X-ray Spectroscopy on Fusion Plasmas

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Mervyn Flowers
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1 X-ray Spectroscopy on s An ongoing discussion between the two Manfreds Manfred von Hellermann for CXRS Manfred Bitter for x-ray spectroscopy G. Bertschinger for many contributers (Bitter, Kunze, Weinheimer, Marchuk, Urnov,..) Forschungszentrum Jülich, Institut für Energieforschung IV (Plasmaphysik), Assoziation FZJ-EURATOM,Partner in the Trilateral Euregio Cluster, FRG 1

2 Introduction Physical quantities measured by x-ray spectroscopy Some spectroscopic basics, line broadening and line shift, line intensities, elements, ionization stages, spectra 1-D results Instruments Imaging Bragg spectrometers 2-D measurements Outlook to ITER 2

3 Impurity sources in fusion plasmas Plasma facing components low z (Be, B, C, O) medium z (Si, Ti, Fe-group, Cu) high z (Mo, Wo) Impurities applied to Plasma (enhanced radiation losses, radiative mantle concept, transport studies) low z (Ne) medium z (Ar, Kr, Ti, Cr, Fe...) 3

4 Spectroscopic Basics : Line Broadening and Shift Doppler effect 0 (1 Thermal (Maxwellian Plasma) P( ) d FWHM mc 2kT Natural line broadening for resonance lines (Lorentz) No Stark and collisional broadening 2 2 exp v c mc kT ln2 0 2 m0c ) ( 0 kt 0 2 ) 2 d T FWHM * 0 T[ kev] 4

Basics : Abundance of Ionization stages X-ray spectroscopy (0.05... 0.

5 Basics : Abundance of Ionization stages X-ray spectroscopy ( nm) medium and high z impurities Medium z elements: He and H-like high z elements Ne-like, at very high temperatures He-like. 5

6 Basics : Excitation of ions (He-like Cr) P.Platz

7 7 Sensitivity of the electron temperature dependencies e sw e e w w s T E T T Y I I exp ) ( 1 ~ * e S n s n s T E I I exp ~ 2) ( 3) ( Satellite to resonance (w) Triplet to singlet Satellite to satellite ) ( ) ( ~ exp ) ( ) ( ~ * * * * e w e l e lw e w e l w l T Y T Y T E T Y T Y I I

8 Temperature dependence of n=2 satellite to resonance line intensity 8

9 Sensitivity of plasma parameters to measured quantities T e ~ (I k / I w ) ( ) v rot ~ line shift Li- / He-like ~ (I q,r / I w ) T i ~ 2 D H- / He-like contribution to triplet-line appr. 10% n 0, H- / He requires detailed spectral modeling estimated accuracy 50% 9

10 Modelling of He-like spectra (argon) Fitting of the spectrum with physically relevant parameters : T i, T e, v rot, He-like, Li/He-like, H/Helike deviation at y~15% 10

11 Theoretical model and fit to experiment Model spectrum about 1000 components T i, v rot, T e, Li- / He-like H- / He-like background 11

12 Ion temperature and plasma rotation (M. Bitter et al. EPS 2000) 12

13 Electron temperature measurement spectroscopic / ECE 13

14 Electron temperature obtained from ratio singlet to triplet (n=3) Measurements and new calculations confirm measurements on PLT and resolve contradictions to the HULLAC code 14

15 Li-like Ar 15+ for ohmic and Neutral beam heated plasmas relative to coronal expectations 15

16 Density of Li-like Ar 15+ for ohmic plasmas with cascades Cascades reduce Lilike abundance by about 20% asymptotic behaviour is compatible to coronal expectations rates for calculations of coronal are correct 16

17 Estimate of H-like argon Li-like abundance and recombination of H-like provide diffusion coefficient and density of neutral hydrogen hydrogen density between 1*10 8 and 2*10 7 cm -3 support by transport codes radial profiles recommended 17

18 Comparison of new calculations with previous gas puff experiments (XUV and x-ray spectroscopy) X-ray He-like/RITM XUV 18

19 Principle of an imaging Bragg spectrometer Eggs, Ulmer 1965 Bitter, Fraenkel

20 Shape of focal lines Bragg condition is fulfilled on a cone around the crystal normal Focal lines curved Focal curves on detector : conical intersections Aperture to the plasma curved too 20

21 21

250 53.4 mm 200 intensity / a. u. 150 100 50 0 3.93 3.94 3.95 3.96 3.97 3.98 3.99 4 4.01 wavelength / Angstrom 400 middle 350 300 intensity / a. u. 250 200 150 100 50 0 3.93 3.94 3.95 3.96 3.97 3.98 3.99 4 4.01 wavelength / Angstrom 300-53.

22 mm 200 intensity / a. u wavelength / Angstrom 400 middle intensity / a. u wavelength / Angstrom mm 250 intensity / a. u wavelength / Angstrom 6000 W He-like, singlet Q,R Li-like Z He-like, triplet intensity (arb. units) y (mm) intensity 500 (arb. units) y (mm) intensity (arb. units) y (mm)

23 Ion and electron temperature, toroidal plasma rotation Properties of the spectrometer as expected Provides local plasma parameters Room for developments (ITER, W7-X) 23

24 M.Bitter et. al. APS

25 M.Bitter et. al. APS

26 M.Bitter et. al. APS

deg (toroidal rotation) For the edge spectrometers problems

27 X-ray spectrometers for ITER (EU design) 6 imaging spectrometers 3 perpendicular (poloidal rotation) 3 angle 30 deg (toroidal rotation) For the edge spectrometers problems with the detectors, arrays of non-imaging spectrometers will do the job 27

28 Crystals and Bragg angles for the ITER x-ray spectrometer 28

29 Crystal support Narrow range of Bragg angles deg All elements share the same aperture Very simple change mechanism for different crystals Rotational stage only In situ calibration by x- ray lines 29

30 Expected signal for He-like Kr, fraction 10 ppm, includes background and count statistics 30

31 Conclusions X-ray spectroscopy measures T i, v rot, T e, concentration and ionisation stage of medium-z impurities and estimate density of neutral hydrogen Simple spectra, well understood, no background lines Toroidal and poloidal rotation Highest accuracy in the center, lower at edge Novel detectors with very high dynamic range Will be installed on ITER by US Simple and robust Complementary to CXRS 31

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract

This work was performed under the auspices of the U.S. Department of Energy by under contract DE-AC52-7NA27344. Lawrence Livermore National Security, LLC The ITER tokamak Tungsten (W) is attractive as