Wave nonlinear interaction effect on beam-plasma reciprocal influence
The authors have examined the oscillation excitation by an extensive nonrelativistic beam of electrons in the beamplasma discharge in the magnetic field when the beam power is about hundreds of kilowatts. It is demonstrated that lowfrequency (LF) ion waves from the range of the low hybrid (LH) reson...
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Buts, V.A. Kovpik, O.F. Kornilov, E.A. 2015-04-04T19:46:29Z 2015-04-04T19:46:29Z 2005 Wave nonlinear interaction effect on beam-plasma reciprocal influence / V.A. Buts, O.F. Kovpik, E.A. Kornilov // Вопросы атомной науки и техники. — 2005. — № 2. — С. 131-133. — Бібліогр.: 10 назв. — англ. 1562-6016 PACS: 52.40.Mj https://nasplib.isofts.kiev.ua/handle/123456789/79797 The authors have examined the oscillation excitation by an extensive nonrelativistic beam of electrons in the beamplasma discharge in the magnetic field when the beam power is about hundreds of kilowatts. It is demonstrated that lowfrequency (LF) ion waves from the range of the low hybrid (LH) resonance play the determinative role in maintaining the beam-plasma discharge. Excitation of such waves is stimulated by the nonlinear interaction between electron plasma oscillation modes of the decay type. The electromagnetic radiation emission from the discharge of pulses is stimulated by the above-mentioned nonlinear interaction, which also causes the wave stochasticity and stabilizes the beam instability. Приведені результати досліджень збудження коливань довгим нерелятивістським електронним пучком при потужності сотні кіловат в пучково-плазмовому розряді в магнітному полі. Показано, що в підтримці пучково- плазмового розряду визначаючу роль відіграють низькочастотні іонні хвилі із області нижчегібридного резонансу. Їх збудження зумовлено нелінійною взаємодією електронних плазмових мод коливань типу розпаду. Електромагнітне випромінювання з розряду імпульсів обумовлене вище вказаною нелінійною взаємодією. Вона і приводить до стохастизації та стабілізації пучкової нестійкості. Проведены результаты исследований возбуждения колебаний протяженным нерелятивистским электронным пучком при мощности сотни киловатт в пучково-плазменном разряде в магнитном поле. Показано, что в поддержании пучково-плазменного разряда определяющую роль играют низкочастотные ионные волны из области нижнегибридного резонанса. Их возбуждение обусловлено нелинейным взаимодействием электронных плазменных мод колебаний типа распада. Электромагнитное излучение из разряда импульсов обусловлено выше указанным нелинейным взаимодействием. Оно же приводит к стохастизации волн и стабилизации пучковой неустойчивости. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Plasma electronics Wave nonlinear interaction effect on beam-plasma reciprocal influence Вплив нелінійної взаємодії хвиль на пучково-плазмову взаємодію Влияние нелинейного взаимодействия волн на пучково-плазменное взаимодействие Article published earlier |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| title |
Wave nonlinear interaction effect on beam-plasma reciprocal influence |
| spellingShingle |
Wave nonlinear interaction effect on beam-plasma reciprocal influence Buts, V.A. Kovpik, O.F. Kornilov, E.A. Plasma electronics |
| title_short |
Wave nonlinear interaction effect on beam-plasma reciprocal influence |
| title_full |
Wave nonlinear interaction effect on beam-plasma reciprocal influence |
| title_fullStr |
Wave nonlinear interaction effect on beam-plasma reciprocal influence |
| title_full_unstemmed |
Wave nonlinear interaction effect on beam-plasma reciprocal influence |
| title_sort |
wave nonlinear interaction effect on beam-plasma reciprocal influence |
| author |
Buts, V.A. Kovpik, O.F. Kornilov, E.A. |
| author_facet |
Buts, V.A. Kovpik, O.F. Kornilov, E.A. |
| topic |
Plasma electronics |
| topic_facet |
Plasma electronics |
| publishDate |
2005 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Вплив нелінійної взаємодії хвиль на пучково-плазмову взаємодію Влияние нелинейного взаимодействия волн на пучково-плазменное взаимодействие |
| description |
The authors have examined the oscillation excitation by an extensive nonrelativistic beam of electrons in the beamplasma discharge in the magnetic field when the beam power is about hundreds of kilowatts. It is demonstrated that lowfrequency (LF) ion waves from the range of the low hybrid (LH) resonance play the determinative role in maintaining the beam-plasma discharge. Excitation of such waves is stimulated by the nonlinear interaction between electron plasma oscillation modes of the decay type. The electromagnetic radiation emission from the discharge of pulses is stimulated by the above-mentioned nonlinear interaction, which also causes the wave stochasticity and stabilizes the beam instability.
Приведені результати досліджень збудження коливань довгим нерелятивістським електронним пучком при потужності сотні кіловат в пучково-плазмовому розряді в магнітному полі. Показано, що в підтримці пучково- плазмового розряду визначаючу роль відіграють низькочастотні іонні хвилі із області нижчегібридного резонансу. Їх збудження зумовлено нелінійною взаємодією електронних плазмових мод коливань типу розпаду. Електромагнітне випромінювання з розряду імпульсів обумовлене вище вказаною нелінійною взаємодією. Вона і приводить до стохастизації та стабілізації пучкової нестійкості.
Проведены результаты исследований возбуждения колебаний протяженным нерелятивистским электронным пучком при мощности сотни киловатт в пучково-плазменном разряде в магнитном поле. Показано, что в поддержании пучково-плазменного разряда определяющую роль играют низкочастотные ионные волны из области нижнегибридного резонанса. Их возбуждение обусловлено нелинейным взаимодействием электронных плазменных мод колебаний типа распада. Электромагнитное излучение из разряда импульсов обусловлено выше указанным нелинейным взаимодействием. Оно же приводит к стохастизации волн и стабилизации пучковой неустойчивости.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/79797 |
| citation_txt |
Wave nonlinear interaction effect on beam-plasma reciprocal influence / V.A. Buts, O.F. Kovpik, E.A. Kornilov // Вопросы атомной науки и техники. — 2005. — № 2. — С. 131-133. — Бібліогр.: 10 назв. — англ. |
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| fulltext |
WAVE NONLINEAR INTERACTION EFFECT ON BEAM-PLASMA
RECIPROCAL INFLUENCE
V.A. Buts, O.F. Kovpik, E.A. Kornilov
National Science Centre Kharkov Institute of Physics & Technology, Kharkov, Ukraine
The authors have examined the oscillation excitation by an extensive nonrelativistic beam of electrons in the beam-
plasma discharge in the magnetic field when the beam power is about hundreds of kilowatts. It is demonstrated that low-
frequency (LF) ion waves from the range of the low hybrid (LH) resonance play the determinative role in maintaining the
beam-plasma discharge. Excitation of such waves is stimulated by the nonlinear interaction between electron plasma
oscillation modes of the decay type. The electromagnetic radiation emission from the discharge of pulses is stimulated by
the above-mentioned nonlinear interaction, which also causes the wave stochasticity and stabilizes the beam instability.
PACS: 52.40.Mj
INTRODUCTION
For understanding the physical nature of the collective
beam-plasma (BP) interaction it is important to study the
process of transition of the continuous regime of generation
of plasma potential oscillations (further denoted as
microwaves) to the discontinuous radiation emission
(EMR) interaction under the condition of augmenting the
beam power (current) [1]. Being of the analytical interest,
these investigations also have the practical value for the
elaboration of beam-plasma generators of microwaves. In
the given report, we submit the results of the experimental
investigations of this phenomenon. We will demonstrate
that the basic processes that stimulate this transition are
conditioned by the plasma no linearity during the excitation
of microwaves, characterized by the electric field strength
of large amplitudes. The tests are based on the correlation
between the plasma parameters, oscillation amplitude and
the function of beam electron distribution in energy during
time intervals of EMR emission.
TEST BENCH AND RESULTS OF
INVESTIGATIONS
The researches were conducted in terms ω pe.> ω He (
ω pe ω He-electron plasma end cyclotron frequency). The
pulse beam parameters are the following: the duration is
250µs, the energy is~40keV, the current is (1-15) A and the
beam diameter is 20 mm. The interaction occurs in a glass
tube of the diameter 200 mm and the length 1.5m. Zones of
the tube and gun differ in pressure: in the gun it makes
2*10-4 Pa, whereas the pressure in the interaction area is
(10-2-10-1) Pa. Hydrogen, helium and argon are used as the
plasma-generating gases. The gun and interaction area are
placed into the magnetic field (8*104-1.6*105) A/M. The
plasma density spatial distribution (ne) and the electron
temperature (Te) distribution over the beam-plasma
discharge (BPD) radius are determined by the optical
method, elaborated in [2]. The beam energy spectrum is
investigated with the electrostatic analyzer of the resolution
0.1% and the temporal resolution smaller than 0.1µs. The
EMR is received with an antenna, registering the magnetic
component. The signal is analyzed with the help of a set of
filters and a tunable resonator. The time of the plasma
formation in BPD is (5-50) µs (ne ~(1-5)×1012 cm-3; Te = (30-
100) eV). The plasma is characterized by the spatial
anisotropy of ion energy. The ions of the energy about
several
keV are detected along the discharge, whereas in the radial
direction the ions of the energy up to (30-50) eV are
registered. All the investigations have been carried out after
50µs since the current pulse initiation.
Fig. 1
In Fig.1, one can see the following oscillograms: the
beam energy (1); the beam current pulse (2); EMR pulses
(3); the light integral radiation emitted by the plasma (4);
the lines 5015 Ǻ (5). The oscillograms (4) and (5) indicate
that the plasma average density is maintained constant
during the pulse duration. At the same time, EMR is
registered in the form of pulses ~1µs, the repetition period
being (1-1.5) µs. The frequencies less than the electron-
plasma frequency are registered in the EMR spectrum. As it
is found out, the EMR pulse duration depends on the beam
power. If the beam power makes several kW, the EMR
emission duration can reach 1µs. If the beam power is
about several hundreds of kW, the pulse duration makes
tenths parts of µs, and the pulse repetition period is chaotic.
It is also discovered that notwithstanding a high level of
LF ion oscillations that provide Bohm coefficient of the
plasma diffusion (3×105cm2/s), the radial gradients of ne do
not change their values during the time~1µs. That is, the
BPD geometry is preserved.
In Fig.2, the radial distributions of ne and Te over the
BPD central cross-section are presented. depicts that the
BPD geometry is close to the form of a tube. The distribution
of ne in radius is obtained by averaging the measurements
over a large number of the pulses. The experimental data
indicate that the detected phenomena have to be determined
Problems of Atomic Science and Technology. Series: Plasma Physics (11). 2005. № 2. P. 131-133 131
by a specificity of the beam interaction with the annular
waveguide.
Fig. 2
Fig.3
In Fig.3, we have plotted the functions of the beam electron
distribution in energy, registered in the time intervals of the
EMR emission (B) and its absence (A). As one can clearly
see, the beam is substantially scattered in energy. The beam
energy losses during EMR emission (B) are heavier than
during its absence. The accelerated electrons of energies
much higher than the average beam energy are registered.
The estimations indicate that the beam energy expenditure
on the electron acceleration is commensurable with the
EMR energy about 30% of the beam energy content. The
derivative of the distribution function of electrons in
energy, taken with respect to their velocity, is negative.
Dynamics of changes in the beam spectra permits
supposing the following: (1). Either in BPD start periodic
nonlinear processes that alter the wave polarization, or (2)
the beam stimulates the excitation of microwave potential
oscillations that periodically transfer into EMR. However, a
high coefficient of the microwave transformation into EMR
is inexplicable with the help of linear mechanisms for the
BP interaction. Besides, according to [3-4], the inclined
microwave excitation effectiveness is not high under the
experimental conditions. It is more probably that EMR
emission is stimulated by the wave nonlinear transformation
with the participation of oscillations from the range of low
hybrid (LH) resonance at the frequency ω h=( ω He ω
Hi)1/2 (here ω Hi are the ion cyclotron frequencies). This
supposition is confirmed by the existence of EMR
amplitude modulation at LH frequency. Besides, the LF
oscillation spectrum enrichment with small-scale
longitudinal ion oscillations from the LH resonance range,
which occurs during the beam power increase, also serves
as a characteristic feature of the LH oscillation participation
in the wave nonlinear interaction.
The analysis given to the beam interaction with a tubular
plasma waveguide indicates that the waveguide
electrodynamic characteristics favor the wave nonlinear
interaction development.
According to [5-7], in a tubular waveguide can exist
axially-symmetric potential microwaves of the three types:
spatial waves and surface waves with the normal and
abnormal dispersion, emitted at the frequencies lower than
the electron-plasma one ω pe. Approaching this frequency,
the wave phase velocities become low and close to one
another. This means that at certain moments the beam,
losing its energy, can interact with a pair of waves, exciting
them simultaneously, which favors the establishment of
nonlinear coupling between these waves. In particular, the
coupling is strengthened when the difference in the
microwave mode frequencies is equal to the wave
frequency. In this case, microwaves transfer their energy to
this wave ω h=( ω He ω Hi)1/2 However, before the
realization of the given condition, the microwave excited by
the beam can be decomposed into the electromagnetic and
LH waves. An important aspect of the wave nonlinear
interaction is that the initial value of LF wave amplitude is
large. The presence of an initial disturbance in plasma
diminishes the threshold values of the microwave electric
field strength, after the excess of which the decay-type
nonlinear interaction begins [8]. If the beam excites
microwaves in an annular waveguide, the electric field
strength threshold values, required for the decay nonlinear
process realization, can be diminished due to the
phenomenon of the double resonance. The beam excites
two microwave modes at close frequencies and LF mode at
the difference frequency. At the same time, at the kinetic
stage in the instability development, when the beam
distribution function in velocity f(ve) becomes spatially
inhomogeneous (in addition, d (ve)/dvez), the beam can
directly excite LF wave at the same difference frequency
[9]. The analysis indicates that the beam characterized by
the distribution function presented in Fig.3 can excite
oscillations from the LH resonance range, the increment of
growth of which is equal to the ion-plasma frequency
period.
For the EMR emission, the waveguide proper waves
must participate in the decay process. However, for the
beam of the energy examined in the experiment, this
scheme is unrealizable. Under the experimental conditions,
the wave can be decomposed just into an improper
electromagnetic wave and a LH one. The correlation
between the amplitude and shape of the oscillations from
the LH resonance range and the amplitude of EMR testifies
that in the experiments can exist the given sequence of
decays. The examination of the oscillations from the LH
resonance range in the probe current has indicated that their
pulse duration is by (30-40)% longer than the duration of
EMR pulse.
If the LF oscillation amplitude is longer than one third
of the maximum value, there happens the amplitude
modulation, which results in the formation of short LF
pulse trains. The emergence of modulation and LF
oscillation trains is accompanied by the EMR emission. At
the front of LF oscillation amplitude decay, the oscillations
do not restore their regular shape. When the oscillations of
the LH resonance range vanish, the EMR emission is not
detected. That is, if LF oscillations are correlated with the
phenomenon of decay of the waves excited by the beam,
this process goes in the two stages. At the first stage, the
excitation of LF oscillations is not accompanied by EMR
emission. At the second stage, simultaneously there exist
LF oscillations and EMR emission.
We have checked experimentally the existence of the
decays, in which simultaneously participate potential
132
microwaves excited by the beam and EMR emission. The
beam is modulated by two microwave signals at frequencies
lower than ω He, and their difference is equal to the LH
frequency. As it found out, if one of the microwave
modulating signals is augmented in power, there takes place
an increase in the amplitude of the oscillations at the
frequency of LH resonance range and they change their
shape. Simultaneously, there starts the EMR emission. An
increase in the microwave signal amplitude reduces the
time of intensification of the oscillations at the frequency
ω h=( ω He ω Hi)1/2 and there occurs the transition to their
pulse excitation. There arise trains of LF oscillations and
EMR emission with the same periodicity. The existence of
the decay process detected in the experiment is confirmed
by the coincidence of the measured LH wave phase velocity
((107-2×108) cm/s) with the calculated value, where the
velocities of the microwave excited by the beam and EM
waves are taken into account.
According to [10], the decay process must cause
stochasticity of microwaves and diminish the effectiveness of
their coupling with the mono-energetic beam injected into
plasma. Besides, there takes place an intensive absorption of
LH waves in plasma, to which microwaves excited by the
beam transfer their energy, along with the microwave
absorption itself. All these circumstances have to cause the
BPD derangement. The experimental trials have confirmed
this supposition. There exists a threshold value of the LH
oscillation field strength, the exceeding of which is
accompanied by the BPD extinction. When LF power is
injected, at first the suppression of drift oscillations in BPD is
observed, and further there takes place the discharge
derangement. The discharge extinction is detected under the
LH oscillation electric field strength equal to 500 V/cm.
CONCLUSIONS
On the basis of the above-presented scheme of the beam-
plasma interaction in BPD, formed by the no relativistic
electron beam, one can state that the generation of pulses of
EMR is stimulated by the following factors:
1. Formation of BPD by several proper modes of
microwaves;
2. The cascade-like nature of the decay processes that
occur in microwaves excited by the beam;
3. The beam instability stabilization due to stochasticity
of the waves, conditioned by the process of their decay and
by a high effectiveness of their attenuation.
REFERENCES
1. A.N. Antonov, Yu.P. Blioh, E.A. Kornilov, et al. //
Plasma Physics. 2000, v.26, №12, p. 1097-1109.
2. E.V. Lifshits // Journal of Optician and Spectroscopy.
1965, v. ΧΙΧ, №1, p. 2 (in Russian).
3. E.S. Erohin, S.S. Moiseev. Questions of Theory of
plasma. /Ed. M.A. Leontovich. “Atomizdat”, 1973, №7,
p. 146 (in Russian).
4. V.N. Tsitovich. Nonlinear effects in plasma. Moscow:
“Nauka”, 1967, p. 65 (in Russian).
5. A.N. Kondratenko. Superficial and by Volume Waves in
the Limited Plasma. M.: “Energoatomizdat”, 1985, p. 100
(in Russian).
6. M.P. Azarenkov, Yu.A. Akimov, A.N. Kondratenko,
V.P. Olifer // Problems of Atomic Science and
Technology, 2002, 62(18), №559, p. 47 (in Russian).
7. A.F. Aleksandrov, L.S. Bogdankevich, A.A. Ruhadze.
Bases of ElectroDynamics of Plasma. M.:’’Visshaya
shkola’’, 1978, p. 68 (in Russian).
8. S.M. Krivoruchko, A.S. Bakay, E.A. Kornilov // Letters
in GETF. 1971, v.3, p. 369.
9. A.B. Mihaylovskiy, E.A Pashitskiy.// JTP. 1966, v.ХVI,
N5, p. 763.
10. V.A. Buts, I.K. Kovalchuk, E.A. Kornilov,
D.V.Tarasov // Problems of Atomic Science and
Technology, 2003, №4, p.109 (in Russian).
ВЛИЯНИЕ НЕЛИНЕЙНОГО ВЗАИМОДЕЙСТВИЯ ВОЛН
НА ПУЧКОВО-ПЛАЗМЕННОЕ ВЗАИМОДЕЙСТВИЕ
В.А. Буц, О.Ф. Ковпик, Е.А. Корнилов
Проведены результаты исследований возбуждения колебаний протяженным нерелятивистским электронным
пучком при мощности сотни киловатт в пучково-плазменном разряде в магнитном поле. Показано, что в
поддержании пучково-плазменного разряда определяющую роль играют низкочастотные ионные волны из
области нижнегибридного резонанса. Их возбуждение обусловлено нелинейным взаимодействием электронных
плазменных мод колебаний типа распада. Электромагнитное излучение из разряда импульсов обусловлено выше
указанным нелинейным взаимодействием. Оно же приводит к стохастизации волн и стабилизации пучковой
неустойчивости.
ВПЛИВ НЕЛІНІЙНОЇ ВЗАЄМОДІЇ ХВИЛЬ НА ПУЧКОВО-ПЛАЗМОВУ ВЗАЄМОДІЮ
В.О. Буц, О.Ф. Ковпік, Є.О. Корнілов
Приведені результати досліджень збудження коливань довгим нерелятивістським електронним пучком при
потужності сотні кіловат в пучково-плазмовому розряді в магнітному полі. Показано, що в підтримці пучково-
плазмового розряду визначаючу роль відіграють низькочастотні іонні хвилі із області нижчегібридного резонансу. Їх
збудження зумовлено нелінійною взаємодією електронних плазмових мод коливань типу розпаду. Електромагнітне
випромінювання з розряду імпульсів обумовлене вище вказаною нелінійною взаємодією. Вона і приводить до
стохастизації та стабілізації пучкової нестійкості.
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