Influence of gas mixture with various mass numbers of gases on operation pressure range of plasma electron source with hollow cathode
The influence of electric nonsymmetry in plasma electron source with hollow cathode as well as gas mixture with various mass numbers of gases on performances of the source was investigated. The operating pressure ranges for various working gases were determined. The intensive low-energy electron bea...
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| Дата: | 2002 |
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| Формат: | Стаття |
| Мова: | English |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2002
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| Назва видання: | Вопросы атомной науки и техники |
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| Цитувати: | Influence of gas mixture with various mass numbers of gases on operation pressure range of plasma electron source with hollow cathode / V.N. Borisko, А.А. Petrushenya // Вопросы атомной науки и техники. — 2002. — № 4. — С. 179-181. — Бібліогр.: 5 назв. — англ. |
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irk-123456789-802962016-04-15T13:22:18Z Influence of gas mixture with various mass numbers of gases on operation pressure range of plasma electron source with hollow cathode Borisko, V.N. Petrushenya, A.A. Low temperature plasma and plasma technologies The influence of electric nonsymmetry in plasma electron source with hollow cathode as well as gas mixture with various mass numbers of gases on performances of the source was investigated. The operating pressure ranges for various working gases were determined. The intensive low-energy electron beams were obtained in fore-vacuum working pressure range at relatively low extraction potentials. 2002 Article Influence of gas mixture with various mass numbers of gases on operation pressure range of plasma electron source with hollow cathode / V.N. Borisko, А.А. Petrushenya // Вопросы атомной науки и техники. — 2002. — № 4. — С. 179-181. — Бібліогр.: 5 назв. — англ. 1562-6016 PACS: 52.50.Dg http://dspace.nbuv.gov.ua/handle/123456789/80296 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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English |
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Low temperature plasma and plasma technologies Low temperature plasma and plasma technologies |
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Low temperature plasma and plasma technologies Low temperature plasma and plasma technologies Borisko, V.N. Petrushenya, A.A. Influence of gas mixture with various mass numbers of gases on operation pressure range of plasma electron source with hollow cathode Вопросы атомной науки и техники |
| description |
The influence of electric nonsymmetry in plasma electron source with hollow cathode as well as gas mixture with various mass numbers of gases on performances of the source was investigated. The operating pressure ranges for various working gases were determined. The intensive low-energy electron beams were obtained in fore-vacuum working pressure range at relatively low extraction potentials. |
| format |
Article |
| author |
Borisko, V.N. Petrushenya, A.A. |
| author_facet |
Borisko, V.N. Petrushenya, A.A. |
| author_sort |
Borisko, V.N. |
| title |
Influence of gas mixture with various mass numbers of gases on operation pressure range of plasma electron source with hollow cathode |
| title_short |
Influence of gas mixture with various mass numbers of gases on operation pressure range of plasma electron source with hollow cathode |
| title_full |
Influence of gas mixture with various mass numbers of gases on operation pressure range of plasma electron source with hollow cathode |
| title_fullStr |
Influence of gas mixture with various mass numbers of gases on operation pressure range of plasma electron source with hollow cathode |
| title_full_unstemmed |
Influence of gas mixture with various mass numbers of gases on operation pressure range of plasma electron source with hollow cathode |
| title_sort |
influence of gas mixture with various mass numbers of gases on operation pressure range of plasma electron source with hollow cathode |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2002 |
| topic_facet |
Low temperature plasma and plasma technologies |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/80296 |
| citation_txt |
Influence of gas mixture with various mass numbers of gases on operation pressure range of plasma electron source with hollow cathode / V.N. Borisko, А.А. Petrushenya // Вопросы атомной науки и техники. — 2002. — № 4. — С. 179-181. — Бібліогр.: 5 назв. — англ. |
| series |
Вопросы атомной науки и техники |
| work_keys_str_mv |
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| first_indexed |
2025-07-06T04:15:48Z |
| last_indexed |
2025-07-06T04:15:48Z |
| _version_ |
1836869588761968640 |
| fulltext |
INFLUENCE OF GAS MIXTURE WITH VARIOUS MASS
NUMBERS OF GASES ON OPERATION PRESSURE RANGE OF
PLASMA ELECTRON SOURCE WITH HOLLOW CATHODE
V.N. Borisko, А.А. Petrushenya
Kharkov National University, Department of Physics and Technology,
31 Kurchatov Ave., 61108, Kharkov, Ukraine
E-mail:Borisko@pht.univer.kharkov.ua
The influence of electric nonsymmetry in plasma electron source with hollow cathode as well as gas mixture
with various mass numbers of gases on performances of the source was investigated. The operating pressure ranges
for various working gases were determined. The intensive low-energy electron beams were obtained in fore-vacuum
working pressure range at relatively low extraction potentials.
PACS: 52.50.Dg
INTRODUCTION
At present effective electron sources operating at
fore-vacuum pressures [1, 2] are required for a row of
technological processes, such as annealing and melting
of materials, treatment of surfaces etc [2, 3]. For these
purposes it are widely used the plasma electron sources
on basis of reflective discharge with hollow cathode.
However, such sources effectively operates only using
of high extraction potentials owing to existence of the
potential barrier for electrons between emitting plasma
and extraction electrodes. Moreover, increased working
gas pressure in accelerating gap results in reduction of
the breakdown strength of accelerating gap [1, 2] that
complicates the application of such sources at fore-va-
cuum pressures. Therefore, the perspectives of their use
are connected with extension of the operating pressure
range and providing of the needed current and power ef-
ficiencies at relatively low extraction potentials.
In the present paper, we suggested to use the
mixture with light and heavy gases, such as argon and
hydrogen, as well as the electric nonsymmetry between
reflective cathodes to extend the operating characteristic
of the plasma electron sources on basis of reflective dis-
charge with hollow cathode.
SOURCE CONSTRUCTION
The construction of the plasma electron source on
basis of penning cell with hollow uncooled cathode is
schematically shown in Fig.1. The electrode system
consisted of hollow cathode 1, reflective cathode 2, cyl-
indrical anode 3, extraction electrode 4 and collector 5.
The anode was 18 mm in inner diameters and 18 mm in
length. The hollow cathode cavity diameter and length
were 4,7 mm and 35 mm, respectively. The hollow cath-
ode 1 and the reflective cathode 2 were made of graph-
ite, but the anode 3 was stainless steel. The interelec-
trode clearances between cathodes and anode were
9 mm each. The electrode system was placed in the uni-
form axial magnetic field.
The electron beam was extracted from discharge in
axial direction from emissive orifice of the cathode 2,
which was 3,5 mm in diameter. The extraction voltage
Uext = (0 ÷ 600) V was applied between the cathode 2
and the extraction electrode 4, but the collector potential
was about extraction voltage.
To increase the electron extraction efficiency of the
source the electric nonsymmetry was created between
cathodes [4]. In run of experiments it were used both the
symmetric and nonsymmetric electric circuits connect-
ing the cathodes. In the first case both cathodes were
grounded. In the other case, the cathode 2 was groun-
ded, but the potential of the hollow cathode 1 was var-
ied in range of UC1 = (0 ÷ −600) V. The electric non-
symmetry was created by the potential difference
between cathodes dU = UC1 – UC2, where UC1 is the po-
tential of the cathode 1, but UC2 is the potential of the
cathode 2. The anode was always under positive poten-
tial.
The base pressure of vacuum chamber was about 4⋅
10−6 Torr.
Fig. 1. Plasma electron source diagram.
1 - hollow cathode, 2– reflective cathode, 3 – anode,
4 - extraction electrode, 5 – collector, 6, 7, 8, 9 - power
supplies.
EXPERIMENTAL METHODS AND OPER-
ATING CONDITIONS
The investigation were carried out in a stationary
discharge burning regime at operating pressures
Р = (0,01 ÷ 4)⋅10−2 Torr, at magnetic induction
B = (0,01 ÷ 0,1) T , at anode voltages Ua = (0 ÷ 4) kV
and anode currents Ia = (0 ÷ 0,9) А. The plasma density
no ∼ (0,1 ÷ 2)⋅1011 cm−3 and the electron temperature
Problems of Atomic Science and Technology. 2002. № 4. Series: Plasma Physics (7). P. 179-181 179
R
Z
С
dU Uа mА
mА mА mА
+
_
1 3 2 4 5
Leak-in
+
_
+
_
B
6 7
8
9
Uext
0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6
0
100
200
300
400
500
600
700
800
ar
go
n
hy
dr
og
en
ar
go
n
- h
yd
ro
ge
n
m
ix
tu
re
I a, m
A
Uа, kV
10-4 2 3 4 5 6 7 8 9 10-3 11 12 13 14 15 16 17 18 10-2
0
50
100
150
200
250
300
350
400
argon
argon - hydrogen mixture
hydrogen
2 3 4 5 6 7 8 9
I a, m
A
Р, Torr.
Те ∼ (1 ÷ 4) eV in emitting region were determined by
probe techniques. Collector 5 measured the total extrac-
ted electron current. The retardation curves of extracted
electrons were obtained by using a multigrid electrostat-
ic analyzer.
Argon, clear hydrogen and argon-hydrogen mixture
were used as working gases. The working gases, such as
argon and hydrogen, flowed into the hollow cathode.
When the source was operated with the gas mixture, ar-
gon and hydrogen flowed into the hollow cathode via
gas mixer. The working gas flow rate was varied in rang
of vflow = (0,1 ÷ 1,1) Atm⋅cm3⋅c-1.
EXPERIMENTAL RESULTS
The reflective discharge initiated a discharge burn-
ing regime with hollow cathode. The high voltage dis-
charge burning regime with growing volt-ampere char-
acteristic was realized at low discharge currents (Fig.2).
The initiation of the hollow cathode burning regime was
accompanied by increase of the discharge current and
reduce of the anode voltage. These changes of discharge
burning regimes are marked in Fig.2 by dotted lines. For
hydrogen the initiation currents Ia ∼ (250 ÷ 550) mA
were significantly higher, but the discharge voltages
Ua = (0,3 ÷ 0,4) kV were lower, than their values for ar-
gon (Ia ∼ (50 ÷ 180) мA, Ua = (0,55 ÷ 0,8) kV). For ar-
gon-hydrogen mixture the initiation currents
(Ia ∼ (40 ÷ 200) мA) corresponded to those for argon, as
to the discharge voltages (Ua = (0,3 ÷ 0,4) kV) for same
mixture they corresponded to those for hydrogen.
When hydrogen was used the initiation of the hollow
cathode discharge burning regime was observed under a
higher operating pressure (Рo > 3⋅10−3 Torr), then for ar-
gon and argon-hydrogen mixture (Рo > 10−4 Torr), as
seen from Fig.3.
Fig.2. Volt-ampere characteristics of the plasma elec-
tron source. H = 600 Oe, dU = 0 V, Uext ∼ 400 V.
Working gas - hydrogen.
P = 10−2 Torr, v flow = 1,1 Atm⋅cm3/c.
Working gas - argon.
P = 10−3 Torr, v flow = 0,5 Atm⋅сm3/c.
Working gas – argon - hydrogen mixture.
Р = 10−3 Torr,
hydrogen - v flow = (0,7 ÷ 0,8) Atm⋅сm3/c,
argon - v flow = (0,3 ÷ 0,4) Atm⋅сm3/c.
Such behaviour of a reflective discharge is responsible
for peculiarities of existence of high-current discharge
burning regime at various working pressures, anode
voltages and working gas sorts [3, 5].
Upper bound of the operating pressure range was de-
termined by appearing the electrical breakdown of the
accelerating gap. The electrical breakdown was oc-
curred at the operating pressures: Рmax > 4⋅10−3 Torr for
argon, Рmax > 3⋅10−2 Torr for hydrogen and Рmax > 1,5⋅10−
2 Torr for argon-hydrogen mixture. The operating pres-
sure ranges for various working gases are shown in
Fig.3 by arrows.
Fig.3. Dependencies of initiating current values Ia on a
working gas pressure P. H = 600 Oe, dU = 0 V,
Uext ∼ 400 V.
Working gas - hydrogen.
v flow = 1,1 Atm⋅cm3/c.
Working gas - argon.
v flow = 0,5 Atm⋅сm3/c.
Working gas – argon - hydrogen mixture.
Hydrogen – v flow = (0,7 ÷ 0,8) Atm⋅сm3/c,
argon – v flow = (0,3 ÷ 0,4) Atm⋅сm3/c.
The main disadvantages of application of clear gases
were the restriction of the operating pressure for argon
because of electrical breakdown of accelerating gap and
the impossibility to operate at low working pressures
and discharge currents for hydrogen. The application of
argon-hydrogen mixture allowed to extend the operating
characteristics of the source at the expense of reduce of
discharge currents and voltages, as well as extension of
operating pressure range.
The electric nonsymmetry in the discharge resulted
in significant increase of the extracted electron currents
and the power efficiency of the source for all working
gas sorts. The dependencies of the extracted electron
current Ibeam on a potential difference dU between cath-
odes is shown in Fig.4. At an operation with hydrogen,
the power efficiency of the source and the extracted
electron current reached of Н = 0,77 mА/W and
Ibeam = 250 mA, respectively, at dU = -100 V. At dU <
-100 V it was observed disruption of a hollow cathode
regime. In this case, the anode voltage increased, but
the anode current decreased abruptly.
180
Fig.4. Dependencies of extracted electron currents Ibeam
on a potential difference between cathodes dU.
Uext ∼ 400 V.
Working gas - hydrogen.
P = 10−2 Torr, Ia = 800 mA, H = 800 Oe,
v flow = 1,1 Atm⋅cm3/c.
Working gas - argon.
P = 10−3 Torr, Ia = 300 mA, H = 600 Oe,
v flow = 0,5 Atm⋅сm3/c.
Working gas – argon-hydrogen mixture.
Р = 10−3 Torr, Ia = 300 mA, H = 600 Oe,
hydrogen – v flow = (0,7 ÷ 0,8) Atm⋅сm3/c,
argon – v flow = (0,3 ÷ 0,4) Atm⋅сm3/c.
For argon the power efficiency and the extracted
electron current were Н = 0,43 mА/W and I = 145 mА,
respectively at dU = -600 V.
For argon-hydrogen mixture their values
(Н = 1 mА/W, Ibeam = 460 mA) at dU = −500 V, were a
higher, than for clear gases. However, further increase
of the extracted electron current was impossible without
forced cooling of constructive elements of the source.
When the electric nonsymmetry was used, the
amount of change of the extracted electron current cor-
responded to change of the hollow cathode current for
all working gas sorts. Besides, the extraction of elec-
trons was effective at relatively low extraction poten-
tials Uext. As can been seen from Fig.5 (curve 1), with
increasing Uext, the electron emission rises and at
Uext > 100 V the extracted electron current is saturated.
In this case, the beam energy was about 15 eV in all
range of operating pressures (Fig.5, curves 2, 3).
CONCLUSIONS
As a result of performed experiments it was shown,
that the electric nonsymmetry in plasma source of given
type resulted in increase of the electron stream incoming
into discharge from hollow cathode cavity.
Fig.5. Dependence of extracted electron current on an
extraction potential (1) and retardation curves of ex-
tracted electrons (2, 3).
Working gas – argon-hydrogen mixture.
Р = 10−3 Torr, H = 600 Oe,
hydrogen – v flow = (0,7 ÷ 0,8) Atm⋅сm3/c,
argon – v flow = (0,3 ÷ 0,4) Atm⋅сm3/c.
1 – Р = 10−3 Torr, Ia = 300 mA, dU = -400 V,
2 – Р = 10−3 Torr, Ibeam = 100 mA, dU = -440 V,
Uext = 300 V.
3 – Р = 10−2 Torr, Ibeam = 100 mA, dU = -270 V,
Uext = 300 V.
This provides the high electron extraction efficiency at
relatively low extraction potentials. The application of
argon-hydrogen mixture permits to extend the operation
pressures in fore-vacuum range at conservation of elec-
tron beam performances.
The obtained experimental results can be used for
create of new technological plasma electron sources
with high performances.
REFERENCES
1. Yu.А. Burachevskiy, V.А. Burdovitsin, A.V. Mit-
nikov, Ye.M. Oks. Journal of technical physics,
2001, Vol.71, No.2, p.48-50.
2. V.А. Burdovitsin, M.N. Kuzmechenko, Ye.M. Oks.
Journal of technical physics, 2002, Vol.72, No.7,
p.134-136.
3. Yu.Ye. Krendel. Plasma electron sources. M.: Ener-
goatomizdat, 1977.
4. V.N. Borisko, A.A. Petrushenya. The Journal of
Kharkov National University, No.559, physical
series «Nuclear, Particles, Fields», Issue 2/18/
2002, p.67-71.
5. E.M. Reiyhrudel, G.V. Smirnitskay, G.A. Yegiz-
aryan. Journal of technical physics, 1973,
Vol.XLIII, No.1, p.130-135.
Problems of Atomic Science and Technology. 2002. № 4. Series: Plasma Physics (7). P. 179-181 181
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argon - hydrogen mixture
I be
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INFLUENCE OF GAS MIXTURE WITH VARIOUS MASS
NUMBERS OF GASES ON OPERATION PRESSURE RANGE OF
PLASMA ELECTRON SOURCE WITH HOLLOW CATHODE
V.N. Borisko, А.А. Petrushenya
The influence of electric nonsymmetry in plasma electron source with hollow cathode as well as gas mixture with various mass numbers of gases on performances of the source was investigated. The operating pressure ranges for various working gases were determined. The intensive low-energy electron beams were obtained in fore-vacuum working pressure range at relatively low extraction potentials.
PACS: 52.50.Dg
INTRODUCTION
EXPERIMENTAL METHODS AND OPERATING CONDITIONS
|