1. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Recent state and progress in negative ion modeling by means ONIX code Mochalskyy Serhiy 1, Dirk Wünderlich 1, Benjamin Ruf 1, Peter Franzen 1 Ursel Fanz 1 and Tiberiu Minea 2 1 Max-Planck-Institut fuer Plasmaphysik EURATOM Association Boltzmannstr. 2,D-85748 Garching 2 LPGP, Univerisity Paris-Sud, CNRS F-91405 Orsay, France

2. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Outline Introduction Code improvement Code validation Code benchmarking Realistic parameters Results Conclusions and future plans 2/32

3. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Introduction: Negative ion plasma source system Driver Expansion region Extraction region NI surface and volume production The goal is to produce negative ion 48A H - (40A D - ) (j~20mA/cm 2 ) beam with I NI /I e ~1 at low pressure 0.6pa during continuous 1 hour operation. 3/32

4. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Introduction: ONIX (Orsay Negative Ions eXtraction) code  3D Particle-in-Cell Monte Carlo Collision electrostatic code specially developed for modeling NI production and following extraction from ITER NBI plasma source.  Fully paralellized via MPI using domain and particle decomposition techniques.  Able to deal with complex geometries as in the case of the extraction aperture. Simulation domain 19 mm 14 mm Plasma grid Extraction grid 4/32

5. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Code improvement: Second order charge and E field assignment routine (1) First order Potential distribution Second order Potential distribution E(x) distribution P (V) Ex (V/cm) 5/32 x (mm) y (mm)

6. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Code improvement: Second order charge and E field assignment routine (2) First order Second order E(z) distribution Ex ( E(y) distribution Ey (V/cm) Ez (V/cm) 6/32 x (mm) y (mm)

7. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Code improvement: NI flux from PG (1) – injection method Trajectories of NI Flux at the given x plane Z (mm) y (mm) 7/32

8. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Code improvement: NI flux from PG (2) – extracted electron and NI current Extracted NI currentExtracted e current 8/32

9. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Code improvement: NI flux from PG (3) – potential well in vicinity to PG Old routine (normal injection, 1eV) New routine (random injection, 1eV) New routine (random injection, random energy 0.01 - 1eV) 9/32 X (mm) PG X (mm) y (mm) Potential (V)

10. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Code improvement: Addition to the simulation H 3 + ion and H - in the volume H 3 + density y (mm) H - from volume density Y (mm) n H3+ (m -3 ) Extracted electron and NI current 10/32 n H3+ (m -3 ) PG

11. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Code validation: Potential well test in simplified model Potential well test Potential sheath test X (mm) Potential (V) X (mm) Density (m -3 ) 11/32

12. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 0V -5V -10V 0V FIG. 10. Schematic of possible steady-state plasma potential profiles near a positively biased plate. Curve A corresponds to a large plate. Curve B corresponds to a small plate. Noah Hershkowitzb, Phys. Of Plasma (2005) 055502 Code validation: Potential well test in simplified model (2) Negative bias 0V 5V 10V 12/32 Potential (V) x (mm) Positive bias

13. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Code validation: different mesh size (real domain) Electrons current 13/32 PG x (mm) y (mm) Potential (V)

14. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Code benchmark: ONIX vs KOBRA3D 2 completely different codes with different approaches: 1) ONIX – uses plasma parameters (density, temperature,…) to calculate the extraction current and meniscus shape; 2) KOBRA 3D –uses the extraction current to calculate the potential and meniscus shape PI extraction test (2 runs) Density 0.8, 1.6,*10 17 m -3, e:100%, H + :100%; T e =2eV, T PI =1eV Extraction potential: -5kV; B field is switch off, no collisions PG aperture 8 mm diameter 14/32

15. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Code benchmark: ONIX vs KOBRA3D (2) PI extraction test (4 runs) Density 0.8, 1.6, 2.4, 3.2*10 17 m -3, e:100%, H + :100%; T e =2eV, T PI =1eV Extraction potential: -5kV; B field is switch off, no collisions PG aperture 8 mm diameter and 4mm length (2mm to PG knife and 2 mm after) ONIX KOBRA3D 15/32

16. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Realistic parameters: Magnetic field map 16/32 Filter field Deflecting field axial x direction vertical z direction

17. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Realistic parameters: Magnetic field map  Complete 3D magnetic field structure and thus 3D model is necessary to perform realistic simulation of NI extraction. Filter field Deflecting field axial x direction vertical z direction BxBx PG BzBz 17/32

18. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Realistic parameters: Magnetic field map ByBy 18/32 Filter field Deflecting field axial x direction vertical z direction

19. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Realistic parameters: Magnetic field map ByBy BzBz BxBx 19/32

20. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Realistic parameters: Plasma parameters in ONIX simulations Probe measurements ONIX NI emission rate BACON Full 3D magnetic field map 3D field simulation Geometry of the plasma grid Engineering specification OES CRDS n=3*10 17 m -3 n e =90%; n NI =10%, n H+ =40%, n H2+ =40%, n H3+ =20% T e =2, T H- =0.1,T H+ =0.8, T H2+ =0.1, T H3+ =0.1 (eV) j NI,PG =660A/m 2 n H =1*10 19 m -3, T H =0.8eV n H2 =4*10 19, T H2 =0.1eV 20/32

21. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Typical evolution of extracted NI currents  NI from the surface is dominant;  NI current from the inner surface of the PG is higher than one from outer side;  Co-extracted electron current ~3.5 times higher than total NI current in no PG bias test. Conical PG surface flat PG surface PG ONIX resultsBATMAN results (no PG bias) 21/32

22. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Results: Limitation of the NI extraction Potential distribution in vicinity to PG PG Potential (V) 22/32 x (mm) y (mm)

23. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Results: Potential at the wall Emission rate ~250A/m2 (~-3V) Emission rate ~800A/m2 (~-13V) Emission rate ~2000A/m2 (~-20V) 23/32 x (mm) PG x (mm) y (mm) Potential (V)

24. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Limitation of the NI extraction NI density produced from the conical surface of PG NI density produced from the flat surface of PG NI density produced at the volume Results: Total NI density along domain 24/32 x (mm) y (mm) Density (m -3 ) PG

25. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Results: Ion –Ion plasma calculation (NI current) No B field With B field 25/32 z vertical direction y horizontal direction current (mA)

26. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Results: Ion –Ion plasma calculation (NI density distribution) No B field With B field x (mm) y (mm) 26/32 Density (m -3 )

27. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Results: Ion –Ion plasma calculation (e current) No B field With B field 27/32 z vertical direction y horizontal direction z vertical direction y horizontal direction current (mA)

28. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Results: Ion –Ion plasma calculation (e density distribution) No B field With B field x (mm) y (mm) 28/32 Density (m -3 )

29. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Results: Ion –Ion plasma calculation (H + density distribution - meniscus) No B field With B field 29/32 x (mm) y (mm) Density (m -3 )

30. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Results: Ion-ion plasma simulations (5 runs) e current densityNI current density 30/32

31. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Results: Meniscus shape for several ion-ion plasmas (5 runs) H + density 95:5=e:NI (%) 75:25 50:50 25:75 5:95 PG 31/32

32. Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013 Thank you for your attention Project is supported by the Alexander von Humboldt foundation 32/32