Grzegorz P. Karwasz , Kamil Fedus Institute of Physics

1. Electron (and positron) scattering cross sectionsfor low temperature plasmas:experimental and semiempirical Grzegorz P. Karwasz, Kamil Fedus Institute of Physics Faculty of Physics, Astronomy and Applied Informatics, University Nicolaus Copernicus , 87100 Torun, Poland IAEA Experimental Network Meeting, Wien, 19-21.11.2018

2. Plasma temperature ← integral cross sections Ramsauer minimum (zero in s-wave) V. Godyak, Sendai 2006

3. The ITER Tokamak Be h=29 m W R=6 m Credit: prof. D. J. Campbell (2014)

4. Rationale: edge and divertor plasma Guillemaut et al. Nucl.Fusion 54 (2014) 093012

5. Rationale: electron T and power irradiated Electron temperature during three points of density ramp: good agreement Power irradiated (0.5-1.5 MW) simulation: JET-C <10% JET-ILW factor 3! Guillemaut et al. Nucl.Fusion (2014)

6. Carbon sputtering by CH4 and C2Hy ions Nakano et al. Nucl.Fusion 54 (2014) 043004

7. Data needed: I Neutrals (H, C, C2, Be, BeH2, CH4) 2. Partial cross sections: 1. Total cross section elastic scattering e+A →e+A rotational excitation e+CH4 (J=0) → e+CH4 (J=2) vibrational excitation e+AB(v=0) → e+AB(v>0) electron attachment (dissociative) e+AB → A- + B electronic excitation e+A →e+A* emission lines: A* → A + hv neutral dissociation e+AB → A + B + e emisison from dissociation e + AB → A* + B + e + hv ionization e+A →A++2e dissociative ionization e+AB → A + B+ + 2° ionization into excited states e + A → (A+)* + 2e

8. Data needed: II Positive ions (BeH+) 2. Partial cross sections: • Recombination: A+ + e → A • 1a. dissociative recombination: AB+ + e → A* + B vibrational excitation e+AB(v=0) → e+AB(v>0) electronic excitation e+A+ →e+A+* double ionizatione+A+ →A2+ + 2e

9. Databases

10. Experimental methods: total attenuation method I = I0 exp(-σnL); precision <5% H. Nishimura et al., J.Phys. Soc. Japan 72 (2003) 1080 Sullivan et al. (2008)

11. Experimental methods: total attenuation method I = I0 exp(-σnL); precision <5% (apart from angular resolution error) Szmytkowski & collaborators > 1984

12. Review case study: CH4 1. Total cross section: ±5% M.-Y. Song, J. S. Yoon, H. Cho, Y. Itikawa, G. Karwasz, V. Kukooulin, Y. Nakamura, J. Tennyson, to be published

13. Total:experiment vs. theory (NF3) • Problems with theoretical • determining their • position and amplitude • Amplitude (and width) are • too high ←neglecting • nuclear motion • - Position: underestimeated • interaction potential (?) Goswami et al. (2013)

14. Positron – total cross sections FIRST ACCELERATOR REMODERATOR STAGE INJECTION OPTICS DEFLECTOR Karwasz eet al.. 2002

15. … Argon: a flat cross section up to Ps threshold ?

16. Idziaszek & Karwasz, Phys. Rev. A 73, 064701 (2006)

17. Low energies: Modified Effective Range Theory Two fitting parameters: A – scattering length R – effective range (for s and p partial waves) CH4 K. Fedus, G. Karwasz, Eur. J. Phys. D (2014)

18. Semi-empirical methods: elastic (MERT) Link between elastic, total, MTCS: in some simple cases, and low energies CH4 Links elastic, total, MTCS: for atoms, spherical molecules @ energies <1 eV K. Fedus, G. Karwasz, Eur. J. Phys. D (2014)

19. Positron total: experiment vs theory PRA 2015

20. A simple semi-empirical mode

21. we have even more than one explanation But this is still only a model, not mechanism

22. Swarm experiments: diffusion coefficients → cross sections Experiment is simple, but requires guessing cross sections, that can form non unique set

23. Analogy: NO swarm data Josic et al., CPL (2003)

24. NO resonances N2 and O2 – like

25. Resonances: theory

26. NO – congruent set of cross sections Confirmed by beam experiments (ANU Canberra, Fribourg Uni)

27. High-energy total cross sections Angular resolution error !

28. High energies total: in search for additivity rule CH4, CF4, SiH4, ... WF6 → CH2F2, SiF4 ... → H, C, Si, ... W G. Karwasz et al., Phys. Rev. A 59 (1999) 1341

29. High energy limit (Born-Bethe plot) σ (E) = A / E + B log (E)/E CH4 C2H2 1. Trento experiment was underestimated in high-energy limit (>1000 eV) 2. We still have no idea, how do parameters link to other molecular features Mi-Young Song et al., JCPRD 2017

30. Experimental methods: ionization If two ions are formed (for example CH4→CH3+ + H+ + 2e) the ionization is counted twice R. Basner, M. Schmidt, K. Becker, Int. J. Mass Spectr. 233 (2004) 25

31. Experimental methods: ionization (2) SiCl+ from single, double, triple ionization of SiCl4 B. G. Lindsay et al., JCP 129 (2004), S J King nad S D Price, JCP134 (2011) 074311

32. Ionization (excellent!): CH4 Ionization total: ±10% M.-Y. Song, J. S. Yoon, H. Cho, Y. Itikawa, G. Karwasz, V. Kukooulin, Y. Nakamura, J. Tennyson, JPCRD (2016)

33. Ionization (fair): C2H2 M.-Y. Song, J. S. Yoon, H. Cho, Y. Itikawa, G. Karwasz, V. Kukooulin, Y. Nakamura, J. Tennyson, JPCRD (2017)

34. Ionization: BEB formula Experiment overestimes counting ionization (due to dissociative ionization) Normalized energies: t= E/In, un=Ekin/ In Only two values needed from QCh See: G. Karwasz, P. Mozejko, M.-Y. Song, Int. J. Mass Spectrometry (2014) and poster by Gupta

35. Ionization (BEB): CH4, CH3F, ... CF4 Thumb rule (?) σmax = 4/3 α G. Karwasz, P. Mozejko, M.-Y. Song, Int. J. Mass Spectrometry (2014)

36. Ionization (BEB) & elastic: H6N2Cl2Pt No theories, no experiments B. Żywicka, P. Możejko, Eur. J. Phys. D (2012)

37. Ionization (Fe+24): CCC theory Fursa et al. (2016)

38. Experimental methods: excitation (electronic, vibrational) e- + O2 (v=0) – e- + O2 (v=0, 1, 2, etc.) Experiments by: I. Linert, M. Zubek (Gdansk) J. Phys. B 39 (2006) M. Khakoo et al. (Fullerton California) M. Allan (Freiburg University)

39. Electronic excitation H2 (in 1996)

40. Electronic excitation: H2 (experiment) Differences by 5-folds Courtesy: Ursul Fantz

41. Electronic excitation: H2 (theory) Agreement within error bar with experiments CCC: Tapley, Fursa et al. J. Phys. B (2018)

42. Electronic excitation: H2 (theory) B 1Σ+u C 1Σ+u Agreement within error bar with experiments Hargreaves et al.. J. Phys. B (2017)

43. Electronic excitation: CH4 Electronic excitation: reasonable agreement between dissociation into-neutrals experiment and R-Matrix calculation W. J. Brigg, J. Tennyson, M. Plummer J. Phys. B 47 (2014) 185203 R-Matrix

44. Dissociation into neutrals (CF4, CH3F…) x 3 volatile organotellurides x 2 x 1 Additivity rule: cross section = sum of paths Motlagh and Moore, JCP109 (1988) 432

45. Heavier, ITER-like targets G. Karwasz, K. Fedus, FS&T (2013), experimental data: Szmytkowski and collaborators

46. WF6 - few data ? ? GK, work in progress

47. BeH: electronic and vibrational excitation X2 Σ + (v=0) → A2П (v’) Cross section Rate coefficients R Celiberto, K L Balujaand R K Janev, Plasma Sources Sci. Technol. 22 (2013) 015008 Mott-Massey Schr. eq. No experiments to compare with

48. Tungsten, berillium (model potentials) W Be [15] Zatsarinny (2015) F. Blanco et al. (2017)

49. Polar targets: large uncertainties Positron scattering on H2O molecules (polar target) ANU Canberra

50. ITER-like: NH3 ? NH3 μ =1,47 D Jones et al. PRA 78, 042714 (2008)