Method of suppressing the multipactoring discharges
The present paper describes a method of suppressing the multipactoring discharges between electrodes in an accelerating structure of an evacuated resonator of an accelerator. The method consists in synchronous exciting the superposition of radio-frequency electric fields at a resonator operating fre...
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 2002 |
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| Мова: | English |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2002
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| Цитувати: | Method of suppressing the multipactoring discharges / L.D. Lobzov, N.G. Shulika // Вопросы атомной науки и техники. — 2002. — № 2. — С. 93-94. — Бібліогр.: 8 назв. — англ. |
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Lobzov, L.D. Shulika, N.G. 2015-04-12T06:51:04Z 2015-04-12T06:51:04Z 2002 Method of suppressing the multipactoring discharges / L.D. Lobzov, N.G. Shulika // Вопросы атомной науки и техники. — 2002. — № 2. — С. 93-94. — Бібліогр.: 8 назв. — англ. 1562-6016 PACS: 29.17.+W https://nasplib.isofts.kiev.ua/handle/123456789/80127 The present paper describes a method of suppressing the multipactoring discharges between electrodes in an accelerating structure of an evacuated resonator of an accelerator. The method consists in synchronous exciting the superposition of radio-frequency electric fields at a resonator operating frequency from two self-excited oscillatory circuits, the parameters of one circuit being independent on the shunt effect of discharges being suppressed. In this method the priority of fields is of equal value with meeting the condition that every of them could ensure the exceeding of the upper discharge range limit of any multipactoring which appears, while another field provides a main contribution into a required level of the operating electric field in the accelerator. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Theory and technics of particle acceleration Method of suppressing the multipactoring discharges Способ подавления резонансных вторичноэлектронных разрядов Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| title |
Method of suppressing the multipactoring discharges |
| spellingShingle |
Method of suppressing the multipactoring discharges Lobzov, L.D. Shulika, N.G. Theory and technics of particle acceleration |
| title_short |
Method of suppressing the multipactoring discharges |
| title_full |
Method of suppressing the multipactoring discharges |
| title_fullStr |
Method of suppressing the multipactoring discharges |
| title_full_unstemmed |
Method of suppressing the multipactoring discharges |
| title_sort |
method of suppressing the multipactoring discharges |
| author |
Lobzov, L.D. Shulika, N.G. |
| author_facet |
Lobzov, L.D. Shulika, N.G. |
| topic |
Theory and technics of particle acceleration |
| topic_facet |
Theory and technics of particle acceleration |
| publishDate |
2002 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Способ подавления резонансных вторичноэлектронных разрядов |
| description |
The present paper describes a method of suppressing the multipactoring discharges between electrodes in an accelerating structure of an evacuated resonator of an accelerator. The method consists in synchronous exciting the superposition of radio-frequency electric fields at a resonator operating frequency from two self-excited oscillatory circuits, the parameters of one circuit being independent on the shunt effect of discharges being suppressed. In this method the priority of fields is of equal value with meeting the condition that every of them could ensure the exceeding of the upper discharge range limit of any multipactoring which appears, while another field provides a main contribution into a required level of the operating electric field in the accelerator.
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| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/80127 |
| citation_txt |
Method of suppressing the multipactoring discharges / L.D. Lobzov, N.G. Shulika // Вопросы атомной науки и техники. — 2002. — № 2. — С. 93-94. — Бібліогр.: 8 назв. — англ. |
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2025-11-24T15:58:12Z |
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| fulltext |
METHOD OF SUPPRESSING THE MULTIPACTORING DISCHARGES
L.D. Lobzov, N.G. Shulika
National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
e-mail: demchenko@kipt.kharkov.ua
The present paper describes a method of suppressing the multipactoring discharges between electrodes in an
accelerating structure of an evacuated resonator of an accelerator. The method consists in synchronous exciting the
superposition of radio-frequency electric fields at a resonator operating frequency from two self-excited oscillatory
circuits, the parameters of one circuit being independent on the shunt effect of discharges being suppressed.
In this method the priority of fields is of equal value with meeting the condition that every of them could ensure
the exceeding of the upper discharge range limit of any multipactoring which appears, while another field provides a
main contribution into a required level of the operating electric field in the accelerator.
PACS: 29.17.+W
The multipactoring discharges (the secondary
electron resonance discharges), observed in evacuated
resonators of linear and cyclic accelerators at an initial
stage of RF power input, can cause the failing of the
stable operation of accelerators. Thereby, the
multipactoring can appear not only between the
electrodes of the accelerating structure but also in
different spaces with conditions for its resonance
development (both for two-electrode and single-
electrode discharge at the resonator surface, input
hermetizing window, etc) [1].
The above-mentioned multipactoring exerts an
influence being the most dangerous for stable operation
of the single-resonator accelerator with a simplified (1-
3 cascades in the oscillatory channel) self-oscillatory RF
power supply system with a positive feedback (PFB)
from the resonator, due to the change of equivalent
accelerator parameters and disturbance of self-excited
oscillator amplitude ratios, as well as during operation
of the self-excited oscillator with an internal or external
PFB onto the evacuated resonator due to disturbing the
conditions of matched power transmission into the
accelerator.
To prevent the multipactoring action some
precautions are taken to decrease the secondary-electron
emission coefficient, namely: coating the radio-
frequency surfaces with a thin layer of titanium-nitride
[2], changing the electrode shape [3], setting the
additional electrodes, nearby but off the working gaps,
with applying into them a positive (electron
“absorbing”) voltage of several kilovolts [4]. The
effective technique of suppressing the multipactoring is
the frequency modulation of the working electric field
being excited in the self-excitation mode with PFB from
the evacuated resonator by applying the voltage of an
additional oscillator (AO) having a frequency different
from the accelerator working frequency. The voltage is
turned off after passing the region of the multipactoring
build-up [5] and so on. However, all these special
precautions are accompanied by the increase of radio-
frequency losses that deteriorates the equivalent
parameters of the accelerator resonator such as a figure
of merit, shunt resistance, electric strength. The electric
circuits and design performance, as well as the process
of adjustment and maintaining of the accelerator become
more complicated.
The proposed method for suppressing the
multipactoring is based on the synchronous excitation of
radio-frequency electric fields at a frequency of the
evacuated resonator working oscillation from two self-
oscillatory circuits operating for the general resonator.
One of the circuits with a positive feedback from the
resonator can ensure the conditions for developing and
existing the discharge, and the other one, independent
on the discharge shunt influence, provides a constant
gain of the resonator working field amplitude thereby
disturbing the amplitude conditions for the multipactory
does not have a time to build-up and exist [6].
The effective suppression of the multipactoring
discharges in the evacuated resonator, by synchronous
excitation, from the single self-excited oscillatory rf
power supply system, superposition of two rf electric
fields, was realized at a single-resonator accelerator
MLUD-3 (small-size deuteron linear accelerator) [7].
The resonator accelerating structure [8], formed with
the use of drift tubes attached on the comb-shaped
holders, consists of sixteen parallel accelerating gaps
spaced at a distance increasing from 1.353 cm (first
gap), 1.753 cm (second gap) and to 6.422 cm (last gap).
The resonant frequency of accelerator is 99.34 MHz, Q-
factor is ~5000. The radio-frequency power from the
three-cascade linear amplifier channel embraced by two
oscillatory circuits with positive feedbacks (a coupler
loop of the one is mounted in the resonator and a
coupler loop of the other is mounted in the feeder)
enters into the accelerator in the pulse mode with a pulse
length of 250 µsec and pulse repetition rate of 1Hz.
Input and output circuits of high-frequency cascades of
the amplifier channel are tuned to the working frequency
of the accelerator resonator. The input impedance of the
resonator corresponds to the wave impedance of the
feeder.
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2002, № 2.
Series: Nuclear Physics Investigations (40), p. 93-94. 93
The working pressure is P=5.10-5 mm Hg. The
operating principle of this method is explained in the
figure with the following designations: 1 − evacuated
resonator of the accelerator with a power input element,
2 − coaxial feeder, 3 − amplifier channel, 4 − summator,
5 − coupler loop mounted in the resonator, 6 − coupler
loop mounted in the feeder.
Applying the electric voltage to the oscillator tube of
the amplifier channel, noise, and then rf-oscillations, go
through the feeder to the loop power supply resonator
accelerator. While doing this, at the element PFB
mounted in the resonator, a voltage is induced, which is
proportional to its shunt impedance, and at the element
PFB mounted in the feeder, a voltage is induced, which
is proportional to the output power of the amplifier
channel. The total voltage, being the sygnal of amplifier
channal excitation, determines the value of its output RF
power and, respectively, the level of electrical field in
accelerating gaps of resonator. The synchronism
superposition of electrical fields in the accelerator
origins because of the frequencies of self-oscillation of
each chain are determined by the working frequency of
the high-quality resonator.
During preparation of working surfaces and
accelerating structure electrodes for initiation of electron
release, under RF heating condition from the self-
excited oscillator circuit with PFB from the resonator, in
the first gap of the accelerating structure there arises the
multipactoring evoking the failing of the required level
of the accelerator electric field stability, but maintaining
the conditions for existence of the discharge with a
definite intensity.
Connecting the self-oscillatory circuit, the positive
feedback of which couples the output of the amplifier
channel with its input, provides an increasing character
of synchronous excitation of another electric field in the
resonator.
While one of the electric fields initiates and provides
conditions for building-up of the the multipactoring, the
second electric field, being excited by the oscillatory
circuit independent on the processes taking place in the
resonator, automatically increases the resulting electric
field amplitude in the gaps thereby disturbing the
amplitude conditions of the multipactoring existence.
In the case of simultaneous operation of the two
oscillatory circuits, the amplitude conditions of
multipactory phenomena are disturbed from the very
beginning of electron release and prevent from
multipactoring.
The offered method for suppressing the
multipactoring based on synchronous excitation of
radio-frequency electron fields in the accelerating
channel of the accelerator from the two independent
self-oscillatory circuits embracing the amplifier channel
of the evacuated resonator RF power can be used for
distinguishing the type of discharges when their
unambiguous interpretation is complicated.
REFERENCES
1. Ion linear accelerators. Edited by
B.P. Murin. Moscow: “Atomizdat”, 1978, v. 2,
p. 135 (in Russian).
2. W.D. Cornelius. CW operation of the FMIT
RFQ accelerator. IEEE Transaction on Nuclear
Science, V. NS-32, №5, October, 1985, p. 3139-
3143.
3. D.K. Aitken. Long-transit-time multifactoring
at ultra high frequencies, and the effect of surface
emitting layers // Proc. IEEE. 1958, v. B105,
Suppl., №12, p. 824-828.
4. B.I. Polyakov, B.T. Zarubin, B.B. Kushin.
Electrical strength of the small accelerating gap.
Transaction of Radio-Technical Institute of
Acad.of Sciences USSR, v.1, №2, 1959, p.93 (in
Russian).
5. V.G. Andreev, D.G. Zajdin. Method of
suppressing the secondry electron resonace
discharche. Inventor’s Certificate №263767. Bull.
of Invention №8, 1970 (in Russian).
6. L.D. Lobzov et al. Radio-frequency self-
excited oscillator. Licence SU №1700783 A1,
Bull. of Invention №47, 1991 (in Russian).
7. L.D. Lobzov, Y.P. Mazalov, E.V. Gusev,
N.G. Shulika. Investigation of multipactoring in
the H-type resonator of the linear ion accelerator.
Proc. of XIII Conf. on Charged Particle
Accelerators, Dubna, 1993, v. 1, p. 269-273 (in
Russian).
8. A.S. Beley et al. Project of upgrading the
accelerating structure of a small-size deuteron
linear accelerator // Voprosy Atomnoj Nauki i
Tekhniki, Ser.: Tekhnika fizicheskogo eksperimenta
(35). 1987, № 4, p. 8 (in Russian).
94
L.D. Lobzov, N.G. Shulika
REFERENCES
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