Novosibirsk Mirrors: Past, Present and Future E.P.Kruglyakov, A.V.Burdakov, G.I.Dimov, A.A.Ivanov Novosibirsk, July 5 – 9, 2010 Budker Institute of Nuclear Physics, Novosibirsk, Russia 8th International Conference on Open Magnetic Systems for Plasma Confinement

AUTHORS OF PROPOSAL OF PLASMA CONFINEMENT IN MIRROR TRAPS (1953) THE FIRST EXPERIMENTS: S.N.Rodionov (Institute of Nuclear Physics), Atomnaya Energiya, #6, pp , IT WAS SHOWN THAT CHARGED PARTICLES MADE MORE THAN 10 7 REFLECTIONS FROM MIRRORS. Gibson G., Lawer E.J. Bull. Am. Phys. Soc., v.3, p.412, 1958 INSTITUTE OF NUCLEAR PHYSICS HAS STUDIED PHYSICS OF MIRRORS PRACTICALLY SINCE ITS FOUNDATION (1958)

* * * PLASMA PHYSICS ACTIVITY OF NOVOSIBIRSK IN THE SIXTIES (SELECTED WORKS)

THE MOST IMPORTANT RESULTS OBTAINED BY THEORISTS OF THE “FIRST GENERATION” R.Z.SAGDEEV. PREDICTION OF EXISTANCE OF COLLISIONLESS SHOCK WAVES (Sov. JTP, v. 31, № 10, p.1185, 1961). A.A.GALEEV. PREDICTION OF INSTABILITY LINKED WITH “LOSS CONE” IN MIRRORS ( Sov. JETP, v.49, №2(8), p.672, 1965). A.A,GALEEV, R.Z.SAGDEEV. DISCOVERY OF “NEOCLASSICAL DIFFUSION” ( Sov. JETP, v. 53, № 1, p.343, 1967). V.E.ZAKHAROV, PREDICTION OF COLLAPS OF LANGMUIRE WAVES ( Sov. JETP, v.62, № 5, p. 1745, 1972).

EARLY EXPERIMENTS WITH ALCALINE PLASMA (Q-MACHINE) * TYPICAL ALCALINE PLASMA HAS A DENSITY OF cm -3 AND PLASMA TEMPERATURE, T ≈ 0.3 eV. BUT BECAUSE OF λ∞T 2 /n e MANY PHYSICAL PHENOMENA IN A “DENSE” ( cm -3 ) PLASMA COULD BE STUDIED IN Q-MACHINE. -THE MOST IMPORTANT RESULTS OBTAINED IN NOVOSIBIRSK: 1. OBSERVATION OF “UNIVERSAL” INSTABILITY IN RADIALLY INHOMOGENEOUS POTASSIUM PLASMA IN MAGNETIC FIELD N.S.Buchelnikova, Nuclear fusion, v.4, pp , E - BEAM – PLASMA INTERACTION WITH POTASSIUM PLASMA. OBSERVATION OF ELECTRON HEATING AND PLASMA TURBULENCE. V.T.Astrelin, N.S.Buchelnikova, A.A.Drozdov et al, Sov. JETP, v.58, pp.1553 – 1556, 1970

-DEVELOPMENT OF BASIC DIAGNOSTICS FOR PLASMA STUDY. 1. OPTICAL DIAGNOSTICS. INSTITUTE OF NUCLEAR PHYSICS WAS THE FIRST IN THE SOVIET UNION AND ONE OF THE FIRST IN THE WORLD WHERE DIFFERENT LASER DIAGNO- STIC METHODS (OPTICAL INTER- FEROMETRY AND THOMSON SCAT- TERING) WERE APPLIED ( ). 2. NEUTRAL BEAM INJECTORS FOR PLASMA STUDIES. THE HISTORY OF NEUTRAL BEAM INJECTORS STARTED FROM THE PAPER OF G.I.Budker, G.I.Dimov ”Charge Exchange Injection of Protons into Circular Accelerator”, Proceedings of the International Conference on High Energy Accelerators, Dubna, 1963; ATOMIZDAT, Moscow, 1964, pp PROPOSAL AND THE FIRST EXPERIMENT ON STUDY OF LOCAL PLASMA PARAMETERS WITH THE USE OF NB INJECTORS (E b = 15 keV, I b = 0.3A, d b = 3 cm, Δt = 2·10 -4 s), A.M.Kudryavtsev, A.F.Sorokin, Sov. JETP Letters, v.18, # 8, pp , DIAGNOSTIC INJECTORS DINA-1 AND DINA-2 (E B ~ 25 keV, I B ~ 1 A) WERE WORKED OUT BY DIMOV GROUP AND WERE DISTRI- BUTED AMONG FUSION LABORATORIES OF THE SOVIET UNION.

BLACK CLOUDS 0VER CLASSICAL MIRRORS FIRST YEARS ATTENTION OF PLASMA PHYSICISTS FIRST OF ALL WAS DIRECTED TO MIRRORS, BUT… IN 1960 FLUTE INSTABILITY PREDICTED PREVIOUSLY BY ROSENBLUTH AND KADOMTSEV WAS EXPERIMENTALLY OBSERVED (M.S.Ioffe et al, Sov. JETP Letters, v.39, p.1602, 1960). GREAT DESPONDENCY APPEARED AMONG PLASMA PHYSICISTS. HOW- EVER, IN 1961 (Intern. Conf. of IAEA, Zaltsburg, 1961) M.S. IOFFE HAS DECLARED THAT THE INSTABILITY CAN BE SUPPRESSED (IOFFE BARS) A.A. GALEEV (Sov. JETP, v. 49, № 2 (8), p. 672, 1965), AND R.POST WITH M.N. ROSENBLUTH (Phys. Fluids, v. 9, p. 730, 1966) HAVE PREDICTED INSTABILITIES LINKED WITH “LOSS CONE” IN MIRRORS. ANALYSIS OF ENERGY BALANCE OF MIRROR TYPE FUSION REACTOR MADE BY D.V. SIVUKHIN HAS SHOWN VERY BAD PROSPECTS OF THIS SCHEME EVEN WITHOUT TAKING INTO ACCOUNT OF LOSS CONE INSTABILITIES (D.V.Sivukhin In: “Review of Plasma Physics”, v.4, Consultants Bureau, N.Y., p. 93, 1966; D.V.Sivukhin In: “Voprosy Teorii Plasmy, v.5, p. 439, 1967, Moscow, ATOMIZDAT).

THE FIRST SERIOUS REVISION OF MIRROR CONCEPTS HAS OCCURRED IN 1971 – 1972 PROPOSAL OF MULTI-MIRROR CONCEPT OF LONGITUDINAL PLASMA CONFINEMENT G.I.Budker, V.V.Mirnov, D.D.Ryutov, Sov. JETP Letters, v.14, p. 320, 1971 B.G.Logan, M.A.Lieberman, A.J.Lichtenberg, A.Makhijani, Phys. Rev.Lett, v.28, p.144, 1972

PRINCIPLES OF MULTI-MIRROR CONFINEMENT  R 2 L2L2 i V Ti = R 2 L i    L V Ti  0 0 (λ<<L) ℓ<λ Gain is more than 10 2

PLASMA CONFINEMENT IN MULTI-MIRROR MAGNETIC FIELDS (Experiment with alcaline plasma) G.I.Budker, V.V.Danilov, E.P.Kruglyakov et al, Sov. JETP. Lett., v.17, p.117, 1973 V.V.Danilov, E.P.Kruglyakov, Sov. JETP, v.68, # 6, p.2109, 1975

Physics of transverse “wall confinement” (TRANSVERSE MAGNETIC CONFINEMENT OF VERY DENSE PLASMA (n ~ cm -3) REQUIRES MAGNETIC FIELD STRENGTH OF SEVERAL MEGAGAUSS). Vekshtein G.E., Mirnov V.V., Ryutov D.D., Chebotaev, Journ. of Applied Mechanics and Technical Physics, № 6, p.3, (1974) τ ┴ E ≈ a 2 /χ Plasma and magnetic field behavior after pulsed heating of plasma placed into tube from well conducting metall

HOW TO HEAT A DENSE PLASMA IN LONG LINEAR SYSTEM? THE MOST HIGH POWER SOURCE FOR HEATING CAN BE BUILT ON THE BASIS OF HIGH CURRENT RELATIVISTIC ELECTRON BEAM (REB), BUT… AT ANY RESONABLE LONGITUDINAL SIZE L OF MAGNETIC SYSTEM WITH PLASMA THE COULOMB MEAN FREE PATH OF RELATIVISTIC ELECTRONS, λ e, WILL BE LARGER THAN SYSTEM SIZE, λ e >> L. ONE COULD HOPE ONLY ON MICROINSTABILITIES. THE FIRST EXPERIMENTS ON PLASMA HEATING BY REB WERE MADE IN 1972 V.S.Koidan, V.M.Lagunov, V.N.Lukyanov et al, Proc. 5 th Europ. Conf. on Controlled Fusion and Plasma Physics, v.1, p.161, Grenoble, A.V.Abrashitov, A.V.Burdakov, V.S.Koidan, et al, Sov. JETP Lett., v.18, p.675, 1973.

INAR E b ~1MeV, I b ~ 5 kA, τ b ~ 50 ns

HOW TO HEAT A DENSE PLASMA IN LONG LINEAR SYSTEM? THE FIRST RESULTS HAVE SHOWN PRINCIPLE POSSIBILITY TO USE REBs FOR DENSE PLASMA HEATING. BUT PARAMETERS OF REB (E b = 1 MeV, I b = 5 kA, τ b = ns, Q ≈ 300 J) WERE TOO FAR FROM REQUIREMENTS OF FUSION TECHNOLOGIES. SPECIAL PROGRAM OF DEVELOPMENT OF POWERFUL REB GENERATORS WAS ARRANGED IN THE INSTITUTE. 1.APPLICATION OF ULTRA-PURE WATER AS A HIGH-VOLTAGE INSULATOR (  = 80!). SEVERAL GENERATORS WERE CONSTRUCTED AND TESTED IN THE INSTITUTE. 2. ALABORATION OF HIGH POWER MICROSECOND REBs

1975. GOL - 1, - AN INSTALLATION FOR STUDY OF REB - PLASMA INTERACTION. THE FIRST ACCELERATOR WITH WATER INSULATION WAS USED HERE. Q b =1-2 kJ

ACCELERATOR AQUAGEN ON THE BASIS OF WATER INSULATION (E b = 1 МeV, I b = 300 кА, Q b ≈ 25 kJ), 1977

DEVELOPMENT OF HIGH POWER MICROSECOND BEAMS ACCELERATOR U-1 (LAST VERSION) First version of generator: Q b =22 kJ, E b = 0.5 MeV, I b ≈50 kA, τ b ≈2.5 mcs S.V. Lebedev, V.V. Chikunov, M.A. Scheglov, Sov. JTP Letters, v.8, # 11, p. 693, Q b max = 130 kJ, E b = 1 MeV, I b = 60 kA, after magnetic compression j b = 5 kA/cm 2, τ b ≈ 4.5 mcs. S.G.Voropaev, B.A.Knyazev, V.S.Koidan, Sov. JTP Lett., v.13, # 7, p. 431, 1987 Present day parameters of microsecond beams: Q b = 300 kJ, U b = 1 MeV, I b = 40 kA, τ b ≈ 8 mcs

THE MOST IMPORTANT EXPERIMENTAL RESULTS ON REB -PLASMA INTERACTION, AND STUDY OF MULTI- MIRROR HOT PLASMA CONFINEMENT.

GOL-M. STUDY OF NATURE OF REB-PLASMA INTERACTION THE FIRST DIRECT EXPERIMENTAL EVIDENCE OF EXCITATION OF STRONG LANGMUIRE TURBULENCE CONTAINS IN: Vyacheslavov L.N., Kandaurov I.V., Kruglyakov E.P., et al, Sov. JETP. Lett., v.50, # 9, p. 379, 1989

EXPERIMENTAL EVIDENCE OF EXCITATION OF STRONG LANGMUIR TURBULENCE Precision of absolute measurements

PLASMA HEATING AND CONFINEMENT ON MULTI-MIRROR TRAP GOL-3

GOL-3 facility Plasma Length ~ Density - 12 m m

EFFICIENCY OF REB – PLASMA INTERACTION INAR FROM 1972 UP TO 1988 MAXIMUM EFFICIENCY HAS ACHIEVED 40%. Arzhannikov A.V., Burdakov A.V., Kapitonov V.A., et al, Plasma Physics and Controlled Fusion, v.30, # 11, p. 1571, 1988 GOL – 3 AT PRESENT, MAXIMUM EFFICIENCY IS 50%. Postupaev V.V., Arzhannikov A.V., Astrelin V.T., et al, 37th EPS Conference on Plasma Physics, Dublin, Ireland, June, 2010

Plasma heating by REB in homogeneous (a) and multi- mirror (b) geometry Time behavior of plasma pressure at n e =1.5·10 15 cm -3 ; z = 2.08m Electron component Ion component a b

time, ms DD neutron irradiation after REB plasma- interaction. At present, nτ max ≈ 2·10 18 m -3 ·s Intensity Several diagnostics gave the meaning of temperature OF T i ≈ 2 keV.

SUPPRESSION OF LONGITUDINAL ELECTRON THERMAL CONDUCTIVITY Astrelin V.T., Burdakov A.V., Postupaev V.V., Plasma Physics Reports, v.24, p.414, (1998) Arzhannikov A.V., Astrelin V.N., Burdakov A.V., et al, JETP Letters, v.77, p.358, (2003 ) Direct demonstration of the suppression effect

CORRAGATION OF MAGNETIC FIELD ALONG THE SYSTEM LENGTH LEADS TO INHOMOGENEOUS HEATING OF PLASMA ELECTRONS BY REB (BECAUSE OF Γ∞n b ) THE PRESSURE GRADIENTS BETWEEN PLAGS AND MID PLANE IN EACH CELL LEAD TO PLASMA EXPANSION FROM PLAGS IN BOTH DIRECTIONS. AS A RESULT OF THAT ION HEATING APPEARS. GOL-3. WHY THE IONS ARE HEATING? Г ∞ (n b /n e )·ώ pe

ремя, микросекунд PL5741 TIME, microsecond T ≈ L/V Ti Time behavior of neutron radiation from separate mirror cell of GOL-3

EXCITATION OF DENSITY OSCILATIONS IN SEPARATE CELLS, - BOUNCE INSTABILITY T i2 T i1 T i1 > T i2 Beklemishev A.D., Fusion Science and Technology Trans., v. 51, #2T, P.180, 2007 α2>α*α2>α* α 1 < α* DECELERATION OF IONS CAN LEAD TO THEIR CAPTURE

ABOUT TRANSVERSE HEAT LOSSES OF HOT PLASMA SUPPRESSION OF LONGITUDINAL ELECTRON THERMAL CONDUCT- ANCE IS EXPLAINED BY SIGNIFICANT (SEVERAL THOUSANDS TIMES) INCREASE OF COLLISION FREQUENCY OF PLASMA ELECTRONS. HOWEVER, THE SAME EFFECT SHOULD INCREASE THE TRANSVERSE HEAT LOSSES. FORTUNATELY, SPECIAL EXPERIMENTS WITH THIN REB (D ≈ 1cm INSTEAD OF USUALLY USED BEAM WITH D ≈ 5 cm) HAVE SHOWN THAT SPECIFIC PARAMETERS OF PLASMA AFTER HEATING DOES NOT CHANGE. IT MEANS THAT TRANSVERSE HEAT LOSSES UP TO NOW ARE NEGLIGIBLE. Postupaev V.V., Arzhannikov A.V., Astrelin V.T., et al, 37 th EPS Conference on Plasma Physics, Dublin, Ireland, June, 2010

Generator of oncoming beam E b ~ 100 keV I b ~ 1 kA J b ~ 1 kA/cm 2 τ b ~ 0.1 – 1 ms GOL-3. NEAREST FUTURE PLANS: INJECTION OF ONCOMING BEAM TO OBTAIN SUPPRESSION OF ELECTRON THERMAL CONDUCTION OF HIGH TEMPERATURE PLASMA DURING LONG TIME (0.1 – 1 ms).

CONCEPT OF AMBIPOLAR CONFINEMENT (TANDEM MIRRORS) Dimov G.I., Zakaidakov V.V., Kishinevskii M.E., Sov. Journ. of Plasma Physics, v.2, p. 326, 1976 Fowler T.K., Logan B.G., Comm. Plasma Phys. and Controlled Fusion, v.11, p. 167, 1977

AMBIPOLAR TRAP Ambipolar barrier eφ c = kT e ·ln(n p /n s ) τ ║ ~ τ ii ·(eφ c /kT i )exp(eφ c /kT i ). При eφ c >> kT e τ ║ >> τ ii nene npnp φs φs i n(z) e φcφc φe φe

TANDEM MIRRORS ·IT TURNED OUT THAT TSUKUBA UNIVERSITY AND LIVERMORE ·LABORATORY WERE MORE READY TO CONSTRUCT THE AMBIPOLAR TRAPS. THE FIRST DEMONSTRATION OF AMBIPOLAR PLASMA CONFINEMENT WAS PRESENTED BY Miyoshi S., Yatsu K., Kawabe T., et al ON THE 7 th Intern. Conf. of IAEA (Vienna, IAEA, 1979, v.2, p USING 2XIIB AS END MIRRORS LIVERMORE PHYSICISTS DESIGNED AMBIPOLAR TRAP TMX WITH MORE HIGH PARAMETERS (n ≈ cm -3, Т e ≈ 200 eV, β = 0.4, φ с =300 V). IT WAS STARTED UP IN 1979 AND HAS DEMONSTRATED NINEFOLD GROWTH OF CONFINEMENT TIME: τ ║ ≈ 9τ ii TMX ·THE DESIGN OF THE NOVOSIBIRSK AMBIPOLAR TRAP AMBAL WITH min B HAS STARTED IN HOWEVER, AFTER SHORT CIRCUIT IN ONE OF END MIRRORS IT WAS DECIDED NOT TO RECONSTRUCT AMBAL BUT TO BUILT NEW, FULLY AXISYMMETRIC SYSTEM AMBAL-M HOWEVER, AFTER BREAKUP OF THE SOVIET UNION IT WAS IMPOSSIBLE TO CONSTRUCT LARGE INSTALLATION FOR REASONABLE TIME.

AXISYMMETRIC VERSION OF AMBIPOLAR TRAP AMBAL-M WITH MHD STABILIZATION BY END SEMICUSPS, CONDUCTING WALLS, FLR, etc/ THIS DESIGN WAS IMPLEMENTED ONLY BY 50 %

AMBAL-M (50 % READINESS) BECAUSE OF VERY LIMITED RESOURCES OF THE INSTITUTE IN 90s CONSTRUCTION OF AMBAL-M WAS STOPPED

AMBAL THE MOST IMPORTANT RESULTS EXPERIMENTS WITH NONAXISYMMETRIC END MIRROR OF AMBAL: HOT DEUTERIUM PLASMA (T i ~ 900 eV, n e ~ cm -3 ) WAS OBTAINED IN RESULT OF EXCITATION OF KELVIN – HELMHOLTZ INSTABILITY APPEARED DURING PLASMA INJECTION FROM PLASMA GUN MHD STABLE PLASMA WAS OBTAINED IN LONG CENTRAL TRAP OF FULLY AXISYMMETRIC AMBAL-M (1/2). THE PARAMETERS OF THAT PLASMA WERE AS FOLLOWS: ION TEMPERATURE, T i ≈ 200 – 300 eV, ELECTRON TEMPERATURE, T e ≈ eV, PLASMA DENSITY, n e ≈ 3·10 13 cm -3, PLASMA DIMENSIONS: L ≈ 6 m, D ≈ 40 cm. DECAYING QUIESCENT PLASMA HAS TRANSVERSE DIFFUSION COEFFICIENT CLOSE TO CLASSICAL ONE

GAS DYNAMIC PLASMA CONFINEMENT V.V.Mirnov, D.D.Ryutov, Sov. JTP Lett., v.5, p.678, 1979 λ ii  L ( more exact λ ii /R  L); R = B m / B 0 = S 0 /S m τ ≈ nLS 0 /nV Ti S m = RL/V Ti VERY SIMPLE PHYSICS, ABSENCE OF MICRO-INSTABILITIES IN COLLISIONAL PLASMA. DISADVANTAGE: TOO LARGE LENGTH OF FUSION REACTOR (OF THE ORDER OF 3-5 KILOMETERS) BUT… THERE IS USEFUL APPLICATION OF THIS SCHEME AT PRESENT.

POWERFUL 14 MeV NEUTRON SOURSE ON THE BASIS OF GDT Kotelnikov I.A., Mirnov V.V., Nagorny V.P., Ryutov D.D., Plasma Physics and Controlled Fusion Research, 2, IAEA, Vienna, p.309, 1985 Z

-ARGUMENTS IN FAVOR OF NEUTRON SOURCE ON THE BASIS OF THE GAS DYNAMIC TRAP THE GDT NS HAS THE SIMPLEST VACUUM AND MAGNETIC SYSTEMS BECAUSE OF AXISYMMETRIC GEOMETRY PLASMA PRESSURE IS COMPARABLE WITH MAGNETIC ONE. IT MAKES POSSIBLE TO OBTAIN THE HIGHEST DENSITY OF NEUTRON FLUX FROM UNIT OF VOLUME IN COMPARISON WITH ANY OTHER SCHEMES OF NEUTRON SOURCES INTENSITY OF NEUTRON FLUX IS HIGH ONLY IN OPERATION ZONES. THUS, THE MAIN PART OF THE NEUTRON SOURCE CAN FUNСTION MANY YEARS WITHOUT REPLACEMENT NB INJECTORS WORK IN SIGNIFICANTLY MORE FAVORABLE CONDITIONS THAN THOSE IN TOKAMAK SCHEMES THE PROBLEM OF DISRUPTION DOES NOT EXIST THERE ARE NO DIVERTOR PROBLEMS

SOME COMMENTS ON EXCITATION OF MICROINSTABILITIES IN GDT PLASMA IN PRINCIPLE NB INJECTION INTO “WARM” PLASMA CAN LEAD TO EXCITATION OF MICROINSTABILITIES AND TO DECREASE OF FAST IONS LIFETIME. CORRESPONDINGLY, THE TOTAL NEUTRON FLUX WILL ALSO DECREASE. THAT IS WHY WE SHOULD SELECT THE BEAM AND PLASMA PARAMETERS IN THE RANGE WHERE THE MICRO- INSTABILITIES HAVE NOT BEEN OBSERVED YET. TO AVOID MICROINSTABILITIES SOME RESULTS OBTAINED AT 2XIIB WHERE THEY DID NOT EXCITE, WERE TAKEN INTO ACCOUNT.

COMPARISON OF DIMENSIONLESS PARAMETERS OF 2XIIB WITH THE TURNING POINT PARAMETERS OF THE GDT BASED NEUTRON SOURCE PARAMETERS 2XIIB GDT NS E INJ /T e ω pi /ω Bi (D) 150 (T) a /ρ (D) 5.4 (T) n cold /n hot β 0.1 – IN 2XIIB CASE IN THE RANGE OF PARAMETERS PRESENTED HERE MICROINSTABILITIES WERE NOT OBSERVED. ONE SHOULD EXPECT THE SAME RESULT IN THE CASE OF GDT NS. ·IN THE MOST OF NEUTRON SOURCE VERSIONS ANALIZED IN NOVOSIBIRSK T e VALUE SUPPORTED ON THE LEVEL OF E INJ

EXAMPLES OF CALCULATIONS OF GDT BASED NEUTRON SOURCE PARAMETERS

FOR STANDARD CALCULATIONS OF NEUTRON SOURCE PARAMETERS, THE FOLLOWING ONES ARE FIXED AS A RULE ELECTRIC POWER CONSUMPTION FROM THE GRID (USUALLY) IS FIXED, W e = 60 MW. TOTAL POWER OF NEUTRON FLUX, W = 2 MW IS ALSO FIXED. MAGNETIC FIELD IN MIRRORS, B m = 15 T; MIRROR RATIO R = 15. INJECTION ANGLE, θ = 30 0 INJECTION ENERGY OF D AND T, E INJ = 65 keV. THIS ENERGY IS OPTIMUM (see later). PLASMA DIAMETER AT THE MIDPLANE, 2a = 20 cm RATIO OF ELECTRON TEMPERATURE TO THE INJECTION ENERGY OF D,T ATOMS, T e / E INJ = 10 -2

OPTIMIZED DENSITY OF NEUTRON FLUX VERSUS INJECTION ENERGY FOR DIFFERENT ELECTRON TEMPERATURES E optimal ≈ 65 keV T e =2 keV T e = 1 keV T e =0.5keV T e =0.2keV E inj, keV

NEUTRON FLUX DENSITY AS A FUNCTION OF ELECTRON TEMPERATURE P n, МW/m 2

P n Neutron Flux Density vs Electron Temperature in the Absence of Microturbulences (If there are no limitation on T e /E b ratio)

GDT SOME EXPERIMENTAL RESULTS

GAS DYNAMIC TRAP (GDT)

NEUTRON FLUX DENSITY PROFILE (D-D REACTIONS) IN THE VICINITY OF TURNING POINT IN GDT P n, a.u.

β VALUE AS A FUNCTION OF ENERGY CONTENT OF FAST IONS IN HYDROGEN PLASMA (D 0 -BEAMS) β Q, kJ β IS MEASURED BY MOTION STARK EFFECT MAXIMAL VALUES OF β (β >30%) WERE OBTAINED WITH THE USE OF “VORTEX” CONFINEMENT METHOD, Beklemishev A.D., Bagryansky P.A., Chaschin M.S., and Soldatkina E.I., Fusion Science and Technology, v.57, # 4, p.351, 2010

Time behavior of T e after switching on D 0 neutral beams t, ms T e, eV Thomson scattering measurements on the axis of GDT, in the mid plane, N e = 3·10 13 cm -3. Sloshing ions density in the turning points, N fast = 5·10 13 cm -3.

SHIP EXPERIMENT ( S INTESIZED H OT I ONS P LASMOID) SHORT MIRROR TRAP (L = 30 cm) WAS INSTALLED BETWEEN GDT AND EXPANDER. 1 MW TRANSVERSAL NB INJECTION WAS ARRANGED (E B ≈ 20 keV)

EXCITATION OF ALFVEN ION CICLOTRON INSTABILITY DURING ACCUMULATION OF FAST ANISOTROPIC IONS IN COMPACT MIRROR CELL A=W ┴ /W ║ ≈35 UPPER TRACE IS ENERGY CONTENT OF FAST IONS. BELOW – DEMOSTRATION OF THRESHHOLD OF AIC INSTABILITY nT ┴, m -3 ·keV T, s n fast = 5·10 13 cm -3 ·IT FOLLOWS FROM THE EXPERIMENT THAT AT PARAMETERS OF GDTNS THE INSTABILITY WILL NOT EXCITE AND THE BEHAVIOR OF FAST SLOSHING IONS WILL DESCRIBE BY CLASSIC COULOMB SCATTERING

GDT-Important results High-β (~ 0.6) MHD – stable plasma confinement is achieved in axially symmetric magnetic field Oblique injection of neutral beams at midplane provides formation of fast ion density peaks near turning points Electron temperature is determined by balance between energy transfer from fast ions and gas- dynamic losses through end mirrors Relaxation rates of anisotropic fast ions are classical, there are no microinstabilities

WORKS ON NEUTRAL BEAM INJECTORS IN THE BUDKER INSTITUTE OF NUCLEAR PHYSICS DEVELOPMENT OF POWERFUL NEUTRAL BEAM INJECTORS IS AN IMPORTANT COMPONENT OF THE GDT NEUTRON SOURCE PROGRAM FOCUSED BEAMS ARE REQUIRED BECAUSE OF SMALL DIAMETER OF PLASMA FINALLY, HIGH POWER STEADY - STATE BEAMS ARE NEEDED

PRESENT STATUS OF NB INJECTORS IN THE INSTITUTE POWERFUL FOCUSED DIAGNOSTIC BEAMS ARE DEVELOPED FOR MEASURING OF LOCAL VALUES OF N e, T i, β etc. PRESENT DAY PARAMETERS OF DIAGNOSTIC INJECTORS ENERGY OF ATOMS (HYDROGEN, DEUTERIUM), E B = keV EQUIVALENT BEAM CURRENT, I B, UP TO 7 A DURATION OF THE BEAM, τ B, UP TO 1O SECONDS PARAMETERS OF NEAREST FUTURE FOCUSED DIAGNOSTIC INJECTOR FOR WENDELSTEIN – 7X: E B = 65 keV, I B - UP TO 10 A, DURATION OF THE BEAM, τ B, UP TO 1000 SECONDS. COMISSIONING OF THIS INJECTOR IS IN PROGRESS. GEOGRAPHY OF NOVOSIBIRSK BEAMS USA(2), GERMANY, SWITSERLAND, ITALY, SPAIN, RUSSIA

Madrid, Spain, TJ-IIU 50 keV, 4 A Padua, Italy, RFX 50 keV, 4 A, 50 ms. Lausanne, TCV 50 keV, 3 A, 2 s Yuelich, Germany, TEXTOR 55 keV, 3 A 10 s

55 keV, 7 A, 3 s diagnostic beam on Alcator C-Mod, MIT, USA

STATIONARY AND QUASISTATIONARY FOCUSED NEUTRAL BEAMS FOR PLASMA HEATING -AT PRESENT, THE MOST POWERFUL NB INJECTOR FOR PLASMA HEATING IN THE INSTITUTE HAS THE FOLLOWING PARA- METERS: E B = 40 keV, I B =40 A, τ B =1 s. HOWEVER STORED EXPERIENCE AND PRELIMINARY ANALYSIS ALLOWS ONE TO STATE THAT A MODULE OF STATIONARY FOCUSED NB INJECTOR WITH THE BEAM ENERGY, E B = 40 – 80 keV AND TOTAL POWER, P = 2 – 3 MW CAN BE BUILT. ALSO GOOD EXPERIENCE RELATED TO PRODUCTION OF NEGATIVE IONS HAS ACCUMULATED IN THE INSTITUTE. ON THE GROUNDS OF THIS EXPERIENCE ONE CAN TELL ABOUT CONSTRUCTION OF 1 MeV, MW STATIONARY NEUTRAL BEAM MODULE.

CONCLUSIONS THE PHENOMENA DISCOVERED AT GOL-3 (EFFICIENT PLASMA HEAT- ING BY REB, SUPPRESSION OF ELECTRON THERMAL CONDUCTANCE, BOUNCE INSTABILITY, etc) MAKES MULTI-MIRROR REACTOR MORE REALISTIC. DUE TO BOUNCE INSTABILITY EFFECTIVE ION MEAN FREE PATH DECREASES DOWN TO SINGLE MIRROR CELL SIZE. THUS, REACTOR WILL BE ABLE TO OPERATE WITH MORE RARE (OF ORDER OF 3·10 15 cm -3 ) PLASMA. IT MEANS THAT COMPLETELY MAGNETIC CON- FINEMENT CAN BE USED. SUPPRESSION OF LONGITUDINAL THERMAL CONDUCTION BY AN ELECTRON BEAM CAN TURN OUT USEFUL FOR OTHER OPEN MAGNETIC SYSTEMS. THE DATA OBTAINED IN THE GDT ARE SUFFICIENT TO DESIGN THE NEUTRON SOURCE WITH POWER OF SEVERAL HUNDREDS kW. AT THE SAME TIME, THERE ARE NO PHYSICAL LIMITATION, INHIBITING TO CREATION OF FULL SCALE NEUTRON SOURCE. PROGRESS IN DEVELOPMENT OF SUPERCONDUCTING MAGNETS CAN LEAD TO SIGNIFICANT SIMPLIFICATION OF THE GDTNS DESIGN. BESIDES, THE GDT BASED FUSION REACTOR CAN TURN MORE REALISTIC.