VUV emissive properties of the regenerative soot

by

Shoaib Ahmad

Pakistan Institute of Nuclear Science and Technology, P. O. Nilore, Islamabad, Pakistan

Presentation at JASS’02, SESAME, Jordan 19-28 Oct 2002

Formation of the CarbonaceousPlasma

He, Ne dischargesSooting dischargesRegeneartive soot

HollowAnode

Hollow Cathode

Extractor

To the Monochromator

Hollow CathodeHollow CathodeHollow Cathode

To the Monochromator To the

Velocity Filter

•Ahmad & Riffat NIM B 152, 506 (1999)

200 250 300 350 400 450 500 550 600 6500.0

0.5

1.0

1.5

2.0

2.5

3.0

Neon L

inesNe I λ5852

C ΙΙ

λ28

37

C Ι λ

2478

C Ι λ

1931

Ne ΙΙ

λ36

94

Ne ΙΙ

λ37

27Ne

ΙΙ λ

3713

Ne Ι λ3

520

Ne ΙΙΙ λ

2678

Ne ΙΙ

λ19

16

Inte

nsity

(rel

ativ

e un

its)

Wavelength (nm)

480 500 520 540 560

Ne

I λ53

30N

e I λ

5343

C2(1,0)

C2(0,0)λ5165

λ5635C2(0,1)

Ne

I λ54

00

λ4737

The Swan Band HeadsC2(ν′,ν′′)

• NIM B 171, 552 (2000)• Appl. Phys. Lett. 75, 4100 (1999)

•APL 78, 1499 (2001)•EPJ D 15, 349 (2001)

200 250 300 350 400 450 500 550 6000.0

0.2

0.4

CI,CII& CIII Lines

Rel

ativ

e In

tens

ityb

C2(0,0)

NeI

λ58

52

δ

γβ

α20 mbar

Wavelength (nm)

200 250 300 350 400 450 500 550 6000.0

0.5

1.0

1.5

γ δCII

ICII

aCI,CII& CIII Lines

CI

CI N

eI λ

3520

NeI

λ58

52

0.06 mbar

N

S

VelocityFilter

ExtractorLens

Partic le Detector

HAHC

a

l

0 2000 4000 60000

1

C19

C14

C76

C140

C50

C60

C44

C40

C24

C300

C1055

C4350

C21

C2370

C11

C15

Clu

ster

Inte

nsity

(a.u

.)

ε0 [volts-m-1]

Cluster mass m0

• NIM A 452, 370 (2000)• REDS 153, 35 (2000) • Phys. Lett. A261, 327 (1999)• Eur. Phys. J. Appl. Phys. 5, 111 (1999)

0 100 200 300 400 500 6000

10

Velocity Filter's Deflector Potential (Volts)

b

C6

C60

C200

C21

C11

C15

Inte

nsity

(a.u

.)

0

1

0 200 400 600

a

C1

C3

Transition from C3 to sooting dischargePhys. Rev. E, 79, 026408 (2001)

r

z

20 mm

HollowAnode

Hollow Cathode

•The cusp field, hollow cathode cluster source

Ne DischargeNe Ne++ e-

Ne+ graphite Cm+ e-

1 8 0 2 0 0 2 2 0 2 4 0 5 5 0 6 0 0 6 5 00

1

2

W a v e le n g th (n m )

b

N e I λ λ 5 8 5 2 - 6 4 0 4

Inte

nsity

(rel

. uni

ts)

1 8 0 2 0 0 2 2 0 2 4 0 5 5 0 6 0 0 6 5 00

1

2

CII C

II

a

N e I λ λ 5 8 5 2 -6 4 0 4C

II

C I I λ 2 1 9 5

CII

I λ22

97

C I I λ 2 3 2 5 I C

CI λ

2478

CI λ

1931

2 0 0 2 2 0 2 4 0

CI λ

1993

IC

CII

I λ 2

182

CII

λ23

25 IC

CII

/CII

I

C I I λ 2 1 9 5

CI λ

2478

CI λ

1931

Two modes of the inclusion of carbon into the neon plasma are: (1) The first mode is the high Te and ne regime of the

discharge. Higher values of Vdis and idis initiate the sputtering of the carbon cathode with the subsequent excitation and ionization of the carbon. The singly ionized C content participates efficiently in the kinetic sputtering of the cathode along with NeII.

(2) The second mode of discharge can be classified as the sooting mode which may be associated with high pressure discharges where the density of the ionized species CII and NeII considerably reduces. A constant but gentle surface erosion by potential sputtering dominates this mode.

•The cusp magnetic fields act as:•The traps for high energy electron and low energy ions•The lowest field contours define the outer boundaries of the plasma

1 10 100 1000

1x10-17

1x10-14

1x10-11

1x10-8

CII-CIII

CIII-CIV

CIV-CV

CI-CII

Lotz Calculations For Carbon

Ioni

zatio

n Ra

te

E (eV)

A histogram in which the cumulative Einstein transition probabilities of the three charged states of C are plotted as a function of the wavelength.

Conclusions1. Exploitation of this unique carbonaceous discharge is proposed that is composed of a positive column whose outer boundaries are defined by the cusp magnetic field contours to operate as a source of enhanced VUV light and soft x-rays. These contours confine and trap high energy electrons and low energy C ions. The graphite hollow cathode acts as a cavity that traps the charged species whose radiative decay can yield a strong VUV radiation field that exists between λ=20-80 nm.

2. The main contributions to this field are the radiative and dielectronic recombinations of CII, CIII and CIV. When all three ionized states are present then three distinct regimes of wavelength exist;

(a) below 40 nm, emission from CIV dominate Ephoton~ 40 eV,

(b) (b) between 40-60 nm emissions from CIII, Ephoton~ 25 eV, and

(c) (c) above 60 nm, emissions from CII dominate Ephoton ~ 20 eV. The entrapment of the C ions along the cusp magnet fields and their subsequent collisions with energetic electrons that are similarly trapped but gyrate with different frequencies is the essence of this mechanism.