Calibration activities for ITER high - resolution x -ray crystal imaging spectrometers

1. Calibration activities for ITER high-resolution x-ray crystal imaging spectrometers L. Delgado-Aparicio1 and P. Beiersdorfer2 1Princeton Plasma Physics Laboratory (PPPL) 2Lawrence Livermore National Laboratory (LLNL) Conceptual design review (CDR) of ITER CORE X-RAY CRYSTAL IMAGING SPECTROMETER June 4-5th, 2013

2. Collaborators PPPL M. Bitter, K. W. Hill, N. A. Pablant, R. Feder, R. Bell, B. Stratton, D. Johnson, S. Scott, and J. R. Wilson MIT-PSFC J. Rice, Y. Podpaly,C. Gao, J. Rice,M. L. Reinke,J. Terry, M. Greenwald, E. Marmar,and all the technical team NFRI – KSTAR S. G. Lee (Korea) ASIPP – EAST B. Lu (China) ITER – India S. Varshney (India)

3. Core X-ray crystal imaging spectrometers (USA) • Will measure profiles of ion temperature and plasma flow velocity by Doppler spectrometry (primary) while also providing information on electron temperature profiles (secondary). • Multiple sets of views allow for measurements oftoroidal(vf) rotation measurements [1<vf<200 km/s]. • Wavelength references are needed to derive absolute plasma velocities from Doppler shift. • Different techniques using x-ray tubes and fluorescence are being proposed for pursuing: • a) Spectrometer alignment • b) In-situ measurement of detector uniformity • c) In-situ wavelength calibration.

4. Motivation and outline Reliable measurements of plasma emissivity, ion temperature and toroidal flow velocity profiles, requires: In-situ uniformity calibration of detectorsNeeded for calibrated measurements of the local plasma emissivity and estimates of impurity density and its gradients. In-situ wavelength calibrationNeeded for calibrated measurements of the plasma rotation velocity and spectrometer instrumental function. Crystal/detector temperature monitoring & control Ambient temperature excursions can affect interplanar spacing introducing apparent velocity offsets (NEXT TALK)

5. Motivation and outline Reliable measurements of plasma emissivity, ion temperature and toroidal flow velocity profiles, requires: In-situ uniformity calibration of detectorsNeeded for calibrated measurements of the local plasma emissivity and estimates of impurity density and its gradients. In-situ wavelength calibrationNeeded for calibrated measurements of the plasma rotation velocity and spectrometer instrumental function. Crystal/detector temperature monitoring & control Ambient temperature excursions can affect interplanar spacing introducing apparent velocity offsets

6. EXAMPLE: High resolution x-ray imaging spectrometer at MIT uses Ar & Mo lines Ne-like Mo32+ line falls into H-like Ar spectrum He-like Ar detectors He-like Ar Crystal H-like Ar Detector H-like Ar Crystal Similar imaging systems have been installed in NSTX, KSTAR, EAST and LHD

7. Example: Cd(La1,2) and K (Ka1,2)x-ray lines can be used for calibrating the Ar spectrometers* H-like Ar spectrum He-like Ar spectrum Cd (La1) Theory: 3956.019, Exp: 3956.404 mÅ (on the n=3 sat.) Cd(La2) Theory: 3964.316, Exp: 3965.0138 mÅ (next to the x-line) Cd (Lb1) Theory: 3738.2, Exp: 3738.286 mÅ (in between Lya2 and Mo32+ ) KCl K (Ka1,2) Exp: 3741.296 mÅ Exp: 3744.405 mÅ (next to the Mo32+) *Calibrations proposed for Alcator C-Mod, KSTAR, EAST, LHD, NSTX-U and ITER-India

8. In-situ (white plate) uniformity calibration of Pilatus 100K detectors Use x-ray fluorescenceto select specific low-energy wavelengths Broadband spectrum from radioactive source or x-ray tube l1, l2 Target material (Cd, KCl, etc) • Provide ‘in-situ’ broad-band illumination for determining reliability/degradation of detectors (use of fluorescence screen). • Calibration can be done outside the spectrometer (bypass crystals). • Cd-La and K-Ka fluorescence lines have energies of 3.1 & 3.3 keV.

9. Recent uniformity calibration reveals ‘faulting’ pixels and non-uniformities 2769±148 (~5.3%) 2992±153 (~5.1%) 3037±127 (~4.2%) Non-uniformities within chip-to-chip or pixel-to-pixel are within 5%. ----- Rows (WAVELENGTH)

10. Recent uniformity calibrations reveal ‘faulting’ pixels and non-uniformities 2927±137(~4.6%) 2920±147 (~5%) 2866±146 (~5%) Non-uniformities within chip-to-chip or pixel-to-pixel are within 5%. ----- Rows (WAVELENGTH) ----- Columns (PLASMA HEIGHT) Re-do trim-bit calibration - the original calibration may no longer be valid. # of ‘faulting’ pixels after ~6yrs of operation is approximately 4-5%.

11. Motivation/outline Reliable measurements of plasma emissivity, ion temperature and toroidal flow velocity profiles, requires: In-situ uniformity calibration of detectorsNeeded for calibrated measurements of the local plasma emissivity and estimates of impurity density and its gradients. In-situ wavelength calibrationNeeded for calibrated measurements of the plasma rotation velocity and spectrometer instrumental function. Crystal/detector temperature monitoring & control Ambient temperature excursions can affect interplanar spacing introducing apparent velocity offsets

12. In-situ wavelength calibration tested in C-Mod He-like Ar detectors Use x-ray tubes or fluorescence* to select specific ls H-like Ar detector Cd-La1,2 Cd-Lb1 K-Ka1,2 *Fluorescence in transmission/reflection mode

13. Cd emission from (Cu anode + Cd target) x-ray tube illuminated 70% of Pilatus detector ? 8-10 Watts x-ray tube ⇒ longer integration/power Unexpected background at shorter l’s ? Needs to fill the optics as the plasma. Modern x-ray tube has been recently acquired.

14. Rest wavelength fiducials have recently been proposed for the W64+ ITER core x-rayimaging spectrometer Hf L-shell emission spectra from tungsten (e.g. neon-like) can be produced at the SuperEBIT electron beam ion trap at LLNL. Choose from six characteristic x-ray lines that may be used as rest-energy calibration standards. Other options: Cu Kb1 @ 8905.29 eV Ga Ka1 @ 9251.74 eV Ga Ka2 @ 9224.82 eV The final choice will depend on how much room there is on the detector in the final design. Ir W

15. Novel x-ray tubes will provide wavelengths of interest for ITER calibrations • He- and H-like Ar:Use K-Ka1,2 & Cd-La1,2 lines. • New remotely controlled tubes recently purchased. • Technique to be tested at C-Mod and PPPL (NSTX-U) • and exported to KSTAR, EAST, LHD and W7X. • Export to ITER-India • He-like Fe: Use Ho-La1,2 lines. • Ho-lines bracket the w-line (~60 eV apart). • Technique to be tested at PPPL and LLNL. • Ne-like W: Use Ir-La1,2 & Ga-Ka1,2 lines. • DEIr~76 eV; DEGa~27 eV. • Hf and Cu are also of interest. • Technique to be tested at PPPL and LLNL. • Measure l3D (W64+) line with an accuracy greater than • current estimates and theoretical predictions (<0.5 eV). Ho-La2 Ho-La1 Ir-La1,2 Ga-Ka1,2

16. Roadmap of activities and tasks • Continue R&D for implementation of strategy and options for in-situ wavelength calibrations (based on x-ray tubes). • Test x-ray fluorescence transmission technique using the plasma intrinsic emission and a target foil in front of the crystal. Th La1 Th La2 Consider also similar techniques in the case of using the He-like krypton spectrum. 0.967 If Kr measurement is done in 2nd order we can use Mn Kb1 and Dy La1,2. Test these concepts in controlled environments at PPPL, MIT and LLNL. Export these techniques to spectrometers in Japan, Korea, China, Germany and India, and in the future, ITER.

17. EXTRA

18. Future work • Develop concept for the implementation of fluorescent screen on the ITER CXIS system. • a) Transmission mode. • b) Reflection mode (x-ray tube). • It is important to show that these calibration schemes are plausible from an engineering point of view. • Outstanding issues for development of these calibration schemes for the ITER system • a) Enough x-ray throughput. • b) Materials. • c) High-voltage; low-current. • d) Water cooling. Fluorescence in transmission mode Fluorescence screen lplasma Fluorescence in reflection mode Fluorescence screen ltube