Threshold current density for homogeneous excitation … · Threshold current density for homogeneous excitation of pulsed Xenon excimer DBD ... dielectric barrier discharge ... constant

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.