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

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)

Core X-ray crystal imaging spectrometers (USA) ① Will measure profiles of ion temperature and plasma flow velocity by Doppler spectrometry (primary) while also providing information on electron temperature profiles (secondary). ② Multiple sets of views allow for measurements of toroidal (v  ) rotation measurements [1<v  <200 km/s]. ③ Wavelength references are needed to derive absolute plasma velocities from Doppler shift. ④ 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. 3

Motivation and outline ② In-situ wavelength calibration Needed for calibrated measurements of the plasma rotation velocity and spectrometer instrumental function. Reliable measurements of plasma emissivity, ion temperature and toroidal flow velocity profiles, requires: ① In-situ uniformity calibration of detectors Needed for calibrated measurements of the local plasma emissivity and estimates of impurity density and its gradients. 4 ③ Crystal/detector temperature monitoring & control Ambient temperature excursions can affect interplanar spacing introducing apparent velocity offsets (NEXT TALK)

Motivation and outline ② In-situ wavelength calibration Needed for calibrated measurements of the plasma rotation velocity and spectrometer instrumental function. Reliable measurements of plasma emissivity, ion temperature and toroidal flow velocity profiles, requires: ① In-situ uniformity calibration of detectors Needed for calibrated measurements of the local plasma emissivity and estimates of impurity density and its gradients. 5 ③ Crystal/detector temperature monitoring & control Ambient temperature excursions can affect interplanar spacing introducing apparent velocity offsets

EXAMPLE: High resolution x-ray imaging spectrometer at MIT uses Ar & Mo lines H-like Ar Crystal H-like Ar Detector He-like Ar Crystal He-like Ar detectors Ne-like Mo 32+ line falls into H-like Ar spectrum Similar imaging systems have been installed in NSTX, KSTAR, EAST and LHD 6

Example: Cd (L  1,2 ) and K (K  1,2 ) x-ray lines can be used for calibrating the Ar spectrometers * Cd (L  2 ) Theory: , Exp: m Å (next to the x-line) He-like Ar spectrum Cd (L  1 ) Theory: , Exp: m Å (on the n=3 sat.) H-like Ar spectrum Cd (L  1 ) Theory: , Exp: m Å (in between Ly  2 and Mo32+ ) KCl K (K  1,2 ) Exp: m Å Exp: m Å (next to the Mo32+) * Calibrations proposed for Alcator C-Mod, KSTAR, EAST, LHD, NSTX-U and ITER-India 7

In-situ (white plate) uniformity calibration of Pilatus 100K detectors Broadband spectrum from radioactive source or x-ray tube Use x-ray fluorescence to select specific low-energy wavelengths 1, 2 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-L  and K-K  fluorescence lines have energies of 3.1 & 3.3 keV. 8

Recent uniformity calibration reveals ‘faulting’ pixels and non-uniformities 2769±148 (~5.3%) 2992±153 (~5.1%) 3037±127 (~4.2%) 9 ① Non-uniformities within chip-to-chip or pixel-to-pixel are within 5% Rows (WAVELENGTH)

2927±137(~4.6%) 2920±147 (~5%) 2866±146 (~5%) ① Non-uniformities within chip-to-chip or pixel-to-pixel are within 5% Rows (WAVELENGTH) Columns (PLASMA HEIGHT) ② Re-do trim-bit calibration - the original calibration may no longer be valid. ③ # of ‘faulting’ pixels after ~6yrs of operation is approximately 4-5%. 10 Recent uniformity calibrations reveal ‘faulting’ pixels and non-uniformities

Motivation/outline ② In-situ wavelength calibration Needed for calibrated measurements of the plasma rotation velocity and spectrometer instrumental function. Reliable measurements of plasma emissivity, ion temperature and toroidal flow velocity profiles, requires: ① In-situ uniformity calibration of detectors Needed for calibrated measurements of the local plasma emissivity and estimates of impurity density and its gradients. 11 ③ Crystal/detector temperature monitoring & control Ambient temperature excursions can affect interplanar spacing introducing apparent velocity offsets

In-situ wavelength calibration tested in C-Mod He-like Ar detectors Cd-L  1,2 Cd-L  1 K-K  1,2 H-like Ar detector 12 Use x-ray tubes or fluorescence* to select specific s *Fluorescence in transmission/reflection mode

Cd emission from (Cu anode + Cd target) x-ray tube illuminated 70% of Pilatus detector ① 8-10 Watts x-ray tube ⇒ longer integration/power ① Unexpected background at shorter ’s ? ② Needs to fill the optics as the plasma. ③ Modern x-ray tube has been recently acquired. ? 13

Rest wavelength fiducials have recently been proposed for the W 64+ ITER core x-ray imaging spectrometer Hf Ir ① L-shell emission spectra from tungsten (e.g. neon- like) can be produced at the SuperEBIT electron beam ion trap at LLNL. ② Choose from six characteristic x-ray lines that may be used as rest-energy calibration standards. ③ Other options: Cu K  eV Ga K  eV Ga K  eV ④ The final choice will depend on how much room there is on the detector in the final design. W 14

Novel x-ray tubes will provide wavelengths of interest for ITER calibrations 15 ① He- and H-like Ar: Use K-K  & Cd-L  lines. a)New remotely controlled tubes recently purchased. b)Technique to be tested at C-Mod and PPPL (NSTX-U) and exported to KSTAR, EAST, LHD and W7X. c)Export to ITER-India ② He-like Fe: Use Ho-L  lines. a)Ho-lines bracket the w-line (~60 eV apart). b)Technique to be tested at PPPL and LLNL. ③ Ne-like W: Use Ir-L  & Ga-K  lines.  E Ir ~76 eV;  E Ga ~27 eV. b)Hf and Cu are also of interest. c)Technique to be tested at PPPL and LLNL. d)Measure 3D (W 64+ ) line with an accuracy greater than current estimates and theoretical predictions (<0.5 eV). Ho-L  Ho-L  Ir- L  Ga- K 

Roadmap of activities and tasks ① Continue R&D for implementation of strategy and options for in-situ wavelength calibrations (based on x-ray tubes). ② Test x-ray fluorescence transmission technique using the plasma intrinsic emission and a target foil in front of the crystal. 16 ③ Consider also similar techniques in the case of using the He-like krypton spectrum. ④ If Kr measurement is done in 2 nd order we can use Mn K  1 and Dy L  1,2. ⑤ Test these concepts in controlled environments at PPPL, MIT and LLNL. ⑥ Export these techniques to spectrometers in Japan, Korea, China, Germany and India, and in the future, ITER. Th L  1 Th L 

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Future work ① Develop concept for the implementation of fluorescent screen on the ITER CXIS system. a) Transmission mode. b) Reflection mode (x-ray tube). ② It is important to show that these calibration schemes are plausible from an engineering point of view. ③ 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. 18 Fluorescence screen plasma Fluorescence screen tube Fluorescence in transmission mode Fluorescence in reflection mode