1. NON-EQUILIBRIUM HEAVY GASES PLASMA MHD-STABILIZATION IN AXISYMMETRIC MIRROR MAGNETIC TRAP A.V. Sidorov 2, P.A. Bagryansky 1, A.D. Beklemishev 1, I.V. Izotov 2, V.V.Prikhodko 1, S.V.Razin 2, V.A. Skalyga 2 and V.G. Zorin 2 1 Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia 2 Institute of Applied Physics, 603950, Nizhny Novgorod, Russia

2. Applications Accelerator injectors Technologies Hadron therapy Beta beam project Heavy Ion Fusion High density energy physics Surface processing Ion implantation (SOI-technologies etc) ECR Multicharged Ion Sources

3. Principles of Gas-dynamic ECR Ion Source Operation Gyrotron radiation 100 kW @ 37.5 GHz ECR discharge beam Puller FC L~35 cm Magnetic trap, 2 T, R=5 L p ~30 cm U~30 kV Plasma electrode (PE) N p ~N cutoff ~10 13 cm -3 T e ~70eV τ c =1/ν ei << τ g =L eff /V s High e-i collision frequency Loss cone is filled EDF is isotropic Gas-dynamic regime of confinement Plasma lifetime = τ g λ ii <<L SMIS 37

4. Solenoid Coils Sextupole e - heating µ wave gas ions Minimum-B field Confinement in ECR Ion Source

5. Ø 1 mm Ion beam Magnetic coils MW MHD stabilization: Cusp-type magnetic configuration N: =2 Ag: =3.5 Losses trough the axial slit is too high!

6. GDT experiment parameters (D - beams, Н – plasma)  Center magnetic field: 2.8  3 kG  D-injection power: 3.5 MW  Trapped power: 2 MW  Plasma density: 1.5  3  10 13 cm -3  Electron temperature: 140 eV  Hot ions density:  4  10 13 cm -3

7. Injection Plasma source Injection Limiter (+150 V) Plasma receivers +150 V Vortex confinement: potential profile control V V V V cm V Potential profile β ~ 0.6!! E. I. SOLDATKINA, P. A. BAGRYANSKY and A. L. SOLOMAKHIN. Plasma Physics Reports, 34, 259 (2008).

8. Finite larmor radius (FLR) effect  - ion gyroradius, L – trap length, a – plasma radius. At m=1 mode dominates in spatial spectrum of the flute instability Ion beam emittance ~, so in ECR ion sources ion temperature is low, 1÷10 eV and FLR effects are negligible. GDT SMIS 37

9. Vortex confinement: theory Calculated energy life-time changing in SMIS 37 setup for helium plasma. Times normalized on the time of external layers turning according to internal layers. Initial unperturbed state of the plasma cord (time=0) was chosen axisymmetric with the symmetry center equal to the magnetic system center. τ E =50 correspond to the gas dynamic confinement time. In case of the absence of the shear flow τ E =5.  Calculation results (A. D. Beklemishev) A.D.Beklemishev, Shear Flow Effects in Open Traps, Theory of Fusion Plasmas, AIP Conference Proceedings 1069 (2008) pp.3-14.

10. Discharge vacuum chamber Isolators Limiter Magnetic field coils Expanding chamber Zonds Edge magnetic force line MW 100 kW@ 37.5 GHz Scheme of the experiments

11. Total charge registered by zonds #1-3, Helium Magnetic field at the plug: 1.7 T 123 zonds #1-3

12. Total charge registered by zonds #1-3, Nitrogen Magnetic field at the plug: 1.7 T Critical value of the U limiter in both cases is about of 70 V what is close to electron temperature and it is in good agreement with calculations

13. Mode structure: calculations and experiment Plasma potential and electron temperature distribution in the plasma cord section. Potential is normalized on the electron temperature; 1 – corresponds to limiter radius projection in central plane of the trap. Calculations show that azimuthal modes m=1, m=2 and m=3 have to dominate in the spatial spectrum under conditions of “vortex” confinement. Experiments show that azimuthal modes m=1 and m=2 dominate in the spatial spectrum under conditions of “vortex” confinement what is in good agreement with calculations.

14. “Decay” experiment: microwave pulse-length 400μs Ion saturation current on the center zond (#1) Limiter voltage U lim =150 V Limiter voltage U lim =0 V End of the microwave pulse

15. Future plans In future it is planned to improve electrode-limiter for the opportunity to control the potential profile and to extract the ions from the plasma at the same time. In this case it will be possible to research multicharged ion creation in the plasma of ECR ion source under conditions of “vortex” confinement regime realization. The experiments demonstrated good agreement with calculation: mode structure, critical value of the limiter potential for “vortex” confinement regime realization

16. Thank you for your attention!

18. Photos of the limiter and zond system

19. Decay times cm -2 ms cm -2 ms Differential rotation No rotation