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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.