# Presentation: 569690

## Imaging X-Ray Crystal Spectrometer with Fast Detector for Fast Measurement of Profiles of Ti and Intrinsic Plasma Rotation Velocity without Perturbation by Neutral Beam Injection

- K. W. Hill, M. L. Bitter, S.D. Scott
*Princeton Plasma Physics Laboratory, Princeton, NJ*
- C. Bush
*ORNL*
- S. G. Lee
*NFRC, Korea Basic Science Institute, Daejeon, Korea*
- Presented at the NSTX 5-year plan mini workshop,  PPPL, February 27 2007

## Imaging XCS has high throughput capability

- Proof of principle demonstrated on C-Mod, TEXTOR, and NSTX  (z=+/- 40 cm)
- Saturation of gaseous detector at ~400 kHz count rate limited time resolution to > 100 ms
- Masked crystal to transmit ~ 1% of
- 	available intensity from C-Mod
- mtorr-l/s Ar puff in TEXTOR does not perturb Prad
- In NSTX  < 10-8 torr Ar partial pressure on RGA, not seen on spectrometers
- 10-ms time resolution for ~30 chords should be possible on C-Mod with new detector
- Pilatus detector, with 1 MHz PER PIXEL capability, solves detector saturation problem - 0.172 mm pixel size
- Pilatus significantly alleviates radiation background problem
- Pilatus test at 3.1 keV successful on C-Mod
- Spectra agree well with those from conventional detector
- Peak x-ray rate 850 counts/pixel/s in 20-ms frame
- Peak background rate 19 counts/pixel/s - unshielded

- ~8 cm

- +40 cm

- -40 cm

## New Imaging XCS is being constructed to measure full profiles of Ti and von C-Mod

-  Major upgrade to C-Mod
-   physics capability
-  Prototype for ITER XCS
-  2.4:1 imaging with 0.172
-   mm Pilatus pixel size vs
-  1:1 imaging with gaseous
-   detector (0.5 mm FWHM)
-  3+1 PILATUS detectors
-  ~30% toroidal fraction
-  Fabrication_x0013_is  proceeding
-  Be window  -> MIT
-  Crystal is in hand
-  Detectors to be delivered
-   April 4, 2007

## Greater demagnification could allow 80 cm of NSTX plasma to be imaged onto 2 Pilatus detectors

- MWPC resolution: 0.5 mm FWHM
- Pilatus pixel size: 0.172 mm
- Presently R=3.88 m and M=1/2.4
- With R=1.8m, M=1/5.1 => 80 cm of NSTX imaged onto 16 cm - two Pilatus detectors
- Lateral spread of beam from crystal to center stack (CS) ~ 28 cm for 5-cm crystal
- Viewing beside CS would give ~30% component of v

## Additional Slides

## Pilatus was proven to work at 3.1-keV He-like Ar energy at C-Mod

- w     x y         z

| w | 3.949Å |
| --- | --- |
| x | 3.966Å |
| y | 3.969Å |
| z | 3.994Å |

-  A Pilatus detector was installed on one of the poloidally viewing Hirex
-    spectrometers on C-Mod.
-  Typically used at 8 - 12 keV for protein crystallography experiments

## PILATUS II spectra similar to HIREX spectra

-  Spectra are for the same discharge but with slightly different views
-  No indication of problems in the electrically noisy C-Mod environment

- Raw Spectra

- Normalized Spectra

## Windows allow observation and access

- Be window

## Main Points

- Proof-of-Principle of new imaging x-ray crystal spectrometer (XCS) for Ti- and rotation-profile (v) measurement previously demonstrated
- on NSTX, Alcator C-Mod, and TEXTOR;
- temporal and spectral resolution limited by the available 2d x-ray detector (<400 kHz)
- New pixelated silicon detector with better spatial resolution and 100,000 times higher count-rate capability removes limitations
- New detector tested on existing C-Mod spectrometer
- Imaging XCS being designed to measure full radial profiles of Ti and v on C-Mod, and
- Imaging XCS adopted for ITER
- Calculations of uncertainty in Ti and v measurements predict performance of C-Mod and ITER spectrometers

## Spherical crystal images spectra in vertical direction

## Imaging XCS can measure continuous profiles of Ti and rotation-velocity without NBI

- Proof of principle demonstrated on C-Mod and NSTX  (z=+/- 40 cm)
- Slow detector (400 kHz) limited time resolution to > 100 ms
- Masked crystal to transmit ~ 1% of available intensity from C-Mod
- Ar injection in TEXTOR does not perturb Prad
- Ar in NSTX not seen on spectrometers, < 10-8 torr partial P. on RGA
- New detector (Pilatus) with 1 MHz PER PIXEL capability should enable 10-ms measurements with ~ 30 chords on C-Mod
- Successful test of Pilatus detector at 3.1 keV x-ray energy on C-Mod
- New spectrometer using 4 Pilatus detectors is being
- 	constructed to measure full profiles on C-Mod
- Imaging XCS design adopted for ITER
- Greater demagnification (2.7:1 -> 5:1) would
- 	enable imaging of 80 cm of NSTX onto two
- 	Pilatus detectors

- ~8 cm

- Wavelength ->

- +10 cm

- -10 cm

## C-Mod imaging XCS demonstrated proof-of-principle

- +10 cm

- -10 cm

- Ar XVII

- w       x y            z

## Spectra from NSTX and C-Mod have good resolution

- NSTX

- C-Mod

- +10 cm

- -10 cm

- +40 cm

- -40 cm

- w   x y     z

## Spatially resolved Te, Ti inferred from NSTX Ar XVII spectra

## PILATUS detector solves count-rate and resolution issues

- MWPC rate limit (400 kHz) limited time resolution to > 100 ms
- Delay-line readout; all pulses pass through single electronics chain
- Pileup rejection in TDC and interface latency
- Less than 0.5% of available Ar line intensity used on C-Mod
- 8-cm diameter crystal masked down to 6 mm x 2 mm aperture
- Mylar foils reduced x-ray transmission by factor 1/8
- Background radiation on NB-heated tokamaks can saturate electronics
- PILATUS detector should enable 10-ms measurements
- 487 x 195 pixels, each 0.172 x 0.172 mm2
- Analog and counting electronics on each pixel
- Capable of count rates up to 1 MHz PER PIXEL
- Can use full intensity available from C-Mod
- 30 spatial channels
- ~ 1 MHz per channel

- ~8 cm

## Slide 16

## Pilatus detector has several attractive features

- 487 x 195 pixels
- Size 0.172 x 0.172 mm2 , ~ 2.5 times smaller then for MWPC
- Analog and counting electronics on each pixel
- Count rates up to 1 MHz per pixel
- Modular (5 x 12 array used on SLS)
- Readout time 2.54 ms => 10-ms resolution with full crystal
- Radiation hard (1014 n/cm2)
- Typical n/ background radiation -> negligible effect
- Each pixel receives 1/100,000 background rate of full detector
- Worked well in the electrically noisy C-Mod environment

## PILATUS detector solves count-rate and resolution issues 

-  2-D array of x-ray sensitive pixels
- - Each module is 487 x 195 pixels
- - Each pixel is 0.172 x 0.172 mm2
-  Modular (build array of any size)
-  Each pixel can handle a count rate of 1MHz
- total count rate of previous 10 cm x 30 cm MWPC was 400 kHz (Factor of 100,000 increase)
-  Use of available intensity should allow 10-ms
-   measurements for 30 radial channels
-  Readout time down to 2.54 ms
-  Worked well in the electrically &
-   mechanically noisy C-Mod environment
-  No problems with radiation-induced noise; each
-   pixel has to deal with only 1/100,000 of total
-   detector background noise
-  Radiation hard (tested to 1014 n/cm2)

- ~8 cm

## PILATUS II Ar line time history similar to stored energy

- Measured with 20 ms time resolution
- PILATUS readout time now down to 2.54 ms
- Ar XVII resonance line, w, measured by PILATUS II detector

## Background rate low for unshielded PILATUS detector

- Peak background count rate = 14 counts/pixel/s
- Peak neutron rate = 5.8E13 n/s
- Peak x-ray rate > 1000 counts/pixel/s

## He-filled chamber houses crystals and detectors

- crystals

- detectors

## Hollow emissivity profiles can be inverted

## ITER imaging x-ray spectrometer

- Design options for spectrometer location
-  Ex-port
- 	Better access
- 	Better shielding
-  In-port
- 	Wider view of plasma
- Choice will be based on:
- - Neutronics modelling
** ****Detector radiation hardness**
** ****Detector background rejection**

- Status of ITER x-ray spectroscopy, R Barnsley, IPR, India, 8th Feb 2006.

## Conclusions

- New imaging x-ray spectrometer developed for Ti -, Te - and rotation-profile measurement on NSTX and Alcator C-Mod.
- Imaging concept verified on C-Mod, NSTX, and TEXTOR.
- Very small crystal area provided high count rates from C-Mod
- Suggests small area crystals suitable for ITER
- Detector count-rate limit and position-resolution issues solved by PILATUS II detector. Radiation-background issue greatly alleviated
- Imaging spectrometer being designed for C-Mod.
- Detectors to be delivered in March-April => data in April
- Numerical and statistical analyses provide basis for estimating performance of imaging XCS on C-Mod and on ITER with neutron background.

## Slide 25