Microsecond microwave generation in the diode and accompanying phenomena
The processes of a gas desorption and ion production were investigated during generation of microwave pulses in a microsecond vircator. The influence of vacuum conditions was investigated and the velocity of cathode plasma was determined. Specific values of gas desorption and the partial composition...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2000
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| Zitieren: | Microsecond microwave generation in the diode and accompanying phenomena / V.B. Yuferov, V.G. Kotenko, I.N. Onishchenko, L.G. Sorokovoy, Yu.V. Kholod, E.I. Skibenko // Вопросы атомной науки и техники. — 2000. — № 2. — С. 97-99. — Бібліогр.: 3 назв. — англ. |
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Yuferov, V.B. Kotenko, V.G. Onishchenko, I.N. Sorokovoy, L.G. Kholod, Yu.V. Skibenko, E.I. 2015-05-27T12:29:12Z 2015-05-27T12:29:12Z 2000 Microsecond microwave generation in the diode and accompanying phenomena / V.B. Yuferov, V.G. Kotenko, I.N. Onishchenko, L.G. Sorokovoy, Yu.V. Kholod, E.I. Skibenko // Вопросы атомной науки и техники. — 2000. — № 2. — С. 97-99. — Бібліогр.: 3 назв. — англ. 1562-6016 PACS: 52.75.Kq, 52.75.Pv https://nasplib.isofts.kiev.ua/handle/123456789/82270 The processes of a gas desorption and ion production were investigated during generation of microwave pulses in a microsecond vircator. The influence of vacuum conditions was investigated and the velocity of cathode plasma was determined. Specific values of gas desorption and the partial composition was investigated for different cathodes. The parameters of the diode electron accelerator are the followings: beam energy 300 keV, beam current up to 10 kA, half-period 1,5 µs. Cathode and anode diameters are 10 cm and 20 cm, respectively. Vacuum chamber diameter is 50 cm, anode-cathode gap is 2 cm. The duration of microwave radiation is 0,5 µs, wavelength is about 10 cm, output microwave power is of about 1.5.10⁸ W. The amount of gassing reaches 0.3 n.cm3/pulse. Ion energy reaches 200-300 keV value. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Тheory and technics of particle acceleration Microsecond microwave generation in the diode and accompanying phenomena Генерация микроволновых волн в диоде и сопровождающие явления Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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| title |
Microsecond microwave generation in the diode and accompanying phenomena |
| spellingShingle |
Microsecond microwave generation in the diode and accompanying phenomena Yuferov, V.B. Kotenko, V.G. Onishchenko, I.N. Sorokovoy, L.G. Kholod, Yu.V. Skibenko, E.I. Тheory and technics of particle acceleration |
| title_short |
Microsecond microwave generation in the diode and accompanying phenomena |
| title_full |
Microsecond microwave generation in the diode and accompanying phenomena |
| title_fullStr |
Microsecond microwave generation in the diode and accompanying phenomena |
| title_full_unstemmed |
Microsecond microwave generation in the diode and accompanying phenomena |
| title_sort |
microsecond microwave generation in the diode and accompanying phenomena |
| author |
Yuferov, V.B. Kotenko, V.G. Onishchenko, I.N. Sorokovoy, L.G. Kholod, Yu.V. Skibenko, E.I. |
| author_facet |
Yuferov, V.B. Kotenko, V.G. Onishchenko, I.N. Sorokovoy, L.G. Kholod, Yu.V. Skibenko, E.I. |
| topic |
Тheory and technics of particle acceleration |
| topic_facet |
Тheory and technics of particle acceleration |
| publishDate |
2000 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Генерация микроволновых волн в диоде и сопровождающие явления |
| description |
The processes of a gas desorption and ion production were investigated during generation of microwave pulses in a microsecond vircator. The influence of vacuum conditions was investigated and the velocity of cathode plasma was determined. Specific values of gas desorption and the partial composition was investigated for different cathodes. The parameters of the diode electron accelerator are the followings: beam energy 300 keV, beam current up to 10 kA, half-period 1,5 µs. Cathode and anode diameters are 10 cm and 20 cm, respectively. Vacuum chamber diameter is 50 cm, anode-cathode gap is 2 cm. The duration of microwave radiation is 0,5 µs, wavelength is about 10 cm, output microwave power is of about 1.5.10⁸ W. The amount of gassing reaches 0.3 n.cm3/pulse. Ion energy reaches 200-300 keV value.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/82270 |
| citation_txt |
Microsecond microwave generation in the diode and accompanying phenomena / V.B. Yuferov, V.G. Kotenko, I.N. Onishchenko, L.G. Sorokovoy, Yu.V. Kholod, E.I. Skibenko // Вопросы атомной науки и техники. — 2000. — № 2. — С. 97-99. — Бібліогр.: 3 назв. — англ. |
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2025-11-26T17:30:36Z |
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2025-11-26T17:30:36Z |
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| fulltext |
MICROSECOND MICROWAVE GENERATION IN THE DIODE AND
ACCOMPANYING PHENOMENA
V.B. Yuferov, V.G. Kotenko, I.N. Onishchenko, L.G. Sorokovoy, Yu. V. Kholod, E.I. Skibenko
National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
The processes of a gas desorption and ion production were investigated during generation of microwave pulses
in a microsecond vircator. The influence of vacuum conditions was investigated and the velocity of cathode plasma
was determined. Specific values of gas desorption and the partial composition was investigated for different
cathodes. The parameters of the diode electron accelerator are the followings: beam energy 300 keV, beam current
up to 10 kA, half-period 1,5 µs. Cathode and anode diameters are 10 cm and 20 cm, respectively. Vacuum chamber
diameter is 50 cm, anode-cathode gap is 2 cm. The duration of microwave radiation is 0,5 µs, wavelength is about
10 cm, output microwave power is of about 1.5⋅108 W. The amount of gassing reaches 0.3 n.cm3/pulse. Ion energy
reaches 200-300 keV value.
PACS: 52.75.Kq, 52.75.Pv
I. INTRODUCTION
For creation of high-power microwave pulse
generators of various applications it is necessary to
know, apart from the information about the microwave
generation itself, a number of accompanying effects
determining the energy-weight and resource
characteristics. Therefore, in the present paper besides
the researches on microwave generation, investigations
of values and partial composition of gassing, energy and
direction of ion fluxes were performed.
II. THE SETUP AND DIAGNOSTICS
The experiments were carried out at the setup
VGIK-1 [1] (Fig. 1) with the following diode
parameters: voltage up to 300 kV, current about 10 kA,
the shape of pulses of current and voltage is close to the
sinusoidal one with duration of a half-period about 3.5 µ
s. The size of the anode - cathode gap was varying from
10 up to 25 mm by moving the cathode of 10 cm in
diameter. The anode is the grid from 20 cm diameter
stainless steel with a transparency of about 80%. The
cathode is grounded, a pulse of positive polarity moved
on the anode. Researches of a microwave generator of
such type are described in the papers [2, 3]. The vacuum
chamber of the diode is the pipe from stainless steel
with about 50 cm diameter and 100 cm length. In the
field of the diode there could be an external magnetic
field up to 2 kOe, parallel to the diode axes, i.e. in the
anode-cathode direction.
At the first stage of experiments the system was
pumped with the use of nitrogen-helium sorption and
condensation cryopumps and, at the second stage, with
diffusion oil pumps. The vacuum chamber is made by a
usual, not superhigh vacuum technology, has rubber
seals and could be heated no more than up to 80°?,
however separate parts, for example the cathode, could
be heated up to 500°?. The operating pressure in a
system is about 1⋅10-6 Torr for cryopumps and about 4⋅
10-5 Torr for diffusion pumps.
The installation is provided with the following
diagnostic tools: belts of Rogovsky for current
measurement, and a capacity divider for voltage
measurement, x-ray sensors of an integral type,
microwave calorimeters of a horn and planar type,
microwave diodes with attenuators, vacuum sensors and
a mass-gas-analyzer. Magnetic analyzers using track
prints were used to measure the energy and composition
of the ionic component.
Fig. 1. Schematic diagram of the device. 1−
vacuum chamber, 2− output window, 3 - cathode, 4−
anode, 5–cryopump, 6–accelerating column, 7−high-
voltage current input, 8–Marx generator, 9−mass-
spectrometric analyzer, 10−pure zone.
III. EXPERIMENTAL RESULTS
The oscillograms of diode current and diode voltage,
the shape of microwave signal are shown in Fig. 2. The
comparison of the shape of microwave signal with the
calorimetric data determines the value of microwave
power at a level of 150 MW. The calorimeters are
graduated by current and microwave signals and have
sensitivity about 10 J/K with an accuracy of temperature
measurement by gas thermometers of 5⋅10-2 K. The
value of wavelength is in the range 10-11 cm. It was
estimated by the help of the flashing tubes and the
calorimeter with the adjusting plunger, using the given
parameters of beam and geometry of the system without
magnetic field. The duration of a microwave pulse
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2000, № 2.
Серия: Ядерно-физические исследования (36), с. 97-99.
97
essentially depends on the type of the cathode. For flat
carbon and multipin cathodes it can vary from 200 up to
500 ns.
U, kV
I, kA
µ
, (rel. unit)
µ
µ
s
s
Fig. 2. The oscillograms of diode current and
voltage of microwave signal.
The arrows show the directions of ion fluxes in
Fig. 1, and the main direction is equatorial. The natural
hit of ions on the cathode was not registered. The
registered energies of ions lie in the range of 50 -
250 keV. The main composition of the beam ions is
iron, carbon and hydrogen. The actuation of a magnetic
field reduces an equatorial flux. At present, we cannot
distinguish static and microwave acceleration. The
availability of ions of iron is connected with ablation
processes on the anode grid, where the level of energy
release achieves 10-50 J/cm2. The destruction of the
anode grid occurs, as a rule, at quantity of pulses
exceeding 103. Availability of graphite cathodes,
pumping facilities and the materials of the diode
determine the presence of ions of carbon and hydrogen.
Their availability determines the velocity of cathode
plasma motion as well, which lies in the range 3-4⋅
106 cm/s and, accordingly, the duration of a microwave
pulse.
Deposition of carbon on the anode grid also gives a
carbon ionic component. An interesting observation is
the availability of a pure zone, i.e. a zone without the
deposition of films in the field of a ring with width of
about 2 cm around a high-voltage current input in
accelerating tube. This can testify to magnetic shielding
and focusing of ion fluxes coming from the diode.
Besides, a special type of a print of the cathode on an
output window allows assuming that the role of a
current in a high-voltage current input is exhibited at the
opposite side as well.
To obtain the information about pulse gassing the
vacuum chamber of the diode immediately before the
start of Marx generator was separated from the external
pump by valve KR-100. The start of Marx generator
operation was accompanied by a leap of chamber
pressure, which was registered by a recorder.
The amplitude of a pressure leap registered is
proportional to the value of complete gassing only in
that case, when the pump of internal arrangement
completely is disconnected, i.e. warm. At the presence
in a screen of liquid nitrogen of this pump, the chamber
pressure was lowered up to 4-3⋅105 Torr, and the
registered pressure leap will be proportional to quantity
of noncondensing gases on a nitrogen surface (H2, N2,
CH4, CO3). It is explained large (about 2⋅104 l/s)
pumping speed of noncondensing component (H2O,
CO2) on a nitrogen surface and final constant of time of
a measuring circuit. After filling up of liquid helium in
the helium condensation pump (HCP) of internal
arrangement the value of the registered pressure leap is
determined by total amount of hydrogen, desorbed for a
pulse and besides by relation between pumping speed
and resolving ability of the measuring system.
∆ .
. . . .
Fig. 3. Typical sequence of pressure changes ∆P
from pulse to pulse in experiments with the grid anode,
N is the serial number of pulse.
The diagram in Fig. 3 shows a typical sequence of
pressure changes from pulse to pulse for the mentioned
above cases. From Fig. 3 it is seen, that already after the
first 5-10 pulses the pressure jumps reach some almost
constant average level. The pressure in the diode
chamber behaves in a similar way, remaining
approximately at the same level, despite of increasing
quantity of pulses. After liquid nitrogen filling up into
the HCP screen of internal arrangement, the average
value of registered pressure jump drops approximately
in 4 times. Under the supposition that thus the average
level of the gassing has not varied, such decreasing of
pressure jump testifies that there is approximately to
50% content of components easily condensed at
T= 78 K (with corrections on the sensitivity of the
sensor PMI-2 to various gases) in its composition. The
filling of liquid helium into the HCP lowers the value of
the registered pressure jump more than in 10 times as
compared to the initial one.
Thus, the experiments have shown that under
conditions close to conventional ones, the average value
of complete gassing in the vacuum chamber of the diode
makes 1,0-0,3 cm3 per pulse and grows with the pulse
power (Fig. 4). We have not observed a significant
reduction of the average level of gassing (and pressure)
in accordance with increasing a number of pulses (up to
98
150 in a series). From our point of view, the cause of the
absence of training and cleaning of vacuum surfaces can
be the gas flux coming from such source as a caprolan
isolator. Furthermore, the pre-breakdown effects
stimulate the value of this flux with applying of voltage
pulse to the diode input. This gas is actively adsorbed
by the surfaces cleared during the previous pulse and it
is desorbed under the action of a consequent pulse. The
energy output of desorbed particles makes about 103 eV
or 102 particles per beam electron.
As show additional experiments, not only the
electrodes of the diode gap are subjected to clearing, but
also the areas neighboring to it. For example, the
replacement of the flange from stainless steel (located at
a level of the diode isolator at an angle of 90° to the
latter) with flanges from organic glass resulted in
increase of the average value of gassing at fixed voltage
by a factor of five (point I, Fig. 4).
220 240 260 280 300 320
0,0
0,1
0,2
0,3
0,4
0,5
0,6
3
4
2
1
∆V
, c
m
2 /im
p
U, cm
Fig. 4. Averaged gassing vs diode voltage.
Despite the fact that the surface of the anode was
increased no more than by 20% in experiments with the
anode of disk type it was found that the average value of
gassing on a comparison with the grid anode was
increased in 2 times (point 2, Fig. 4). This fact can be
explained by effective reflection of particle fluxes and
radiation emission to the lateral surface of the chamber
by the anode of disk type. The magnetic field (1.2 kOe)
application resulted in a common reduction of pressure
jump and average value of gassing (point 3, Fig. 4). It is
explained by the fact that the magnetic field lines are
mainly parallel to the lateral surface of the chamber and
the electrical discharge in a longitudinal magnetic field
is localized in the area of the cathode-anode gap.
The contrary effect is observed in experiments with
the grid anode when applying the magnetic field (point
4, Fig. 4). A source of gassing increase in this case
indicates the occurrence of a precise blackening circle
of the cathode print on the bottom of the HCP nitrogen
screen of internal arrangement located 20 cm higher
above the grid anode. Thus, here, the increase of gassing
occurs as a result of gas desorption from the surface of
the nitrogen screen under effect of cathode plasma
fluxes spreading along lines of magnetic field and of
some part of the electron beam and ions.
Gas composition
Gas H2 28 H2O CH4 CO2
∆P, 10-6 Torr 3300 90 57 39 15
% 93 3 2 1 0.4
IV. SUMMARY
Experiments with isolators and cathodes from
various materials showed, that, despite of existence of
some differences in background mass spectra, the value
and the composition of the pulsed gassing (PG) do not
significantly depend on the isolator and cathode
material. A specific PG composition in experimental
conditions under consideration obtained as the average
value of large number of pulses (up to 150 per peak), is
represented in Table. As is seen, some gases give the
contribution to the PG composition at a level more than
1 %. A dominant gas among them is hydrogen. The
experimentally established fact that isolator and cathode
materials have no strong influence on the PG
composition indicates that the main source of hydrogen
is its reduction from the walls of the vacuum chamber
and cathode.
As follows from experiments the essential problem
in development of microwave generators operating in
the frequency mode is the pulsed gassing that causes
complication of the vacuum system. Therefore, it is
supposed to elaborate the measures for gassing
reduction.
REFERENCES
1.V.G. Kotenko, V.I. Kurnosov, V.I. Kuskov,
V.B. Yuferov. Microsecond diode gassing // VANT.
Ser. NPhE, 1990, edition 8(10), p. 12 (in Russian).
2.A.N. Didenko et al. Generation of HF in Systems
with Virtual Cathode // Fizika Plazmy, 1976, v. 2,
edition 3, p. 514 (in Russian).
3.A.N. Didenko, G.P. Fomenko, J.Z. Gleizer et al.
Generation of High Power RF Pulses in the
Magnetron and Reflex Triode System. Proceedings
of the 3rd International Topical Conference on High
Power Electron and Ion Beam Research and
Technology. July 3-6, 1979, Novosibirsk, p. 683.
99
MICROSECOND MICROWAVE GENERATION In the DIODE And ACCOMPANYING PHENOMENA
I. Introduction
II. The Setup and Diagnostics
III. Experimental results
Gas composition
IV. Summary
References
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