A Study on Liquid Dielectric Breakdown in Micro-EDM Discharge
Analysis of Discharge Parameters and Spectroscopic ......Jan 24, 2012 · Typical dielectric...
Transcript of Analysis of Discharge Parameters and Spectroscopic ......Jan 24, 2012 · Typical dielectric...
Analysis of Discharge Parameters and
Spectroscopic Diagnostic of DBDs
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular
Data, Trieste - Italy
Pooja Gulati
Plasma Device Technology, Microwave Tubes Division
CSIR-Central Electronics Engineering Research Institute (CSIR-CEERI) Pilani Rajasthan-
333031
CSIR-Central Electronics Engineering Research Institute (CSIR-CEERI), Pilani
Foundation was laid on 1953.Around 450 Employees
� Leading Research Institute in India in the field of Electronics Devices
3.Semiconductor
• Hybrid Microcircuits
• IC Design
• MEMS and Microsensors
• Nanotechnology & Devices
1.Microwave Tubes
• Gyrotron
• Klystron
• Magnetron
• TWT
2.Electronic Systems
• Agri-Electronics
• Embedded System
• Digital System
• Power Electronics
Major Research Areas at CSIR-CEERI Pilani
• Nanotechnology & Devices
• Photonics & optoelectronics
• Semiconductor Material & Tech.
• TWT
• Plasma Devices Technology
• Power Electronics
Activities in Plasma Devices Group
• High Power Plasma Switches:Thyratrons & Pseudospark
• VUV/UV Excimer Sources based on DBD: Biomedical ApplicationsSurface TreatmentWater Purification (jointly with NEERI)
• Plasma Cathode Electron Gun:• Plasma Cathode Electron Gun:Electron and Ion Source
• Plasma Assisted Microwave Sources:Plasma TWT, Pasotron
• Penning Discharge DevicesIon Sources and VUV Spectroscopy
Motivation and objectives of the work.
Introduction
What is Dielectric Barrier Discharges (DBDs)?
Advantages and open areas of research and applications
of DBDs.
Experiments
Organization of Presentation
Experiments
Experimental Setup and testing
Results and discussions.
Conclusion
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
In recent time it has been observed that Dielectric Barrier
Discharge (DBD) based micro-discharges and micro-array-
discharge plasmas can produce ultraviolet radiation in
germicidal wavelength range UV-C (200-280nm) and VUV(100-
200nm), UV-B(280-315nm), UV-A (315-400nm) that can
effectively treat impure water, and also can be used for
Motivation
effectively treat impure water, and also can be used for
medical and other industrial applications. Our group is
working in this area and I am motivated in the spectroscopic
studies related to this technology which can in future transit
me for large scale plasma related spectroscopic analysis.
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
Objectives
To investigate and analyze the characteristics of discharge
patterns occurring in the volume discharge (VD)
configuration of DBDs filled with inert gases.
The traditional metallic diagnostic technique is not useful
in the very small geometry of the proposed DBD
configuration. Hence to derive the internal electrical and
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
configuration. Hence to derive the internal electrical and
plasma parameters with the help of electrical analysis and
spectroscopic diagnostics is the key component of the
objectives.
Dielectric barrier discharges (DBDs), also known as silent discharges or
barrier discharges, are generated in discharge configurations with at least
one dielectric barrier between the electrodes.
Introduction
What is Dielectric Barrier Discharge(DBDs)?
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
Role of Dielectric layers:
It acts as current limiter and limits the discharge transition from glow to arc.
Possible DBD Geometries
Typical dielectric barrier discharge configurations
(i). Volume discharge, (ii). Surface discharge (iii). Coplanar discharge
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
Fabricated Geometries
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
Cg
Cd1
Cd2
Geometrical Design and Parameters
• Dielectric Thickness= 1 mm• Electrode diameter =36 mm• Electrode Thickness = 1mm• Gas gap = 2 mm• Dielectric Material Used= Quartz• Pressure of Gas=100mbar• Gas Used = Helium
Dielectric barrier capacitance Cd1 = Cd2 = 20.48 pF
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
�Base pressure=1x10-4 mbar
�Gas filling assembly is usedto fill gas at differentpressures.
�Working Pressure~100 mbar
�Sinusoidal voltage supply upto 2kV peak with frequenciesfrom 30 to 90 kHz has been
Experimental Setup
Schematic View of experimental setup
from 30 to 90 kHz has beenused.
�Applied voltage and the totalcurrent are measured usinghigh voltage probe andRogowski-type currenttransformer.
�Oscilloscope and visiblespectrometer are interfacedwith computer.
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
600 Va0.03
Testing & Characterization of He DBD
Experimental Setup for the DBD Source
10 15 20 25 30 35 40 45
-600
-400
-200
0
200
400
600 Va It
Time(u sec)
Va(
V)
-0.03
-0.02
-0.01
0.00
0.01
0.02
It(m
A)
�At breakdown voltage, the discharge begins with
some filaments distributed on the dielectric wall.
�Increasing the applied voltage little bit, number of
filaments increases and for further increase in
voltage, the discharge finally get diffused.
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
dt
tdVCtI d
ddbd
)()( =
dt
tdVCtI g
gdg
)()( =
)(
)())()((
1)(
tC
tItItI
Cdt
tdV
d
dbddisdbd
g
a +−=
tdVCg )(−+=
Total current through DBD and displacement current through gap
(4) (5)
(6)
Diff. (1) with respect to time and replacing (4) and (4) in (1),
Rearranging (6), we will get
)()()( tVtVtV gda += )()()( tItItI scdbdtc += )()()( tItItI dgdisdbd +=(1)
Using Kirchoff’s theorem for the model, we obtain the following equations
(2) (3)
Equivalent electrical circuit of DBDs
dt
tdVCtI
C
CtI a
gdbdd
gdis
)()()1()( −+=
0)(1
)( mdbdd
d VdttIC
tV += ∫
0)(1
)()( mdbdd
ag VdttIC
tVtV −−= ∫
∫−=2/
0
0 )(2
1 T
dbdd
m dttIC
V
(7)
The values of dielectric and gas gap voltages are,
Where Vm0 is memory voltages, ( In case of sinusoidal excitation)
(10)
(9)
(8)
� In case of sinusoidal excitationU N Pal et al, J. Phys. D: Appl. Phys.vol. 42, 045213 (8pp), 2009. U N Pal et al, J. Phys.: Confe. Ser.208, 012142, 2010.
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
0
7
14
-400
-200
0
200
400
Cur
rent
(m
A)
It Idbd Idis.
Vol
atag
e (V
)
Va Vd Vg Vm
Input Parameters:Gap capacitance Cg (11.30 pf) Dielectric barrier capacitance Cd (20.48 pF)
Equations are used from references:U N Pal et al, J. Phys. D: Appl. Phys.vol. 42, 045213 (8pp), 2009.
Results and discussionsResults and discussions
-14
-7
15 20 25 30 35 40-2
0
2
4
Cur
rent
(m
A)
Time (µs)
Pow
er (
W)
Psup. Pdis.
Experimental waveforms of dynamicprocesses occurring in gap (gas: Helium atf= 34.5 kHz) for the Parallel plate DBDGeometry. at 100 mbar.
(8pp), 2009. U N Pal et al, J. Phys.: Confe. Ser.208, 012142, 2010.
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
2.0x10 3
2.5x10 3
3.0x10 3
3.5x10 3
4.0x10 3
4.5x10 3
HeII 6559.7Å HeI 4921.9 Å
HeI 5875.6 ÅInte
nsity
(a.u
)
HeI 6678.1Å
HeI 7065.1Å
Spectroscopic ResultsSpectroscopic Results
3000 4000 5000 6000 7000 80005.0x10 2
1.0x10 3
1.5x10 3
HeI 4921.9 Å
HeI 5015.6ÅHeI 5875.6 ÅIn
tens
ity(a
.u)
Wavelength (Å)
HeI 3888.6Å
HeI 6678.1Å
HeI 7281.3Å
He I 3888.6 Å (23S-33P)He I 4921.9 Å (21P-41D)
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
He I 5015.6 Å (21S-31P)He I 5875.6 Å (23P-33D)
He I 6678.1 Å (21P-31D) He I 7065.1 Å (23P-33S)He I 7281.3 Å (21P-31S)
Neutral Helium Lines:
Intensities of the He I lines are calculated using collisional-radiative (CR) model based ADAS code[H. P. Summers, ADAS
users manual,JET –IR 06 (Abingdon: JET Jointundertaking) (1994)].Withan assumption that the average electron density and temperaturein an emission length x, the photon intensity I (λul ) of a spectralline can be written fromthe CR-model as,
)~
(~
)~
(~
)(~
xNNCPExNNCPEI +=λ
Collisional-Radiative (CR) Model
)~
(~
)~
(~
)(~
xNNCPExNNCPEI geexcitationiegrecombininul +=λ
FromCR-model the ground state populations of atoms and ionsis given by,
egCReiCRig NNSNN
dt
dN
dt
dN−=−= α
Under steady-state approximation,
g
i
CR
CR
N
NS=
α
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
Under equilibrium condition 0=− egCReiCR NNSNNα and CR
CR
g
i S
N
N
α=
So, the condition
For ionizing plasma is 1>>CR
CRS
α and for recombining plasma is 1<<
CR
CRS
α
In true sense the ionizing plasma
Purely Ionizing Condition
HeI
ionizing plasma condition holds well when Ni/Ng << SCR/ CRα [Fujimoto T. and Sawada K., NIFS-DATA-39 (1997)].
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
Under ionizing condition the term is taken tobe negligibly small and the line intensity for a transitionfrom level u to level l is expressed as,
The significance of the line ratio technique is that theexperimentallyobservableintensity ratio of two lines (which
)~
(~
xNNCPE iegrecombinin
)( ulI λ
)~
(~
)(~
xNNCPEI geexcitationul =λ
Intensity line ratios
experimentallyobservableintensity ratio of two lines (whichis not directly dependent on , and ) can be easilyobtained fromthe code as the ratio of corresponding photonemission rate coefficients is given by,
iN gN eN
),(
),(
2
1
2
1
ee
ee
TNPEC
TNPEC
I
I=
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
Temp. Sensitive Intensity Ratios: 7281.3/ 7065.7, 5049/ 4713.1
Density Sensitive Intensity Ratios: 6678.1/ 7281.3, 4921.9/ 5047.7
Temperature & Density CalculationTemperature & Density Calculation
Calculated Values: Electron Temp. = (6.5±0.5) eV, Density = (3.5±1.5) х1011 cm-3
Ref. Summers H P 1994 ADAS Users Manual JET–IR 06(Abingdon: JET Joint Undertaking).R. Prakash, et alJ. Appl. Phys. vol. 97, no.4, p.043301, 2005.
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
1.50x1011
3.00x1011
4.50x1011
6.00x1011
Ne(
cm-3
)
120nsec 105ns 95ns
Simulated results of the electron Density using Simulated results of the electron Density using
OOPIC-Pro
0 5 10 15 20 25 30 35 400.00
Diameter of the electrode (mm)
The statistical mechanics have shown that the many small perturbation (errors)
that affect a physical system almost always force the measurement to follow the
Gaussian distribution. It is usually referred to as simply the “normal distribution”.
Based on this, the average distribution of electron plasma density is derived for
entire system geometry using OOPIC-Pro simulation code and if we take line average of the saturated density it would give nearly similar results to the spectroscopic diagnostic measurements, which are in agreement to each other.
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
The homogeneous type of discharge has been observed at 100mbaroperating pressure for a fixed frequency 34.5 kHz in parallel plateDBD cell filled with helium gas.
The dynamic evolution of the process in the gap provides the usefulinformation about the electrical characterization of the DBD source.
The electron plasma temperatures and electron plasma density
Conclusion
The electron plasma temperatures and electron plasma densityobtained for present configuration at 100mbar gas pressure aretypically (6.5±0.5) eV and (3.5±1.5) х1011cm-3 respectively.
The existence of such density and temperature in this source is usefulfor existence of higher metastable states which needs to be furtherinvestigated.
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
Dr. Ram Prakash, CSIR-CEERI, Pilani
Mr. U.N Pal, CSIR-CEERI, Pilani
and all other group members
Acknowledgement
and all other group members
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy
Thank YouThank YouThank YouThank YouThank YouThank YouThank YouThank You
Joint ICTP-IAEA Workshop on Fusion Plasma Modelling using Atomic and Molecular Data, Trieste - Italy