Study of negative ion surface production in caesium-free H 2 plasma PhD student: Kostiantyn Achkasov Tutors: Gilles Cartry and Alain Simonin 3 rd FUSENET PhD Event in Fusion Science and Engineering in Fusion Science and Engineering University of York, 23 rd - 26 th of July 2013

2 Fundamentals 3 rd FUSENET PhD Event in York: 26 th of June 2013  Controlled thermonuclear fusion is one of the most promising future energy sources

3 Fundamentals 3 rd FUSENET PhD Event in York: 26 th of June 2013

4 Fundamentals  ITER is the world's largest experimental tokamak nuclear fusion reactor being built at the south of France  Controlled thermonuclear fusion is one of the most promising future energy sources 3 rd FUSENET PhD Event in York: 26 th of June 2013

5 Fundamentals  ITER is the world's largest experimental tokamak nuclear fusion reactor being built at the south of France  Required electron temperature: 10 – 20 keV (~10 8 °C)  only 1 keV can be achieved with Ohmic heating  Controlled thermonuclear fusion is one of the most promising future energy sources 3 rd FUSENET PhD Event in York: 26 th of June 2013

6 Fundamentals  ITER is the world's largest experimental tokamak nuclear fusion reactor being built at the south of France  Required electron temperature: 10 – 20 keV (~10 8 °C)  only 1 keV can be achieved with Ohmic heating  Controlled thermonuclear fusion is one of the most promising future energy sources one needs additional heating methods! 3 rd FUSENET PhD Event in York: 26 th of June 2013

7 NBI for ITER NBI - neutral beam injection 3 rd FUSENET PhD Event in York: 26 th of June 2013

5.3 m 4.7 m 15 m 8 NBI for ITER 17 MW & 1 MeV of neutrals Total weight > 900 tons Calorimeter Bushing RIDNeutralizerIon source and accelerator NBI - neutral beam injection 3 rd FUSENET PhD Event in York: 26 th of June 2013

9 Why to use i - ? neutrals of 1 MeV are needed to heat the ITER plasma core and ignite the fusion reactions 3 rd FUSENET PhD Event in York: 26 th of June 2013

10 neutrals of 1 MeV are needed to heat the ITER plasma core and ignite the fusion reactions At such an energy: D + →0% D - → 56% of neutralisation efficiency Ion neutralization Why to use i - ? 3 rd FUSENET PhD Event in York: 26 th of June 2013

11 Ion neutralization Necessary D - current: ~ 50 A (250 A∙m -2 ) Why to use i - ? neutrals of 1 MeV are needed to heat the ITER plasma core and ignite the fusion reactions At such an energy: D + →0% D - → 56% of neutralisation efficiency 3 rd FUSENET PhD Event in York: 26 th of June 2013

12 new large i - source has to be developed! Ion neutralization Necessary D - current: ~ 50 A (250 A∙m -2 ) Why to use i - ? neutrals of 1 MeV are needed to heat the ITER plasma core and ignite the fusion reactions At such an energy: D + →0% D - → 56% of neutralisation efficiency 3 rd FUSENET PhD Event in York: 26 th of June 2013

Present i – source 13 i - source concept RF Driver 3 rd FUSENET PhD Event in York: 26 th of June 2013

i - surface production with Cs deposition has many drawbacks like diffusion of Cs inside the accelerator is presently the only way to meet ITER requirements 14 RF Driver Present i – source i - source concept 3 rd FUSENET PhD Event in York: 26 th of June 2013

Alternative solutions to the use of Cs would be highly valuable for the future fusion i - sources! 15 Present i – source RF Driver i - surface production with Cs deposition has many drawbacks like diffusion of Cs inside the accelerator is presently the only way to meet ITER requirements i - source concept 3 rd FUSENET PhD Event in York: 26 th of June 2013

16 Helicon reactor PHISIS H 2 and D 2 plasma P = 20 – 900 W no magnetic field p reactor = 0.2 – 2 Pa capacitively coupled plasma mode Experimental set-up Graphite sample Pump Pyrex tube Antenna Coils Mass Spectrometer Hiden EQP rd FUSENET PhD Event in York: 26 th of June 2013

17 Experimental set-up Helicon reactor PHISIS H 2 and D 2 plasma P = 20 – 900 W no magnetic field p reactor = 0.2 – 2 Pa capacitively coupled plasma mode 3 rd FUSENET PhD Event in York: 26 th of June 2013

18 Langmuir probe Sample Experimental set-up Mass Spectrometer 3 rd FUSENET PhD Event in York: 26 th of June 2013

19 Measurement principle V MS Vs Vs VpVp Mass Spectrometer Plasma Sample E 0 3 rd FUSENET PhD Event in York: 26 th of June 2013

V MS Vs Vs VpVp Mass Spectrometer Plasma Sample 20 E 0 Negative ion distribution function (NIDF) Measurement principle 3 rd FUSENET PhD Event in York: 26 th of June 2013

21 Modeling of the NIDF 3 rd FUSENET PhD Event in York: 26 th of June 2013

22 Modeling of the NIDF SRIM: the stopping and range of ions in matter 3 rd FUSENET PhD Event in York: 26 th of June 2013

23 Modeling of the NIDF ×× Plasma transmission NIDF of i - emitted by the surface Surface Mass spectrometer transmission 3 rd FUSENET PhD Event in York: 26 th of June 2013

24 Modeling of the NIDF SRIM ×× Plasma transmission NIDF of i - emitted by the surface Surface Mass spectrometer transmission 3 rd FUSENET PhD Event in York: 26 th of June 2013

25 Modeling of the NIDF SRIM SIMION ×× Plasma transmission NIDF of i - emitted by the surface Surface Mass spectrometer transmission 3 rd FUSENET PhD Event in York: 26 th of June 2013

26 good agreement between F’’(E) and F measured (E) Modeling of the NIDF 3 rd FUSENET PhD Event in York: 26 th of June 2013

27 good agreement between F’’(E) and F measured (E) SRIM calculation: C-H layer with 30% of hydrogen on the surface Modeling of the NIDF 3 rd FUSENET PhD Event in York: 26 th of June 2013

NIDF study of different carbon materials 28  highly oriented pyrolitic graphite (HOPG) 3 rd FUSENET PhD Event in York: 26 th of June 2013

29 NIDF study of different carbon materials  highly oriented pyrolitic graphite (HOPG) 3 rd FUSENET PhD Event in York: 26 th of June 2013

30 F”(E,θ) 30% H NIDF study of different carbon materials  highly oriented pyrolitic graphite (HOPG) 3 rd FUSENET PhD Event in York: 26 th of June 2013

31 F”(E,θ) 30% H NIDF study of different carbon materials  highly oriented pyrolitic graphite (HOPG) 3 rd FUSENET PhD Event in York: 26 th of June 2013

32 F”(E,θ) 20% H F”(E,θ) 30% H NIDF study of different carbon materials  highly oriented pyrolitic graphite (HOPG) 3 rd FUSENET PhD Event in York: 26 th of June 2013

33 H coverage on HOPG decreases with temperature F”(E,θ) 20% H F”(E,θ) 30% H NIDF study of different carbon materials  highly oriented pyrolitic graphite (HOPG) 3 rd FUSENET PhD Event in York: 26 th of June 2013

34  yield comparison NIDF study of different carbon materials 3 rd FUSENET PhD Event in York: 26 th of June 2013

35  yield comparison NIDF study of different carbon materials 3 rd FUSENET PhD Event in York: 26 th of June 2013

36  yield comparison NIDF study of different carbon materials % H 3 rd FUSENET PhD Event in York: 26 th of June 2013

37  yield comparison NIDF study of different carbon materials % H Boron-doped diamond: BDD 3 rd FUSENET PhD Event in York: 26 th of June 2013

38  yield comparison NIDF study of different carbon materials % H biasing problems below 400°C % H Intrinsic diamond: ID 3 rd FUSENET PhD Event in York: 26 th of June 2013

39  yield comparison % H Raman spectroscopy: sp 3 /sp 2 BDD sp 3 /sp 2 HOPG biasing problems below 400°C NIDF study of different carbon materials 3 rd FUSENET PhD Event in York: 26 th of June 2013

40  sp 3 /sp 2 phase ratio J. Robertson, Materials Science and Engineering, R37 (2002) Raman spectroscopy: sp 3 /sp 2 BDD sp 3 /sp 2 HOPG NIDF study of different carbon materials 3 rd FUSENET PhD Event in York: 26 th of June 2013

 HOPG gives the highest i - yield at T room  ID gives the highest i - yield at elevated T: 500°C Conclusions 41 3 rd FUSENET PhD Event in York: 26 th of June 2013

 HOPG gives the highest i - yield at T room  ID gives the highest i - yield at elevated T: 500°C  proper use of MS diagnostic and modeling allows to determine H coverage on the sample surface Conclusions 42 3 rd FUSENET PhD Event in York: 26 th of June 2013

 HOPG gives the highest i - yield at T room  ID gives the highest i - yield at elevated T: 500°C  proper use of MS diagnostic and modeling allows to determine H coverage on the sample surface  MS combined with Raman spectroscopy shows: the phase ratio sp 3 /sp 2 changes when increasing T which alters the H surface coverage and the i - yield Conclusions 43 3 rd FUSENET PhD Event in York: 26 th of June 2013

 HOPG gives the highest i - yield at T room  ID gives the highest i - yield at elevated T: 500°C  proper use of MS diagnostic and modeling allows to determine H coverage on the sample surface  MS combined with Raman spectroscopy shows: the phase ratio sp 3 /sp 2 changes when increasing T which alters the H surface coverage and the i - yield  New materials with the optimal sp 3 /sp 2 state have to be probed deeper understanding is crucial Conclusions 44 3 rd FUSENET PhD Event in York: 26 th of June 2013

Perspectives 45 3 rd FUSENET PhD Event in York: 26 th of June 2013 Next steps  prove experimentally the H surface coverage change with T: Infrared Spectroscopy Temperature Programmed Desorption Spectroscopy

Perspectives 46 3 rd FUSENET PhD Event in York: 26 th of June 2013 Next steps  prove experimentally the H surface coverage change with T: Infrared Spectroscopy Temperature Programmed Desorption Spectroscopy  try out new materials: low work-function materials (Gd, Ba,...) large band-gap insulators (Si, GaAs,…)

Perspectives 47 Next steps  prove experimentally the H surface coverage change with T: Infrared Spectroscopy Temperature Programmed Desorption Spectroscopy  try out new materials: low work-function materials (Gd, Ba,...) large band-gap insulators (Si, GaAs,…) 3 rd FUSENET PhD Event in York: 26 th of June 2013 Final steps Final steps  Test the chosen material in a real negative ion source (Cybele) equipped with an extraction device and a particle accelerator (MANTIS) in CEA-Cadarache

The End Thank you for your attention and time! 48 3 rd FUSENET PhD Event in York: 26 th of June 2013