# Presentation: 173863

## FIDA Imaging Proposal

_**Objectives**_** **
**Much better spatial resolution**
**Velocity space discrimination**

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

**FIDA Imaging Proposal**

## FIDA imaging: Put bandpass filter in front of a camera

***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

**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 D****B****) 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 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**

## 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.**