First Technical Meeting on Spectroscopic and Collisional Data for W from 1 ev to 20 kev IAEA, Vienna, December 13 15, 2010

Transcription

1 Exploratory studies towards experimental data for electron-impact ionization, electron-ion recombination and photoionization i ti of tungsten t ions Alfred Müller Institut für Atom- und Molekülphysik JUSTUS-LIEBIG- A MP UNIVERSITÄT GIESSEN I A M P First Technical Meeting on Spectroscopic and Collisional Data for W from 1 ev to 20 kev IAEA, Vienna, December 13 15, 2010

2 Outline I. Introduction II. Electron-ion recombination III. Photoionization of ions IV. Electron impact ionization of ions V. Outlook and plans

3 Outline I. Introduction atomic data needs atomic data situation II. Electron-ion recombination III. Photoionization of ions IV. Electron impact ionization of ions V. Outlook and plans

4 Evolution of tungsten ion charge states in a plasma T Pütterich, R Neu, R Dux, A D Whiteford, M G O Mullane and the ASDEX Upgrade Team Plasma Phys. Control. Fusion 50 (2008) rate coefficients for ionization and recombination required Ionization: CADW calculations of Ludlow et al. (2005) Recombination: Burgess Merts ( ) with ad hoc modifications

5 Recombination rate coefficients of Fe Fe 15+ Rate coefficie ent ( cm 3 /s ) Murakami et al Arnaud Raymond 1992 Brooks et al Isler et al G et al Gu et al Fe Plasma temperature ( K ) Even for a relatively simple Na-like ion, care has to be taken when applying existing data

6 Recombination rate coefficients of Fe Fe 15+ Rate coefficie ent ( cm 3 /s ) Murakami et al Arnaud Raymond 1992 Brooks et al Isler et al G et al 2004 ADAS (Z. Altun) TSR experiment Gu et al Fe Plasma temperature ( K ) Even for a relatively simple Na-like ion, care has to be taken when applying existing data

7 Recombination of Au 25+ ( 4f 8 ) 0-8 cm 3 s -1 ) Me erged be eams rate coeffic cient ( Hoffknecht et al., J. Phys. B 31, 2415 (1998) Flambaum et al Electron-ion collision energy ( ev ) Huge cross sections no individual resonances in spite of high resolution new theoretical access to be developed* *See e.g. Flambaum et al. Electron recombination with multicharged ions via chaotic manyelectron states Phys. Rev. A 66, (2002)

8 Data situation Theoretical predictions for ionization and recombination of complex many-electron ions such as W q + ( with q << Z ) are very unreliable. Experiments are needed to test and to guide theoretical approaches

9 Available experimental cross section data for electron-impact ionization of W q+ Single ionization: q=1,,10 Double ionization: q=1,,6 Triple ionization: q=1,,4 photoionization of W q+ Single ionization: q=0 electron-ion recombination of W q+ no absolute cross section measurements available

10 Electron-impact ionization of W cm 2 ) 17 Cross section ( σ 1+ 1,2 for W Stenke et al Montague & Harrison Electron-ion collision energy ( ev )

11 Outline I. Introduction II. Electron-ion recombination experimental status what can be done what has to be done III. Photoionization of ions IV. Electron impact ionization of ion V. Outlook and plans

12 Storage ring experiments TSR Heidelberg CRYRING Stockholm ESR at GSI Darmstadt ca. 15 m

13 The storage ring TSR

14 Comparison of advanced theory with experiments e - + C 3+ (1s 2 2s) C 2+ (1s 2 2p 4l) C 2+ (1s 2 2s 2 ) + photons (10-10 cm -3 /s) Recom mbinatio on rate d 3 D 2p 2p 4f 3 F, 2p 4f 1 F 4d 3 P 2p MBPTheory Lindroth CRYRING S. Mannervik et al, PRL 81 (1998) 313 TSR S. Schippers et al., ApJ 555 (2001) 2p 4f 3 G p 4f 3 D Electron energy (ev) 2p 4d 1 P

15 Fe 17+ Fe 18+ Fe 19+ Fe 20+ Dielectronic recombina- tion of Fe L- shell ions: a joint US-German project for astrophysics Columbia- Astrophysics Laboratory Justus-Liebig- Universität Fe 21+ Fe 22+ Giessen Max-Planck- Institut für Kernphysik

16 Conclusions so far Merged-beam electron-ion recombination experiments deliver high-accuracy data Atoms of all elements in any given charge state are accessible at ion storage rings State of the art theory provides good predictions for light few-electron ions For complex ions the theory situation is not satisfying; new theoretical approaches to recombination of many-electron ions have to be developed d Only experiments can guide such developments

17 Outline I. Introduction II. Electron-ion recombination III. Photoionization of ions IV. Electron impact ionization of ions V. Outlook and plans

18 Time s arrow recombination e - A q+ [ A (q-1)+ ]** A (q-1)+ photoionization [[ A (q-1)+ (q-1)+ ]** ]** A q+ e - A (q-1)+

19 Time reversal symmetry: detailed balance Statistical weight g PI-parent =2 Binding energy I A σ PI hν +C 3+ (1s 2 2s) C 4+ (1s 2 )+e ev σ Rec Energy E e = hν -I A σ PI σ Rec ( E ) (E + I ) e g = PI parent e A ( hν = E + I ) g E 2m c e A PI product e e 2 2

20 Photoionization of ions by synchrotron radiation ion source IAMP in collaboration with R. A. Phaneuf et al., University of Nevada, Reno

21 Time reversal of C 3+ photo ionization Two totally different independently absolute measurements. σ DR ( Mb ) CRYRING ALS DR data: Mannervik et al., PRA 55, 1819 (1997) C 3+ (1s [2s2p 3 P] 2 P 0 ) 0.10 dielectronic CRYRING data time reversed ALS data recombination of C 4+ (1s 2 1 S) C 3+ (1s [2s2p 3 P] 2 P 0 ) photo excitation of C 3+ (1s 2 2s 2 S) E ev E e ALS data resolution 47 mev Voigt-fit R-matrix calculation resolution 47 mev Mb ) σ PI ( A. Müller, S. Schippers, R.A. Phaneuf et al. J. Phys. B 42 (2009) Photon energy ( ev )

22 Summary on photoionization of ions complements electron-ion recombination studies employing detailed balance very high h energy resolution possible detailed spectroscopy py of excited states of ions accessible

23 Outline I. Introduction II. Electron-ion recombination III. Photoionization of ions IV. Electron impact ionization of ions V. Outlook and plans

24 Electron-ion crossed- beams setup at IAMP Versatile apparatus for studying atomic collisions

25 Electron-ion crossed-beams setup at IAMP

26 Electron-ion interaction region collector energy-defining g electrode ions cathode electron current: 450 ma at 1 kev

27 Ionization of complex ions: Xe 2+ A. Borovik et al., work in progress cm 2 ) 18 section ( x Xe 2+ (4d 10 5s 2 5p 4 ) Cross 50 Giessen absolute Giessen energy scan Electron energy ( ev )

28 Ionization of complex ions: Xe 2+ A. Borovik et al., work in progress cm 2 ) 18 section ( x10-1 Cross Xe 2+ (4d 10 5s 2 5p 4 ) Giessen absolute Giessen energy scan Lotz 3-parameter formula Electron energy ( ev )

29 Ionization of complex ions: Xe 2+ A. Borovik et al., work in progress cm 2 ) 18 section ( x Xe 2+ (4d 10 5s 2 5p 4 ) Cross 50 0 Giessen absolute Giessen energy scan CADW Loch et al Electron energy ( ev )

30 Assumptions, expectations, general wisdom Theory is expected to provide better predictions for more highly hl charged ions in an iso-electronic i sequence DW calculations for the direct and the excitationautoionization contributions should be good for highly charged ions

31 Ionization of Xe Xe 22+ Cros ss sectio on ( x10-18 cm 2 ) DW direct Mandelbaum et al. DW direct + EA Electron-ion collision i energy ( ev ) P. Mandelbaum, M. Cohen, J.L. Schwob, A. Bar-Shalom, EPJD 33, 213 (2005)

32 Ionization of Xe Xe 22+ Cros ss sectio on ( x10-18 cm 2 ) DW direct Mandelbaum et al. DW direct + EA Giessen absolute Giessen scan A. Borovik et al., work in progress Electron-ion collision i energy ( ev ) Similar discrepancies found for other highly charged ions

33 Importance of multiple ionization A. Borovik et al., work in progress Xe 2+ ) n ( cm 2 section Cross single ionization double ionization Electron energy ( ev )

34 Conclusion on electron-impact single ionization Present state of the art theory can predict cross sections for direct single ionization of few-electron ions with high accuracy Present state of the art theory has difficulties to predict single ionization of complex manyelectron ions where excitation-autoionization processes prevail There is no theory for multiple ionization of complex ions

35 Summary so far Total cross sections for single ionization and for recombination as well as for photoionization of few-electron ions are quite well understood; theoretical data of benchmark quality are (becoming) available for few-electron systems Understanding of collisions and structure of complex ions is not satisfying Experiments with complex many-electron systems are required to test and to guide theoretical approaches

36 Outline I. Introduction II. Electron-ion recombination III. Photoionization of ions IV. Electron impact ionization of ions V. Outlook and plans

37 Plans for the future: recombination of W q+ ions using storage rings TSR ion storage ring in Heidelberg unique facility with optimal features for the purpose cooler plus target excellent energy resolution qupto50 q up to 50 reached

38 Recombination of W 20+ ions at the TSR storage ring S. Schippers et al., in preparation

39 Plans for the future: photoionization of W q+ ions using synchrotron radiation Photon-ion spectrometer at PETRA III: PIPE photons 2m highest brilliance cw synchrotron radiation up to 3 kev s -1 per 0.01% 01% b.w.

40 First results on photoionization of W q+ ions obtained at the ALS in Berkeley A. Müller, S. Schippers, A.L.D. Kilcoyne, preliminary results ts) 400 W 3+ W mev res 10 mev step 400 ross sec ction (a arb. uni Cr Nominal photon energy (ev)

41 Plans for the future: electron-impact single and multiple ionization of W q+ ions New versatile high power, high energy electron gun high electron currents observed: 1A at 3 kev electron energies beyond 6 kev accessible no other electronion experiment in the world can compete with respect to sensitivity and energy resolution.

42 Electrical currents of isotope-resolved W q+ ions from an all-permanent permanent-magnet magnet ECR source 30 O 2+ C + ( na ) Ion cu urrent W W 22+ optimized for W 21+ W 20+ W W 18+ W W W Magnetic field ( G )

43 Highest charge states of W q+ ions observed Ne 3+ N A= =182 A=183 A=184 A W 29+ W A=1 86 W Ion curre ent (na A) W W 27+ W W Magnetic field ( G )

44 First results on electron-impact ionization of W 17+ ions obtained in Giessen J. Rausch, K. Spruck, A. Becker, K. Huber, S. Schippers, A. Müller, preliminary results ( cm 2 ) Cross section e + W 17+ W e energy scan measurement absolute cross sections ionization thresholds: Kramida & Shirai Scofield Carlson et al Electron-ion collision energy ( ev )

45 Cooperation IAMP, Giessen Present group members Alfred Müller Stefan Schippers Kurt Huber Sandor Ricz Carsten Brandau Alexander Borovik Dietrich Bernhardt Kristof Holste Jan Rudolph Katrin Müller Kaija Spruck Josephina Werner Arno Becker Jonas Hellhund Joachim Rausch Collaboration of IAMP with: Atomic Physics Groups at GSI, Darmstadt MPI-K, Heidelberg University of Stockholm Physics Department, University of Nevada, Reno Columbia University, Astronomy & Astrophysics, New York Scientific Support Groups at TSR, MPI-K, Heidelberg ESR, GSI, Darmstadt ALS, LBL, Berkeley Atomic Theory Groups at Giessen University University of Stockholm University it of Strathclydeth Queen s University, Belfast Auburn University Curtin University, Perth And others occasionally