Anodic electron sheaths in low pressure hollow cathode discharge with large size anode
Researches of the features of “electron” sheath formed between the negative glow plasma and the anode of hollow cathode discharge in oxygen and nitrogen at low pressure are performed. Peculiarities of behavior of spatial distributions of current onto the anode, plasma density and electron temperatur...
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| Date: | 2015 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2015
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| Cite this: | Anodic electron sheaths in low pressure hollow cathode discharge with large size anode / V.Yu. Bazhenov, S.V. Matsevich, V.M. Piun, V.V. Tsiolko // Вопросы атомной науки и техники. — 2015. — № 1. — С. 224-227. — Бібліогр.: 11 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859833941652930560 |
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| author | Bazhenov, V.Yu. Matsevich, S.V. Piun, V.M. Tsiolko, V.V. |
| author_facet | Bazhenov, V.Yu. Matsevich, S.V. Piun, V.M. Tsiolko, V.V. |
| citation_txt | Anodic electron sheaths in low pressure hollow cathode discharge with large size anode / V.Yu. Bazhenov, S.V. Matsevich, V.M. Piun, V.V. Tsiolko // Вопросы атомной науки и техники. — 2015. — № 1. — С. 224-227. — Бібліогр.: 11 назв. — англ. |
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| container_title | Вопросы атомной науки и техники |
| description | Researches of the features of “electron” sheath formed between the negative glow plasma and the anode of hollow cathode discharge in oxygen and nitrogen at low pressure are performed. Peculiarities of behavior of spatial distributions of current onto the anode, plasma density and electron temperature are determined at different gas pressure and discharge current.
Проведены исследования свойств электронного слоя, формирующегося между плазмой отрицательного свечения и анодом разряда с полым катодом в кислороде и азоте низкого давления. Установлены особенности поведения пространственного распределния плотности тока на анод, плотности плазмы и электронной температуры при различных давлениях газов и разрядных токах.
Проведено дослідження властивостей електронного шару, що формується між плазмою негативного світіння та анодом розряду з порожнистим катодом у кисні та азоті низького тиску. Встановлено особливості поведінки просторового розподілу густини струму на анод, густини плазми та електронної температури при різних тисках газів та розрядних струмах.
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| first_indexed | 2025-12-07T15:33:51Z |
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ISSN 1562-6016. ВАНТ. 2015. №1(95)
224 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2015, № 1. Series: Plasma Physics (21), p. 224-227.
ANODIC ELECTRON SHEATHS IN LOW PRESSURE HOLLOW
CATHODE DISCHARGE WITH LARGE SIZE ANODE
V.Yu. Bazhenov, S.V. Matsevich, V.M. Piun, V.V. Tsiolko
Institute of Physics, Kyiv, Ukraine
E-mail: smatsevich@gmail.com
Researches of the features of “electron” sheath formed between the negative glow plasma and the anode of
hollow cathode discharge in oxygen and nitrogen at low pressure are performed. Peculiarities of behavior of spatial
distributions of current onto the anode, plasma density and electron temperature are determined at different gas
pressure and discharge current.
PACS: 52.80.-s, 52.25.Ya
INTRODUCTION
Anodic sheaths, that is, zones in vicinity of positively
charged electrodes are investigated since Langmuir’s
day. Such interest is due to fact that in gas discharges
namely in this zone a transition from axially uniform
and radially non-uniform positive column plasma to
location of electron loss at equipotential anode surface
occurs. Appearance of spatial charge layers (electron,
ion or double, in dependence on the system parameters)
in vicinity of the anode results in considerable influence
on the plasma features in the near-anode zone. In case
of low pressure discharges, anode region properties are
defined, first of all, by non-local kinetics behavior of
electrons [1].
Works devoted to researches of plasma parameters in
the near-anode sheaths can be roughly subdivided into
two groups, one of them dealing with the sheaths near
discharge anode [2-5], and another one – with the
sheaths occurring near positive electrode placed into
preliminarily formed uniform positive column plasma
[6-9]. In spite of certain differences in these systems, in
both cases it is assumed that creation and heating of
”bulk” plasma is performed by electric field, and spatial
profile of electron flow onto the anode/positive
electrode is close to the plasma density profile. Edge
effects at the anode are usually neglected.
Peculiarity of the hollow cathode discharge plasma
consists in fact that main role in its generation and
heating is performed by fast electrons accelerated in the
near-cathode region up to energy of about eUd (Ud is the
discharge voltage), and electric field in the plasma is
small just about 0.01…0.1 eV. Actually, hollow
cathode discharge plasma is the negative glow one.
Typical design of such discharge is cylindrically shaped
cathode with anode placed near one of the ends. At
location far from the anode, electric field of cathode
sheath is perpendicular to the cathode surface (that ism
parallel to the anode plane). Due to fact that, at energy
up to 50…100 eV, electron scattering in elastic
collisions occurs mainly in forward direction, fast
electrons have low chance to come the anode before the
loss of their energy in non-elastic processes. The
situation is complicated in case of acceleration of
secondary electrons emitted from the cathode surface in
vicinity of the anode. In this case, probability of fast
electrons coming to the anode before the loss of major
portion of their energy is considerably higher because:
a) electric field of cathode sheath has a component
directed towards the anode; b) anode may become in the
scattering cone. These effects should be essentially
exhibited in case of the anode size being close to the
cathode diameter.
A general goal of our researches was the study of
features of “electron” sheath formed between the
negative glow plasma of hollow cathode discharge in
oxygen and nitrogen and the discharge anode at
different discharge parameters. Results of the first stage
of these researches are presented in this paper.
1. EXPERIMENT SET-UP AND
MEASUREMENTS
The measurements were performed in the discharge
chamber having 38 cm diameter and 42 cm length,
which simultaneously served as the discharge cathode,
at that the discharge anode having 30.5 cm diameter was
located near back side of the chamber. Chamber was
evacuated down to pressure of about 5 10
-3
Pa, and
after that working gas O2 or N2) was supplied to the
chamber until reaching of predetermined pressure value.
Working gas pressure P in the chamber was varied in
range of 1…16 Pa.
The discharge power supply was provided by DC
source with controlled voltage and current values in
ranges of 400…800 V and 100…600 mA, respectively.
Power introduced in the discharge varied in range of
50…350 W, which corresponded to specific power in
the discharge Wd ≈ 1…7 W/cm
-3
.
The plasma density, electron temperature and electric
field in the plasma were measured using single
Langmuir probes made of a 100 μm tungsten wire with
the collecting length 10…12 mm. The probe
characteristics were measured using the home-made PC-
controlled system [10]. To avoid the effect of
contamination of the probe surface on the probe current-
voltage characteristic, the probes were heated to
≈ 800°C after each measurement.
The plasma potential was determined from the
inflection point of the probe current−voltage
characteristic, and the plasma density was calculated
from a saturation of the electron current to the probe.
Temperature of the plasma electrons was determined
from semi-logarithm dependency of current to the probe
on the voltage.
In [10, 11] it was shown that electron energy
distribution function (EEDF) in the plasma of hollow
ISSN 1562-6016. ВАНТ. 2015. №1(95) 225
cathode discharges in nitrogen and oxygen possesses
essentially non-Maxwellian behavior. In discharges in
N2, there is a significant dip in the EEDF in the energy
range ε = 2…4 eV. The dip is associated with the
vibrational excitation of N2 molecules. In the energy
range of 0.2 < ε < 2 eV, the EEDF is Maxwellian with a
temperature T1 0.2…0.3 eV. In the case of O2 plasma,
the EEDF can be described by two Maxwellian
functions with different temperatures –
T1 0.2…0.3 eV in the energy range 0…2 eV and
T2 3…4 eV at 2 eV. Two-temperature EEDF
behavior in energy range of ≈ 0…10 eV is, first of all, is
due to influence of excitation of metastable states and
vibrational levels of О2. In subsequent considerations
namely “cold” electron temperature T1 in energy range
0…2 eV will be used.
Radial distributions of discharge current onto the
anode were measured by means of 7 mini-collectors,
each having 0.1 cm
2
square, located with 20 mm step at
the anode. Planes of receiving sections of the mini-
collectors were flush with the anode plane.
2. EXPERIMENTAL RESULTS
At the first stage of researches, measurements of
radial dependencies of current density onto anode Ja at
different discharge current values Id were performed
with oxygen use as working gas at 4 and 11 Pa pressure
values (Figs. 1,a,b). At Id variation from 80 to 480 mA,
the discharge voltage Ud grew from 550 up to
700 V, and from 400 up to 500 В at O2 pressure
values 4 and 11 Pa, respectively.
One can see from the figures that: a) behavior of the
dependencies at various О2 pressure values are
essentially different; b) at the same pressure value,
behavior of the dependencies does not change with Id
current variation. At smaller pressure value, radial
dependence of Ja has non-monotonous behavior – Ja
density initially grows up slightly with R increase,
reaches a maximum at R 30 mm, after that decreases
down to minimum value at R 100 mm and, finally,
grows up monotonously till the anode edge. At the same
time, at Р = 11 Pa current density Ja grows up
practically monotonously with R increase at all Id
values. But the most interesting feature consists in fact
that behaviors of these Ja dependencies do not correlate
with radial dependencies of the plasma density ne
inherent to the main part of the discharge plasma
(Fig. 2). Although the plasma density at 4 Pa pressure
decreases monotonously with R increase, current
density Ja exhibits essentially non-monotonous
behavior. Inverted behavior is observed at oxygen
pressure increase up to 11 Pa – non-monotonous one for
radial distribution of ne and monotonous Ja growth with
R increase. Thus it is obvious that in vicinity of anode
deformations of initial distributions of plasma density,
as well as and electric field, occur.
For determining how essential is dependence of this
effect on the gas kind, subsequent set of the
measurements was performed with the use of nitrogen
as working gas at the same values of pressure and
current density, as in the case of oxygen use. One can
see from Fig. 3 that, in spite of certain differences,
behavior of dependencies Ja vs R remains the same –
non-monotonous one al lower pressure value, and
practically monotonous Ja growth with R increase at
P = 14 Pa.
0 40 80 120 160 200
0,0
0,1
0,2
0,3
0,4
0,5
a)
Anode
C
a
th
o
d
e
A
n
o
d
e
c
u
rr
e
n
t
d
e
n
s
it
y
J
a
,
m
A
/c
m
2
R, mm
480 mA
400 mA
3200 mA
2400 mA
1600 mA
80 mA
0 40 80 120 160 200
0,0
0,2
0,4
0,6
0,8
1,0
1,2 b)
C
a
th
o
d
e
Anode
A
n
o
d
e
c
u
rr
e
n
t
d
e
n
s
it
y
J
a
,
m
A
/c
m
2
R, mm
480 mA
400 mA
320 mA
240 mA
160 mA
80 mA)
Fig. 1. Radial dependencies of current onto anode at
different current values Id of the discharge in oxygen:
a) Р = 4 Pa; b) Р = 11 Pa
0 40 80 120 160 200
0,0
0,4
0,8
1,2
1,6
2,0
0,0
0,2
0,4
0,6
0,8
1,0
1,2
A
n
o
d
e
c
u
rr
e
n
t
d
e
n
s
it
y
J
d
,
m
A
/c
m
2
P
la
s
m
a
d
e
n
s
it
y
n
e
*1
0
-1
0
,
c
m
-3
R, mm
Fig. 2. Radial dependencies ne (close points) and Ja
(open points) obtained at close values of current Id.
Dependencies of ne vs R are taken at distance
L = 200 mm from the anode.
-■- P = 4 Pa; -●- P = 11 Pa
a
b
226 ISSN 1562-6016. ВАНТ. 2015. №1(95)
Measurements of radial distribution of the plasma
density far from the anode (L 180 mm) have also
shown absence of correlation of these dependencies
with Ja radial dependencies.
For determining changes of the plasma parameters in
vicinity of anode, measurements of the plasma potential
Up, electron temperature T1 and plasma density were
performed at distances of 7 and 107 mm from the
anode.
The measurements have shown that plasma potential
in the main volume of the plasma is about 5…10 V
lower than the anode potential practically in all studied
regimes of the discharge glow. This value is less than
ionization potentials of O2 and N2 (12.1 and 15.6 eV,
respectively), so that additional gas ionization by the
plasma electrons can be neglected.
0 40 80 120 160 200
0,0
0,2
0,4
0,6
0,8 a)
Anode
C
a
th
o
d
e
A
n
o
d
e
c
u
rr
e
n
t
d
e
n
s
it
y
J
a
,
m
A
/c
m
2
R, mm
480 mA
400 mA
320 mA
240 mA
160 mA
80 mA
0 40 80 120 160 200
0,0
0,2
0,4
0,6
0,8 b)
C
a
th
o
d
e
Anode
A
n
o
d
e
c
u
rr
e
n
t
d
e
n
s
it
y
J
a
,
m
A
/c
m
2
R, mm
480 mA
400 mA
320 mA
240 mA
160 mA
80 mA
Fig. 3. Radial dependencies of current density onto
anode Ja at different current values Id of the discharge
in nitrogen: a) Р = 4 Pa; b) Р = 14 Pa
One can see from Fig. 4 that at 107 mm distance
temperature Т1 generally decreases with R increase, and
by its value corresponds to Т1 in the main plasma
volume [10], whereas at small L abrupt decrease of
temperature T1 is observed. It should be noted once
again that here “cold” electrons with energy in range of
0…2 eV are considered, that is, actually, the electrons
of isotropic section of EEDF. It should be noted that
EEDF in high energy range should be also “distorted” at
the expense of electric field influence in the anode
electron sheath. Accurate EEDF measurements (taking
into account its becoming anisotropic under action of
longitudinal electric field) in this energy range are
required for clarification of nature of the processes
taking place in the near-anode region.
Abrupt T1 decrease at short distance from the anode
can be due to formation of potential well with negative
field in vicinity of the anode [2, 3]. It results in forming
two groups of electrons – trapped and free ones, at that
trapped electrons cooled down to low temperature under
certain conditions.
0 40 80 120 160 200
0,00
0,05
0,10
0,15
0,20
0,25
0,30
C
a
th
o
d
e
Anode
E
le
c
tr
o
n
t
e
rm
p
e
ra
tu
re
T
1
,
e
V
R, mm
L = 107 mm
L = 7 mm
Fig. 4. Radial dependencies of electron temperature Т1
at different distances L from the anode. Nitrogen
pressure Р = 4 Pa, Id = 160 mA
0 40 80 120 160 200
0
1
2
3
4
5
C
a
th
o
d
e
Anode
P
la
s
m
a
d
e
n
s
it
y
n
e
*1
0
-9
,
c
m
-3
R, mm
L = 107 mm
L = 7 mm
Fig. 5. Radial dependencies of plasma density ne at
different distances L from the anode. Nitrogen pressure
Р = 4 Pa, Id = 160 mA
Distribution of cold electron density ne vs R at
L = 7 mm (Fig. 5) exhibits behavior which is similar
enough to that of Ja radial dependence at low values of
the discharge current (see Fig. 3,a), thus also giving an
evidence to essential change of the plasma parameters.
Somewhat unexpected is also difference of ne radial
distribution at L = 107 mm from bell-shaped in central
part of the discharge, which may tell about an influence
of the processes in anode sheath also on “bulk” plasma
parameters.
a
b
ISSN 1562-6016. ВАНТ. 2015. №1(95) 227
Researches of the anode sheath parameters at high
discharge current values, as well as those with the use of
atomic gases, are planned in the future.
CONCLUSIONS
It was determined that at pressure of working gases
of 12…14 Pa, radial distribution of the density of
electron flow to the anode Je was in qualitative
agreement with radial distribution of the plasma density
possessing maxima at mid-values of the chamber radius,
whereas the pressure decrease down to 2…4 Pa
resulted in drastic change of the situation. Although in
this case ne in the main volume of the discharge
monotonously decreased from the system radius
towards the periphery, Je radial distribution exhibited
essentially non-monotonous behavior – at first, it
reached intermediate maximum at certain R value, and
in subsequent, after passing a minimum it grew up
again. The measurements also have shown that similar
behavior near the anode is exhibited as well by the
plasma density. Abrupt cooling of electrons with energy
of 0…2 eV in vicinity of the anode is also determined.
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p. 3025-3031.
3. Yu.B. Golubovskii, V.O. Nekutchaev, and
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8. L. Conde, C. Ferro Fontan, J. Lambas. The transition
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Article received 15.01.2015
АНОДНЫЕ ЭЛЕКТРОННЫЕ СЛОИ В РАЗРЯДЕ НИЗКОГО ДАВЛЕНИЯ С ПОЛЫМ КАТОДОМ
И БОЛЬШИМ АНОДОМ
В. Ю. Баженов, С.В. Мацевич, В.М. Пиун, В.В. Циолко
Проведены исследования свойств электронного слоя, формирующегося между плазмой отрицательного
свечения и анодом разряда с полым катодом в кислороде и азоте низкого давления. Установлены
особенности поведения пространственного распределния плотности тока на анод, плотности плазмы и
электронной температуры при различных давлениях газов и разрядных токах.
АНОДНІ ЕЛЕКТРОННІ ШАРИ В РОЗРЯДІ НИЗЬКОГО ТИСКУ З ПОРОЖНИСТИМ КАТОДОМ
ТА ВЕЛИКИМ АНОДОМ
В.Ю. Баженов, С.В. Мацевич, В.М. Піун, В.В. Ціолко
Проведено дослідження властивостей електронного шару, що формується між плазмою негативного
світіння та анодом розряду з порожнистим катодом у кисні та азоті низького тиску. Встановлено
особливості поведінки просторового розподілу густини струму на анод, густини плазми та електронної
температури при різних тисках газів та розрядних струмах.
|
| id | nasplib_isofts_kiev_ua-123456789-82231 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T15:33:51Z |
| publishDate | 2015 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Bazhenov, V.Yu. Matsevich, S.V. Piun, V.M. Tsiolko, V.V. 2015-05-26T19:04:13Z 2015-05-26T19:04:13Z 2015 Anodic electron sheaths in low pressure hollow cathode discharge with large size anode / V.Yu. Bazhenov, S.V. Matsevich, V.M. Piun, V.V. Tsiolko // Вопросы атомной науки и техники. — 2015. — № 1. — С. 224-227. — Бібліогр.: 11 назв. — англ. 1562-6016 PACS: 52.80.-s, 52.25.Ya https://nasplib.isofts.kiev.ua/handle/123456789/82231 Researches of the features of “electron” sheath formed between the negative glow plasma and the anode of hollow cathode discharge in oxygen and nitrogen at low pressure are performed. Peculiarities of behavior of spatial distributions of current onto the anode, plasma density and electron temperature are determined at different gas pressure and discharge current. Проведены исследования свойств электронного слоя, формирующегося между плазмой отрицательного свечения и анодом разряда с полым катодом в кислороде и азоте низкого давления. Установлены особенности поведения пространственного распределния плотности тока на анод, плотности плазмы и электронной температуры при различных давлениях газов и разрядных токах. Проведено дослідження властивостей електронного шару, що формується між плазмою негативного світіння та анодом розряду з порожнистим катодом у кисні та азоті низького тиску. Встановлено особливості поведінки просторового розподілу густини струму на анод, густини плазми та електронної температури при різних тисках газів та розрядних струмах. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Низкотемпературная плазма и плазменные технологии Anodic electron sheaths in low pressure hollow cathode discharge with large size anode Анодные электронные слои в разряде низкого давления с полым катодом и большим анодом Анодні електронні шари в розряді низького тиску з порожнистим катодом та великим анодом Article published earlier |
| spellingShingle | Anodic electron sheaths in low pressure hollow cathode discharge with large size anode Bazhenov, V.Yu. Matsevich, S.V. Piun, V.M. Tsiolko, V.V. Низкотемпературная плазма и плазменные технологии |
| title | Anodic electron sheaths in low pressure hollow cathode discharge with large size anode |
| title_alt | Анодные электронные слои в разряде низкого давления с полым катодом и большим анодом Анодні електронні шари в розряді низького тиску з порожнистим катодом та великим анодом |
| title_full | Anodic electron sheaths in low pressure hollow cathode discharge with large size anode |
| title_fullStr | Anodic electron sheaths in low pressure hollow cathode discharge with large size anode |
| title_full_unstemmed | Anodic electron sheaths in low pressure hollow cathode discharge with large size anode |
| title_short | Anodic electron sheaths in low pressure hollow cathode discharge with large size anode |
| title_sort | anodic electron sheaths in low pressure hollow cathode discharge with large size anode |
| topic | Низкотемпературная плазма и плазменные технологии |
| topic_facet | Низкотемпературная плазма и плазменные технологии |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/82231 |
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