Generation of compensated ion beams from source with oscillating electrons
The generation of compensated ion beams from electrically unsymmetrical reflecting discharge was investigated. The spatial location of a compensation zone, the optimal values of operating gas pressures Ð = (0,8 ÷ 1)×10⁻⁴ Torr and potential difference between cathodes ΔU = 80Â were determined. The wa...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2000
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| Cite this: | Generation of compensated ion beams from source with oscillating electrons / V.N. Borisko, A.A. Petrushenya, N.N. Yunakov // Вопросы атомной науки и техники. — 2000. — № 3. — С. 93-95. — Бібліогр.: 7 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860247010801614848 |
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| author | Borisko, V.N. Petrushenya, A.A. Yunakov, N.N. |
| author_facet | Borisko, V.N. Petrushenya, A.A. Yunakov, N.N. |
| citation_txt | Generation of compensated ion beams from source with oscillating electrons / V.N. Borisko, A.A. Petrushenya, N.N. Yunakov // Вопросы атомной науки и техники. — 2000. — № 3. — С. 93-95. — Бібліогр.: 7 назв. — англ. |
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| description | The generation of compensated ion beams from electrically unsymmetrical reflecting discharge was investigated. The spatial location of a compensation zone, the optimal values of operating gas pressures Ð = (0,8 ÷ 1)×10⁻⁴ Torr and potential difference between cathodes ΔU = 80Â were determined. The way to control the current compensation degree of the extracted ion beam from a several to 100% was found.
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Problems of Atomic Science and Technology. 2000. N 3. Series: Plasma Physics (5). p. 93-95 93
UDC 533.9
GENERATION OF COMPENSATED ION BEAMS
FROM SOURCE WITH OSCILLATING ELECTRONS
V.N. Borisko, A.A. Petrushenya, N.N. Yunakov.
Kharkov National University, Department of Physics and Technical,
61108, 31 Kurchatov Ave., Kharkov, Ukraine
The generation of compensated ion beams from electrically unsymmetrical reflecting discharge was
investigated. The spatial location of a compensation zone, the optimal values of operating gas pressures
Ð = (0,8 ÷ 1)⋅10-4 Torr and potential difference between cathodes ∆U = 80Â were determined. The way to
control the current compensation degree of the extracted ion beam from a several to 100% was found.
Introduction
The ion beam compensation problem arises during
the ion beam treatment of dielectrical or solitary
conductive surfaces under the condition of high
vacuum. The necessity of neutralization both the ion
space charge and total current of an ion beam is
responsible for two undesirable effects. One of them is
the influence of the local electrical fields created by the
uncompensated space charge of an ion beam. The other
is the high stationary potential of a treated surface,
which is set with equality of the total currents of
charged particles incoming to the surface and leaving
one. If the ion beam compensation is not realized these
effects result in limitation of an extractable ion current,
sufficient deceleration of ions and cessation of their
inflow on a treated surface.
At the pressure when the gas neutralizaton is not
effective [1] the ion beam compensation is realised by
injection of opposite sign charged particles in the beam.
Usually, the electrons produced by heated emitters
placed on the ion beam path are used as a compensating
component [2]. However, the using of heated emitters
sets the limitation on the lifetime of such devices and
does not permit to apply them during the operation with
chemically active working substances. Therefore, the
ion sources, which have not the heated emitters, are
very promising for generation of compensated ion
beams.
In present paper the results of experimental
investigation of compensated ion beam generation from
plasma of the electrically unsymmetrical reflective
discharge are presented. The experiments were
performed in the high-voltage regime of discharge
burning [3]. In this regime the excitation of intensive
high-frequency oscillations in the anode layer are
accompanied by generation of the electrons with
anomalously high energy [4-5]. In this cause under
certain external parameters of discharge burning the
current compensation of the extracted ion beam was
observed [6]. However, the main disadvantages of
compensated beams obtained in such way were the low
intensity of extracted ion current and high spatial
inhomogeneity of compensation degree in the beam.
The use of an electrically unsymmetrical reflective
discharge permits sufficiently to increase the intensity
of extracted beams of charged particles [7]. The
perspectives of application of the ion sources based on
such discharge for the surface treatment are connected
with resolving of the ion beam compensation problem.
Techniques and experimental results
The experiments were performed on a penning
discharge set-up as schematically shown in Fig. 1. The
electrode system consisted of a cylindrical anode 4 and
cathode 5 with 8 cm and 4 cm in length, respectively, as
well as a flat cathode 3 were placed in vacuum chamber
1. The each of electrodes was 8 cm in diameter. The
interelectrode clearances between anode and cathodes
were 4 cm. The flat cathode 3 was made of a duralumin,
but the cylindrical electrodes were stainless steel. The
highvoltage power pack 8 supplied the discharge current
up to 300 mA at the anode voltage up to 10 kV. The
magnetic system 2 created the uniform magnetic field
with intensity up to 1 kOe. The inhomogeneity of the
magnetic field along system axis did not exceed 2%.
Fig. 1 Experimental installation diagram.
1 - vacuum chamber; 2 - magnetic system; 3, 5 -
cathode; 4 - anode; 6 - collector; 7 - power pack; 8 -
highvoltage power pack; 9, 10, 11, 12 - milliamper-
meters; 13 - thermocouple manometric converter; 14 -
ionization manometric converter; 15 - evacuation; 16 -
leak-in.
In run of experiments the cylindrical cathode 5 was
grounded, but the potential of the flat cathode 3 was
varied in range of Uc1 = (-400 ÷ +400) V. The electrical
unsymmetry in the system was created by the potential
difference between cathodes ∆U = Uc1 – Uc2 , where Uc1
is the potential of cathode 3, Uc2 is the potential of
cathode 5. The base pressure of vacuum chamber was
about 5⋅10-6 Torr.
94
The investigations were carried out in the stationary
discharge burning regime at the pressure of working gas
(nitrogen, oxygen, argon) Ð = (0,1 ÷ 1)⋅10-4 Torr, at the
intensity of external magnetic field Í = (0,1 ÷ 1) kOe,
anode voltage Uà = (0,5 ÷ 3,5) kV and discharge
currents I = (0,1 ÷ 100) mA. The plasma density
ne ∼ (1 ÷ 10)⋅109 cm-3 and the electron temperature
Òå ∼ (20 ÷ 60) eV were determined by probe techniques.
The total current of the charged particles extracted from
side of cylindrical cathode 5 was measured by movable
flat copper collector 6. The charged particles beams
were extracted from discharge along system axis. The
radial distribution of the current density and energy of
charged particles were investigated by Faraday cylinder
and multigrid electrostatic analizer.
In order to determine the range of operating gas
pressures which are most optimal for generation of
compensated beams, it was studied the dependence of
current densities of extracted charged particles on
working gas pressure at ∆U = 0 V, Í = 600 Oe and
Ua = 1,5 kV (Fig. 2). As can be seen from Fig. 2, the
generation of compensated ion beams was observed at
the working gas pressure Ð < 10-4 Torr. When Ð >
10-4 Torr the discharge was passed into the low voltage
regime of discharge burning. In this cause the anode
voltage was reduced up to Ua = (0,7 ÷ 0,8) kV, but the
discharge current was increased sufficiently.
Fig. 2. Dependencies of ion current density (1),
electron current density (2) and discharge cyrrent (3) on
the working gas pressure.
Ua = 1,5 kV, Í = 600 Oe, ∆U = 0 V.
At the working gas pressures in range of 2⋅10-5 Torr to
7⋅10-5 Torr, the large radial inhomogeneity of current
densities of charged particle beams was observed.
Whereas, at Ð = (8 ÷ 10)⋅10-5 Torr this inhomogeneity
was decreased significantly, as seen from Fig. 3.
Also, the dependencies of current densities and
energy spectrums of extracted charged particles on the
potential difference between cathodes ∆U were
investigated. The flows of charged particle to the
discharge electrodes were studied simultaneously. The
dependencies obtained are shown in Fig. 4 - 6. As can
be seen from Fig. 4, the values of ion beam density and
currents on discharge electrodes peeks at ∆U = 80V.
Fig. 3. Radial distribution of ion (1,3) and electron (3,4)
current densities at the distance 1 cm from internal edge
of cylindrical cathode 5. (Ra is anode radius).
Ua = 1,5 kV, Í = 600 Oe.
1, 2 - Ð = 9⋅10-5 Torr, ∆ U = 80 V.
3, 4 - Ð = 4⋅10-5 Torr, ∆U = 0 V;
In this cause, the current compensation region of an ion
beam was located at the distance 1 cm from internal end
of the cylindrical cathode 5. With increasing of ∆U
from 80 V to 300 V the current compensation degree of
an ion beam was decreased up to a several percents at
the same region, but the compensation zone was
removed from cathode. At ∆U < 0 V, the electron
current density exceeded the ion current density
sufficiently. The energy spectrums of extracted ions
were obtained with ∆U = 80V which is a most optimal
for compensated beam generation. In the ion energy
distribution the two peaks with the most probable
energies of 0,4 kV and 1 kV were observed, as shown
in Fig. 5. These energies corresponded to the values of
plasma potentials in the central discharge region on axis
and anode layer, respectively. In the energy distribution
of beam electrons the two electron group were observed
at ∆U < 0Â, as shown in Fig. 6 (curve 2). The most
probable energy of the high-energy electron component
corresponded to the value of a potential difference
between cathodes ∆U. At ∆U > 0 V only one group of
electrons with the most probable energy of about a
several electronvolts was observed (curve 1).
Fig. 4. Dependencies of current densities of electron
beam (1) and ion beam (2), discharge current (3),
charged particle currents to the flat (4) and cylindrical
(5) cathodes on a potential difference between cathodes
∆U. Ua = 1,5 kV, Í = 600 Oe, Ð = 9⋅10-5 Torr.
-400 -300 -200 -100 0 100 200 300 400
0
10
20
30
40
50
0
10
20
30
40
50
5
∆
50
100
150
U, V
200
250
J,m
kA
/cm
2
4
3
2
1
I,
m
A
0 ,00 0 ,25 0 ,50 0 ,75 1 ,00
0 ,00
0 ,05
0 ,10
0 ,15
0 ,20
0 ,25
0 ,70
3
4
1
2
J,
m
A
/c
m
2
R/Ra
2 4 6 8 10 12
0
100
200
300
400
0
100
200
300
400
3
2
1 I, m
A
J,
m
kA
/c
m
2
P , 1 0 - 5Torr
95
Fig. 5. Ion energy distribution.
Ua = 1,5 kV, Í = 600 Oe, ∆U = 80 V, Ð = 9⋅10-5 Torr.
Fig. 6. Electron energy distribution.
Ua = 1,5 kV, Í = 600 Oe, Ð = 9⋅10-5 Torr.
1 - ∆U = 80 V, 2 - ∆U = -150 V.
The optimal location of a treated surface was
determined with help of the flat collector 6. As seen
from Fig. 7, at ∆U = 80 V both the total current of
charged particles to the collector (curve 1) and the
floating potential of collector (curve 2) become zero at
the distance 1 cm from internal end of cylindrical
cathode 5. In this region the radial inhomogeneity of
current compensation degree of an ion beam did not
exceed 5% ÷ 10%. The removing of the collector from
cathode 5 was resulted in increasing the negative values
of current to the collector and its floating potential. It
seems this behavior is responsible for the large radial
component of an ion velocity. Consequently, the ions
leaves the beam, when collector is removed from
cathode. The current efficiency of the ion source with
the optimal value ∆U = 80 V was 10% - 15%.
Fig. 7. Distribution of current to collector (1) and
floating potential of collector (2) along system axis.
Ua = 1,5 kV, Í = 600 Oe, ∆U = 80 V, Ð = 9⋅10-5 Torr.
Conclusions
The possibility of compensated ion beam generation
from electrically unsymmetrical source with oscillating
electrons was experimentally investigated.
The spatial location of ion beam compensation
region, optimal values of operating pressures and
potential difference between cathodes were determined.
The way to control the degree of current
compensation of the ion beam by varying a potential
difference between cathodes was found.
References
1. M.D. Gabovich. Compensated ion beams // J. of
Tech. Phys., 1979, vol.24, ¹2 , p.257-273.
2. V.F. Virchenko, M.D. Gabovich et al. Investigation
of synthesized plasma obtained by neutralization of
ion beam by electrons injected through the ion source
// J. of Tech. Phys., 1974, vol.44, ¹11, p.2296–2301.
3. E.M. Reyhrudel, G.V. Smirnitskaya and G.A.
Yegizaryan. State diagrams of discharge with
oscillating electrons // J. of Tech. Phys., 1973,
vol.XLIII, ¹1, p.130-135.
4. Y.Y. Krendel. Plasma sources of electrons. Ì .:
“Atomizdat”, 1977, p.40.
5. N.A. Kervalishvily. Formation and evolution of
electron vortex in charged plasma in crossed Å⊥ Í
fields // Preprint IF, Tbilisi, 1988, p.20.
6. V.N. Borisko, A.A. Petrushenya, M.V. Sosipatrov.
Technological plasma source of electrons // VANT,
Kharkov, 1999, Issue 2(10), p.15-20.
7. V.N. Borisko, A.V. Maslov, A.A. Petrushenya, I.A.
Ruday. Modified plasma source of electrons //
VISNYK KhNU, ¹469, physical series “Nuclei,
particles, fields”, 2000, Issue 1(9), p.86-88.
0,0 0,5 1,0 1,5
0
1
2
3
4
5
dI
/d
U
E, keV
0 50 100 150 200 250
0
1
2
3
2
1
dI
/d
U
E, eV
2 4 6 8 10
-5,0
-2,5
0,0
2,5
-5,0
-2,5
0,0
2,5
U
, V
I,
m
A
2
1
0
-100
-50
50
Cathode
Z, cm
|
| id | nasplib_isofts_kiev_ua-123456789-82374 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T18:38:13Z |
| publishDate | 2000 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Borisko, V.N. Petrushenya, A.A. Yunakov, N.N. 2015-05-29T07:24:09Z 2015-05-29T07:24:09Z 2000 Generation of compensated ion beams from source with oscillating electrons / V.N. Borisko, A.A. Petrushenya, N.N. Yunakov // Вопросы атомной науки и техники. — 2000. — № 3. — С. 93-95. — Бібліогр.: 7 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/82374 533.9 The generation of compensated ion beams from electrically unsymmetrical reflecting discharge was investigated. The spatial location of a compensation zone, the optimal values of operating gas pressures Ð = (0,8 ÷ 1)×10⁻⁴ Torr and potential difference between cathodes ΔU = 80Â were determined. The way to control the current compensation degree of the extracted ion beam from a several to 100% was found. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Рlasma Dynamics and Plasma-Wall Interaction Generation of compensated ion beams from source with oscillating electrons Article published earlier |
| spellingShingle | Generation of compensated ion beams from source with oscillating electrons Borisko, V.N. Petrushenya, A.A. Yunakov, N.N. Рlasma Dynamics and Plasma-Wall Interaction |
| title | Generation of compensated ion beams from source with oscillating electrons |
| title_full | Generation of compensated ion beams from source with oscillating electrons |
| title_fullStr | Generation of compensated ion beams from source with oscillating electrons |
| title_full_unstemmed | Generation of compensated ion beams from source with oscillating electrons |
| title_short | Generation of compensated ion beams from source with oscillating electrons |
| title_sort | generation of compensated ion beams from source with oscillating electrons |
| topic | Рlasma Dynamics and Plasma-Wall Interaction |
| topic_facet | Рlasma Dynamics and Plasma-Wall Interaction |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/82374 |
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