PKE-Nefedov Symposium - 2004

Institute for High Energy Densities of RAS

Measurements of Ion Drag Force

acting on a Probe Particle in a DC Discharge

A.Usachev, V.Esenkov, A.Zobnin

Content:

1. Electron microscopy of the probe microparticles.

2. Experimental method and results.

3. Comparison experimental results with the modern theories of ion drag force.

Institute for High Energy Densities of RAS

1. Electron microscopy of the probe microparticles.

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MF 4.00 0.08 mHitachi S405A scanning electron microscope

Institute for High Energy Densities of RAS

MF 4.00 0.08 m

Institute for High Energy Densities of RAS

MF 6.86 0.12 m

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MF 6.86 0.12 m

Institute for High Energy Densities of RAS

5.4 5.6 5.8 6 6.2 6.4 6.6 6.8 7 7.2 7.4

D p , m

0

5

10

15

20

25

Np

m

3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6

D p , m

0

5

10

15

20

25

Np

m

Results on Particle Size Measurements

New measurements: Aug.2004

2.8 3.2 3.6 4 4.4d,m km

0

4

8

12

16

20

N

5 .6 6 6.4 6.8 7.2d,m km

0

4

8

12

16

20

N

Old measurements: May.2004

Laser knife

Phantom-5

Laser400 mW

Injector

Cathode

Anode

Sphericaltelescope

Cylindricaltelescope

Mirror

PK-4 tube

Probe particles

Vacuum pump

Fill gas

p = 20, 40, 60 Pа

IDC = 0.5, 1.0, 1.5 мА

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2. Experimental method and results.

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Setup for measurements of Ion drag force

Observation of falling probe particles

Particles – MF-F, r = 2,00 m

Neon pressure p = 60,2 Pа

Discharge current I = 0,5 мА

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Data treatment

а – particle radiusmass densitymn – neon atom mass

nn – neon atoms density

Zd – particle charge

p – velocity of falling probe particlen,th – mean thermal velocity of neon atoms

frF

eF

ionF

gF

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Institute for High Energy Densities of RAS

Determination of Delta

Measured particle velocitiesin neutral gas

a = 2,00 m, p = 60 Pа, p = 7,3 см/s, I = 0 мА.

20 Па 40 Па 60 Паa = 3,43 мкм 1,608 1,607 1,635a = 2,00 мкм 1,49 1,54 1,53

Experimental data on δ:

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20 Па 40 Па 60 Паd=6,86 мкм 1,46 1,46 1,49d=4,00 мкм 1,38 1,42 1,41

a) using passport data on diameter:

b) using measured data on diameter:

Measured particle velocities

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Zd for a = 3,43 m

P , Па I , мА E , В/см Te , эВ Ne , 108 см-3 Zd ММД Zd МОО

20,2 0,5 2,5 9,2 0,9 15000 24500

20,2 1,0 2,0 7,7 1,6 15200 21400

20,2 1,3 2,0 6,8 2,1 14400 19400

40,1 0,5 2,5 9,2 1,2 14000 24500

40,1 1,0 2,0 7,7 2,0 13300 21400

40,1 1,5 2,0 6,8 2,8 12600 19400

60,2 0,5 2,5 8,0 1,4 13400 22000

60,2 1,0 2,0 7,2 2,6 11000 20300

60,2 1,5 2,0 6,4 3,6 11100 18500

Electric force

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P , Па I , мА E , В/см Te , эВ Ne , 108 см-3 Zd ММД Zd МОО

20,3 0,5 2,5 9,2 0,9 8700 14300

20,1 1,0 2,0 7,7 1,6 8900 12500

20,1 1,3 2,0 6,8 2,1 8400 11200

40,2 0,5 2,5 9,2 1,2 8200 14300

40,3 1,0 2,0 7,7 2,0 7600 12500

40,5 1,5 2,0 6,8 2,8 7300 11200

60,3 0,5 2,5 8,0 1,4 7800 12800

60,4 1,0 2,0 7,2 2,6 6400 11800

60,0 1,5 2,0 6,4 3,6 6500 11500

Zd for a = 2,00 мкм

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0 . 4 0 . 8 1 . 2 1 . 6

I , m A

0

2

4

Fio

n, 1

0-13 N

0 . 4 0 . 8 1 . 2 1 . 6

I , m A

0

2

4

Fio

n, 1

0-13 N

Ion drag force vs dc for

а = 2.00 мкм

а = 3.43 мкм

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(P=20 Pа, PP=40 =40 PPаа, P=60 Pа)

experiment

Theory

а = 3.43 мкм

Comparison of different forces acting on a probe particle

P , Па I , мА F ion , 10-13НF e , 10-13НF g , 10-13НF n , 10-13Н dF ion , 10-13Н

20,2 0,5 3,00 6,00 25,06 22,06 1,6

20,2 1,0 1,16 4,87 25,06 21,35 1,4

20,2 1,3 0,90 4,61 25,06 21,35 1,4

40,1 0,5 2,04 5,61 25,06 21,49 1,5

40,1 1,0 1,44 4,26 25,06 22,24 1,4

40,1 1,5 0,84 4,03 25,06 21,87 1,4

60,2 0,5 1,13 5,36 25,06 20,83 1,5

60,2 1,0 0,29 3,52 25,06 21,83 1,3

60,2 1,5 1,21 3,56 25,06 22,71 1,3

a = 3,43 мкм

P , Па I , мА F ion , 10-13

Н F e , 10-13

Н F g , 10-13

Н F n , 10-13

Н dFion, 10-13

N

20,3 0,5 2,31 3,35 4,97 3,93 0,820,1 1,0 1,06 2,28 4,97 3,75 0,620,1 1,2 1,61 2,69 4,97 3,89 0,740,2 0,5 2,58 3,50 4,97 4,05 0,840,3 1,0 2,07 2,84 4,97 4,20 0,740,5 1,5 1,79 2,69 4,97 4,07 0,760,3 0,5 2,36 3,27 4,97 4,06 0,860,4 1,0 1,80 2,49 4,97 4,29 0,760,0 1,2 1,39 2,07 4,97 4,29 0,6

a = 2,00 мкм

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Theoretical models:

1. “Classic” with r=rDion (M.S.Barnes, J.H.Keller, et al., Phys. Rev. 68, 313 (1992) ).

2. Enhanced “classic” with r=rD_el (S.A.Khrapak, A.V.Ivlev, G.E.Morfill, and H.M.Thomas, Phys. Rev. 66, 046414 (2002) ).

3. “Strong interaction” (S.A.Khrapak, A.V.Ivlev, G.E.Morfill, S.K.Zhdanov, and H.M.Thomas, EEE Trans. Plasmas Sci. (2004), to be published ).

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“Classic” model [1]

а – probe particle radiusmi – neon atom mass

s – potential of particle surface

ui – ion drift velocity

qi – ion charge

Qd – particle charge

bc

b

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Enhanced “classic” model [2]

Applicable at

We have

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Analytic approximation of the cross-section is

Applicable for strong interactions)

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Enhanced “classic” model

Comparison of the experimental results with the theoriesfor and d=6.2m :

а) б) в)

0 . 4 0 . 8 1 . 2 1 . 6

I , m À

0

2

4

Fio

n,

10

-13 N

0 . 4 0 . 8 1 . 2 1 . 6

I , m À

0

2

4

Fio

n,

10

-13 N

0 . 4 0 . 8 1 . 2 1 . 6

I , m À

0

2

4

Fio

n,

10

-13 N

Institute for High Energy Densities of RAS

(P=20 Pа, PP=40 =40 PPаа, P=60 Pа)

Barnes et al: Khrapak1 et al: Khrapak2 et al:

Thank you for your attention