threshold current density for homogeneous excitation … · threshold current density for...
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M.Paravia, ICOPS 2008, 6/18/2008, p. 1
Threshold current density for homogeneous excitation of pulsed Xenon excimer DBD
Mark ParaviaKlaus Trampert
Wolfgang Heering
Light Technology InstituteUniversity Karlsruhe
ICOPS 2008
06/18/2008
M.Paravia, ICOPS 2008, 6/18/2008, p. 2
Introduction
Xenon excimer discharge dielectric barrier discharge
nonequilibrium plasma
plasma efficiency up to 65 %
generation of VUV radiation (172 nm)
plane gas discharge
M.Paravia, ICOPS 2008, 6/18/2008, p. 3
Xenon excimer discharge dielectric barrier discharge
nonequilibrium plasma
plasma efficiency up to 65 %
generation of VUV radiation (172 nm)
plane gas discharge
Discharge modeFilamentary, patterned or homogeneous
Introduction
Single pulse NIR images, tint = 1µs
M.Paravia, ICOPS 2008, 6/18/2008, p. 4
spacerelectrode
glass plateactive areaguard
Experimental setup
Xe pressure: 150 mbargas gap: 2 mmactive area: 54 cm²frequency: 40 kHzpower: 20 - 70 mW/cm²
Plane DBDdischarge with and without phosphor
active area with electrical guard
measurement of internal values
M.Paravia, ICOPS 2008, 6/18/2008, p. 5
Experimental setup
barrier
Cgap
zplasma
u
ilamp
iblind iplasma
gap
barri
er
lam
pu
uRoth, M., Neiger, M., 21. IDRC, Nagoya, 2001, p. 893-896
Electrical excitation and measurementresonant pulse ECG as current source
measurement of plasma current iplasma
measurement of gap voltage ugap
UL
S1
S2
DBD
C
D1 D2
D3D4
M.Paravia, ICOPS 2008, 6/18/2008, p. 6
-2000
-1000
0
1000
2000
0 1 2time/µs
lam
p vo
ltage
/V
T pulse = 1.2 µs
-2000
-1000
0
1000
2000
0 5 10 15 20 25time/µs
lam
p vo
ltage
/V
T periode = 25 µs
Internal values during pulsed excitation
Pulsed excitationpulse length tpulse = 1.2 µs (HF period)
variation of current for transition from filamented to homogeneous discharge
M.Paravia, ICOPS 2008, 6/18/2008, p. 7
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
0 500 1000 1500 2000time/ns
plas
ma
curr
ent d
ensi
ty/m
A/c
m²
Iplasma MEss3
aignited = 27 %Aignited = 27 %Aignited = 53 %
Threshold current density
determination of ignited area
comparison of mean current density during ignition
M.Paravia, ICOPS 2008, 6/18/2008, p. 8
0
20
40
60
80
100
0 5 10 15mean current density/mA/cm²
igni
ted
area
/% j plasma (t=t ignition )
Threshold current density
Linear increase of ignited area up to the homogeneous discharge
Threshold current density jplasma = 10 mA/cm²
increased current density after homogeneous discharge
jplasma
M.Paravia, ICOPS 2008, 6/18/2008, p. 9
Reignition of Xe Excimer DBE
variation of pulse length
constant slew rate at the rising voltage edge
discharge is not complete homogeneous for Tpulse = 1.4 µs
-2000
-1000
0
1000
2000
0 500 1000 1500 2000time/ns
lam
p vo
ltage
/V
T pulse =1.2 µs
T pulse =1.4 µs
Tpulse = 1.4 µs
Tpulse = 1.2 µs
M.Paravia, ICOPS 2008, 6/18/2008, p. 10
-15
-10
-5
0
5
10
15
0 500 1000 1500 2000time/ns
pla
sma
curr
ent d
ensi
ty/m
A/c
m²
T pulse =1.2 µs
T pulse =1.4 µs
Reignition of Xe Excimer DBE
Same current density of first ignition
Shift second ignition to 600 ns after first ignition
Tpulse = 1.4 µs
Tpulse = 1.2 µs
M.Paravia, ICOPS 2008, 6/18/2008, p. 11
0
20
40
60
80
100
0 5 10 15 20
mean current density/mA/cm²
igni
ted
area
/%
T pulse = 1.2 µsT pulse = 1.4 µs
Reignition of Xe Excimer DBE
Higher threshold current density jplasma = 12.5mA/cm²
Pulse shape influences the threshold current density
jplasma
M.Paravia, ICOPS 2008, 6/18/2008, p. 12
Summary
current density determines discharge mode
linear increase of ignited area with mean current density
homogeneous discharge above threshold current density
reignition influences threshold current density
M.Paravia, ICOPS 2008, 6/18/2008, p. 13
ICOPS 2008
Thank you for your attention.