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Published byRoy Gallagher Modified over 9 years ago
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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
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Improved Ability to Detect Changes in Fast-ion Profile DATA Db=0 Simulation Data - Simulation Theory (no D B ) 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 2 nd 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.
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