Objectives Much better spatial resolution Velocity space discrimination W. Heidbrink, M. Van...
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Transcript of Objectives Much better spatial resolution Velocity space discrimination W. Heidbrink, M. Van...
![Page 1: Objectives Much better spatial resolution Velocity space discrimination W. Heidbrink, M. Van Zeeland, J. Yu FIDA Imaging Proposal.](https://reader036.fdocuments.us/reader036/viewer/2022070415/5697bf981a28abf838c912fb/html5/thumbnails/1.jpg)
Objectives
•Much better spatial resolution
•Velocity space discrimination
W. Heidbrink, M. Van Zeeland, J. Yu
FIDA Imaging Proposal
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Van Zeeland, PPCF (2008) to be submitted.
•“Imaging” neutral beam (30L) produces red-shifted light (filtered out)
•Oppositely directed fast ions from counter beam (210R) produces blue-shifted light (accepted by filter)
FIDA imaging: Put bandpass filter in front of a camera
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Excellent agreement with expected image in a quiet plasma
•Fast-ion distribution function from TRANSP
•Only one normalization constant in this comparison
![Page 4: Objectives Much better spatial resolution Velocity space discrimination W. Heidbrink, M. Van Zeeland, J. Yu FIDA Imaging Proposal.](https://reader036.fdocuments.us/reader036/viewer/2022070415/5697bf981a28abf838c912fb/html5/thumbnails/4.jpg)
Improved Ability to Detect Changes in Fast-ion Profile
DATA Db=0 Simulation
Data - Simulation
•Theory (no DB) predicts “hole” near center but this is not observed
•Transport less evident for “s-FIDA” equivalent (spatially averaged vertically)
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Velocity-space sensitivity demonstrated by time evolution
•Camera sees counter
•Spectrometer favors co
•Neutrons measure high energy (favor ctr)
#132607 on-axis
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NSTX Camera Will View Co-going Ions
•View beams from Bay L
•Radial view of beams small Doppler shift for injected neutral light
•Large toroidal component for fast ions large blue shift for co-circulating fast ions
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Split light for bremsstrahlung background
•Not feasible to modulate all of the heating beams routinely
•Must measure background simultaneously
•Use custom splitter to image both FIDA light & VB
•Send some light to s-FIDA to monitor spectra
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Some Energy Resolution Feasible
•Used 4-nm wide BES filter to date
•Custom 2-nm wide filters are available
•Can rotate filter to image higher energies
•Narrow filter degrades time resolution (emissivity is ~5 times lower than in DIII-D)
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Rough Cost Estimate
•Port Lens assembly (PPPL)
•Camera $120K
•Custom splitter ($25K?)
•Bandpass filters $12K
•Misc. $20K
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Conclusions
•Imaging provides much better spatial resolution
•Installation will also give velocity-space resolution
•Coarse energy resolution feasible
But…a 2nd tangentially viewing s-FIDA/f-FIDA system can give comparable velocity-space resolution, better energy resolution (but much poorer spatial resolution) for less money
Proposed system is
•Outstanding for NBCD & AE physics
•Of limited value for HHFW physics
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SSNPA Proposal
•Current system: four radii/pitch with ~10 keV energy resolution & ~5 ms temporal resolution
•Sacrifice energy resolution to achieve ~0.1 ms temporal resolution
•Complements f-FIDA with superior pitch resolution
Details: open up apertures, operate in current mode, ~$20K cost
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Measured Spectra Make Sense
•Background of impurity lines, visible bremsstrahlung, and scattered cold & injected neutral light
•Net signal appears at the expected wavelenths
•As expected for vertical views, the blue-shifted and red-shifted spectra are similar.