Peculiarities of glow modes of argon atmospheric pressure radio-frequency capacitive discharge with isolated electrodes
Glow characteristics of capacitive radio frequency discharge with isolated electrodes in low-current α and highcurrent γ modes are determined experimentally. It is shown that transition from α mode to γ mode occurs through a phase of coexistence of both modes in different parts of the discharge gap....
Saved in:
| Published in: | Вопросы атомной науки и техники |
|---|---|
| Date: | 2013 |
| Main Authors: | , , , , |
| Format: | Article |
| Language: | English |
| Published: |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2013
|
| Subjects: | |
| Online Access: | https://nasplib.isofts.kiev.ua/handle/123456789/112185 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Journal Title: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Cite this: | Peculiarities of glow modes of argon atmospheric pressure radio-frequency capacitive discharge with isolated electrodes / V.Yu. Bazhenov, V.V. Tsiolko, V.M. Piun, R.Yu. Chaplinskiy, A.I. Kuzmichev // Вопросы атомной науки и техники. — 2013. — № 4. — С. 171-175. — Бібліогр.: 14 назв. — англ. |
Institution
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
nasplib_isofts_kiev_ua-123456789-112185 |
|---|---|
| record_format |
dspace |
| spelling |
Bazhenov, V.Yu. Tsiolko, V.V. Piun, V.M. Chaplinskiy, R.Yu. Kuzmichev, A.I. 2017-01-17T20:17:34Z 2017-01-17T20:17:34Z 2013 Peculiarities of glow modes of argon atmospheric pressure radio-frequency capacitive discharge with isolated electrodes / V.Yu. Bazhenov, V.V. Tsiolko, V.M. Piun, R.Yu. Chaplinskiy, A.I. Kuzmichev // Вопросы атомной науки и техники. — 2013. — № 4. — С. 171-175. — Бібліогр.: 14 назв. — англ. 1562-6016 PACS: 52.80.Pi, 61.30.Hn, 81.65.-b https://nasplib.isofts.kiev.ua/handle/123456789/112185 Glow characteristics of capacitive radio frequency discharge with isolated electrodes in low-current α and highcurrent γ modes are determined experimentally. It is shown that transition from α mode to γ mode occurs through a phase of coexistence of both modes in different parts of the discharge gap. Експериментально встановлено характеристики горіння ємнісного високочастотного розряду з ізольованими електродами в аргоні атмосферного тиску в слабострумовому (α) та сильнострумовому (γ) режимах. Показано, що перехід з режиму α в режим γ відбувається через фазу одночасного існування двох режимів в різних частинах розрядного проміжку. Экспериментально установлены характеристики горения емкостного высокочастотного разряда с изолированными электродами в слаботочном (α) и сильноточном (γ) режимах. Показано, что переход из режима α в режим γ происходит через фазу одновременного существования двух режимов в разных частях разрядного промежутка. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Плазменно-пучковый разряд, газовый разряд и плазмохимия Peculiarities of glow modes of argon atmospheric pressure radio-frequency capacitive discharge with isolated electrodes Особливості режимів горіння ємнісного високочастотного розряду з ізольованими електродами в аргоні атмосферного тиску Особенности режимов горения емкостного высокочастотного разряда с изолированными электродами в аргоне атмосферного давления Article published earlier |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
Peculiarities of glow modes of argon atmospheric pressure radio-frequency capacitive discharge with isolated electrodes |
| spellingShingle |
Peculiarities of glow modes of argon atmospheric pressure radio-frequency capacitive discharge with isolated electrodes Bazhenov, V.Yu. Tsiolko, V.V. Piun, V.M. Chaplinskiy, R.Yu. Kuzmichev, A.I. Плазменно-пучковый разряд, газовый разряд и плазмохимия |
| title_short |
Peculiarities of glow modes of argon atmospheric pressure radio-frequency capacitive discharge with isolated electrodes |
| title_full |
Peculiarities of glow modes of argon atmospheric pressure radio-frequency capacitive discharge with isolated electrodes |
| title_fullStr |
Peculiarities of glow modes of argon atmospheric pressure radio-frequency capacitive discharge with isolated electrodes |
| title_full_unstemmed |
Peculiarities of glow modes of argon atmospheric pressure radio-frequency capacitive discharge with isolated electrodes |
| title_sort |
peculiarities of glow modes of argon atmospheric pressure radio-frequency capacitive discharge with isolated electrodes |
| author |
Bazhenov, V.Yu. Tsiolko, V.V. Piun, V.M. Chaplinskiy, R.Yu. Kuzmichev, A.I. |
| author_facet |
Bazhenov, V.Yu. Tsiolko, V.V. Piun, V.M. Chaplinskiy, R.Yu. Kuzmichev, A.I. |
| topic |
Плазменно-пучковый разряд, газовый разряд и плазмохимия |
| topic_facet |
Плазменно-пучковый разряд, газовый разряд и плазмохимия |
| publishDate |
2013 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Особливості режимів горіння ємнісного високочастотного розряду з ізольованими електродами в аргоні атмосферного тиску Особенности режимов горения емкостного высокочастотного разряда с изолированными электродами в аргоне атмосферного давления |
| description |
Glow characteristics of capacitive radio frequency discharge with isolated electrodes in low-current α and highcurrent γ modes are determined experimentally. It is shown that transition from α mode to γ mode occurs through a phase of coexistence of both modes in different parts of the discharge gap.
Експериментально встановлено характеристики горіння ємнісного високочастотного розряду з ізольованими електродами в аргоні атмосферного тиску в слабострумовому (α) та сильнострумовому (γ) режимах. Показано, що перехід з режиму α в режим γ відбувається через фазу одночасного існування двох режимів в різних частинах розрядного проміжку.
Экспериментально установлены характеристики горения емкостного высокочастотного разряда с изолированными электродами в слаботочном (α) и сильноточном (γ) режимах. Показано, что переход из режима α в режим γ происходит через фазу одновременного существования двух режимов в разных частях разрядного промежутка.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/112185 |
| citation_txt |
Peculiarities of glow modes of argon atmospheric pressure radio-frequency capacitive discharge with isolated electrodes / V.Yu. Bazhenov, V.V. Tsiolko, V.M. Piun, R.Yu. Chaplinskiy, A.I. Kuzmichev // Вопросы атомной науки и техники. — 2013. — № 4. — С. 171-175. — Бібліогр.: 14 назв. — англ. |
| work_keys_str_mv |
AT bazhenovvyu peculiaritiesofglowmodesofargonatmosphericpressureradiofrequencycapacitivedischargewithisolatedelectrodes AT tsiolkovv peculiaritiesofglowmodesofargonatmosphericpressureradiofrequencycapacitivedischargewithisolatedelectrodes AT piunvm peculiaritiesofglowmodesofargonatmosphericpressureradiofrequencycapacitivedischargewithisolatedelectrodes AT chaplinskiyryu peculiaritiesofglowmodesofargonatmosphericpressureradiofrequencycapacitivedischargewithisolatedelectrodes AT kuzmichevai peculiaritiesofglowmodesofargonatmosphericpressureradiofrequencycapacitivedischargewithisolatedelectrodes AT bazhenovvyu osoblivostírežimívgorínnâêmnísnogovisokočastotnogorozrâduzízolʹovanimielektrodamivargoníatmosfernogotisku AT tsiolkovv osoblivostírežimívgorínnâêmnísnogovisokočastotnogorozrâduzízolʹovanimielektrodamivargoníatmosfernogotisku AT piunvm osoblivostírežimívgorínnâêmnísnogovisokočastotnogorozrâduzízolʹovanimielektrodamivargoníatmosfernogotisku AT chaplinskiyryu osoblivostírežimívgorínnâêmnísnogovisokočastotnogorozrâduzízolʹovanimielektrodamivargoníatmosfernogotisku AT kuzmichevai osoblivostírežimívgorínnâêmnísnogovisokočastotnogorozrâduzízolʹovanimielektrodamivargoníatmosfernogotisku AT bazhenovvyu osobennostirežimovgoreniâemkostnogovysokočastotnogorazrâdasizolirovannymiélektrodamivargoneatmosfernogodavleniâ AT tsiolkovv osobennostirežimovgoreniâemkostnogovysokočastotnogorazrâdasizolirovannymiélektrodamivargoneatmosfernogodavleniâ AT piunvm osobennostirežimovgoreniâemkostnogovysokočastotnogorazrâdasizolirovannymiélektrodamivargoneatmosfernogodavleniâ AT chaplinskiyryu osobennostirežimovgoreniâemkostnogovysokočastotnogorazrâdasizolirovannymiélektrodamivargoneatmosfernogodavleniâ AT kuzmichevai osobennostirežimovgoreniâemkostnogovysokočastotnogorazrâdasizolirovannymiélektrodamivargoneatmosfernogodavleniâ |
| first_indexed |
2025-11-24T04:14:19Z |
| last_indexed |
2025-11-24T04:14:19Z |
| _version_ |
1850841366910730240 |
| fulltext |
ISSN 1562-6016. ВАНТ. 2013. №4(86) 171
PECULIARITIES OF GLOW MODES OF ARGON ATMOSPHERIC
PRESSURE RADIO-FREQUENCY CAPACITIVE DISCHARGE
WITH ISOLATED ELECTRODES
V.Yu. Bazhenov1, V.V. Tsiolko1, V.M. Piun1, R.Yu. Chaplinskiy2, A.I. Kuzmichev2
1Institute of Physics NAS of Ukraine, Kiev, Ukraine;
2National Technical University of Ukraine “KPI”, Kiev, Ukraine
E-mail: chapok86@ukr.net
Glow characteristics of capacitive radio frequency discharge with isolated electrodes in low-current α and high-
current γ modes are determined experimentally. It is shown that transition from α mode to γ mode occurs through a
phase of coexistence of both modes in different parts of the discharge gap.
PACS: 52.80.Pi, 61.30.Hn, 81.65.-b
INTRODUCTION
In past decade atmospheric pressure discharges were
widely used in many applications, including steriliza-
tion, surface treatment, exhaust purification,
nanoscience [1 - 3]. It should be noted that among a
variety of such discharges (dielectric barrier discharges
(DBDs), plasma jets, microwave discharges, radio-
frequency (RF) discharges) the last kind is of the utmost
interest. Advantages of such discharges are low ignition
voltage and ability to create dense uniform plasma in
large volumes. Capacitively coupled plasmas in such
discharges usually are generated between bare metal
electrodes typically at 13.56 MHz. As in case of low
pressure discharges, atmospheric pressure ones can exist
in two modes – low-current α mode, and high-currentр
γ one [4]. Transition from α to γ mode occurs in result
of “breakdown” of space charge layers of the discharge
in α mode, which leads to contraction of the discharge,
and at subsequent voltage growth arcing may occur in
some cases. Due to that, in spite of higher efficiency of
γ-mode discharge owing to its higher current density,
the discharge instability becomes principal drawback in
its practical applications.
In [5, 6] it was proposed to use dielectric barriers for
stabilization of γ mode of RF discharge glow. Experi-
mental and theoretical investigations of RF discharge
with dielectric barriers in helium at atmospheric pres-
sure confirmed possibility of stable operation of γ-mode
discharge at high current values [7, 8].
However, in case of practical application of RF dis-
charges, use of helium as main gas in different mixtures
is not justified due to its high cost. In [9] for creation of
layers for liquid crystal alignment, RF discharge with
dielectric barriers in argon at atmospheric pressure was
successfully used with operation in low-current α mode.
The present paper represents results of experimental
study of glow peculiarities of such discharge at its tran-
sition from low-current α mode to high-current γ mode.
1. EXPERIMENTAL SET UP
AND METHODS
Block diagram of the experimental setup is pre-
sented in Fig. 1. Discharge cell consisted of two flat
copper electrodes, each having 50×41×0.05 mm dimen-
sion, glued onto polycore (Al2O3) dielectric barriers 5
(60×48×1 mm). Discharge gap between barriers 5 had
1 mm thickness.
Fig. 1. Scheme of experimental setup. 1 – camera;
2 – color filter; 3 – lens; 4 – discharge plasma;
5 – dielectric barriers; 6 – impedance matching unit;
7 – RF generator; 8 – gas feed regulation system
For powering the discharge device, RF (13.56 MHz)
generator 7 (MV-1.5, JSC “Selmi”, Sumy) was used
with impedance matching unit 6. Voltage RMS value
after the matching unit could be varied in a range of
0…1600 V. The power was supplied to the electrodes
via capacitive dividers (C1-C2, C3-C4) for setting de-
sired ratio of RF voltage values between the discharge
electrodes. Volume rate of argon feed υ was set in a
range of 0.5…18 l/min by means of gas feed regulation
system 8.
For studies of electrical characteristics of the dis-
charge, capacitive bridge technique was implemented
using the circuit shown in Fig. 1, with capacitors C1-C4
serving as the bridge components, and the discharge cell
included as a diagonal element of the bridge. At that,
kinetics of 3 RF oscillation periods for values of three
voltages (Uin, Uh and Ul) were recorded by means of
digital oscilloscope Tektronix TDS1012 and transferred
to computer for subsequent processing. At first, current
values through capacitors C1-C4 were calculated, and
after that current values through the discharge cell from
high-potential and low-potential sides were determined.
It was found that in all cases of discharge cell use (that
is, with discharge in different operating regimes, as well
as without ignition of the discharge) high side cell cur-
rent value was about 15% higher than low side one. At
that, with discharge cell removed and shorted connec-
tion instead of it, measured current values were equal.
Examination of the discharge cell capacity by means of
low-frequency metering device (with the cell located in
its actual experimental arrangement) has shown that
additionally to 18 pF capacity of the cell itself (includ-
ing the gap and two insulators, each of the dielectric
ISSN 1562-6016. ВАНТ. 2013. №4(86) 172
barrier introducing 180 pF capacity) there are leakage
capacities of high side and low side electrodes with re-
spect to grounded surrounding elements of the setup
comprising 3 and 4 pF respectively (the vales measured
with ±0.1 pF precision). Such situation obviously re-
quired taking into account actual leakage capacities at RF
frequencies for correct determination of the discharge
characteristics. It was done by processing the data with
mentioned leakage capacities taken as starting values,
and subsequent iterations with variation of the values so
that the discharge current values calculated from high
and low side became equal. The technique was cali-
brated for correct absolute value measurements by means
of consequently connected RC circuits instead of the dis-
charge cell with parameters simulating actual discharge
operation. As a result, the technique allowed experimen-
tal determination of principal electrical characteristics
(voltage, current, total power, active power, efficient
capacity and resistance) of the gas discharge itself, that
is, at the gas space between dielectric barriers.
Measurements of the discharge emission spectrum
were performed by means of CCD-spectrometer SL40-
2-1024USB (SOLAR TII, Minsk, Republic of Belarus).
Emission distribution across the discharge was studied
by means of long focal length system, which was im-
plemented on a basis of DSLR camera Canon 350D
with its own lens removed and single lens with claimed
focal length of 1 m and 25 mm aperture installed at spe-
cial rigid mount (actual magnification of the system was
determined experimentally by the image processing). At
that the necessity of correct imaging of the whole depth
of the discharge in the cell (about 5 cm) was taken into
consideration. Particularly, for studied red region of the
spectrum centered at about 650 nm, Rayleigh length
criterion allowed maximum possible optical resolution
at the discharge cell location of about
45 10 0.65⋅ ⋅ μm ≈180 μm, and used distance between
the lens and the discharge cell of about 4 m provided
approximate match with the diffraction divergence. Im-
ages taken by the camera in RAW mode were converted
to 16-bit bitmap files with linear law of intensity con-
version so that they could be immediately used for ob-
taining profiles of discharge intensity distribution. Re-
sults presented in this paper were obtained with red fil-
ter with cutoff wavelength of about 600 nm installed
before the camera. Other zones of visible spectra (green
and blue) accepted by the camera have demonstrated
similar behavior of spatial intensity distributions, how-
ever, with worse signal-to-noise ratio, as compared to
red zone of visible spectrum.
2. EXPERIMENTAL RESULTS
AND DISCUSSION
2.1. RESULTS OF THE ELECTRICAL
MEASUREMENTS
At conducting the researches, the following values
were determined experimentally: RMS values of dis-
charge current density Jd and voltage at the discharge
gap between dielectric barriers Ug (gas voltage), mean
active discharge power Wd, and effective (averaged over
RF oscillation period) values of gas space capacity Cg
and active resistance of the discharge plasma Rd.
One can see from Fig. 2 that discharge ignition volt-
age Uign is practically independent on volume rate of
argon flow through the discharge gap. At the same time,
discharge quenching voltage Uquen grows up from ≈ 60
to ≈ 110 V (that is, practically twice) at increase of ar-
gon flow rate υ from 1 to 12 l/min.
0 2 4 6 8 10 12
0
50
100
500
550
600
Uquen
Uign
R
M
S
ga
s
vo
lta
ge
U
g,
V
Ar flow rate, l/min
Fig. 2. Dependencies of voltage of discharge ignition
Uign and quenching Uquen on volume rate of argon flow
υ. Each point at the plot represents data averaged over
15-20 measurements for each dataset
Possible reason for such effect may be due to plasma
generation in the discharge not only at the expense of
ionization of argon atoms in ground state, but as well at
the expense of ionization of the atoms in metastable states
Ar(1p5) and Ar(1p3). In discharges on argon-containing
mixtures specific portion of metastable argon atoms Q
(that is, ratio of concentration of metastable argon atoms
to that of the atoms in ground state) can reach values of
10-5…10-3 depending on discharge parameters and mix-
ture content. Such quantity of metastable atoms can pro-
vide essential influence on kinetics of processes in dis-
charge plasmas, since ionization of argon atoms from
their metastable states can occur with high enough effi-
ciency. It is due both to lower energy threshold of such
processes, and to higher values of their cross sections.
Particularly, cross section of argon atom ionization from
ground state reaches maximum value of ≈ 3·10-16 cm2
(at 100 eV) with the process threshold of 15.8 eV, and
maximum cross section for ionization from metastable
state 1s5 ≈ 8·10-16 cm2 (at ≈ 15 eV) with the threshold of
≈ 4 eV [10, 11]. In [12] it was shown that in low pressure
discharge, depending on parameters, contribution of ioni-
zation from metastable states can reach up to 20…25%.
Contribution of metastable atoms to ionization increases
with pressure growth. First of all, it is due to fact that
decrease of electron energy with pressure growth leads
to increase of contribution of “low energy” ionization
from metastable states, as compared to “higher energy”
ionization from ground state.
Figs. 3-5 present measured dependencies of main
discharge parameters on RMS gas voltage Ug. One can
see from Fig. 3 that behavior of discharge power Wd
dependence on Ug is similar for both values of argon
flow rate – initial slow (practically linear) Wd increase
after Ug ≈ 210 V is substituted by faster growth.
Similar behavior is also demonstrated by dependen-
cies of gas space capacity Cg (see Fig. 4) dependence on
flow rate is absent; b) at low values of Ug the capacity
values are practically independent on Ug and start abrupt
growth at Ug ≥ ≈ 210 V.
ISSN 1562-6016. ВАНТ. 2013. №4(86) 173
120 140 160 180 200 220 240 260
0
20
40
60
80
100
D
is
ch
ar
ge
a
ct
iv
e
po
w
er
W
d,
W
RMS gas voltage Ug, V
1 l/min
6 l/min
Fig. 3. Dependencies of active discharge power Wd on
gas voltage Ug for different volume rates of argon flow
Possible reason of such behavior of Cg dependence
on Ug may consist in change of the discharge glow
mode at increase of the voltage value above ≈ 210 V. At
discharge glow in α mode, thicknesses of space charge
layers (and, consequently, gas space capacity Cg) are
practically independent on Ug. Breakdown of space
charge layers in α-mode discharge at increase of voltage
Ug above certain threshold (≈ 210 V in the above case)
leads to abrupt decrease of thickness of the layers and,
consequently, to rapid growth of gas space capacity Cg.
Thus, rapid increase of Cg observed in the experiment
gives evidence to transition (total or partial) of dis-
charge glow from α mode to high-current γ mode.
120 140 160 180 200 220 240 260
40
50
60
70
G
as
s
pa
ce
c
ap
ac
ity
C
g,
pF
RMS gas voltage Ug, V
1 l/min
6 l/min
Fig. 4. Dependencies of discharge gas space capacity
Cg on gas voltage Ug for different volume rates of argon
flow
120 140 160 180 200 220 240 260
50
60
70
80
90
100
110
Pl
as
m
a
re
si
st
ac
e
R
d,
O
hm
RMS gas voltage U
g
, V
1 l/min
6 l/min
Fig. 5. Dependencies of discharge plasma resistance Rd
on gas voltage Ug for different volume rates of argon flow
As it is shown above, both discharge power Wd, and
gas space capacity Cg are practically independent on
volume argon flow rate at its variations in range
1…6 l/min. Other kind of behavior is demonstrated by
dependence of discharge plasma active resistance Rd on
Ug (see Fig. 5).
Although these dependencies are qualitatively simi-
lar, resistance Rd at flow rate of 6 l/min is about 15%
higher than analogous value at lower flow rate in the
whole range of Ug variation. Rd growth at flow rate in-
crease gives indirect evidence to our assumption about
the role of metastable argon atoms in the ionization
processes in the discharge under study.
Now let us consider current-voltage characteristics
(CVC) of the discharge (Fig. 6). One can see that
change of argon flow rate from 1 to 6 l/min almost have
no influence on the discharge CVC. One can also see
from the figure that at increase of discharge current den-
sity from ≈ 20 to 45 mA/cm2, voltage at gas space Ug
grows up practically linearly from ≈ 120 до 220 V, and
after that Ug growth is considerably reduced, so that at
Jd increase from 45 toдо 65 mA/cm2 it reaches just
≈ 240 V.
20 30 40 50 60 70
120
160
200
240
R
M
S
ga
s
vo
lta
ge
U
g,
V
RMS current density Jd, mA/cm2
1 l/min
6 l/min
Fig .6. Dependencies of gas voltage Ug on discharge
current density Jd for different volume rates of argon flow
As in case of the discharge CVC, growing depend-
ence of the discharge gas space capacity Cg on Jd exhib-
its a bend at discharge current density of about
45 mA/cm2 (Fig. 7). However, in this case, rate of Cg
growth at Jd ≥ 45 mA/cm2 increases.
20 30 40 50 60 70
40
45
50
55
60
65
70
G
as
s
pa
ce
c
ap
ac
ity
C
g,
pF
RMS current density Jd, mA/cm2
1l/min
6 l/min
Fig. 7. Dependencies of the discharge gas space capac-
ity Cg on discharge current density Jd for different
volume rates of argon flow
Increase of argon flow rate from 1 to 6 l/min leads to
Rd increase in the whole range of Jd variations. How-
ever, unlike the case of Rd dependence presented in
Fig. 8, in this case for both flow rate values, discharge
ISSN 1562-6016. ВАНТ. 2013. №4(86) 174
active resistance is practically independent on Jd when
current density is higher than about 50 mA/cm2.
20 30 40 50 60 70
50
60
70
80
90
100
110
Pl
as
m
a
re
si
st
an
ce
R
d,
O
hm
RMS current density Jd, mA/cm2
1 l/min
6 l/min
Fig. 8. Dependencies of active resistance of the
discharge plasma Rd on discharge current density Jd
for different volume rates of argon flow
Thus, presented results of measurements of electric
characteristics of the discharge provide dual impression.
On one side, abrupt growth of the discharge power Wd
and gas space capacity Cg after increase of Ug and Jd
above respective threshold values, undoubtedly give
evidence to discharge transition from α mode to higher
current γ mode. On another side, one can see from
Fig. 6 that in whole range of discharge current density
variations, plasma exhibits positive differential conduc-
tance. However, as it was shown in [6], RF discharge
transition from α mode to γ mode should be accompa-
nied by change of sign of plasma differential conductiv-
ity. For clarifying this issue, we have performed re-
searches of characteristics of the discharge plasma
emission.
2.2. RESULTS OF THE OPTICAL
MEASUREMENTS
One can see from Fig. 9 that emission spectrum of
RF discharge plasma in argon can be conditionally sub-
divided into two portions – emission of argon UV-VIS
continuum in wavelength range ≈ 350…650 nm and
emission of atomic argon spectrum lines in range
≈ 700…900 nm (mainly, it is emission of transitions
2p10-1…1s2-5). The reason for appearance of emission of
NOβ system is presence of air admixture coming from
the walls of gas feeding tubes.
For the first time, emission of argon UV-VIS con-
tinuum in such wide range of spectrum (up to 650 nm)
was discovered in [13] at study of pulsed discharge in
argon at 4 bar pressure. (Emission spectrum of the con-
tinuum due to photorecombination of atomic ions Ar+
shows sharp edge at about 460 nm). Authors of that
paper supposed that on the analogy of atomic Ar+ ions,
the electron could be captured by molecular Ar+
2 ions
and transferred into Ar*
2 energy levels with the emission
of a photon: Ar+
2 +e → Ar*
2 + hν.
Estimation of the plasma density was done with the
use of ratios of emission intensities of transitions
2p1-1s2, 750.4 nm; 2p3-1s4, 738.4 nm; 2p6-1s5, 763.5 nm
by means of method proposed in [14], which has shown
that plasma density in the discharge at Wd = 30 W and
gas flow rate 6 l/min is ~ 1012 cm-3.
400 500 600 700 800 900
0,0
0,2
0,4
0,6
1
4
NOβ
Ar
7
63
.5
Ar continuum
Ar
8
11
.5
Ar
7
50
.4
Ar
7
38
.4
In
te
ns
ity
, a
.u
.
Wavelength, nm
Fig .9. Emission spectrum of the discharge plasma.
Argon flow rate 6 l/min, Wd = 30 W
Study of the discharge emission spatial distribution
by means of long focal length optical setup described
above have shown that the bend occurring in electrical
characteristics of the discharge is accompanied by
change of the emission profile in direction across the
discharge gap – while at lower discharge power the dis-
charge exhibited distinct dark regions near both isolator
(Fig. 10, curve 1), at higher power values discharge
emission had a tendency of filling the whole gap space.
0,5 1,0 1,5 2,0 2,5
0
2
4
6
8
10
12
14 21
In
te
ns
ity
, a
.u
.
x, mm
Fig. 10. Emission profiles across the discharge gap.
The discharge glows in α (1) and γ (2) modes
However, it occurred only in part of the gap under
center of the electrodes. By investigating the emission
profiles when viewing the cell at different angles in the
gap plane (up to 300 with respect to the axis) it was
found that the discharge changes only in a spot lying
exactly under center of the electrodes where power sup-
ply wires were soldered. For obtaining the discharge
emission profile in the spot, calculation of intensity dis-
tribution was done, at which measured profile corre-
sponding to the gap center was modified by partial sub-
traction of the profile measured outside of the spot, at
that the part was defined by portion occupied by the
spot along the line of view taken relatively to the whole
discharge length (5 cm). Normalized resulted profile is
shown in Fig. 10, curve 2. One can see two maxima
spaced by about the size of the discharge gap thickness.
Taking into account diffraction broadening of the im-
age, one can state that the discharge emission occurs
mainly in two regions located very close to the dielec-
tric barriers, which gives undoubted evidence to dis-
charge transition to γ mode in center portion of the cell.
Uncontrolled variations of the size of this portion repre-
ISSN 1562-6016. ВАНТ. 2013. №4(86) 175
sent a reason for increased spread of electrical parame-
ters of the discharge when it was investigated at higher
power values.
Thus, the results of optical measurements have clari-
fied the situation with the discharge transitions between
glow modes. Indeed, the discharge switches from α to γ
mode of glow after reaching threshold of the current
density of about 45 mA/cm2. However, γ mode dis-
charge glow coexists with α mode one, at that the last
occupies major portion of the discharge volume. As a
result, in spite of higher local current density in γ mode,
averaged electrical characteristics only partially resem-
ble the switch of the discharge glow modes. Particu-
larly, differential plasma conductivity may locally
change its sign, as it is expected accordingly to [6]. Re-
alization of uniform discharge glow in γ mode should
undoubtedly improve its operation efficiency.
REFERENCES
1. R. Foest, E. Kindel, A. Ohl, M. Stieber, and
K.D. Weltmann. Non-thermal atmospheric pressure
discharges for surface modification // Plasma Phys.
Control. Fusion. 2005, v. 47, p. B525-36.
2. M.G. Kong, G. Kroesen, G. Morfill, et al. Plasma
medicine: an introductory review // New J. Phys.
2009, v. 11, p. 115012.
3. D. Janasek, J. Franzke, and A. Manz. Scaling and
the design of miniaturized chemical-analysis sys-
tems // Nature. 2006, v. 442, № 7101, p. 374-380.
4. X. Yang. Comparison of an atmospheric pressure,
radio-frequency discharge operating in the α and γ
modes // Plasma Sources Sci. Technol. 2005, v. 14,
№ 2, p. 314-320.
5. S.Y. Moon, W. Choe, B.K. Kang. A uniform glow
discharge plasma source at atmospheric pressure //
Appl. Phys. Let. 2004, v. 84, № 2, p. 188-190.
6. J.J. Shi, D.W. Liu, M.G. Kong. Plasma stability con-
trol using dielectric barriers in radio-frequency at-
mospheric pressure glow discharge // Appl. Phys.
Let. 2006, v. 89, p. 081502.
7. J.J. Shi, D.W. Liu, M.G. Kong. Mitigation plasma
constriction using dielectric barriers in radio-
frequency atmospheric pressure glow discharges //
Appl. Phys. Let. 2007, v. 90, p. 031505.
8. J.J. Shi, D.W. Liu, M.G. Kong. Effect of dielectric
barriers in radio-frequency atmospheric glow dis-
charges // IEEE Trans. Pl. Sci. 2007, v. 35, № 2,
p. 137-142.
9. V.Yu. Bazhenov, R.Yu. Chaplinskiy, R.M. Kravchuk,
et al. Treatment of polyimide films by an atmos-
pheric pressure plasma of capacitive RF discharge
for liquid crystal alignment // Problems of Atomic
Science and Technology. Series “Plasma Physics”
(19). 2013, № 1, p. 177-179.
10. P. McCallion, M.B. Shah and H.E. Gilbody.
A crossed beam study of the multiple ionization of
argon by electron impact // J. Phys. B: At. Mol. Opt.
Phys. 1992, v. 25, p. 1061-1071.
11. M. Asgar Ali, P.M. Stone. Electron impact ioniza-
tion of metastable rare gases: He, Ne and Ar // Int. J.
Mass Spectr. 2008, v. 271, p. 51-57.
12. M.W. Kiehlbauch and D.B. Graves. Modeling argon
inductively coupled plasmas: The electron energy
distribution function and metastable kinetics //
J. Appl. Phys. 2002, v. 91, № 6, p. 3539-3546.
13. A.B. Treshchalov and A. A. Lissovski. VUV–VIS
spectroscopic diagnostics of a pulsed high-pressure
discharge in argon // J. Phys. D: Appl. Phys. 2009,
v. 42, 245203 (14 p.).
14. X.M. Zhu, Y.K. Pu, N. Balcon and R. Boswell.
Measurement of the electron density in atmospheric-
pressure low-temperature argon discharges by line-
ratio method of optical emission spectroscopy //
J. Phys. D: Appl. Phys. 2009, v. 42, 142003 (5 p.).
Article received 08.04.2013.
ОСОБЕННОСТИ РЕЖИМОВ ГОРЕНИЯ ЕМКОСТНОГО ВЫСОКОЧАСТОТНОГО РАЗРЯДА
С ИЗОЛИРОВАННЫМИ ЭЛЕКТРОДАМИ В АРГОНЕ АТМОСФЕРНОГО ДАВЛЕНИЯ
В.Ю. Баженов, В.В. Циолко, В.М. Пиун, Р.Ю. Чаплинский, А.И. Кузмичев
Экспериментально установлены характеристики горения емкостного высокочастотного разряда с изоли-
рованными электродами в слаботочном (α) и сильноточном (γ) режимах. Показано, что переход из режима α
в режим γ происходит через фазу одновременного существования двух режимов в разных частях разрядного
промежутка.
ОСОБЛИВОСТІ РЕЖИМІВ ГОРІННЯ ЄМНІСНОГО ВИСОКОЧАСТОТНОГО РОЗРЯДУ
З ІЗОЛЬОВАНИМИ ЕЛЕКТРОДАМИ В АРГОНІ АТМОСФЕРНОГО ТИСКУ
В.Ю. Баженов, В.В. Ціолко, В.М. Піун, Р.Ю. Чаплінський, А.І. Кузмічов
Експериментально встановлено характеристики горіння ємнісного високочастотного розряду з ізольова-
ними електродами в аргоні атмосферного тиску в слабострумовому (α) та сильнострумовому (γ) режимах.
Показано, що перехід з режиму α в режим γ відбувається через фазу одночасного існування двох режимів в
різних частинах розрядного проміжку.
|