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 - - Champaign Champaign University of Illinois at Urbana � � 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 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 Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005
The “ “pure IEC pure IEC” ” uses beam convergence in uses beam convergence in The spherical geometry spherical geometry Gas Feed Line Spherical Vacuum Chamber Grid To Vacuum Pump High-Voltage Feedthrough High-Voltage Power Supply Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005
The “ “pure Dipole pure Dipole” ” has most plasma has most plasma The in a weak field region in a weak field region 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 begins The area of bad curvature that can drive the plasma unstable beg 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 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 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 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 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 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 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 e and n n e Values of T e and 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- -Maxwellian Maxwellian plasma. plasma. non 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 – – 800 Gauss 800 Gauss from 0 Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005
Double Probe I- -V Curve is used to V Curve is used to Double Probe I determine T e and n n e .(B=0). Valid for =0). Valid for determine T e and e .(B Maxwellian distribution. distribution. Maxwellian Doubl e Pr obe I -V cur ve No B f i el d 25mTor r DC ( 20mA 3kV) 50 40 30 20 oA) 10 cr 0 m i -80 -60 -40 -20 0 20 40 60 80 ( p -10 I -20 -30 -40 -50 Vp ( V) Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005
I- -V curve (B V curve (B- -Field on) is used to Determine Field on) is used to Determine I Distorted Maxwellian Maxwellian Distribution Function Distribution Function Distorted f l oat +80V -80V Doubl e Pr obe 245Gauss DC( 25mTor r 20mA 3kV) 80 60 40 20 oA) cr 0 mi -80 -60 -40 -20 0 20 40 60 80 ( p I -20 -40 -60 -80 Vp ( V) Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005
Analysis of I- -V curve to determine V curve to determine f(v f(v) and ) and n n e . Find Analysis of I e . Find density increases up to 30x and temp up to 5x. density increases up to 30x and temp up to 5x. 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. 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 of 40 of 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. Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005
Future Work to include to include… …. . Future Work ! Optimization studies of magnetic field for ! Optimization studies of magnetic field for operating condition. operating 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 Trends in Fusion Research, Washington DC , Trends in Fusion Research, Washington DC , March 10, 2005 March 10, 2005
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