The magnetic field effect on electron beam generation in magnetron injection guns with secondary-emission cathodes
Magnetron guns with secondary-emission cathodes appear promising for the use as electron sources in high-power microwave devices [1, 2]. For stable beam generation, the magnetic field in the gun is calculated to be between 0.5 to 5 kG, depending on the cathode voltage amplitude and the gun dimension...
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| Published in: | Вопросы атомной науки и техники |
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| Date: | 1999 |
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| Language: | English |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
1999
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| Cite this: | The magnetic field effect on electron beam generation in magnetron injection guns with secondary-emission cathodes / A.N. Dovbnya, V.V. Zakutin, N.G. Reshetnyak, V.P. Romas’ko, A.M. Bovda, O.M. Utva, V.F. Pokas, L.V. Jeran, M.A. Krasnogolovets, Yu.Ya. Volkolupov // Вопросы атомной науки и техники. — 1999. — № 4. — С. 34-35. — Бібліогр.: 4 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859475656494022656 |
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| author | Dovbnya, A.N. Zakutin, V.V. Reshetnyak, N.G. Romas’ko, V.P. Bovda, A.M. Utva, O.M. Pokas, V.F. Jeran, L.V. Krasnogolovets, M.A. Volkolupov, Yu.Ya. |
| author_facet | Dovbnya, A.N. Zakutin, V.V. Reshetnyak, N.G. Romas’ko, V.P. Bovda, A.M. Utva, O.M. Pokas, V.F. Jeran, L.V. Krasnogolovets, M.A. Volkolupov, Yu.Ya. |
| citation_txt | The magnetic field effect on electron beam generation in magnetron injection guns with secondary-emission cathodes / A.N. Dovbnya, V.V. Zakutin, N.G. Reshetnyak, V.P. Romas’ko, A.M. Bovda, O.M. Utva, V.F. Pokas, L.V. Jeran, M.A. Krasnogolovets, Yu.Ya. Volkolupov // Вопросы атомной науки и техники. — 1999. — № 4. — С. 34-35. — Бібліогр.: 4 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | Magnetron guns with secondary-emission cathodes appear promising for the use as electron sources in high-power microwave devices [1, 2]. For stable beam generation, the magnetic field in the gun is calculated to be between 0.5 to 5 kG, depending on the cathode voltage amplitude and the gun dimensions. On the other hand, the beam transport in the resonance system of the microwave device also calls for rather high magnetic fields. The generation of these fields of significant extent to produce and transport the beam is a rather grave problem. It is generally solved by using water-cooled solenoids [3], that gives rise to considerable difficulties. In recent years, constant magnets have been used [3] to generate extended solenoidal magnetic fields. So, it was of interest to investigate both the generation of such fields and their effect on beam production and parameters in the magnetron gun.
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| first_indexed | 2025-11-24T11:41:45Z |
| format | Article |
| fulltext |
THE MAGNETIC FIELD EFFECT ON ELECTRON BEAM
GENERATION IN MAGNETRON INJECTION GUNS WITH
SECONDARY-EMISSION CATHODES
A.N.Dovbnya, V.V. Zakutin, N.G. Reshetnyak, V.P. Romas’ko, A.M. Bovda, O.M. Utva,
V.F.Pokas, L.V.Jeran, M.A. Krasnogolovets*, Yu.Ya. Volkolupov*
NSC KIPT, Kharkov, Ukraine; *Kharkov State University for Radioelectronics, Kharkov,
Ukraine
Magnetron guns with secondary-emission
cathodes appear promising for the use as electron
sources in high-power microwave devices [1, 2]. For
stable beam generation, the magnetic field in the gun is
calculated to be between 0.5 to 5 kG, depending on the
cathode voltage amplitude and the gun dimensions. On
the other hand, the beam transport in the resonance
system of the microwave device also calls for rather
high magnetic fields. The generation of these fields of
significant extent to produce and transport the beam is a
rather grave problem. It is generally solved by using
water-cooled solenoids [3], that gives rise to
considerable difficulties. In recent years, constant
magnets have been used [3] to generate extended
solenoidal magnetic fields. So, it was of interest to
investigate both the generation of such fields and their
effect on beam production and parameters in the
magnetron gun.
In experiments on electron beam production in
magnetron guns with secondary-emission cathodes, two
methods have been used to generate magnetic fields:
(i) condenser discharge through a pulsed solenoid and
(ii) direct current supply to a water-cooled solenoid.
In case (i) (Fig. 1), at a high field uniformity
along the solenoid axis (±5%) and the field value
between 5 and 6 kG, the pulse repetition rate is about
1 Hz. This method of magnetic field generation is
inconsistent with the operating conditions of microwave
devices, where the pulse frequency is hundreds of Hz.
On the other hand, with the magnetron gun operating at
a low pulse frequency, the cathode surface gets
contaminated, for the time between the pulses, with
impurities appearing in the anode-cathode gap under the
electron bombardment action. This may result in a
vacuum breakdown of the gap [4].
In (ii) case, the generation of a constant magnetic
field by passing direct current through the solenoid calls
for a high power supply and water-cooling. In this case,
the magnetic field value is restricted by heating of
solenoid, and the magnetic field distribution along the
solenoid axis has a worse uniformity (Fig. 1). The
constant magnetic field enables operation at a high pulse
rate.
Permanent magnets from different magnetic
materials are used in microwave devices to generate
constant magnetic fields for the beam transport [4].
Identical magnets can also be used to produce electron
beams in magnetron guns. Experiments were made to
produce a longitudinal field by the use of axially
magnetized NdFeB rings. The model of total length
4.7 cm, consisting of 0.3 cm thick rings, 4 cm in I.D.
and 1.9 cm in O.D., generated a magnetic field of
0.9 kG on the axis of rings. Over a length of 4 cm the
field nonuniformity was ±10% (Fig. 2). At present,
experiments are performed to investigate the possibility
of creating extended (10-20 cm) magnetic fields with 2
to 3 kG fields for their subsequent use in magnetron
guns and magnetic periodic focusing systems to
transport the beam.
0
200
400
600
800
1000
1200
1400
1600
1800
2000
10 20 30 40 50
Z (cm)
FC A C
1
2
B (G)
Fig. 1. Magnetic intensity distribution along the
solenoid axis and magnetron gun location (FC - Faraday
cup, A - anode, C - cathode).
1 – pulsed magnetic field; 2 constant magnetic field.
20 40 60
1200
800
400
Z, mm
B, G
∅
31
SN NS NS SN
47
Z
∅
20
Fig. 2. Intensity distribution of the magnetic field
generated by a set of NdFeB rings.
Experiments were made to investigate the effect
of longitudinal magnetic field value and distribution on
bean current generation in the experimental device
described in ref. [1]. Threshold dependence of beam
current rise and falloff was obtained as a function of
pulsed magnetic field strength. Thus, in the magnetron
gun with a cathode diameter of 5 mm and an anode
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. № 4.
Серия: Ядерно-физические исследования (35), с. 34-35.
34
diameter of 26 mm, for the cathode voltage between 38
and 40 kV the current appeared at a pulsed magnetic
field intensity B~1350G. The current value was
measured to be ~16 to 20 A and was only slightly
dependent on the magnetic field value ranging from
1500 to 3000 G. Over this range, the gun perveance is
independent of the magnetic field value. At B~3200 G
an abrupt disruption of the process of secondary-
emission multiplication of electrons took place, and the
current was not registered by the Faraday cup. The
function obtained is associated with variations in
trajectories and conditions of energizing by electrons in
the interelectrode gap as the magnetic field value is
changed. Variations in the magnetic field distribution in
the gun lead to changes in the shape and height of beam
current pulse amplitude. Thus, as the magnetic field in
the magnetron gun (cathode diameter - 5 mm, anode
diameter - 50 mm, cathode voltage - 60 kV) changed
from 1.4 kG to 2 kG, the beam current changed from 1
to 10 A.
40
20
20
10
U, kV
t, ns
U, kV
I, A
10 ns
t, ns
Fig. 3. Oscillograms of voltage (top) and current
(bottom) pulses
Experiments on magnetron guns with different
geometrical dimensions (cathode diameter 5 ... 40 mm,
anode diameter 22 ... 78 mm) have shown that their
operating conditions provide for the spiking mode of
beam current modulation with a frequency between 1
and 200 MHz. According to the experimental conditions
(magnetic field strength, cathode voltage), either a full
disruption of the process of secondary-emission electron
multiplication or a modulation making 10 to 70% of the
amplitude beam current (Fig. 3) was observed. We
assume this to be due to the conditions of space charge
appearance and their oscillations. The frequency of
these oscillations depends on both the electron cloud
density and the magnetic intensity. As the increasing
magnetic field reached a certain value, the current pulse
top was flattened.
Magnetron guns can provide high powers in the
electron beam. For example, at a cathode voltage of 100
kV and a magnetic field of 1100 G, the magnetron gun
with a cathode 40 mm in diameter, and an anode, 78
mm in diameter, generated a beam current of about 50
A, this corresponding to a beam power of 5 Mw.
Another way of increasing the beam power lies
in using the system including several (6 to 10)
magnetron guns having small transverse dimensions.
Experiments were carried out with systems consisting of
6 and 8 magnetron guns. In the first case, for the
cathode diameter of 5 mm, anode diameter of 26 mm,
cathode voltage of 40 kV, magnetic field strength of
2 kG, the total beam current reached 100 A. In the
second case, for the cathode diameter of 5 mm, anode
diameter of 22 mm, cathode voltage of 20 kV, magnetic
field strength of 1.4 kG, the total beam current was
about 30 A. Presently, this gun is being put into
operation to provide a beam power up to 6 Mw.
The results give evidence that these guns can be
used in high-power microwave devices, and the
magnetic field value must range from 1000 to 2500 G.
This can be achieved with the use of the magnetic
systems described above.
CONCLUSION
The undertaken experiments have shown that a
variation in the magnetic field can give rise to space
charge oscillations in the interelectrode (anode-cathode)
gap of the magnetron gun. These effects observed
during beam generation and transport must be taken into
account when using a magnetron gun in high-power
microwave devices.
REFERENCES
1. A.N. Dovbnya, V.V. Mitrochenko,, N.G. Reshetnyak,
V.P. Romas’ko, Yu.D. Tur, V.V. Zakutin. Obtaining the
linear electron beam by using the magnetron injection
gun with cold secondary-emission metallic cathodes.
Proc. of PAC 97, Vancouver 1997, v.3, pp.2820-2822.
2. Y.M. Saveliev, W. Sibbett, D.M. Parkes. Cross-field
secondary-emission electron source. Plasma Physics. v.
4, No.7 (1997) pp.2319-2321.
3. I.I. Kifer. Tests of ferromagnetic materials (in Russ.).
M.-L. Gosehnergoizdat publ. 1962. 543 p.
4. A.N. Dovbnya, V.V. Zakutin, V.F. Zhiglo, V.P.
Romas’ko, N.G. Reshetnyak. Experimental study of a
magnetron gun with a cold cathode. Vopr. Atomn.
Nauki i Tekhn., ser. YaFI, iss. 1/28/1997, pp. 53-57.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. № 4.
Серия: Ядерно-физические исследования (35), с. 34-35.
34
|
| id | nasplib_isofts_kiev_ua-123456789-81522 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-24T11:41:45Z |
| publishDate | 1999 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Dovbnya, A.N. Zakutin, V.V. Reshetnyak, N.G. Romas’ko, V.P. Bovda, A.M. Utva, O.M. Pokas, V.F. Jeran, L.V. Krasnogolovets, M.A. Volkolupov, Yu.Ya. 2015-05-17T16:27:22Z 2015-05-17T16:27:22Z 1999 The magnetic field effect on electron beam generation in magnetron injection guns with secondary-emission cathodes / A.N. Dovbnya, V.V. Zakutin, N.G. Reshetnyak, V.P. Romas’ko, A.M. Bovda, O.M. Utva, V.F. Pokas, L.V. Jeran, M.A. Krasnogolovets, Yu.Ya. Volkolupov // Вопросы атомной науки и техники. — 1999. — № 4. — С. 34-35. — Бібліогр.: 4 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/81522 Magnetron guns with secondary-emission cathodes appear promising for the use as electron sources in high-power microwave devices [1, 2]. For stable beam generation, the magnetic field in the gun is calculated to be between 0.5 to 5 kG, depending on the cathode voltage amplitude and the gun dimensions. On the other hand, the beam transport in the resonance system of the microwave device also calls for rather high magnetic fields. The generation of these fields of significant extent to produce and transport the beam is a rather grave problem. It is generally solved by using water-cooled solenoids [3], that gives rise to considerable difficulties. In recent years, constant magnets have been used [3] to generate extended solenoidal magnetic fields. So, it was of interest to investigate both the generation of such fields and their effect on beam production and parameters in the magnetron gun. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники The magnetic field effect on electron beam generation in magnetron injection guns with secondary-emission cathodes Влияние магнитных полей на генерацию электронных пучков в магнетронных пушках с вторично-эмиссионными катодами Article published earlier |
| spellingShingle | The magnetic field effect on electron beam generation in magnetron injection guns with secondary-emission cathodes Dovbnya, A.N. Zakutin, V.V. Reshetnyak, N.G. Romas’ko, V.P. Bovda, A.M. Utva, O.M. Pokas, V.F. Jeran, L.V. Krasnogolovets, M.A. Volkolupov, Yu.Ya. |
| title | The magnetic field effect on electron beam generation in magnetron injection guns with secondary-emission cathodes |
| title_alt | Влияние магнитных полей на генерацию электронных пучков в магнетронных пушках с вторично-эмиссионными катодами |
| title_full | The magnetic field effect on electron beam generation in magnetron injection guns with secondary-emission cathodes |
| title_fullStr | The magnetic field effect on electron beam generation in magnetron injection guns with secondary-emission cathodes |
| title_full_unstemmed | The magnetic field effect on electron beam generation in magnetron injection guns with secondary-emission cathodes |
| title_short | The magnetic field effect on electron beam generation in magnetron injection guns with secondary-emission cathodes |
| title_sort | magnetic field effect on electron beam generation in magnetron injection guns with secondary-emission cathodes |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/81522 |
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