ICC/1-1Ra 23rd IAEA FEC 11-16 Oct. 2010 … Saturn, Uranus, and Neptune •Confinement and stability...

D.T. Garnier, M.S. Davis, J.L. Ellsworth, J. Kesner, M.E. Mauel, and P.P. Woskov

Department of Applied Physics, Columbia University, New York, USAPlasma Science and Fusion Center, MIT, Cambridge, USA

LDX: Superconducting Levitated Dipole High-β dipole-confined plasma

Turbulent Particle Pinch in Levitated Superconducting Dipole

ICC/1-1Ra23rd IAEA FEC 11-16 Oct. 2010

H. Saitoh, Z. Yoshida, J. Morikawa, Y. Yano, T. Mizushima, Y. Ogawa, M. Furukawa, K. Harima,Y. Kawazura, K. Tadachi, S. Emoto, M. Kobayashi, T. Sugiura, and G. Vogel

Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, JAPAN

TransdisciplinarySciences, GSFSRT-1

RT-1: Superconducting Levitated Dipole High-β dipole-confined plasma

High-Beta Plasma Confinement and Inward ParticleDiffusion in the Magnetospheric Device RT-1High-Beta Plasma Confinement and Inward ParticleDiffusion in the Magnetospheric Device RT-1

EXC/9-4Rb23rd IAEA FEC 11-16 Oct. 2010

Magnetospheric Levitated Dipoles:Space Physics for Laboratory Plasma Confinement

400-600 MWDT Fusion

• Akira Hasegawa, 1987

• Two interesting properties of active magnetospheres:

‣ High beta, (eg. of order unity magnetosphere of Jupiter)

‣ Pressure and density profiles are strongly peaked

‣ “invariant profiles” turbulent activity increases peakedness

J. Spencer

Physics of dipole plasma confinement is now well established

• More than 50 years of magnetospheric exploration: Earth, Jupiter, Saturn, Uranus, and Neptune

• Confinement and stability based on magnetic compressibility

• Gold (1959): Plasma pressure is centrally peaked with p ~ 1/Vγ ~ R-20/3

• Melrose (1967): Plasma density is centrally peaked with〈n〉~ 1/V ~ R-4

• Farley (1970): Turbulence causes strong inward particle pinch (radiation belts)

R

V =

�d�

B∝ R4

Physics of dipole plasma confinement is now well established

• Natural or “Invariant” profiles are stationary solutions to low frequency turbulent mixing that preserve adiabatic invariants

R

V =

�d�

B∝ R4

∂(pV γ)

∂t=

∂

∂ψD

ψψ ∂(pV γ)

∂ψ+ �H�

∂(nV )

∂t=

∂

∂ψDψψ ∂(nV )

∂ψ+ �S�

∂

∂ψ

�DψψV

∂n

∂ψ+ nDψψ ∂V

∂ψ

�

dipole geometry has large pinch term

Superconducting Levitated Dipole Experiments

2 m

LDX (MIT - USA)Nb3Sn Dipole 1.2 MAInductively Charged

3 Hour Float Time 25 kW CW ECRH

5 m• Strong superconducting dipole for

long-pulse, quasi-steady-state experiments

• Large vacuum chamber for unequalled diagnostic access and large magnetic compressibility

• Upper levitation coil for robust axisymmetric magnetic levitation

• Lifting/catching fixture for re-cooling, coil safety, and physics studies

• ECRH for high-temperature, high-beta plasmas

Components of a Levitated Dipole Experiment:

Superconducting Levitated Dipole Experiments

2 m

LDX (MIT - USA)Nb3Sn Dipole 1.2 MAInductively Charged

3 Hour Float Time 25 kW CW ECRH

5 m

RT-1 (U. Tokyo - Japan)HTS Bi-2223 Dipole 0.25 MA

Electrically Charged w/SC Switch6 Hour Float Time 45 kW CW ECRH

2 m

LDX & RT-1: Two Key Experimental Results

ECRH generates very high-beta plasmas consisting of centrally-peaked well-confined energetic electrons and warm collisional plasma…

‣ Pressure profiles measured with magnetic equilibrium analysis

‣ Peak local beta observed in RT-1 reaches 70%

‣ Global energy confinement times up to 60 ms. LDX show levitated plasmas contain 40-70% of stored energy in collisional plasma with peak density n ~ 1018 m-3.

Plasma density profiles are centrally peaked caused by a strong inward turbulent particle pinch…

‣ Near invariant density profiles measured with multi-chord interferometer

‣ Rate of inward pinch (~ 25 ms) observed in LDX to be consistent with fluctuations measurements

1

2

RT-1 discharge with low gas fueling (also typical of LDX)

Initial unstable phase with rising neutral pressure

‣When gas pressure exceeds a critical value (~ 1 μTorr), energetic electrons are stable

Plasma density, plasma stored energy, increase dramatically

‣Peak local beta reaches 70%

‣Removing geomagnetic error field improves confinement

Two decay times indicate collisional thermal plasma and energetic electron component

High Beta Dipole Plasma with Optimal Gas Fueling

RT-1

Low-betaLow-gas pressure

High-betaHigh-gas pressure

Afterglow

Soft X-ray Imaging on RT-1

RT-1 soft X-ray emission (0.1-10keV) shows isotropic plasma

Probe target x-rays show energetic electrons near fundamental ECRH resonance zones‣ 2.45 GHz has mid-plane

resonance

‣ 8.2 GHz resonance crosses coil

2.45 GHz heating creates higher stored energy

LDX hard X-ray (> 40 keV) shows anisotropic mirror trapped fast electrons localized on outer mid-plane

2.45GHz Heating

Visible

LDX Fast Electrons: Anisotropic at ECRH Resonance

Visible

LDX Fast Electrons: Anisotropic at ECRH Resonance

X-RayE > 40 keV

(a) Diamagnetic loop signal and maximum local β estimated from Grad-Shafranov analysis, and

(b) Line averaged density measured with µwave interferometers.

New geomagnetic field compensation system and optimized operation (coil levitation, discharge cleaning, etc.) realized improvements of the plasma.

High-β and high density (>ncutoff, possibly due to EBW) plasma is generated, Diamagnetic loop signal ΔΦ=4.2mWb (maximum local β~70%).

Parameter ranges designated as high-density, high-β, and unstable states, according to the filling neutral gas pressure.

High-β state is characterized by large stored energy, strong x-ray, and depression of visible light strength and fluctuations.

RT-‐1 Improved plasma proper1es with increasing gas

Energy confinement time and β values

Energy confinement time estimated from from stored energy and injected RF power

‣ τE1 ~ 60 ms.

τE1 is shorter than that estimated from diamagnetic decay time τE2 ~ 500ms.

‣ τE2 up to 10 s on LDX.

Ratio of fast to slow decay gives estimate of bulk plasma energy content

‣ 40-70% stored energy in bulk plasma

Plasma pressure (diamagne1c signal) and energy confinement 1me in RT-‐1

0.0!

0.2!

0.4!

0.6!

0.8!

1.0!

0.0! 0.5! 1.0! 1.5! 2.0! 2.5! 3.0! 3.5!

Ho

t E

lectr

on

En

erg

y F

racti

on!

Diamagnetic Flux (mWb)!

Supported 2.5 kW (2.45 GHz source)!

Levitated 2.5 kW (2.45 GHz source)!

Levitated 15 kW!

Hot Electron Fraction on LDX

Supported

Levitated

Studies with a Levitated Dipole show Centrally Peaked Density and the Strongest Turbulent Pinch

Density profiles are centrally-peaked with a levitated dipole

‣Density profiles are “flat” with a supported dipole

Light emission show the ionization source is NOT centrally-peaked

‣The inward turbulent pinch is directly observed

The centrally-peaked profile shape is “invariant” with gas and ECRH power modulation

The strength of the pinch is consistent with measured turbulent fluctuations and magnetospheric physics

Light Emission Shows Outer Gas Fueling

Launcher Inserted

Launcher Withdrawn

Density (!10 Particles/cc)0.8

0.6

0.4

0.2

0.0

Supported

Levitated

0.6 0.8 1.0 1.2 1.4 1.6 1.8

Radius (m)

"S# Flux-Tube Integrated ParticleSource from Light Emission (A.U.)

0

10

20

30

40

Supported

Levitated

Heating modulation demonstrates existence of inward pinch

10 Hz 10 kW (10.5 GHz) ECH modulation‣ Density modulation follows power: profile shape remains unchanged near nV=constant

‣ Source moves radially outward, requiring pinch to create increased central density

High Power

nL2

nL30

5

10

15S100528019

1.0

1.2

1.4

1.6

1.8Line Density Ratio (nL2/nL3)

0

5

10

15

20

25ECRH Power (kW)

5.00 5.05 5.10 5.15time (s)

5.20

Interferometer (Rad)

Low Power0.6 0.8 1.0 1.2 1.4 1.6 1.8

Radius (m)

Density (!!10 Particles/cc)121.0

0.8

0.6

0.4

0.2

0.0

0

10

20

30

15 kW ECRH

""S##Flux-Tube IntegratedParticle Source fromLight Emission (A.U.)

25 kW ECRH

S1005280195.100 sec5.150 sec

High Power

nL2

nL30

5

10

15S100528019

1.0

1.2

1.4

1.6


0

5

10

15

20

25ECRH Power (kW)

5.00 5.05 5.10 5.15time (s)

5.20

Interferometer (Rad)

Low Power0.6 0.8 1.0 1.2 1.4 1.6 1.8

Radius (m)

Density (!!10 Particles/cc)121.0

0.8

0.6

0.4

0.2

0.0

0

10

20

30

15 kW ECRH


25 kW ECRH

S1005280195.100 sec5.150 sec

nV constant = 1.5

Invariant Profile is Robust: Large Gas Puff

Fueling experiment: Gas puff at t=6 s‣ Source (particles/flux) from PDA array peaks to the outside, core density doubles

0.6 0.8 1.0 1.2 1.4 1.6 1.8Radius (m)

Density (!!10 Particles/cc)12 S1005270125.700 sec6.400 sec

1.0

0.8

0.6

0.4

0.2

0.0

0

10

20

30

Gas Puff

Before Gas Puff


02468101214

Interferometer (Radian) S100527012

1.0

1.2

1.4

1.6


0.0

0.5

1.0

1.5Vacuum Pressure (E-6 Torr Eq)

5.6 5.8 6.0 6.2 6.4time (s)

nL2

nL3

After Gas Puff

0.6 0.8 1.0 1.2 1.4 1.6 1.8Radius (m)

Density (!!10 Particles/cc)12 S1005270125.700 sec6.400 sec

1.0

0.8

0.6

0.4

0.2

0.0

0

10

20

30

Gas Puff

Before Gas Puff


02468101214

Interferometer (Radian) S100527012

1.0

1.2

1.4

1.6


0.0

0.5

1.0

1.5Vacuum Pressure (E-6 Torr Eq)

5.6 5.8 6.0 6.2 6.4time (s)

nL2

nL3

After Gas Puff

nV constant = 1.5

Peaked density profiles on RT-1

Similar large increase of peakedness for levitated plasmas‣ 3 chord interferometer fit to radial power law

‣ Profiles have consistent shape over all power levels

‣ Confirms result of near equal number of particles per flux tube

Inward diffusion also seen in non-neutral (pure electron) plasmas‣ Pure electron plasma stably confined for 300 s.

Yoshida et al., PRL 104, 235004 (2010)

Does turbulence match pinch?

Nimrod simulation of LDX‣Central heating with edge

fueling

C.C. Kim, B.A. Nelson

RT-1 low frequency density fluctuations

RT-1 interferometer TFD

Edge probe array measures low frequency turbulence

Array measures low frequency turbulent spectrum (0.1 - 10 kHz)

Instantaneous ExB radial flow of 35 km/s

FIG. 1: A top-down view of LDX at the midplane. This viewshows the extent of the probe array and its relative positionto the levitated coil and the vessel walls.

A. Experimental Setup

Early data from floating probes at the LDX edge in-dicated that low-frequency potential fluctuations occur[5], but the probes were too distantly spaced to properlycapture the phenomenon with su!cient spatial resolu-tion. A vertically movable probe array with tight angu-lar spacing has been constructed to provide more spatialinformation in hopes to di"erentiate whether the poten-tial fluctuations are convection related or related to someother phenomenon. The electrostatic probe array is com-posed of twenty-four cylindrical, tungsten-tipped floatingpotential Langmuir probes. The array is positioned at aradius of one meter and sweeps out a ninety degree arc atthe bottom of the LDX vacuum vessel as shown in figure1. This gives a probe separation of about 7 centimeters,giving the array a resolution of 14 centimeters. This res-olution corresponds to a detectable mode number rangeof 1 to 46. The flow velocities arising from E ! B driftscan be measured by computing the electric field from theplasma potential. The vertical height of the array is re-motely adjustable, and can be changed during or betweenshots for probe insertion scans. The probe modularity al-lows other kinds of probes to be inserted into the arrayat future date.

The potential signals from the probes are read fromthe probe tips by inverting operational amplifiers with1.1 M# input resistors and a 10k# feedback resistors.This gives the amplifiers a gain of -0.0098, and the veryhigh input resistance causes the probes to float (draw al-most no current). The signals are digitized by two 16channel, 16-bit INCAA Computers TR10 bipolar digitiz-ers sampling at 80kHz.

II. RESULTS

The shots analyzed are all deuterium plasmas, and theshort-time “stripey” and correlation plots are all fromperiods where all heating sources are on. The phasevelocities were all calculated during periods where ev-ery heating source was on as well. Since the potentialis measured by the probes, the azimuthal/toroidal elec-tric field can be directly determined from the gradientof the potential as shown in equation 1 [6]. The electricfield can be used to compute the E !B drift velocity, asshown in equation 2 [7] . These drifts are directly relatedto convection, and measuring their magnitude shows itsstrength in transporting particles to and from the core ofthe plasma.

!E = "#$ (1)

!vE!B =!E ! !B

B2(2)

!vplasma = R"#

"t(3)

FIG. 2: Stripey plot showing the electric field in color andthe drift velocity as a vector field. The root of the arrowsemanates from the point where the drift occurs and the lengthof the arrow shows the strength of the drift relative to thepoints.

An eight millisecond period from shot 81003019 isshown in figure 2. It is a “stripey plot,” which is con-structed by plotting each signal from the probe arrayside by side and representing the signal amplitude withcolor. The stripey plot shown in Fig. 2 is similar tomost of the shots taken and displays the features set outto examine here. Therefore, it is the only one reported.The magnetic field is about 360 Gauss at the probe tipsand this yields a computed average radial E ! B driftvelocity over the plotted period of -0.11 mm/s. The in-stantaneous velocity, however, ranges from 34.7 km/s to-20.8 km/s, depending on position and time. The soundspeed for cold ions and for 25 eV electrons as measuredon a swept Langmuir probe is cs = c

!

Te/mic2 $= 35 kms

[8]. The E !B drift velocities have a near-zero mean are





II. RESULTS


!E = "#$ (1)

!vE!B =!E ! !B

B2(2)

!vplasma = R"#

"t(3)



!

Te/mic2 $= 35 kms






II. RESULTS


!E = "#$ (1)

!vE!B =!E ! !B

B2(2)

!vplasma = R"#

"t(3)



!

Te/mic2 $= 35 kms






II. RESULTS


!E = "#$ (1)

!vE!B =!E ! !B

B2(2)

!vplasma = R"#

"t(3)



!

Te/mic2 $= 35 kms


2 3 4 5 6 7 8 9 10x 10−6

2

4

6

8

10

12

Neutral Pressure (Torr)

Phas

e Ve

loci

ty (k

m/s

)

Shots 90312001−90312044

Deuterium Shots5th degree polynomialHelium Shots

FIG. 5: The plasma rotational velocity plotted against thevessel neutral pressure. There is a maximum at 5µTorrwhere the plasma density is greatest. Phase velocity decreaseswith neutral pressure when the plasma density is constant (> 5µTorr). Below 5µTorr, the plasma density is not constantwith neutral pressure, and the velocity/pressure relationshipis unclear.

FIG. 6: Plasma density vs. neutral pressure. Measured withthe microwave interferometer on LDX. The plasma densitylevels out at 5 µTorr for deuterium plasmas.[9]

sure above 5µTorr, but there is another trend at lowerpressures. The velocities lower than 5µTorr decrease andthen increase again at lower pressures. This may be be-cause the plasma density is not constant below 5µTorr,as seen in figure 6, and may give rise to a more com-plicated relation between neutral pressure and phase ve-locity. Above 5µTorr, the plasma density seems to berelatively constant, and the velocities decrease with neu-tral pressure as expected.

The auto and cross-correlations of the probe signalscharacterize the spatial and temporal dynamics of thestructures at the edge of the plasma. The probe arraysamples a slice of these structures, and if the slice hasvery long correlation lengths and times, we can deducethat the system is not turbulent since a static structurestays intact for many rotational lifetimes. A “velocity”can be determined from the correlation length and timethat can be compared to the phase velocity of individual

FIG. 7: The cross-correlation of probe channel 2 with all otherprobe channels at 6 seconds in shot 81003019. All heatingsources are on at this time, and the plasma phase velocity is 16m

s. The auto-correlation of channel 2 (the largest blue curve)

shows the time it takes for a signal to decorrelate (go from 1to < .2) is about 15 data points or 190 µs. The correlationlength can be seen by the number of probe lengths away thesignal takes to decorrelate. Here it is about 8 probe lengths, or54 cm. The second “bump” around 31 lag points correspondsto one rotation around the vessel and is very poorly correlatedto the original signal.

waves.

If the correlation velocity is greater than the phasevelocity, the structures in the plasma decorrelate fasterthan a rotational lifetime and the structure can be re-garded as transient. If the correlation velocity is muchslower than the phase velocity, the structure can con-versely be regarded as static. As shown in figure 7, atypical correlation lengths and times in LDX are 52 cmand 150 µs, respectively. This corresponds to to a corre-lation velocity of 347 km

s, which is much faster than the

phase velocity of 16 kms

at this time. Therefore, the edgeof LDX is turbulent since the structures present are verytransient and change configuration much faster than thebulk flow.

Figure 8 shows the floating potential and electric fieldvalues over the course of shots 81002020 and 81002027,respectively. Shot 81002020 had the floating coil fully lev-itated, and shot 81002027 had the floating coil physicallysupported. Results by Garnier, et al. have shown thatlevitation causes the density profile in LDX to peak inthe core revealing an inward pinch [9]. The particle lossto the supports is fast since the plasma stays “hollow,”or with a density drop o! in the center, during supportedmode. The sonic (collisional) loss time to the coil goeslike L(Bmin/Bmax)/Cs, where L is the radial distance atthe midplane. This time is about 100-200 µs near coiland 2.5 ms at L = 1.6 m. This is fast enough so thatradial turbulent pinch cannot overcome the field-alignedlosses.

This indicates that, although both plasmas exhibitsimilar edge turbulence, in the supported case the lossto the supports dominates over the pinch. This is aninteresting result because without these measurements

2 3 4 5 6 7 8 9 10x 10−6

2

4

6

8

10

12

Neutral Pressure (Torr)

Phas

e Ve

loci

ty (k

m/s

)

Shots 90312001−90312044

Deuterium Shots5th degree polynomialHelium Shots

FIG. 5: The plasma rotational velocity plotted against thevessel neutral pressure. There is a maximum at 5µTorrwhere the plasma density is greatest. Phase velocity decreaseswith neutral pressure when the plasma density is constant (> 5µTorr). Below 5µTorr, the plasma density is not constantwith neutral pressure, and the velocity/pressure relationshipis unclear.

FIG. 6: Plasma density vs. neutral pressure. Measured withthe microwave interferometer on LDX. The plasma densitylevels out at 5 µTorr for deuterium plasmas.[9]

sure above 5µTorr, but there is another trend at lowerpressures. The velocities lower than 5µTorr decrease andthen increase again at lower pressures. This may be be-cause the plasma density is not constant below 5µTorr,as seen in figure 6, and may give rise to a more com-plicated relation between neutral pressure and phase ve-locity. Above 5µTorr, the plasma density seems to berelatively constant, and the velocities decrease with neu-tral pressure as expected.

The auto and cross-correlations of the probe signalscharacterize the spatial and temporal dynamics of thestructures at the edge of the plasma. The probe arraysamples a slice of these structures, and if the slice hasvery long correlation lengths and times, we can deducethat the system is not turbulent since a static structurestays intact for many rotational lifetimes. A “velocity”can be determined from the correlation length and timethat can be compared to the phase velocity of individual

FIG. 7: The cross-correlation of probe channel 2 with all otherprobe channels at 6 seconds in shot 81003019. All heatingsources are on at this time, and the plasma phase velocity is 16m

s. The auto-correlation of channel 2 (the largest blue curve)

shows the time it takes for a signal to decorrelate (go from 1to < .2) is about 15 data points or 190 µs. The correlationlength can be seen by the number of probe lengths away thesignal takes to decorrelate. Here it is about 8 probe lengths, or54 cm. The second “bump” around 31 lag points correspondsto one rotation around the vessel and is very poorly correlatedto the original signal.

waves.

If the correlation velocity is greater than the phasevelocity, the structures in the plasma decorrelate fasterthan a rotational lifetime and the structure can be re-garded as transient. If the correlation velocity is muchslower than the phase velocity, the structure can con-versely be regarded as static. As shown in figure 7, atypical correlation lengths and times in LDX are 52 cmand 150 µs, respectively. This corresponds to to a corre-lation velocity of 347 km

s, which is much faster than the

phase velocity of 16 kms

at this time. Therefore, the edgeof LDX is turbulent since the structures present are verytransient and change configuration much faster than thebulk flow.

Figure 8 shows the floating potential and electric fieldvalues over the course of shots 81002020 and 81002027,respectively. Shot 81002020 had the floating coil fully lev-itated, and shot 81002027 had the floating coil physicallysupported. Results by Garnier, et al. have shown thatlevitation causes the density profile in LDX to peak inthe core revealing an inward pinch [9]. The particle lossto the supports is fast since the plasma stays “hollow,”or with a density drop o! in the center, during supportedmode. The sonic (collisional) loss time to the coil goeslike L(Bmin/Bmax)/Cs, where L is the radial distance atthe midplane. This time is about 100-200 µs near coiland 2.5 ms at L = 1.6 m. This is fast enough so thatradial turbulent pinch cannot overcome the field-alignedlosses.

This indicates that, although both plasmas exhibitsimilar edge turbulence, in the supported case the lossto the supports dominates over the pinch. This is aninteresting result because without these measurements

D = R2�E2ϕ�τc

φ

t

Low frequency fluctuations consistent with turbulent pinch

ECRH Power (kW)

ECRH Heating Pulse

!

"

#!

#"

!$!

!$"

#$!

!

%!

&!

'!

!

"!

#!!

!%&'(

Outer Flux Loop (mV sec)

137 GHz Radiometer Temperature (eV)

5.0 5.2 5.4 5.6 5.8

time (s)

Increased Thermal EnergyDuring Levitation

Increased Central Line Density

Hot Electron EnergySupported Dipole

Supported Levitated

Probe Array (@ R = 1 m)Probe Array

S81002020S81002027

"$!! "$!% "$!&

)*+, -./

!

%

&

'

"$"! "$"% "$"&

Levitated

SupportedECRH

!

%

&

'

(a) Short Half-Second Heating Pulse (b) Visible Light from Supported and Levitated Plasma

(c) Line Density from Supported and Levitated Plasma

3 msec

25 msec

(Eq. 1)

Interferometer (Radian)

Electric Field (V/m RMS)

(!

Figure 4

∂N

∂t= �S�+ ∂

∂ψD∂N

∂ψ, (1)

where �S� is the net particle source within the flux-tube, and the diffusioncoefficient is D = R2�E2

ϕ�τcor in units of (V · sec)2/sec.

DIII-D: L-mode Density Profile Consistency

Lagrangian Transport Description with Preserved Adiabatic Invariants

After Ramp-Up Flat Top

After Ramp-Down Flat Top

Baker and Rosenbluth (1998), Baker (2002)

Summary

The magnetospheric levitated dipole offers a unique avenue to study magnetic confinement bridging space and the laboratory

‣ Large flux expansion allows steep profiles to be formed with turbulent transport

Superconducting levitated dipoles achieve stable, high-beta, well-confined, plasmas

‣ Error field corrected, optimized RT-1 plasmas show peak local ~ 70%.

‣ Energetic particle population stabilized with sufficient neutral fueling

‣ Global energy confinement time ~ 60 ms. LDX shows 40-70% of stored energy in “warm” collisional electron population

“Natural” invariant density profiles have been formed in a laboratory dipole confined plasmas

‣ Both devices have demonstrated peak profiles near nV = constant

‣ Peaked density profile formation shown to be consistent with low frequency turbulent pinch in LDX

Important research ready to be pursued on LDX

Measure adiabatic index of turbulent transport: ‣ i.e. If p ~ V-γ what is γ?

‣ Thomson scattering diagnostic planned to measure electron temperature profile

Achieve and study high density plasma with warm ions:‣ Installation of 1 MW, ICRH transmitter planned to increase density and heat ions

‣ What is the effect FLR and Ti/Te ratio on turbulence?

‣ TOF neutral particle analyzer will measure ion heating

Continued study of non-local turbulent transport:‣ Non-linear studies of drift wave turbulence predict formation of zonal flows. Are

predicted zonal flows evident? Do they lead to transport barriers?

‣ Reflectometer core fluctuation diagnostic planned

‣ High speed fluctuation imaging collaboration

Future tasks for RT-‐1 project Ion heating: In the present study, the plasma is generated and sustained by ECH, and Ti<~10eV, while hot-electrons are stably generated. ICRH is in a planning stage including the design of antenna and matching circuit. Beta limit for magnetospheric plasma: is not experimentally realized and is one of important issues to be studied. Effects of enhanced beta and peaked spatial structures (pressure profiles) of the plasma on the stability properties will be investigated. Investigating two-fluid effects experimentally: In the parameter range of low-density plasma in RT-1 (ne~1017m-3 by 2.45 and 8.2GHz ECH), ion inertia length Δi=vA/ωci~1m is comparable to or larger than the structure length L0~0.1m.Thus, plasma equilibria are treated by Hall MHD without neglecting the ion inertia effects. Hall MHD theory predicts diversity of novel plasma structures such as

• Double Beltrami state*: ultra high-beta (possibly >100%) state, where plasma pressure is balanced by the dynamic pressure of fast flow, and • Formation of toroidal ion flow caused by strong diamagnetism**.

* 1998 Mahajan and Yoshida, PRL 81, 4863; 2002 Yoshida and Mahajan, PRL 88, 095001.**2010 Yoshida, PoP, to be published.

ICC/1-1Ra 23rd IAEA FEC 11-16 Oct. 2010 … Saturn, Uranus, and Neptune •Confinement and stability...

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Transcript of ICC/1-1Ra 23rd IAEA FEC 11-16 Oct. 2010 … Saturn, Uranus, and Neptune •Confinement and stability...