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8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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(1)Title
Physics of High Pressure Helicon Plasma
and Effect of Wavenumber Spectrum
Interdisciplinary Graduate School of Engineering Sciences,
Kyushu Univeristy, Japan Shunjiro SHINOHARA
Scientific Center Institute for Nuclear Research, Kiev, Ukraine
Konstantin SHAMRAI
1. Introduction
High Density Plasma Source cf. Plasma Application Studies
Study on Helicon Source (Physics)Critical Issues: Plasma Generation Mechanism & Application
Comparison:Experiment & Computation
Future Plan:Large & Small Volume Plasmas
2. Experimental Setup + Theory
Large Diameter Plasma Device
Antenna Structure
Theoretical Model (TG Wave: Mode Conversion)3. Results
Good Agreement between Experimental Results and
Computed Ones Based on H-TG Model
Antenna Loading , Power Absorption, Wave StructuresTE-H Model: Poor Agreement
Future PlanSmall & Large Plasmas
3. Summary
8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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(2)Intro
Introduction
Importance of High Density Plasma SourcePlasma Processing, Accelerator, Laser, Confinement Devices.
Study on Helicon Source (Physics)e.g.,Diameter5 -45 cm[1-5], Change of Antenna Spectra [6-9]
Critical IssuesPlasma Generation Mechanism, Density Jump, Control of
Discharge and Optimization ..... Application
Control of Discharge Regime and Wave Structures
Comparison: Experiment & Computation
1) Antenna Spectra (2 Loops, Current Direction)
2) Magnetic Field (0 - 1000 G)
3)RF Input Power( 3 kW)
4) Pressure (Ar : 6, 51 mTorr)
Antenna Loading & Density Jump, Wave Structures
Power Absorption (Bulk & Edge)
cf.TG Wave(Mode Conversion)
Future Plan (Large & Small Volume)
References[1] S. Shinohara, Y. Miyauchi and Y. Kawai, Plasma Phys. Control. Fusion 37
(1995) 1015.
[2] S. Shinohara, Y. Miyauchi and Y. Kawai, Jpn. J. Appl. Phys. 35 (1996) L731.[3] S. Shinohara, S. Takechi and Y. Kawai, Jpn. J. Appl. Phys. 35 (1996) 4503.[4] S. Shinohara, Jpn. J. Appl. Phys. 36 (1997) 4695.[5] S. Shinohara, S. Takechi, N. Kaneda and Y. Kawai, Plasma Phys. Control.
Fusion 39 (1997) 1479.[6] S. Shinohara, N. Kaneda and Y. Kawai, Thin Solid Films 316 (1998) 139.[7] S. Shinohara and K. Yonekura, Plasma Phys. Control. Fusion 42 (2000) 41.[8] S. Shinohara and K. P. Shamrai, ibid. 42 (2000) 865.[9] K. P. Shamrai and S. Shinohara, Phys. Plasmas 8 (2001) 4659.
8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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Schematic View of Experimental Device
Axial Magnetic Field Coils
ToPump
170 cm
Ar Gas
B
Magnetic Probe
80 cm
Magnetic Probe
Langmuir Probe
Loop Antenna
Microwave Interferometer
z0
20 cm
Chamber(Yoko)M
8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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Schematic View of Antenna Structures
(a) Parallel Current (b) Anti-Parallel Current
d = 1 cm
L = 2 cm
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
kz (cm-1)
Parallel
Anti-Parallel
Power Spectra of Antenna Wavenumber j (kz
)2
(d = 1 cm, L = 2 cm)
AntennaMM
8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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(5)thmodelM.doc
THEORETICAL MODEL
H-TG Model cf. Ez = 0 (TE-H Model)
Maxwell Equations cE = iBcB = iD + 4ia(rr0)
Boundary and Joining Conditions Et(z =R,L) = 0{ }Et
0rr== 0, { }Bt
0rr== 4ia/c
Antenna Current and Fields ia
=ikz
sinkzz
kz =lz/(RL), lz=1,2lzmax E =(Esinkzz + zEzcoskzz)
B =(Bcoskzz + zBzsinkzz)
Permittivity Tensor K1 = 1
2ce
2e
2
e2pe
i2
2pi
,
K2 =)( 2
ce
2
e
2
ce2pe
, K3 = 1 +)()/(i1
)(11
ee
2
De
2
w
w
rkz
Collisions and Landau Damping
e,i= 1+i(e,i/), e=en+ei , =e/kzvTe
Plasma Load Impedance Zp = [42r0(RL)/c]|ikz/Ia|2 (r=r0)Plasma Density Profile n (r) =n0 (n0 nedge)(r/r0)
2_______________________________________________________________________________________
Ref.: K. P. Shamrai, V. P. Pavlenko and V. B. Taranov: Plasma Phys. Control. Fusion 39(1997)505. K. P. Shamrai and S. Shinohara: Phys. Plasmas 8 (2001) 4659.
ra
Ia2
za
CFCFm=0 antenna
Double
Rd
b
Plasma
Vacuum
Ia1
r0
zL
8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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Fig.1(a,b)(51mT,para/anti,H)M
109
1010
1011
1012
1013
10141000 G
650 G
500 G300 G
50 G
30 G
100 G
(a) Parallel
109
1010
1011
1012
1013
1014
10 100 1000
Pin
(W)
1000 G
650 G
500 G
300 G
100 G50 G30 G
(b) Anti-Parallel
[ Electron Density as a Function of Input Power ]
P = 51 mTorr
Lower Wave Number Spectrum Part and/or Lower Magnetic Field is
Necessary for Obtaining High Density Plasma with Low RF Power
(Experiment)
8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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2Loop(AP).G4M3m
[ Plasma Density ne as a Function of Pressure P ]
Lower Wavenumber Spectrum Part is Necessary
for Plasma Initiation in Lower Pressure Range
10 10
10 11
10 12
10 13
10 14
0.001 0.01 0.1
P (Torr)
L = 1.5 cm
2 cm
4 cm7.5 cm
15.5 cm
Oscillation
O (10 12 cm -3 )
L: Distance between Two Loop Antennae
with Opposite Current Directions
8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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(8)PoP_colorM(13,18,20) 13
[ Fractions of Total Power Absorbed ]
(Calculation)
(a) Under Antenna Region (4 cm
l
), (b) Edge Layer (r
=2 mm),(c) Edge Layer of Under Antenna Region
Role of TG Wave, Mode Converted from Helicon Wave(Edge, Downstream, HighB0)
8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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(9)PoP_colorM(13,18,20) 18
[ Comparison:Measured and Computed Resistances ]
H-TG Model: Good Agreement
(ICP)
nedge = 0.5 (PC)
1.0 (AC)
-----------------------------
nedge = 0.5 (PC)
1.0 (AC)
nedge = 0.2 (PC)
8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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(10)PoP_colorM(13,18,20)20
[ Comparison:Measured and Computed Bz Profiles ]
H-TG Model: Good Agreement
PAr = 51 mTorr,B0 = 300 G
Before
Density Jump
AfterDensity Jump
8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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(11)PoP_f11M.doc
[ Power Absorption Profiles (mW/cm3) in log Scale ]PAr = 6 mTorr,ne = 2 10
12cm
-3,B0 = 100 G, Parallel Currents (1 A each)
(Calculation)
(a) H-TG Model
Uniform Plasma
(b) H-TG Model
Non-Uniform Plasma
(nedge = 0)
-----------------
(c) TE-H Model
Uniform Plasma
- 4 0
- 3 0
- 2 0
- 1 0
0
zHc mL0.5
1
1.5
2
2.5
r
Hc m
L
0
1
- 4 0
- 3 0
- 2 0
- 1 0
0
zHc mL0
1
- 4 0
- 3 0
- 2 0
- 1 0
0
zHc mL0. 5
1
1. 5
2
2. 5
rHc mL
0
1
- 4 0
- 3 0
- 2 0
- 1 0
0
zHc mL0
1
- 4 0
- 3 0
- 2 0
- 1 0
0
zHc mL0 . 5
1
1 .5
2
2 . 5
rHc mL
- 2
- 1
0
- 4 0
- 3 0
- 2 0
- 1 0
0
zHc mL- 2
- 1
0
8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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(12)Large Diameter
[ Large Volume Plasma Production by Helicons ]
Sh[ Kyushu Univ. ]Large Diameter Plasma:45 cm, 170 cml, 2 kG3 - 15 MHz, 5 kW, Spiral Antenna (4 Turns, 18 cm
)
Cusp, Divergent & Convergent Fields (Uniformity, Wave Studies)
(Present:BaODischarge)
[ Institute of Space & Astronautical Science ]Device for High Density Plasma Production:75 cm, 490 cml, 2 kG
Plan: 1.8 - 30 MHz, 1 kW (or more), Spiral Antenna (5 Turns, 22 cm)Production of Target Plasma (Space and Basic Fields), Profile Control
Plasma Propulsion (cf. Muses C (Asteroid): 2002~), Wave Studies------------------------------
cf. UCLA (Wave Studies)LAPD by Gekelman (80 cm
1,800 cm
l)
Large Linear Plasma Device by Stenzel (150 cm
250 cml)
8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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(13)SMALL _M0.doc
[ Small Source ] Initial Data
Single-Loopm = 0 Antenna in the MidplaneCalculation:L = 4 cm; r0 = 2 cm; ra = 2.2 cm; Te = 4 eV;
f= 100MHz (f/fce = 0.36 forB0 = 100 G)
(a)
(ICP)
---------------------------------------
(b) (c)
[ Plasma Loading Resistance vs. Plasma Density ]
8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp
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(14)Concl
Summary
Comparison between Experiment and ComputationFuture Plan: Large and Small Sources
High Pressure (6, 51 mTorr)
Antenna Spectra (2 Loops Same & Opposite Directions)
f= 7 MHz,B = 0 - 1000 G cf. 4 Loops
Mode Conversion (Helicon & TG Waves) Bulk & Edge
(Results Good Agreements were found Between Experiment and
Computation Results (H-TG Model) on Antenna Loading, Density
Jump and Wave Structures under Various Parameters.
High Pressure, High Field, Opposite Current DirectionsHigh Threshold Power for Density Jump
With the Increase in the Magnetic Field, Density and Edge
Density Ratio, Larger Antenna Loading and Enhanced Edge
Absorption(TG Wave,z Direction), and Absorption Spectra with
Higherkz Component were Found (Computation).
Absorption near Antenna Region Increased with Density, but
Decreased with the Magnetic Field (Computation).
Effects of Pressure and Antenna Spectra were also Investigated
(Computation).
The H-TG Model is Better to Explain Obtained Results than the
TE-H Model.
Future Plan
Studies on Large & Small Diameter Plasmas for Basic and Plasma
Propulsion Studies were Discussed Shortly.