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Dipole Assisted Dipole Assisted Inertial Electrostatic Inertial Electrostatic Confinement Confinement Yoshikazu Takeyama, Robert Thomas, G.H. Miley Yoshikazu Takeyama, Robert Thomas, G.H. Miley Fusion Studies Laboratory Fusion Studies

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Dipole Assisted Dipole Assisted Inertial Electrostatic Inertial Electrostatic Confinement Confinement

Yoshikazu Takeyama, Robert Thomas, G.H. Miley Yoshikazu Takeyama, Robert Thomas, G.H. Miley Fusion Studies Laboratory Fusion Studies Laboratory University of Illinois at Urbana University of Illinois at Urbana -

  • Champaign

Champaign

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Contents Contents

! ! Introduction

Introduction

! ! Experimental Setup

Experimental Setup

! ! Plasma Diagnostics

Plasma Diagnostics

! ! Preliminary Results and Analysis

Preliminary Results and Analysis

! ! Conclusion

Conclusion

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Dipole Assisted IEC Dipole Assisted IEC

! ! Dipole Fields Enhance Plasma Density in the Center

Dipole Fields Enhance Plasma Density in the Center Region of the IEC Region of the IEC

! ! Combined IEC and Dipole Confinement Properties

Combined IEC and Dipole Confinement Properties Reduce Plasma Losses Reduce Plasma Losses

! ! Provides Control of potential at the center region of IEC

Provides Control of potential at the center region of IEC

! ! Compliments aspects of Levitated Dipole Experiment

Compliments aspects of Levitated Dipole Experiment (LDX) Being Conducted at MIT and Columbia (LDX) Being Conducted at MIT and Columbia

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

The The “ “pure IEC pure IEC” ” uses beam convergence in uses beam convergence in spherical geometry spherical geometry

Grid Spherical Vacuum Chamber Gas Feed Line To Vacuum Pump High-Voltage Feedthrough High-Voltage Power Supply

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

The The “ “pure Dipole pure Dipole” ” has most plasma has most plasma in a weak field region in a weak field region

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

The area of bad curvature that can drive the plasma unstable beg The area of bad curvature that can drive the plasma unstable begins ins from the mid from the mid-

  • plane pressure peak outward to the chamber wall. This is

plane pressure peak outward to the chamber wall. This is illustrated for the LDX experiment at Columbia/MIT illustrated for the LDX experiment at Columbia/MIT

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Dipole IEC Experimental Device Dipole IEC Experimental Device

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Dipole Assisted IEC Schematic Dipole Assisted IEC Schematic

Coil Inner Radius = 2 cm Outer Radius = 8cm Height = 4cm 20cm radius 2cm x 1cm spacing

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Double probe is inserted from the Double probe is inserted from the side and measurement is done on side and measurement is done on the surface of dipole coil the surface of dipole coil

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Dipole Field Produced by Coil Dipole Field Produced by Coil provides the focus of ion beam provides the focus of ion beam

  • 12 gage of Square magnet wire
  • (copper)
  • 17 x 26 turns of Coil.
  • Current varied in the range of

0~20Amp.

  • Maximum field strength of 0.1 T

At the center of dipole

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Plasma More Focused Through Plasma More Focused Through Center With Field On Center With Field On

B-Field Off B-Field On

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Double Probe Used to Determine Double Probe Used to Determine Values of T Values of Te

e and

and n ne

e

Basis of Selection Basis of Selection

  • Less disturbance of Plasma than

Less disturbance of Plasma than single single

  • Well suited for IEC operating

Well suited for IEC operating condition with presence of magnetic condition with presence of magnetic field field

  • Capable of measuring properties of

Capable of measuring properties of non non-

  • Maxwellian

Maxwellian plasma. plasma.

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Operating Conditions Operating Conditions

! ! Pressure Varied from 20

Pressure Varied from 20 – – 80 80 m mm mTorr Torr

! ! Discharge Voltage 3 kV

Discharge Voltage 3 kV – – 500 V 500 V

! ! Central Potential Bias up to +

Central Potential Bias up to +-

  • 160 V

160 V

! ! Magnetic Field in Dipole Center Varied

Magnetic Field in Dipole Center Varied from 0 from 0 – – 800 Gauss 800 Gauss

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Double Probe I Double Probe I-

  • V Curve is used to

V Curve is used to determine T determine Te

e and

and n ne

e.(B

.(B=0). Valid for =0). Valid for Maxwellian Maxwellian distribution. distribution.

Doubl e Pr

  • be

I

  • V

cur ve No B f i el d 25mTor r DC ( 20mA 3kV)

  • 50
  • 40
  • 30
  • 20
  • 10

10 20 30 40 50

  • 80
  • 60
  • 40
  • 20

20 40 60 80

Vp ( V) I p ( m i cr

  • A)
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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

I I-

  • V curve (B

V curve (B-

  • Field on) is used to Determine

Field on) is used to Determine Distorted Distorted Maxwellian Maxwellian Distribution Function Distribution Function

Doubl e Pr

  • be

245Gauss DC( 25mTor r 20mA 3kV)

  • 80
  • 60
  • 40
  • 20

20 40 60 80

  • 80
  • 60
  • 40
  • 20

20 40 60 80

Vp ( V) I p ( mi cr

  • A)

f l

  • at

+80V

  • 80V
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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Analysis of I Analysis of I-

  • V curve to determine

V curve to determine f(v f(v) and ) and n ne

  • e. Find

. Find density increases up to 30x and temp up to 5x. density increases up to 30x and temp up to 5x.

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Control of center line potential is done Control of center line potential is done by biased inner ring in dipole opening. by biased inner ring in dipole opening.

! ! CL potential can block ion flow unless

CL potential can block ion flow unless controlled. controlled.

! ! Biases to 80 V tested.

Biases to 80 V tested.

! ! Improved density up to 40x.

Improved density up to 40x.

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Conclusions Conclusions

! ! Results confirmed that Dipole Fields Enhance Plasma

Results confirmed that Dipole Fields Enhance Plasma Density in the Center Region of the IEC Density in the Center Region of the IEC

! ! Presence of B Presence of B-

  • Field(245 G) increases the electron density at the

Field(245 G) increases the electron density at the

  • center. 25 times higher density.
  • center. 25 times higher density.

! ! Results confirmed Control of potential at the center

Results confirmed Control of potential at the center region of IEC region of IEC

! ! Presence of bias +80 V enhances the electron density by factor Presence of bias +80 V enhances the electron density by factor

  • f 40
  • f 40

! ! Encouraging results suggest future scale up of

Encouraging results suggest future scale up of experiment to fusion conditions feasible. experiment to fusion conditions feasible.

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Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005

Future Work Future Work to include to include… …. .

! ! Optimization studies of magnetic field for

Optimization studies of magnetic field for

  • perating condition.
  • perating condition.

! ! Optimize the shape of coil to enhance the density Optimize the shape of coil to enhance the density increase. increase.

! ! Analyze and Optimize Control potential at the

Analyze and Optimize Control potential at the center. center.

! ! Develop the physics model of dipole assisted

Develop the physics model of dipole assisted IEC IEC