Excitation of self-sustained secondary emission by gas discharge and hollow beam generation in magnetron injection gun
The electron beam is frequently used for the energy input into the plasma. However, the strong transverse field hampers the charged-particle beam penetration into a closed magnetic trap. This problem can be solved by means of a new electron gun. It is an electron gun with a cold-cathode develope...
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| Zitieren: | Excitation of self-sustained secondary emission by gas discharge and hollow beam generation in magnetron injection gun / S.A. Cherenshchykov, V.D. Kotsubanov, I.K. Nikolskii // Вопросы атомной науки и техники. — 2009. — № 1. — С. 162-164. — Бібліогр.: 9 назв. — англ. |
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irk-123456789-886472015-11-20T03:01:45Z Excitation of self-sustained secondary emission by gas discharge and hollow beam generation in magnetron injection gun Cherenshchykov, S.A. Kotsubanov, V.D. Nikolskii, I.K. Низкотемпературная плазма и плазменные технологии The electron beam is frequently used for the energy input into the plasma. However, the strong transverse field hampers the charged-particle beam penetration into a closed magnetic trap. This problem can be solved by means of a new electron gun. It is an electron gun with a cold-cathode developed on the principle of self-sustained secondary electron emission. In experiments described below the gun ignition was for the first time observed at 2…6 kV direct voltage in the range of pressures ~ 10⁻²…10⁻¹ Pa. The gun produced the hollow electron beam with current exceeding 1 А and pulse duration up to 1 ms. After ignition the gun can principally operate at any higher vacuum. Введення енергії в плазму може бути зроблено за допомогою електронного пучка. Однак, сильне поперечне магнітне поле перешкоджає проникненню пучків заряджених часток в замкнуту магнітну пастку. Ця проблема може бути частково вирішена шляхом використання нової електронної гармати. Принцип дії такої гармати з холодним катодом – вторинна електронна емісія, що самопідтримується. В описаних експериментах уперше запалювання гармати спостерігалося при постійній напрузі 2...6 кВ у діапазоні тиску 10⁻²…10⁻¹ Па. Гармата утворювала електронний пучок зі струмом більшим ніж 1 А та тривалістю 1 мс. Після запалювання робота такої електронної гармати принципово можлива і при більш високому вакуумі. Ввод энергии в плазму зачастую можно произвести электронным пучком. Однако, сильное поперечное магнитное поле препятствует проникновению пучков заряженных частиц в замкнутую магнитную ловушку. Проблема может быть разрешена путем применения новой электронной пушки. Принцип действия новой электронной пушки с холодным катодом - самоподдерживающаяся вторичная электронная эмиссия. В описанных экспериментах зажигание пушки впервые наблюдалось при постоянном напряжении 2…6 кВ в диапазоне давлений 10⁻²…10⁻¹ Па. Пушка создавала полый электронный пучок с током выше 1 А и длительностью до 1 мс. После зажигания работа такой электронной пушки принципиально возможна и при более высоком вакууме. 2009 Article Excitation of self-sustained secondary emission by gas discharge and hollow beam generation in magnetron injection gun / S.A. Cherenshchykov, V.D. Kotsubanov, I.K. Nikolskii // Вопросы атомной науки и техники. — 2009. — № 1. — С. 162-164. — Бібліогр.: 9 назв. — англ. 1562-6016 PACS: 52.50.Gj http://dspace.nbuv.gov.ua/handle/123456789/88647 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| language |
English |
| topic |
Низкотемпературная плазма и плазменные технологии Низкотемпературная плазма и плазменные технологии |
| spellingShingle |
Низкотемпературная плазма и плазменные технологии Низкотемпературная плазма и плазменные технологии Cherenshchykov, S.A. Kotsubanov, V.D. Nikolskii, I.K. Excitation of self-sustained secondary emission by gas discharge and hollow beam generation in magnetron injection gun Вопросы атомной науки и техники |
| description |
The electron beam is frequently used for the energy input into the plasma. However, the strong transverse field
hampers the charged-particle beam penetration into a closed magnetic trap. This problem can be solved by means of a
new electron gun. It is an electron gun with a cold-cathode developed on the principle of self-sustained secondary
electron emission. In experiments described below the gun ignition was for the first time observed at 2…6 kV direct
voltage in the range of pressures ~ 10⁻²…10⁻¹ Pa. The gun produced the hollow electron beam with current exceeding
1 А and pulse duration up to 1 ms. After ignition the gun can principally operate at any higher vacuum. |
| format |
Article |
| author |
Cherenshchykov, S.A. Kotsubanov, V.D. Nikolskii, I.K. |
| author_facet |
Cherenshchykov, S.A. Kotsubanov, V.D. Nikolskii, I.K. |
| author_sort |
Cherenshchykov, S.A. |
| title |
Excitation of self-sustained secondary emission by gas discharge and hollow beam generation in magnetron injection gun |
| title_short |
Excitation of self-sustained secondary emission by gas discharge and hollow beam generation in magnetron injection gun |
| title_full |
Excitation of self-sustained secondary emission by gas discharge and hollow beam generation in magnetron injection gun |
| title_fullStr |
Excitation of self-sustained secondary emission by gas discharge and hollow beam generation in magnetron injection gun |
| title_full_unstemmed |
Excitation of self-sustained secondary emission by gas discharge and hollow beam generation in magnetron injection gun |
| title_sort |
excitation of self-sustained secondary emission by gas discharge and hollow beam generation in magnetron injection gun |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2009 |
| topic_facet |
Низкотемпературная плазма и плазменные технологии |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/88647 |
| citation_txt |
Excitation of self-sustained secondary emission
by gas discharge and hollow beam generation
in magnetron injection gun / S.A. Cherenshchykov, V.D. Kotsubanov, I.K. Nikolskii // Вопросы атомной науки и техники. — 2009. — № 1. — С. 162-164. — Бібліогр.: 9 назв. — англ. |
| series |
Вопросы атомной науки и техники |
| work_keys_str_mv |
AT cherenshchykovsa excitationofselfsustainedsecondaryemissionbygasdischargeandhollowbeamgenerationinmagnetroninjectiongun AT kotsubanovvd excitationofselfsustainedsecondaryemissionbygasdischargeandhollowbeamgenerationinmagnetroninjectiongun AT nikolskiiik excitationofselfsustainedsecondaryemissionbygasdischargeandhollowbeamgenerationinmagnetroninjectiongun |
| first_indexed |
2025-07-06T16:31:05Z |
| last_indexed |
2025-07-06T16:31:05Z |
| _version_ |
1836915854894170112 |
| fulltext |
EXCITATION OF SELF-SUSTAINED SECONDARY EMISSION
BY GAS DISCHARGE AND HOLLOW BEAM GENERATION
IN MAGNETRON INJECTION GUN
S.A. Cherenshchykov1, V.D. Kotsubanov2, I.K. Nikolskii2
1Institute of High Energy Physics and Nuclear Physics, NSC “Kharkov Institute of Physics and
Technology”, Kharkov, Ukraine, E-mail: cherench@kipt.kharkov.ua;
2Institute of Plasma Physics, NSC “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
The electron beam is frequently used for the energy input into the plasma. However, the strong transverse field
hampers the charged-particle beam penetration into a closed magnetic trap. This problem can be solved by means of a
new electron gun. It is an electron gun with a cold-cathode developed on the principle of self-sustained secondary
electron emission. In experiments described below the gun ignition was for the first time observed at 2…6 kV direct
voltage in the range of pressures ~ 10-2…10-1 Pa. The gun produced the hollow electron beam with current exceeding
1 А and pulse duration up to 1 ms. After ignition the gun can principally operate at any higher vacuum.
PACS: 52.50.Gj
1. INTRODUCTION
For the electron beam generation one usually uses the
electron guns with a heated cathode. The cathode heating
to high temperatures involves some very complex
problems in the plasma facility operation on the whole,
particularly, if closed magnetic traps are used.
Let us consider the most complicated case including all its
problems, as well as, the ways to solve them by
conventional methods.
1. A cathode should be heated to the temperature close to
the melting temperature, and, therefore, it should be
protected from the direct plasma contact. It is necessary to
prevent the cathode overheating and cathode material
evaporation into the plasma what is undesirable for fusion
plasma devices.
2. As the transversal magnetic field hampers the electron
beam injection, the gun and the cathode should be placed
in close proximity to the plasma in the strong magnetic
field region.
3. To compensate the electrons escaping from the plasma
the currents of high values should be used. Therefore it is
necessary to increase the cathode area or the total area of
cathodes, if more than one gun is used, or to increase the
voltage and the temperature of the cathode. Thus, the
hazard of plasma contamination with heavy elements
increases.
In practice the use of plasma guns does not eliminate
all difficulties. A charge from a solid (condensed)
electrode should be injected into the gun plasma anyway.
From the cold electrode the high current can be extracted
only by forming a cathode spot on it. In other word, in
this case the cathode sputtering will be significant too.
2. PROBLEM STATEMENT
In 1990, a multipurpose cold-cathode electron source
was developed in NSC KIPT by one of the authors of this
report, due to the support and participation of
B.G. Safronov [1]. Its advantage is the possibility to
obtain high electron currents during unlimited lifetime.
Furthermore, the cathode may be made of a material
resistant to the high-temperature plasma action. For the
material be suitable a maximum value of its secondary-
electron emission coefficient should be higher than unity.
Most of materials and alloys possess this property.
The principle of operation of the source under
consideration is based on the self-sustained secondary
emission in the crossed fields. Electron bombardment at
an energy corresponding to the maximum of secondary
emission, i.e. to the value of about thousands of electron-
volts depending on the material, does not change
properties of metal surface. Therefore, with the source
operating by this principle, the plasma is contaminated no
more than the first wall of fusion reactor having the same
area. At the same time, it is established experimentally,
that such-type source is capable to generate currents
higher than 1000 amperes at enough high voltages [2]. It
is rather simple and has a robust construction, and, also,
allows the operation of many guns simultaneously from
single power source. The strong magnetic field is the
«natural environment» of its operation.
3. DESIGN OF ELECTRON SOURCE
AND DESCRIPTION OF EXPERIMENTAL
FACILITY
The design of the source under consideration is rather
simple [2, 3]. Two coaxial electrodes are placed parallel
to the magnetic field direction. The negative high-voltage
pulse supplies an internal electrode. Thus, the hollow
(tubular) electron beam, propagating along the magnetic
field, is formed.
The experiments were carried out at the facility
“Rassvet” (“Sunrise”) after it has been upgraded. The
facility (Fig.1) comprises the following: solenoid, hollow
anode (drift tube) with the internal diameter of 54 mm,
cathode and collector. The gun cathode of 20 mm in
diameter is connected directly to the storage capacitor via
the protective resistor of 1 kΩ.
The beam trace on the collector was recorded by the
luminescence of a phosphor deposited on the transparent
162 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2009. № 1.
Series: Plasma Physics (15), p. 162-164.
mailto:cherench@kipt.kharkov.ua
plate covered by the fine-structure metal gauze for
protection of charge accumulation. The collector circuit
included the resistor of 5 Ω for current signal
measurement.
163
Fig.1. Facility “Rassvet” (“Sunrise”)
1- cylindrical vacuum chamber (ceramic insulator);
2- collector with luminescence cover; 3 - tube anode
(stainless steel); 4 - coils of pulse magnetic field;
5- cathode; 6- metal flange for cathode maintaining;
7- protective resistor; 8 - kilovoltmeter; 9 - oscilloscope
with memory; 10 - digital camera; 11 - signal resistor;
12-high-v oltage source; 13 - storage capacitor;
14 -optical windows for observation.
4. DESCRIPTION OF EXPERIMENTS
The self-sustained secondary emission in the gun was
excited by the residual gas ionization. The similar method
of secondary emission excitation in the magnetron was
used by Vaughan [4]. The gas throttling procedure was
applied to increase the pressure to the secondary-emission
excitation threshold. If the residual gas pressure is
increased to several units of 10-2 Pa. the conditions for
secondary-emission ignition becomes possible.
With magnetic field switched on, the electron beam pulse
with a current of about 1 A and duration of about 1 ms
was generated. The oscillograms of beam current pulses
are shown in Fig. 2. One can see the current oscillations
which are not resolved by the oscilloscope. This
phenomenon was observed earlier by one of the authors
[2, 5] and by other authors [6].
Sometimes, the electron beam generation was broken up
by a low-voltage (arc) discharge formation.
The beam cross-section was registered by taking the
photo of the collector luminescence. The corresponding
pictures are shown on a Fig. 3. It is seen that the beam has
a characteristic tubular structure.
After long series of pulses it has been observed that
the gun cathode is covered by a brown deposit (snuff) that
proves the presence of intense electron bombardment of
the cathode. It is impossible to prevent the oil vapor
penetration into the vacuum chamber because in the
facility the oil fore pump is used. The oil film is
polymerized under electron bombardment [8]. As a result,
the brown layer of products of oil film polymerization is
formed.
Another confirmation of intensive bombardment of
the cathode is the bright blue luminescence from the
cathode area arising due to the transition radiation of
electrons bombarding the cathode [9].
Fig.2. Oscillations of the beam current and arc
breakdown at three shots of magnetic field are shown.
Start voltage 4 kV; start pressure 0.01 Pa;
storage capacitor 4 µF
Fig.3. The beam trace as it is seen on the luminescent
screen. Voltage 6 kV; pressure 0.1 Pa;
storage capacitor 100 pF
5. DISCUSSION OF RESULTS
AND PROSPECTS OF APPLICATION
The phenomenon of high-current hollow electron
beam fragmentation is known in [7]. This is possible
when the beam is propagating for a long distance with
low gun voltage and at high enough current. This
phenomenon is caused by the action of space-charge
forces. It should be noted, that the beam fragments diffuse
across the magnetic field due to the collective effects in
the beam, as is seen on photos of the beam trace (not
shown here) [7].
The time increasing magnetic field may be a favorable
factor for the electron injection into the closed magnetic
traps. The vortex field component can send electrons to
the plasma center and increase its negative potential.
The self-modulation operating mode [2, 6], with the
beam consisting of separated bunches, may be considered
as some advantage of such-type gun. The bunch repetition
rate observed in [2, 7] is within the limits of
10…200 MHz. This can provide the direct excitation of
high-frequency oscillations in the plasma. Thus, in this
case it is not necessarily for the beam to reach the plasma
164
boundary. The excitation of oscillations is possible due to
the plasma oscillation field penetration into vacuum.
In addition to the effective injection of the charge and
energy, such an approach will provide the stable plasma
ignition at the lowest pressure, even at a low power of the
gun.
6. CONCLUSIONS
The described experiments have been carried out with
a novel type of an electron source, with cold metal
cathode. In earlier publications on this subject the gun has
been excited by short pulse with voltage of tens kilovolts
and higher [1, 2, 6].
The results presented above demonstrate that such an
electron gun can be ignited with a rather low voltage
(≥ 2 kV) in a not high vacuum (10-2…10-1 Pa) and show
the prospect of its application in experimental fusion
installations.
ACKNOWLEDGEMENTS
Experiments were executed with the support of STCU
foundation within the framework of the project 1968. We
express gratitude to director of Institute of High-Energy
Physics and Nuclear Physics A.N. Dovbnya and to
director of Institute of Plasma Physics V.I. Tereshin for
the support during organization of experiments, to
V.S. Voitsenya for the support and attention and to
A.D. Komarov for useful discussions.
REFERENCES
1. S.A. Cherenshchikov, B.G. Safronov, V.S. Balagura.
Short-pulses Electron Guns with no Heating Cathodes for
Linear Accelerators// Problems of Atomic Science and
Technology. Series “Nuclear physics research” (25).
1991, N 4, p. 48-51 (in Russian).
2. S. Cherenshchykov, A. Opanasenko. High-Current
Electron Gun with Secondary Emission// Brookhaven
National Laboratory Accelerator Physics Seminars,
November 14, 2003,
www.agsrhichome.bnl.gov/AP/BNLapSeminar/HighCurr
entElectronGun.ppt.
3. S.A. Cherenshchikov. The Maltipactor Emission of
Electrons in the Cold-cathode-Magnetron Gun// Proc. of
13th. Conference of Particle Accelerators, Dubna, 1993,
v. 2, p. 142-144 (in Russian).
4. J.R.Vaughan. Gas-filled magnetron with cold cathode//
Crossed Field Microwave Devices/New York: “Academic
Press”, 1961, v. 2, p. 268-279.
5. S.A. Cherenshchikov, B.G. Safronov. Possibility of
Full Operation with Fast-Acting in no Heating Cathode
Magnetron Gun// Reports of 13th. Kharkov Seminar on
Linear Accelerator, Kharkov, 1993, p.27. (in Russian).
6. Y.M. Saveliev, W. Sibbett, and D.M. Parkes. Crossed-
Field Secondary Emission Electron Source // Proceeding
of the 11-th Int. Pulsed Power Conference, Baltimore,
1997, p. 340-345.
7. C.C. Cutler. Instability in Hollow and Strip Electron
Beams // J. Appl. Phys. 1956, v. 27, N 9, p. 1028-1029
8. R.W. Christy. Formation of thin polymer-films by
electron bombardment// J Appl. Phys., 1960, v. 31, N 9,
p. 1680-1683.
9. I.M. Frank. Transition radiation and optic properties of
substance// Uspekhi Fizicheskikh Nauk. 1965, v. 87(4),
p. 189-210. (in Russian).
Article received 10.10.08
Revised version 30.01.09
ВОЗБУЖДЕНИЕ САМОПОДДЕРЖИВАЮЩЕЙСЯ ВТОРИЧНОЙ ЭЛЕКТРОННОЙ ЭМИССИИ
ГАЗОВЫМ РАЗРЯДОМ И ГЕНЕРАЦИЯ ТРУБЧАТОГО ПУЧКА В МАГНЕТРОНОЙ ПУШКЕ
С.А. Черенщиков, В.Д. Коцубанов, И.К. Никольский
Ввод энергии в плазму зачастую можно произвести электронным пучком. Однако, сильное поперечное
магнитное поле препятствует проникновению пучков заряженных частиц в замкнутую магнитную ловушку.
Проблема может быть разрешена путем применения новой электронной пушки. Принцип действия новой
электронной пушки с холодным катодом - самоподдерживающаяся вторичная электронная эмиссия. В
описанных экспериментах зажигание пушки впервые наблюдалось при постоянном напряжении 2…6 кВ в
диапазоне давлений 10-2…10-1 Па. Пушка создавала полый электронный пучок с током выше 1 А и
длительностью до 1 мс. После зажигания работа такой электронной пушки принципиально возможна и при
более высоком вакууме.
ЗБУДЖЕННЯ ВТОРИННОЇ ЕЛЕКРОННОЇ ЕМІСІЇ, ЩО САМОПІДТРИМУЄТЬСЯ, ГАЗОВИМ
РОЗРЯДОМ ТА ГЕНЕРАЦІЯ ТРУБЧАСТОГО ПУЧКА У МАГНЕТРОННІЙ ГАРМАТІ
С.О.Черенщиков, В.Д.Коцубанов, І.К.Нікольский
Введення енергії в плазму може бути зроблено за допомогою електронного пучка. Однак, сильне поперечне
магнітне поле перешкоджає проникненню пучків заряджених часток в замкнуту магнітну пастку. Ця проблема
може бути частково вирішена шляхом використання нової електронної гармати. Принцип дії такої гармати з
холодним катодом – вторинна електронна емісія, що самопідтримується. В описаних експериментах уперше
запалювання гармати спостерігалося при постійній напрузі 2...6 кВ у діапазоні тиску 10-2...10-1 Па. Гармата
утворювала електронний пучок зі струмом більшим ніж 1 А та тривалістю 1 мс. Після запалювання робота такої
електронної гармати принципово можлива і при більш високому вакуумі.
http://www.agsrhichome.bnl.gov/AP/BNLapSeminar/HighCurrentElectronGun.ppt
http://www.agsrhichome.bnl.gov/AP/BNLapSeminar/HighCurrentElectronGun.ppt
EXCITATION OF SELF-SUSTAINED SECONDARY EMISSION BY GAS DISCH
S.A. Cherenshchykov1, V.D. Kotsubanov2, I.K. Nikolskii2
|