Mariya Korzhavina Budker Institute of Nuclear Physics, Novosibirsk, Russia

1. 8th International Conference on Open Magnetic Systems for Plasma Confinement Study of microinstabilities in anisotropic plasmoid of thermonuclear ions Mariya Korzhavina Budker Institute of Nuclear Physics, Novosibirsk, Russia

2. View of the Gas Dynamic Trap facility

3. General layout of gas dynamic trap (GDT) Target plasma: 1013-1014cm-3, 150 eV Fast ions (H+,D+): ~1013cm-3, <E>≈10 keV Length 7 m Magnetic field: center0.3 Т mirrorup to 12 Т Mirror ratio Bm/Bc≈ 35

4. Experiment with compact mirror cell at the Gas Dynamic Trap

5. Compact mirror cell GDT central cell Compact mirror at GDT Experiment: 2ρfi << aw; nf / nw>>1; β <<1; E>>E||. Compact mirror cell (CM): L = 30 cm, D = 70 cm. Magnetic field: B0 = 2.4 T, Bm = 5.2 T Background plasma: hydrogen, nw ≈ 1013 cm-3,Tw ≈ 150 eV, aw = 9 cm. CM NBI system:hydrogen, E0 = 20keV, θ = 90º, Pinj ≈1 MW, τinj= 4 ms, af = 8-10 cm. Compact mirror cell Strong high-frequency oscillations of plasma potential during accumulation of the fast ions in the compact mirror

6. Early studies of microinstabilities M.S.Ioffe, B.B.Kadomcev, Uspekhi Fizicheskih Nauk, vol. 100, № 4, 1970 R.F.Post, Nuclear fusion, Vol.27, 1987 F.H.Coensgen,et al. Phys.Rev.Letters, Vol.35, 1975, [2XIIB] T.A.Casper, G.R.Smith, Phys.Rev.Letters, Vol.45, 1982, [TMX] M. Ichimura, et al. Phys.Rev.Letters, Vol.70, 1993, [Gamma-10]

7. Microinstabilities in anisotropic plasma DCLC The drift-cyclotron losscone instability k║ « k┴ k|| = 0 ω ≈ ωci AIC The Alfven ion-cyclotron instability k║ » k┴ k┴ = 0 ω < ωci

8. Estimation of developing DCLC and AIC in the compact mirror of GDT AIC Instability grows if: β┴A > const GDT CM: A ≡ <E┴>/<E║> ≈ 50, β┴ ≈0.02 βA ≈ 1 DCLC Stabilization by addition of small amount of warm ions: nw /nf > 0.06 GDT CM: nw /nf ≈ 0.1 R.F.Post, Nuclear fusion, Vol.27, 1987 M.J.Gerver, The Phys. of Fluids, Vol.19,1976 D.C.Watson, Phys.Fluids 23,1980

9. 10 mm High-frequency oscillations in plasmoid have been observed with special HF Langmuir and magnetic probes Set of special HF Langmuir probes Tree orthogonal loops of the HF magnetic probe.

10. Layout of the HF Langmuir probes system in the compact mirror of GDT Modes: k = m/rp rp = 4.5 cm m ≈ 1-6

11. HF magnetic probe

12. Cross amplitude spectrum fosc fci Oscillation frequency: fosc= 39.7 ±0.2 MHz Bmidplane=27.6±0.3 kGs fci=42±0.5 MHz

13. Voltage oscillations induced in loops of magnetic probe

14. Rotation of the wave magnetic field vector Rotation in the direction of ion gyration

15. Mode structure analysis, azimuthal modes Azimuthal modem = 1 , rarely 2.

16. Azimuthal vs radial induced loop voltages. The field vector rotates in the direction of ion gyration. Cross amplitude spectrum m=1 Phase variation, radian m=2 Azimuthal probe separation, radian Observation of AIC in the compact mirror of the GDT RF Langmuir probes:frequency, azimuthal modesMagnetic probes: polarization Частотный спектр колебаний f0 f0 fci fci Azimuthal number m ~ 1-2 Main frequency f0 < fci The magnetic field vector of the wave rotates in the direction of ion gyration. AIC

17. Threshold of the oscillations Diamagnetism of fast ions in the compact mirror Amplitude of HF oscillations induced on magnetic probe Anisotropy of the ion plasmoid n >3 х 1013 сm-3 A ≈ 40; β┴=0.02 => ┴A ~ 1. сi/аp ≈ 0.23

18. Results: • Microinstability developing in the compact mirror is Alfven ion-cyclotron (AIC). This was proved by observing small azimuthal modes numbers m = 1–2, oscillation frequency below the diamagnetically depressed ion-cyclotron frequency and rotation of the magnetic field of the wave in the direction of ion gyration. • The threshold of the AIC fluctuation was determined relative to the density of hot ions, ratio of ion pressure to magnetic field pressure β, anisotropy A and the ion gyroradius to the plasmoid radius ratio ai/Rp. AIC microinstability developed when the density of hot ions nf was greater than 3x1013 cm-3, β≈ 0.02, anisotropy A ≈ 50, for the ratio ai/Rp of about 0.23. • Experimentally was confirmed the criteria which defines the stability region A < 1. • Alfven ion cyclotron instability developing in the CM GDT does not lead to the significant particle loss and plasma parameters limitation.

19. Thank you!

20. Dependence of fast ion density in the compact mirror of GDT on the trapped power Dots – experimental data, solid line – calculation(ITCS).

21. Регистрация AIC на TMX Электрические зонды:частота и модовый состав Магнитные зонды:поляризация |m| ≈ 4 f0 < fci Вращение магнитного поля волны в направлении ларморовского движения ионов AIC T.A.Casper, G.R.Smith, Phys.Rev.Letters , Vol.45, 1982

22. Анализ модового состава, продольные моды DCLC: набег фазы между средним зондом в КП и зондом в расширителе, силовая линия 15.5 cm – от выстрела к выстрелу случайный DCLC нет

23. Оценки для DCLC мод в КП ГДЛ Параметры ГДЛ: c / Rpωci ≈ 18 ; ω2ci / ω2pi ≈ 6.4•10-4 Стабилизация теплыми ионами: nw /nf > 0.06 ГДЛ: nw /nf ≈ 0.1 R.F.Post, Nuclear fusion, Vol.27, 1987 M.J.Gerver, The Phys. of Fluids, Vol.19,1976

24. Оценки для AIC мод в КП Критерий развития неустойчивости: При β║ ~ β┴ « 1 β║ < const * β┴2 или (β║ , β┴) → (A , β┴) : β┴A> const Параметры ГДЛ: β║< β┴~0.02 ГДЛ: A ≡ <W┴>/<W║> = 50, β=0.02 βA ≈ 1 T.A.Casper, G.R.Smith, Phys.Rev.Letters , Vol.45, 1982 βA2> 8 TMX ? D.C.Watson, Phys.Fluids 23,1980

25. DCLC и AIC на установках 2X||B и TMX 2XIIB : основная неустойчивость – DCLC, TMX: основная неустойчивость – AIC,

26. Корреляционный анализ Взаимная корреляционная функция: Сигналы с зондовφ1(t) , φ2(t) → БПФ → Спектральная плотность взаимной корреляционной функции:

27. Сделаем преобразование Фурье