
 r toroidal rotation collapse during ELM crashes from the CER channels\
 , accompanied by Sigma/Pi ratio changes over a similar timescale from 
 the MSE channels. However\, non-equilibrium neutral beam excited state
  populations appear to play a large role in pedestal MSE line ratios\,
  as qualitatively predicted by the NOMAD quantum collisional codebase.
  Complex neutral beam physics has also been observed and successfully 
 reproduced with a physics forward model\, revealing a continuum of bea
 m energies that further complicate the MSE spectrum. These effects and
  their impact on the MSE fitting process during fast ELM dynamics in t
 he DIII-D pedestal will be discussed\, as well as the implications for
  fast magnetic beam-emission measurements – and therefore bootstrap 
 current analysis – in H-mode pedestals generally. Simultaneous magne
 tic pitch\, beam populations\, and rotation measurements will be shown
  during type-1 ELMs at 5 kHz\, along with next steps towards further d
 isentangling population and pitch effects within the MSE spectrum duri
 ng large density fluctuations.    [1] Albosta R et al.: Rev Sci Instru
 m. 2022<br>\n[2] Albosta R et al.: Rev Sci Instrum. 2024<br>\n*Support
 ed by US DOE grants DE-FG02-89ER53296\, DE-FG02-08ER54999 and DE-FC02-
 04ER54698.
URL:https://www.physics.wisc.edu/events/?id=9327
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