plasma efficiency and losses for pulsed xe excimer dbds at ......mark paravia – plasma efficiency...
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KIT – University of the State of Baden-Württemberg andNational Large-scale Research Center of the Helmholtz Association
Light Technology Institute, University Karlsruhe, Germany
www.kit.edu
Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power DensitiesMark Paravia, Michael Meisser, Wolfgang HeeringGEC, Saratoga Springs 2009
Mark Paravia – Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Light Technology InstituteUniversity Karlsruhe
2/ 21.10.2009
Dielectric Barrier Discharges
Non-equilibrium plasma Xenon excimer Radiation around 172 nmPlasma efficiency up to 65 % [1]
Phosphor coated lamps forUV water disinfectionAdvanced oxidation processes
[1] Vollkommer, Hitzschke, US000005604410A (1994)
Mark Paravia – Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Light Technology InstituteUniversity Karlsruhe
3/ 21.10.2009
Experimental setupLamp overview
barrier: fused silicagas gap: 4,5 - 5,5 mmxenon: 210 - 400 mbarfrequency: 20 - 200 kHz
Investigation:radiation fluxoptical lossesplasma efficiency estimation
gas gap spacer
glass solder
electrode
glass plate
barrier: glassgas gap: 2 mmxenon: 50 - 350 mbarfrequency: 20 - 200 kHz
Investigation :luminanceinner electrical valuesNIR (823 nm, 828 nm)
Mark Paravia – Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Light Technology InstituteUniversity Karlsruhe
4/ 21.10.2009
Experimental setupVUV goniometer
wavelength range from 115 nm < λ< 1700 nmabsolute calibration from VUV to NIRphotometric distance = 120 cm (max lamp size = 12cm)ability to measure angular distribution of radiant intensity
Mark Paravia – Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Light Technology InstituteUniversity Karlsruhe
5/ 21.10.2009
angular distribution of radiant intensity (ARI) shows optical thin plasmaXe2
* spectra is overlapped with transmission edge of fused silica (~155 nm)
Results for silica lamps:angular distribution and spectra
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
150 160 170 180 190 200 210 220wavelength [nm]
spec
tal
radi
atio
n in
tens
ity [µ
W/(s
r nm
)]
pXe = 210 mbarλ = 172 nm
Mark Paravia – Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Light Technology InstituteUniversity Karlsruhe
6/ 21.10.2009
Results for silica lamps:Calculation of plasma efficiency
light flux:
extraction efficiency Teff:transmission of silica net-shaped electrodeabsorption of inner barrier
plasma efficiency:isotropic emission of Xe2
* (4π)
155 160 165 170 175 180 185 190 1950
20
40
60
80
100
0
20
40
60
80
100
kl
Shl
äk
[]
T = 20 °CT = 100 °CT = 180 °CXe2*
Plasmaeff
Φη =ARI T P⋅ ⋅
14 ( , )
Mess
n
i ji
ARI Iλ
ϕπ λ λ ϕ ==
Φ = ⋅ ⋅∆ ⋅∑
2
1
2
0 0
( , , ) sin( )I d d dΦ = ∫ ∫ ∫λ π π
λ
λ ϕ γ γ λ γ ϕ
wavelength [nm]
trans
mis
sion
[%]
spec
tral r
adia
nce
inte
nsity
[a.u
.]
Mark Paravia – Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Light Technology InstituteUniversity Karlsruhe
7/ 21.10.2009
maximum optical power density: PVUV = 0,12 W/cm² at pXe = 300 mbarpower density rises with pressure, but …transition of homogeneous into filamented discharge(pressure depended)
Results for silica lamps:efficiency
Variation of repetition rate:
f [kHz]
PV
UV
[W/c
m2 ]
0,00
0,02
0,04
0,06
0,08
0,10
0,12
0,14
0 25 50 75 100 125 150 175
210 mbar300 mbar400 mbar
Mark Paravia – Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Light Technology InstituteUniversity Karlsruhe
8/ 21.10.2009
0,00
0,02
0,04
0,06
0,08
0,10
0,12
0,14
0,0 0,2 0,4 0,6 0,8 1,0
Pel [W/cm²]
210 mbar
300 mbar
400 mbar
Results for silica lamps:efficiency
maximum plasma efficiency ~ 52 % (at Pel = 0,07 W/cm²)
plasma efficiency declines to ~ 34 % (at Pel = 0,8 Wcm²)
why is the efficiency declining?
0
0,1
0,2
0,3
0,4
0,5
0,6
0,0 0,2 0,4 0,6 0,8 1,0Pel [W/cm²]
210 mbar300 mbar
400 mbar
f
f
Pel [W/cm²] Pel [W/cm²]
PV
UV
[W/c
m2 ]
Pla
sma
effic
ienc
y
Mark Paravia – Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Light Technology InstituteUniversity Karlsruhe
9/ 21.10.2009
Results for flat lamp:power and efficiency
comparable results for flat lamp as for silica lampsabove p = 200 mbar slight pressure dependency when repetition rate is adjusted
Pel [mW/cm²] Pel [mW/cm²]
Lum
inan
ce [c
d/m
²]
Lam
p ef
ficie
ncy
[lm/W
]
0
5000
10000
15000
20000
25000
0 200 400 600 800 1000
350 mbar250 mbar150 mbar100 mbar50 mbar
f0
5
10
15
20
25
0 200 400 600 800 1000
350 mbar
250 mbar
150 mbar
100 mbar
50 mbar
f
Mark Paravia – Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Light Technology InstituteUniversity Karlsruhe
10/ 21.10.2009
Lam
p vo
ltage
[V]
NIR
[a.u
.]
Results for flat lamp:voltage and IR
pulse shape matched for double ignitionfor f = 200 kHz no ignition in first positive half-wave, despite voltage excite ignition voltage
time [ns] time [ns]
-2000
-1500
-1000
-500
0
500
1000
1500
2000
2500
0 500 1000 1500 2000
f = 20 kHz
f = 200 kHz
-0,2
0
0,2
0,4
0,6
0,8
1
1,2
0 500 1000 1500 2000
f = 20 kHz
f = 200 kHz
Mark Paravia – Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Light Technology InstituteUniversity Karlsruhe
11/ 21.10.2009
Results for flat lamp:pre ignition current and gap voltage
Due to high frequency increasing plasma current density before ignition, that separates the remaining charges and lowers the gas gap voltage.Plasma becomes a glow discharge.
plas
ma
curr
ent d
ensi
ty [m
A/c
m²]
time [ns]
-20
-15
-10
-5
0
5
10
15
0 500 1000 1500 2000
f = 20 kHz
f = 200 kHz
-800
-600
-400
-200
0
200
400
600
800
1000
1200
0 500 1000 1500 2000
f = 20 kHz
f = 200 kHz
time [ns]
gap
volta
ge [V
]
Mark Paravia – Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Light Technology InstituteUniversity Karlsruhe
12/ 21.10.2009
Summary
VUV goniometer to measure the total radiance of a lamp between 115 nm and 1700 nm
Measurements of power density and efficiency for high power Xe2
* DBDs
Limiting factors:Transition into filamented dischargeRemaining charges and plasma current density
Mark Paravia – Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Light Technology InstituteUniversity Karlsruhe
13/ 21.10.2009
GEC 2009, Saratoga Springs
Thank you for your attention.
Mark Paravia – Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Light Technology InstituteUniversity Karlsruhe
14/ 21.10.2009
Electrical excitation / measurementresonant pulse ECG as current sourcemeasurement of plasma current iplasma
measurement of gap voltage ugap
Experimental setupECG
Roth, M., Neiger, M., 21. IDRC, Nagoya, 2001, p. 893-896
UL
S1
S2
DBD
C
D1 D2
D3D4
-2000
-1000
0
1000
2000
0 5 10 15 20 25time/µs
lam
p vo
ltage
/V
T periode = 25 µs