NON-EQUILIBRIUM HEAVY GASES PLASMA MHD-STABILIZATION IN

AXISYMMETRIC MIRROR MAGNETIC TRAP

A.V. Sidorov2, P.A. Bagryansky1, A.D. Beklemishev1, I.V. Izotov2, V.V.Prikhodko1, S.V.Razin2, V.A. Skalyga2 and V.G. Zorin2

1Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia2Institute of Applied Physics, 603950, Nizhny Novgorod, Russia

Applications

Accelerator injectorsTechnologies

Hadron therapy

Beta beamproject

Heavy Ion Fusion

High density energyphysics

Surface processing

Ion implantation(SOI-technologies etc)

ECR Multicharged Ion Sources

Principles of Gas-dynamic ECR Ion Source Operation

Gyrotron radiation 100 kW @ 37.5 GHz

ECR dischargeECR discharge beam

PullerFC

L~35 cm

Magnetic trap, 2 T, R=5

Lp~30 cm

U~30 kV Plasma electrode

(PE)

Np~Ncutoff~1013cm-3

Te~70eV

τc=1/νei << τg=Leff/Vs

High e-i collision frequency

Loss cone is filled

EDF is isotropic Gas-dynamic regime of confinementGas-dynamic regime of confinement

Plasma lifetime = τg

λii<<L

SMIS 37

Solenoid Coils

Sextupole

e- heatingµ wave

gas

ions

Minimum-B field Confinement in ECR Ion Source

Ø 1 mm

Ion beam

Magnetic coils

MW

MHD stabilization: Cusp-type magnetic configuration

sg 10810n

N: <Z>=2Ag: <Z>=3.5

Losses trough the axial slit is too high!

GDT experiment parameters (D - beams, Н – plasma)

Center magnetic field: 2.83 kG D-injection power: 3.5 MW Trapped power: 2 MW

Plasma density: 1.531013 cm-3

Electron temperature: 140 eV Hot ions density: 41013 cm-3

Injection

Plasma source InjectionLimiter (+150 V)

Plasmareceivers

+150 V

Vortex confinement: potential profile control

VV

VV

cm

V

Potential profile

β ~ 0.6!!

E. I. SOLDATKINA, P. A. BAGRYANSKY and A. L. SOLOMAKHIN. Plasma Physics Reports, 34, 259 (2008).

Finite larmor radius (FLR) effect

21,

L

a

- ion gyroradius, L – trap length, a – plasma radius.

At m=1 mode dominates in spatial spectrum

of the flute instability

21,

L

a

Ion beam emittance ~ , so in ECR ion sources ion temperatureis low, 1÷10 eV and FLR effects are negligible.

iT

GDT

SMIS 37

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. τE=50 correspond to the gas

dynamic confinement time.

In case of the absence of the shear flow

τE=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.

Discharge vacuum chamber

Isolators

Limiter

Magnetic field coils

Expanding chamber

Zonds

Edge magnetic force line

MW100 kW@ 37.5 GHz

Scheme of the experiments

0 20 40 60 80 1000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

Q (

a.u

.)

U, limiter (V)

Total charge registered by zonds #1-3, Helium

Magnetic field at the plug: 1.7 T

1 2 3

zonds #1-3

Total charge registered by zonds #1-3, Nitrogen

Magnetic field at the plug: 1.7 T

0 20 40 60 80 100 1200.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Q (

a.u

.)

U, limiter (V)

Critical value of the U limiterin both cases is about of70 V what is close to electrontemperature and it is in goodagreement with calculations

Mode structure: calculations and experimentPlasma 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.

“Decay” experiment: microwave pulse-length 400μs

Ion saturation current on the center zond (#1)

Limiter voltage Ulim=150 V Limiter voltage Ulim=0 V

13700 13800 13900 14000 14100

0.0

0.5

1.0

1.5

2.0

2.5

(s

Cu

rre

nt

(a.u

.)

Time (s)

13700 13800 13900 14000 14100-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

(s

Cu

rren

t (a

.u.)

Time (s)

End of the microwave pulse

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 theplasma 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

Thank you for your attention!