Beam instability stabilization in hybrid plasma waveguide
The authors submit the results of investigations of the beam-plasma instability derangement in the hybrid plasma waveguide. The latter, placed into the longitudinal magnetic field, consists of a chain of cavities connected inductively and its passage channel is filled with plasma. In this plasma, th...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
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| Цитувати: | Beam instability stabilization in hybrid plasma waveguide / A.N. Antonov, O.F. Kovpik,E.A. Kornilov, V.G. Svichensky // Вопросы атомной науки и техники. — 2005. — № 2. — С. 155-157. — Бібліогр.: 9 назв. — англ. |
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irk-123456789-797822015-04-05T03:02:09Z Beam instability stabilization in hybrid plasma waveguide Antonov, A.N. Kovpik, O.F. Kornilov, E.A. Svichensky, V.G. Plasma electronics The authors submit the results of investigations of the beam-plasma instability derangement in the hybrid plasma waveguide. The latter, placed into the longitudinal magnetic field, consists of a chain of cavities connected inductively and its passage channel is filled with plasma. In this plasma, the excitation of low-frequency oscillations that belong to the low-hybrid resonance range is examined. The investigations are carried out in the beam-plasma oscillator. The plasma is generated and maintained due to the beam-plasma discharge. Приведені результати дослідження зриву пучково-плазмової нестійкості у гібридному плазмовому хвилеводі, розміщеному в поздовжньому магнітному полі, що складається з ланцюга індуктивно зв’язаних резонаторів, пролітний канал якого заповнений плазмою, при збудженні низькочастотних коливань в його плазмі із області нижнєгібридного резонансу зовнішнім генератором. Гібридний плазмовий хвилевід використовується в пучково-плазмовому генераторі. Плазма створюється і підтримується за рахунок пучково-плазмового розряду. Приведены результаты исследования срыва пучково-плазменной неустойчивости в гибридном плазменном волноводе, помещенном в продольное магнитное поле, состоящем из цепочки индуктивно связанных резонаторов, пролетный канал которой заполнен плазмой, при возбуждении низкочастотных колебаний в его плазме из области нижнегибридного резонанса внешним генератором. Гибридный плазменный волновод используется в пучково-плазменном генераторе. Плазма образовывается и поддерживается за счет пучково- плазменного разряда. The authors are grateful to A.P. Tolstolugsky for the calculation of the spiral aerial, loaded with plasma and to L.D. Lobzov for the oscillator adjustment. S.S. Pushkarev’s help in the elaboration of the technique of registering the probing pulses in plasma with probes is gratefully acknowledged. We also wish to thank V.A. Buts for the discussion of the results and valuable suggestions in the course of the work fulfillment. 2005 Article Beam instability stabilization in hybrid plasma waveguide / A.N. Antonov, O.F. Kovpik,E.A. Kornilov, V.G. Svichensky // Вопросы атомной науки и техники. — 2005. — № 2. — С. 155-157. — Бібліогр.: 9 назв. — англ. 1562-6016 PACS: 52.40.Mj http://dspace.nbuv.gov.ua/handle/123456789/79782 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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English |
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Plasma electronics Plasma electronics |
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Plasma electronics Plasma electronics Antonov, A.N. Kovpik, O.F. Kornilov, E.A. Svichensky, V.G. Beam instability stabilization in hybrid plasma waveguide Вопросы атомной науки и техники |
| description |
The authors submit the results of investigations of the beam-plasma instability derangement in the hybrid plasma waveguide. The latter, placed into the longitudinal magnetic field, consists of a chain of cavities connected inductively and its passage channel is filled with plasma. In this plasma, the excitation of low-frequency oscillations that belong to the low-hybrid resonance range is examined. The investigations are carried out in the beam-plasma oscillator. The plasma is generated and maintained due to the beam-plasma discharge. |
| format |
Article |
| author |
Antonov, A.N. Kovpik, O.F. Kornilov, E.A. Svichensky, V.G. |
| author_facet |
Antonov, A.N. Kovpik, O.F. Kornilov, E.A. Svichensky, V.G. |
| author_sort |
Antonov, A.N. |
| title |
Beam instability stabilization in hybrid plasma waveguide |
| title_short |
Beam instability stabilization in hybrid plasma waveguide |
| title_full |
Beam instability stabilization in hybrid plasma waveguide |
| title_fullStr |
Beam instability stabilization in hybrid plasma waveguide |
| title_full_unstemmed |
Beam instability stabilization in hybrid plasma waveguide |
| title_sort |
beam instability stabilization in hybrid plasma waveguide |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2005 |
| topic_facet |
Plasma electronics |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/79782 |
| citation_txt |
Beam instability stabilization in hybrid plasma waveguide / A.N. Antonov, O.F. Kovpik,E.A. Kornilov, V.G. Svichensky // Вопросы атомной науки и техники. — 2005. — № 2. — С. 155-157. — Бібліогр.: 9 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-07-06T03:45:50Z |
| last_indexed |
2025-07-06T03:45:50Z |
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1836867702409396224 |
| fulltext |
BEAM INSTABILITY STABILIZATION IN HYBRID PLASMA
WAVEGUIDE
A.N. Antonov, O.F. Kovpik, E.A. Kornilov, V.G. Svichensky
NSC Kharkov Institute of Physics & Technology, Kharkov, Ukraine
The authors submit the results of investigations of the beam-plasma instability derangement in the hybrid plasma
waveguide. The latter, placed into the longitudinal magnetic field, consists of a chain of cavities connected inductively
and its passage channel is filled with plasma. In this plasma, the excitation of low-frequency oscillations that belong to
the low-hybrid resonance range is examined. The investigations are carried out in the beam-plasma oscillator. The
plasma is generated and maintained due to the beam-plasma discharge.
PACS: 52.40.Mj
Earlier we have already investigated the excitation of
microwaves by the electron beam at the plasma
characteristic electron frequencies in the hybrid plasma
waveguide (HPW). The investigations have indicated that
the microwave power is to a considerable extent
determined by low frequency (LF)- and ion oscillations of
plasma [1,2]. A chain of inductively connected cavities
with the plasma-filled passage channel is traditionally
used for the beam-plasma (BP) oscillators and amplifiers
[3]. Ion-acoustic (IA) and low-hybrid (LH) waves are LF
proper waves of this waveguide [4].
Seemingly, the pressure of microwaves stimulated
directly by the beam makes one of the most probable
nonlinear mechanisms for the excitation of ion-acoustic
oscillations in HPW [2]. As ion-acoustic oscillations come
into existence, there arise temporal changes in the
absolute magnitude of the plasma density and in its
longitudinal gradient. These factors cause alterations both
in the microwave excitation effectiveness and directly in
the dispersion of the microwaves driven by the beam. As a
result, both the microwave group velocity and the excited
wave energy flow change directions of their motion. At
the HPW edges, the amount of microwave maximum
power is being periodically changed in time. [4].
Augmentation of the beam current is accompanied by an
increase in the microwave power. However, when it
achieves a certain threshold value, there occurs the
microwave excitation derangement [1-2]. Even if the
excitation still takes place, there arise just separate
sporadic pulses, short in a space of time. Before the
derangement, one can always detect an increase in
amplitudes of LF oscillations of the low-hybrid range. It is
perfectly legitimate to suppose that these LF oscillations
make a certain contribution to the microwave excitation
derangement. As it is known, if BP discharge is
unbounded in its radius, the excitation of LF oscillations
from the low-hybrid resonance area is accompanied by the
acceleration of plasma ions and their heating as well as by
the plasma going away from the beam area along the beam
radius. That is, the process of excitation of LF oscillations
is accompanied by a decrease in the plasma density in the
beam area [5]. Via the mechanism for the nonlinear
coupling with microwaves, LF oscillations make a certain
contribution to stochastization of microwaves so that they
become irregular. In this case, the electron beam of a
narrow energy spectrum, continuously coming to HPW, is
incapable of any effective transfer of its energy to
irregular waves. This can result in the microwave
excitation derangement [6]. In HPW, where BP discharge
maintains plasma, can take place these processes as well.
This supposition is confirmed by a series of the tests
performed by the authors (for this purpose, we used the
installation, where the dispersion of HPW proper LF
waves had been measured earlier [7]). The method of
introducing external disturbances into HPW is applied.
These disturbances have the form of a probe wave, the
frequency of which belongs to the low-hybrid oscillation
range. Short LH waves are excited with a helical aerial,
fed from a driving oscillator with the tunable frequency.
The spiral, installed in front of HPW, is axially-
symmetric with respect to the electron beam, injected into
HPW. The waveguide is located in the homogeneous
magnetic field (up to 0.2 Tl). In the tests, the beam energy
ranges within (10-20) keV and the current is (1-10)A per
pulse of the duration 2 ms. The power of the oscillations
under excitation at the frequencies (4-4.5)GHz varies
from 100W up to 40kW. The nitrogen pressure in the
chain of inductively connected cavities varies within (1.33
·10-2-1.33·10-1) Pa. The oscillation power transferred from
the driving oscillator to the spiral does not exceed 100 W
at the frequencies (50-75) MHz per pulse of the duration
250 µs.
Let us dwell on certain specificities of correlation
between microwaves excited by the beam and LF waves
from the low-hybrid range, detected when BP discharge is
being maintained in HPW.
I. If regular microwaves are excited by the electron
beam at the frequency ω 0, the introduction of a wave at
the frequency ω h from LH-range into the HPW plasma
is accompanied by the emergence of the combination
frequency ω = ω 0- ω h in the spectrum ω 0. The
amplitude of microwaves at the frequency ω 0 decreases.
To restore the amplitude initial value, it is necessary to
augment the energy of the beam injected into HPW.
The combination oscillation amplitude increases as the
microwave amplitude grows. At the same time, the
probing LH wave, excited by the oscillator and
propagating in HPW, is being attenuated if the beam
parameters are fixed. This specificity of the generated
Problems of Atomic Science and Technology. Series: Plasma Physics (11). 2005. № 2. P. 155-157 155
wave behavior indicates that the energy is continuously
being transmitted from microwaves excited by the beam
to LH waves.
As the amplitude of excited probing LF waves increases,
the phase velocity of LH waves increases as well. To start
from a certain amplitude value, there arise harmonics and
the probing wave is subjected to bifurcation. That is, in
the dispersion function of LH waves D( ω ,k), which
determines their phase velocity in plasma of HPW, the
wave vector k depends on the wave field strength. LH
waves are nonlinear if the microwave power takes the
above-mentioned value. Generation of high-frequency
components and their harmonics in the LF oscillation
spectrum is detected experimentally already when the
microwave field strength is on the order of hundreds of
V/cm (see [7]).
In Fig.1, one can see the oscillograms that depict
changes in the frequency and amplitude of the LH wave,
excited by the oscillator, after the wave passage through
HPW. It is clearly demonstrated that at the HPW output
the frequency has reached the value 4 times as high,
whereas the amplitude has become 5 times as small.
Fig.1. Evolution of the probing signal during its
propagation through HPW
The following designations are used:
1 - marks the oscillations excited in plasma by the master
oscillator at the frequency 47.9MHz;
2 - denotes the oscillations registered with the probe at the
beam input into HPW;
3 - designates oscillations registered with the probe at the
HPW output (the oscillograph sensitivity is 5 time as high
as in the oscillograms 1 and 2).
II. A certain regular dependence is established between
amplitudes of LH oscillations and microwaves. The higher
is the LH waves amplitude assigned, the smaller is the
critical power of microwaves excited by the beam in
HPW. That is, one can observe a diminution in the
microwave power amount, the excess over this limit is
accompanied by the microwave derangement. This fact
indicates that not only ion-acoustic waves [2] but also LH
ones affect the limiting values, imposed on the microwave
power amount attainable in BP-oscillator that contains
HPW.
In Fig.2, oscillograms illustrate the microwave
suppression during the LH wave excitation in HPW. In
the upper oscillogram, the detected pulse of LF
oscillations, sent to the spiral from the master oscillator, is
presented. In the lower oscillogram, one can see the
signal, coming from microwaves excited by the beam of
the power 30 kW and detected at the HPW output section.
The oscillograms demonstrate that the oscillation
excitation by the master oscillator is accompanied by the
total suppression of microwaves. Tracing the process of
changes in the power of microwaves excited by the beam
during the duration of LF oscillation power pulse,
transferred to the spiral aerial, one can notice the
following pattern.
If the LF oscillation power is introduced (at the pulse
leading edge), the amount of which makes (15-20)% of
the value that corresponds to the microwave suppression,
the microwave power decreases in time by (50-80)%
approximately in the direct proportion. However, up to
80% of the LF oscillation power is required for the
microwave total suppression (20%). Besides, before the
total derangement, there always exists a stage, during
which the microwave amplitude steeply decreases (the
stage duration is rather short - several µs). In the
experiment, when the LF oscillation power pulse leading
edge makes 60 µs, the first stage lasts approximately
during (10-15)µs, the final stage duration is (2-5)µs.
Fig.2. Oscillograms of envelopes of the oscillations from
the LH range, excited by the oscillator at the frequency
70MHz, and the envelope of oscillations in the band
4GHz, excited by the electron beam (the pulse power is
30kW)
At the same time, the process of restoration of
microwave excitation is of “explosive” nature. Microwave
power is restored up to 70% at the LF oscillation probing
pulse rear edge during the time shorter than 5µs. The
functional dependence of microwave power (P)
restoration in time has the following form:
P≈A0
2⋅1 −e
t0−t /3 . 2109
Here A0 is the amplitude of microwaves excited by the
beam in the absence of the probing LF signal; t0 denotes
the time corresponding to the end of the probing pulse
plateau; t is running time.
The character of temporal changes in the microwave
amplitude, observed under the condition of alterations in
the amount of the probing signal power transferred to the
antenna, additionally confirms the existence of LF wave
absorption. That is, the nonlinear coupling between
microwaves and LH LF waves is realized under the
condition of strong absorption of the latter in plasma. One
of the consequences of this absorption can become the gas
extra ionization so that the plasma density increases. The
following fact can indirectly confirm this statement. For
the maintenance of the effective excitation of microwaves
by the beam when the probing LF signal is sent, the beam
energy must be augmented. As it is known [7], the
156
electron wave phase velocity increases as the plasma
density in the waveguide grows.
The authors consider that the oscillograms in Fig.2
confirm that LH wave amplitudes affect the process of
microwave excitation in BP oscillator. One can suppose
that only the mechanisms for suppressing LF oscillations
from LH wave range can permit augmenting the maximum
amount of microwave power, attainable in HPW of BP
oscillator.
CONCLUSIONS
Generally speaking, the results of the given work and
the works fulfilled earlier [1-4] confirm that the HPW
proper LF ion oscillations play an important role in the
excitation of microwaves by the electron beam. LF
oscillations are excited due to the plasma non-linearity in
the BP discharge.
Excitation of ion-acoustic oscillations in HPW is
accompanied by the formation of the plasma density
longitudinal gradient during certain time intervals. This
gradient maintains the auto-resonance between the beam
losing the energy in HPW and the microwave excited.
During these time intervals, the microwave electric field
strength in plasma increases up to the value, under which
the microwave “splits” to one of the HPW proper
microwave modes and a LH wave. In the long run, an
increase in the amplitude of the latter causes the beam
instability derangement, “extinction” of BP discharge and
sporadic generation of microwave short single pulses.
The totality of the results of the investigations indicates
the following. Microwaves in BP system of HPW can be
stable and regular only when their power does not reach a
critical value, under which the excitation of long-wave LF
ion oscillations in plasma becomes possible due to the
microwave pressure.
In BP oscillator, a large amount of power and a high
efficiency are obtainable when the device operates in
vicinity to the critical power value. Besides, the HPW
input and output sections must be connected to a common
load. In BP microwave devices where HPW is used, high
power is obtainable if the waveguide cross-section of a
large size is taken. As it is known, the power at the
oscillator output is field strength, the wave group velocity
and the plasma cross-
section in the waveguide. Consequently, if the wave
electric field strength is fixed, the oscillator power is
directly proportional to the HPW cross-section size and to
the coefficient of coupling with the electron beam.
Seemingly, for BP-oscillator or a high-power microwave
amplifier, a waveguide in the form of a coaxial line,
loaded with disks on both electrodes and the passage
channel filled with plasma is one of prospective models of
HPW [8,9].
The authors are grateful to A.P. Tolstolugsky for the
calculation of the spiral aerial, loaded with plasma and to
L.D. Lobzov for the oscillator adjustment. S.S.
Pushkarev’s help in the elaboration of the technique of
registering the probing pulses in plasma with probes is
gratefully acknowledged. We also wish to thank V.A.
Buts for the discussion of the results and valuable
suggestions in the course of the work fulfillment.
REFERENCES
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O.F.Kovpik, E.A. Kornilov, K.V. Matyash,
V.G.Svichensky. Measurement of Dispersion of Low-
Frequency Ion Oscillations in Hybrid Plasma Waveguides
// Problems of Atomic Science and Technology. This
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СТАБИЛИЗАЦИЯ ПУЧКОВОЙ НЕУСТОЙЧИВОСТИ В ГИБРИДНОМ ПЛАЗМЕННОМ ВОЛНОВОДЕ
А.Н. Антонов, О.Ф. Ковпик, Е.А. Корнилов, В.Г. Свиченский
Приведены результаты исследования срыва пучково-плазменной неустойчивости в гибридном плазменном
волноводе, помещенном в продольное магнитное поле, состоящем из цепочки индуктивно связанных
резонаторов, пролетный канал которой заполнен плазмой, при возбуждении низкочастотных колебаний в его
плазме из области нижнегибридного резонанса внешним генератором. Гибридный плазменный волновод
используется в пучково-плазменном генераторе. Плазма образовывается и поддерживается за счет пучково-
плазменного разряда.
СТАБІЛІЗАЦІЯ ПУЧКОВОЇ НЕСТІЙКОСТІ В ГІБРИДНОМУ ПЛАЗМОВОМУ ХВИЛЕВОДІ
О.М. Антонов, О.Ф. Ковпік, Є.О. Корнілов, В.Г. Свіченський
157
Приведені результати дослідження зриву пучково-плазмової нестійкості у гібридному плазмовому хвилеводі,
розміщеному в поздовжньому магнітному полі, що складається з ланцюга індуктивно зв’язаних резонаторів,
пролітний канал якого заповнений плазмою, при збудженні низькочастотних коливань в його плазмі із області
нижнєгібридного резонансу зовнішнім генератором. Гібридний плазмовий хвилевід використовується в
пучково-плазмовому генераторі. Плазма створюється і підтримується за рахунок пучково-плазмового розряду.
158
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