shunjiro shinohara and konstantin shamrai- physics of high pressure helicon plasma and effect of...

8/3/2019 Shunjiro Shinohara and Konstantin Shamrai- Physics of High Pressure Helicon Plasma and Effect of Wavenumber Sp

1/14

(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


2/14

(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.


3/14

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


4/14

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


5/14

(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


6/14

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)


7/14

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


8/14

(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)


9/14

(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)


10/14

(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


11/14

(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


12/14

(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)


13/14

(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 ]


14/14

(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.

shunjiro shinohara and konstantin shamrai- physics of high pressure helicon plasma and effect of...

Documents