Studying the electron flow formation in magnetron guns with a secondary emission metallic cathode
Presented are the results of studies concerning the multybeams systems and considering the possibility to increase the output current amplitudes by changing the geometrical dimensions of guns.
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| Published in: | Вопросы атомной науки и техники |
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| Date: | 2001 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2001
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| Cite this: | Studying the electron flow formation in magnetron guns with a secondary emission metallic cathode / A.N. Dovbnya, N.G. Reshetn’yak, V.V. Zakutin // Вопросы атомной науки и техники. — 2001. — № 1. — С. 109-111. — Бібліогр.: 10 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860006697477603328 |
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| author | Dovbnya, A.N. Reshetn’yak, N.G. Zakutin, V.V. |
| author_facet | Dovbnya, A.N. Reshetn’yak, N.G. Zakutin, V.V. |
| citation_txt | Studying the electron flow formation in magnetron guns with a secondary emission metallic cathode / A.N. Dovbnya, N.G. Reshetn’yak, V.V. Zakutin // Вопросы атомной науки и техники. — 2001. — № 1. — С. 109-111. — Бібліогр.: 10 назв. — англ. |
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| container_title | Вопросы атомной науки и техники |
| description | Presented are the results of studies concerning the multybeams systems and considering the possibility to increase the output current amplitudes by changing the geometrical dimensions of guns.
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| first_indexed | 2025-12-07T16:39:06Z |
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STUDYING THE ELECTRON FLOW FORMATION IN MAGNETRON
GUNS WITH A SECONDARY EMISSION METALLIC CATHODE
A.N. Dovbnya, N.G. Reshetn’yak, V.V. Zakutin
National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
Presented are the results of studies concerning the multybeams systems and considering the possibility to
increase the output current amplitudes by changing the geometrical dimensions of guns.
PACS: 84.40.Cb.
INTRODUCTION
The problem of extending the life-time and
increasing of the pulse and average power of many RF-
sources is closely related to the design of their electron
guns. As it is known, the magnetron injecting guns with
secondary emission metallic cathodes (SEMI) are
specified by the high current emission density and long
life-time. The main goal of these investigations is to
determine the advantages and limitations of using
SEMIGs as the electron source in high-power RF
devices and accelerator injector systems. At this stage
we have studied some questions concerning the
operational beam stability, voltage and current
increasing. The experiments have been performed by
using the experimental setup to investigate SEMIG
linear electron beam parameters from single and
multiple beams gun assemblies with the anode voltage
up to 100 kV, pulse duration up to 10 µs, repetition rate
50 Hz and 0.1-0.2 T magnetic field strength. Pulse-to-
pulse long-term stability of the annular electron beams
(internal diameter nearly equal to the cathode diameter,
wide of ring 1-2 mm (wavelength of cyclotron
oscillations)) with beam density up to 70 A/cm2
(1010-
1011 e-/cm3) has been achieved. It is shown, that the
cathode diameter extension provides a proportionate
increasing of the beam current, and in the case of
multiple beam gun assemblies we have separate
identical electron beams with the similar parameters of
single-beam gun.
A task of creating the long-lived high-energy
electron sources is one of the main problems in the
acceleration engineering. As it was shown earlier [1, 2]
the so-called secondary-emission magnetron guns
(SEMIG) with cold metal cathodes are specified by a
high beam density, high lifetime and instantaneous
operation readiness. On our opinion the guns of such a
type are highly promising for the use in RF-sources and
accelerators, in particular, in multybeam and cluster
klystrons [3, 4] as well as in high-current injector
systems, for example, in the installation such as RK
TBA [5], CESTA TEST FACILITY [6] and ion
accelerators driving ring electron beams [7].
The present paper continues the experimental study
of characteristics of such guns. We studied the current-
voltage and spatial characteristics, conditions of beam
generation and stability. The amplitude modulation of
the emission current in the variable electric fields was
investigated. Presented are the results of studies
concerning the multybeams systems and considering the
possibility to increase the output current amplitudes by
changing the geometrical dimensions of guns.
FACILITY DESCRIPTION
Investigations on the beam generation in magnetron
guns with secondary-emission cathodes were conducted
at the facility the layout of which is represented in
Fig. 1. In these experiments the pulse of a negative
polarity from modulator 1 forming the voltage pulse
(amplitude 4 to 100 kV, duration 4 to 10 µm and
repetition rate 50 Hz) is fed to cathode 5 of the gun and
its anode 6 is grounded via resistor R3 and connected to
generator 2. The process of secondary-emission electron
multiplication took place at the fall of the voltage pulse
being formed with modulator 1 or generator 2.
The magnetic field for the beam generation and
transport was created with solenoid 4 consisting of 4
sections having 550 mm length and being supplied from
independent current sources that allowed one to change
the spatial distribution of the magnetic field and its
amplitude. The beam transport was performed at a
distance 80 to 160 mm from the anode cut to the
Faraday cup.
Measurement of the beam current was conducted
with applying Faraday cup 7 made as a section of the
coaxial line and resistor R4=12 Ohm equal to the wave
resistance of the line; the cathode voltage was measured
with the use of divider R1R2; the beam dimensions -
with the use of a dent on the X-ray film and on the
molybdenum foil disposed at the coaxial line end. The
magnetron gun with a copper cathode and an anode
made from the stainless-steel or copper having 120 mm
length was placed inside vacuum chamber 3 evacuated
to a pressure of ≤ 10-6 Torr.
EXPERIMENTAL RESULTS AND
DISCUSSION
The electric field in the anode-cathode gap, which is
required for the beam generation in the magnetron gun,
should have two time intervals: the first is the section
with the field fall where the secondary-emission
multiplication and the formation of an electron cloud
around the cathode occur, and the second is the section
with a constant field providing the steady-state stage of
the secondary-emission process and beam generation
[8,9]. The fall sharpness and duration determine the
PROBLEMS OF ATOMIC ENERGY AND TECHNOLOGY. 2001, № 1.
Series: Nuclear Physics Investigations (37), p. 109-111.
109
stability of beam generation and temporary instability of
beam current pulse front generation. A non-uniformity
at the flat - top part of the pulse can lead to the beam
current pulse modulation or to the current pulse blowout
as well as to generation of several electron clusters in
the single voltage pulse [8] and determines also the
permissible spread of the electron beam energy.
Fig. 1
The given time dependency of the electrical field
between the cathode and the anode is gained by forming
the voltage pulse of a special form with the
burst at the top having a short fall and long flat
part at the cathode or with simultaneous feeding of two
voltage pulses towards the cathode and anode forming
the given electric field.
The first method was based on forming a cathode
voltage pulse of a special form with the blowout at the
top. In the modulator with a complete discharge of the
forming line a voltage pulse with the blowout and flat
part can be obtained using a correcting capacity C
(Fig. 1) connected in parallel to the forming line [10].
Changing the C value one can regulate the burst
amplitude.
A feasibility of forming the burst at the cathode voltage
pulse was checked experimentally. The forming line had
the wave resistance of 40 Ohm, pulse duration at a half-
height of 4.5 µm. The voltage pulse of a modulator
being “on no load” at C=0 had the burst of 25% of the
voltage pulse amplitude (Fig. 2). When connecting the
capacity C =15 nF the burst amplitude was 50% (curve
1) of the voltage pulse amplitude. In one of the
operating modes when generating the 9A electron beam
the burst amplitude was ~ 60 kV, the amplitude of the
flat part during “on no load” operation was 37 kV and
“with the beam” ~ 30 kV.
U (kV)
t (µs)
Fig. 2
The second method (Fig. 2) consists in summation
(with a total load - cathode, two voltage pulses) of the
long pulse with a flat top and the short pulse with a
sharp fall, and formation of the voltage pulse having the
form close to that of above mentioned one.
Experimental study of this scheme for forming the
pulse was conducted at a wave resistance of the forming
line ρ=15 Ohm. The burst amplitude was ~ 15 kV, flat-
topped pulse amplitude at a beam current of 23 A was ~
13 kV (Fig. 3). The burst amplitude and the amplitude
of a main part of the pulse during beam generation are
almost equal. The fall duration in this scheme, like to
the first method, equals to hundreds of nanoseconds that
is connected with the influence of stray parameters of
the modulator output circuit.
Fig. 3
U (kV) J(A)
t (µs)
Fig. 4
The third method is the summation in the anode-
cathode gap of the electrical fields of two pulses: long
flat - topped pulse being fed towards the cathode, and
short pulse with a sharp fall being fed towards the gun
anode in order to obtain the given time dependence of
the summated electrical field [8]. The electrical fields of
these pulses are summed in the anode-cathode gap. In
this scheme the sharing of pulse feeding circuits permits
to use a wide-band transmission line. Duration of the
fall pulse at the anode providing a process of secondary-
emission multiplication and beam current pulse timing
can achieve several nanoseconds (Fig. 4).
Investigations of beam parameters were carried out
with the use of all the described above methods of
forming a voltage pulse. The experiments have shown
that the beam current amplitude at the Faraday cup has a
threshold dependence on the fall sharpness and does not
110
depend on the scheme of secondary-emission process
excitation. The minimum fall sharpness at which one
observes beginning of the process of secondary-
emission multiplication and beam generation equals 20
to 30 kV/µs. In Fig. 5 represented is the dependence of
the current towards the Faraday cup on the voltage
amplitude at the cathode with a diameter of d=2 mm and
anode diameters D=10 mm; D=22 mm and D=50 mm.
The figure shows that the measurement results are in
accordance with the calculation by the “3/2”law. In the
process of measuring, in each of points, the magnetic
field value was set respectively to the maximum beam
current value. In this figure given are the magnetic field
values at which the beam generation takes place. In the
gun with a cathode diameter of 2 mm and an anode
diameter of 50 mm with a voltage amplitude at the
cathode of 50 kV a beam current of 7 A was gained.
The magnetic field strength was 2550 Oe.
U (kV)
Fig. 5
We have carry out research on generation of electron
beams in the magnetron guns of a large aspect ratio with
a cathode diameter of 2 mm and an anode diameter of
50 mm and 78 mm depending on the magnetic field
value. It is shown that for the voltage amplitude of
flatted-top pulse 40 to 50 kV and low magnetic fields
(700 to 1200 Oe) one observes the generation of
electron beams with a current of 0.5 to 1.5 A (the Hall
cutoff field was ~ 600 Oe and ~ 400 Oe, respectively).
Here the outside beam diameter was ~ 15 mm. In this
case the beam from the magnetron gun with a cathode
diameter of 2 mm and an anode diameter of 50 mm at a
distance of 130 mm from the anode cut had an outside
diameter of 4 mm and inside diameter of 2 mm. The
measurement results are given in the table.
d
mm
D
mm
U kV I A H Oe
2 50 40…55 0,8 800…1200
2 50 40…55 7 2500
2 78 40…55 1,0 700…1200
REFERENCES
1. F. Skrowron. The Continuous-Cathode (Emitting-
Sole) Crossed Field Amplifier // Proc. of the IEEE,
1973, v. 61, № 3, p. 330-356.
2. A.N. Dovbnya et al. Secondary Emission Magnetron
Injection Gun as High Current Durable Electron
Source. Proc. of 1994 Pulsed RF Source for Linear
Colliders Workshop (RF’94), October 1994,
Montauk, Long Island, New York. AIP Conference
proceeding, 1995, p. 350-359.
3. R.B. Palmer et al. An Immersed Field Cluster
Klystron // Particle Accelerators. 1990, v. 30,
p. 197-209.
4. R.B. Palmer et al. Status of the BNI - MIT - SLAC
Cluster Klystron Project - Proc. of 1994 Pulsed RF
Source for Linear Colliders. Workshop (RF’94),
October 1994, Montauk, Long Island, New York.
AIP Conference Proceeding. 1995, p. 12.
5. G.A. Westenskow et al. Relativistic Klystron Two-
Beam Accelerator. Special Issue on High Power
Microwave Generation // IEEE Transaction on
Plasma Science. 1994, v. 22, N 5, p. 750-755.
6. I. Wilson. CLIC Test Beam Facilities-Status and
Results - Proc. of the XVIII Jnt. Linear Accel.
Conference, Geneva, 1996, v. 1, p. 552-557.
7. V.P. Sarantsev et al. Kollektivnoe uskorenie ionov
elektronnymi koltsa, M., Atomizdat, 1979 (in
Russion).
8. A.N. Dovbnya et al. Obtaining of high-power
electron beams on magnetron guns with secondary-
emission cathodes // Journ/ of Tekhn. Phys. 2001, v.
46, №2, p.98-104 (in Russian).
9. S.A. Tsherenshikov. On switsh magnetron wlth
secondary-emission cathode // Elektronnaya
tekhnika, ser. 1. 1973, №6, p. 20-28 (in Russian).
10. G.A. Mesyats. Generirovanie moshnikh na-
nosekundnikh impulsov. М: “Sov. radio”. 1974, 256
p.
111
National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
INTRODUCTION
FACILITY DESCRIPTION
EXPERIMENTAL RESULTS AND DISCUSSION
REFERENCES
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| id | nasplib_isofts_kiev_ua-123456789-78536 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T16:39:06Z |
| publishDate | 2001 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Dovbnya, A.N. Reshetn’yak, N.G. Zakutin, V.V. 2015-03-18T18:32:36Z 2015-03-18T18:32:36Z 2001 Studying the electron flow formation in magnetron guns with a secondary emission metallic cathode / A.N. Dovbnya, N.G. Reshetn’yak, V.V. Zakutin // Вопросы атомной науки и техники. — 2001. — № 1. — С. 109-111. — Бібліогр.: 10 назв. — англ. 1562-6016 PACS: 84.40.Cb. https://nasplib.isofts.kiev.ua/handle/123456789/78536 Presented are the results of studies concerning the multybeams systems and considering the possibility to increase the output current amplitudes by changing the geometrical dimensions of guns. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Theory and technics of particle acceleration Studying the electron flow formation in magnetron guns with a secondary emission metallic cathode Исследование формирования пучка электронов в магнитных пушках с металлическим катодом вторичной эмиссии Article published earlier |
| spellingShingle | Studying the electron flow formation in magnetron guns with a secondary emission metallic cathode Dovbnya, A.N. Reshetn’yak, N.G. Zakutin, V.V. Theory and technics of particle acceleration |
| title | Studying the electron flow formation in magnetron guns with a secondary emission metallic cathode |
| title_alt | Исследование формирования пучка электронов в магнитных пушках с металлическим катодом вторичной эмиссии |
| title_full | Studying the electron flow formation in magnetron guns with a secondary emission metallic cathode |
| title_fullStr | Studying the electron flow formation in magnetron guns with a secondary emission metallic cathode |
| title_full_unstemmed | Studying the electron flow formation in magnetron guns with a secondary emission metallic cathode |
| title_short | Studying the electron flow formation in magnetron guns with a secondary emission metallic cathode |
| title_sort | studying the electron flow formation in magnetron guns with a secondary emission metallic cathode |
| topic | Theory and technics of particle acceleration |
| topic_facet | Theory and technics of particle acceleration |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/78536 |
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