Objectives

•Much better spatial resolution

•Velocity space discrimination

W. Heidbrink, M. Van Zeeland, J. Yu

FIDA Imaging Proposal

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

Excellent agreement with expected image in a quiet plasma

•Fast-ion distribution function from TRANSP

•Only one normalization constant in this comparison

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)

Velocity-space sensitivity demonstrated by time evolution

•Camera sees counter

•Spectrometer favors co

•Neutrons measure high energy (favor ctr)

#132607 on-axis

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

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

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)

Rough Cost Estimate

•Port Lens assembly (PPPL)

•Camera $120K

•Custom splitter ($25K?)

•Bandpass filters $12K

•Misc. $20K

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

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

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.