Trapped particles influence on the electron production with anomalously high energy
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2000
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| Cite this: | Trapped particles influence on the electron production with anomalously high energy / A.A. Bizyukov, E.D. Volkov , I.K. Tarasov // Вопросы атомной науки и техники. — 2000. — № 6. — С. 106-108. — Бібліогр.: 7 назв. — англ. |
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| author | Bizyukov, A.A. Volkov, E.D. Tarasov, I.K. |
| author_facet | Bizyukov, A.A. Volkov, E.D. Tarasov, I.K. |
| citation_txt | Trapped particles influence on the electron production with anomalously high energy / A.A. Bizyukov, E.D. Volkov , I.K. Tarasov // Вопросы атомной науки и техники. — 2000. — № 6. — С. 106-108. — Бібліогр.: 7 назв. — англ. |
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UDC 533.9
106 Problems of Atomic Science and Technology. 2000. № 6. Series: Plasma Physics (6). p. 106-108
TRAPPED PARTICLES INFLUENCE ON THE ELECTRON
PRODUCTION WITH ANOMALOUSLY HIGH ENERGY
A.A. Bizyukov1, E.D. Volkov 2, I.K. Tarasov 2
1 - Kharkov National University, Kurchatov Ave. 31, 61108, Kharkov, Ukraine. 2 - Institute
of Plasma physics, NSC «Kharkov Institute of Physics and Technology», Academicheskaya
Str. 1,61108, Kharkov, Ukraine. Itarasov@ipp.kharkov.ua
Introduction
Diocotron instability may be considered as growing
electrostatic wave that propagates across the magnetic
field. Radial widening of this wave and further capture
of azimuthally drifting electrons are usually explained to
be caused by nonlinear saturation of the wave. The
diocotronic instability in the system of hollow annular
electron cord, with the central electrode situated along
the axis, is studied in [1]. The central electrode made it
possible to control the radial electric field. The
variations of frequency and density of electron plasma
on the nonlinear stage of the diocotronic oscillations in
an annular electron cord are examined in [2]. Nonlinear
diocotronic mode is studied theoretically by the method
of perturbations of endless electron plasma cord [3].
Electrons of anomalously high energy with
periodical diocotron oscillations impulses are observed
during examination of the instability of overmagnetted
electrons in high-voltage discharge of low pressure
inmagnetic field [4].
The capture of particles into the field of electrostatic
wave is investigated in [5], where also the wave profile
dynamics is studied experimentally and theoretically.
In the foregoing work of the authors [6] it is shown
that, during the diocotron instability evolution, the
spatial redistribution takes place in the beam's cross-
section, which is connected, probably, with drift of
electrons in longitudinal magnetic field, radial, and
azimuthal electric fields of the diocotrone wave.
Experimental results
A detiled describtion of the experimental setup is
given in [6].
Stimulation and suppression of the diocotron
oscillations were performed with the axial electrode.
The effect was produced by short impulses, the duration
of the impulse being less than semi period of the
diocotron oscillations, as well as impulses with the
duration comparable with the time of existence of the
oscillations. It's necessary to note that the impulses
being short, stimulation or suppression of the diocotron
oscillations wasn't strongly pronounced. The amplitude
could vary in the range of 10-20% of its maximum.
Even when series of the short impulses were applied, the
frequency of the impulses being equal to that of the
diocotron oscillations, no swinging or damping of the
oscillations was observed. When the durable impulses
were applied an intensive stimulation or suppression of
the diocotron oscillations was observed, in accordance
to the polarity of the impulse applied.
Fig.1. Stimulation of the diocotron oscillation: a) axial
electrode (τ=10µs); b) additional beam (τ=100µs)
The oscillogrammes of the diocotron oscillations,
which demonstrate the incentive effect of the negative
polarity impulses, applied to the axial electrode
relatively to the drift tube, are presented on Fig.1a. In
this case, the diocotron oscillations were observed on
one of the π-electrodes. In further experiments on
stimulation and suppression of the diocotron oscillations
an additional beam was used, which was injected with
the same radius as the basic one but with different
duration and intensity. The additional impulse was
injected after the termination of the basic impulse. The
incentive effect of such additional beam can be seen on
Fig 1 b. The beam was overlayed on the oscillations that
existed after the termination of the injection impulse and
as a result the amplitude and the time of existence of the
oscillations increased. The electric charge brought by
the beam into the drift space created an additional
transversal electric field that stimulated the rise of the
diocotron oscillations.
Fig.2 presents the dynamics of beam electrons'
distribution function by the velocity that has been
averaged on a large number of impulses with different
beam parameters in the regime of the effects observed.
The curves of the velocity distribution were taken in the
drift space of electron beam in three cross-sections: in
the initial part of the drift tube, in the middle part and in
mailto:Itarasov@ipp.kharkov.ua
107
the terminal part of the drift gap. The distributions were
taken for the direct, the inverse and the azimuthal
electron flows. The dynamics of the distribution
functions for the direct flows reflects the fact that there
existed a group of high-energy particles in the middle
part of the drift space, because the maximum of the
distribution had a 10 eV shift in its middle region to the
hand of high energies, while the distribution taken in the
terminal part of the drift space had no shift. On the other
hand the shift existing only in the central part of the
tube, the fast particles could escape from the drift space
or could live only in a finite part of it, independently
from the major flow of the
particles.
Fig.2. Dynamics of beam electrons distribution
function by the velocity in three cross-sections, for the
direct, the inverse and the asimuthal electron flows
A group of slow particles also appeared during the
drift of electrons in the direct course. This phenomenon
is brightly manifested in the middle part of the drift
space and not in the same street in the initial and the
terminal parts. Thus, the slow particles showed the same
behavior as the fast ones. According to the dynamics of
the distribution functions we could assume the shift of
the distributions in the middle part was caused by
particles captured into the field of electrostatic trap,
which was formed by the movement of particles along
the drift space.
A side from the velocity distribution functions of the
direct electron flow the distributions of the inverse
particle flows as well as the azimuthal flows were taken.
These functions are presented on Fig.2 b. They differ
from the distribution of the direct flows in the middle
part of the drift space by a plateau-like increase of a
number of high-energy particles and by 10 eV shift of
maximum to the hand of lower velocities.
Fig.3 demonstrates the oscillogrammes of the
diocotron oscillations in the case when the ππππ-electrodes
were used as a probes. The form of the diocotrone
oscillations in dependence of their amplitude may be
sinusoidal or nonsinusoidal with the highest harmonics.
Fig.3. Oscillogrammes of the diocotron oscillation:
a) during the injection; b) after the injection
A modulation of the diocotron oscillations happens
when the amplitudes are high and close to saturation. As
a rule the oscillations in the presence of the modulation
have non-sinusoidal character. The period of the
modulation is proportional to the energy and the electric
current of the electron beam and may reach ∼ 10 fD. It is
seen from the oscillogramme that the times of rise and
fall of the modulative oscillations may differ in 2-3
times. It's important to note that the frequency of the
diocotrone oscillations varies accordingly with the
modulative impulses and decreases during the impulse.
The modulative impulses may arise not only during the
injection impulse but also after its termination Fig.3 b.
Fig.4. The output electrons across the magnetic field:
a) by the electrostatic analyzer; b) by the coaxial thread
108
Fig.4a, b demonstrates a series of oscillogrammes
relating to the cases when the diocotron oscillations
were traced by the π-electrodes, while the output of the
electrons across the magnetic field was traced by the
electrostatic analyzer and by the coaxial thread. Either
the electrostatic analyzer or the thread were situated
strictly in the center of the drift space, on its axis. It can
be seen from the oscillogramme that the period of the
outlet of the particles across the magnetic field
corresponds to the period of the modulative oscillations.
Its maximum falls to the falling region. It makes it easy
for us to assume that the appearance of the fast particles
in the drift space may be connected with the rising and
the falling of the diocotron oscillations in the form of the
modulative oscillations.
It is experimentally shown that:
1) the radial electric field in the form of
potential on the axial electrode or an additive negative
charge in the drift space produces stimulation of the
diocotron oscillations;
2) the dynamics of the velocity distribution
functions of the particles demonstrates that there
exists a group of particles with higher or lower, in
comparison to the main part of the beam, velocities in
the central part of the drift space.
3) The distribution functions of the inverse and
the azimuthal flows point at the presence of the
trapped particles.
4) The diocotron oscillations are modulated by
amplitude in the form of exponentially rising and
falling impulses with different exponent indexes,
decrease of the oscillations frequency with rise of the
impulse testifying to the loss of the particles during
the impulse.
5) Synchronous outflow of the particles during
the fall of the impulse in the transversal direction
testifies to the same thesis.
Using the experimental results as a basis we may
assume the presence of a group of the slow particles in
the middle part of the drift space, which is resonance by
the velocity for the diocotrone wave spreading in
azimuthal direction. The evaluation of the phase
velocity of the diocotrone wave gives:
where d - beams diameter,
T - diocotron oscillation period,
f - diocotron oscillation frequency,
The corresponding wave phase velocity for the
frequency of the diocotron oscillations being 50 kHz
during the injection impulse is Vph = 3*105 cm/s.
After the termination of the injection impulse the
diocotron frequency is ~ 10 kHz which corresponds to
the phase velocity of the wave is Vph = 6*104 cm/s.
These results support the conclusions made in [8] and
contain new information about the mechanism of
cooling and separation of the cold particles in the
conditions of the experiment.
References
1. G. Posental, G. Dimonte, and A.Y. Wong.
Stabilisation of the diocotron instability in an annual
plasma // Phys. Fluicts 30 (10) October 1987, 3257.
2. K.S. Fine, C.F. Driscoll, J.H. Malmberg.
Measurements of a nonlinear diocotron made in pure
electron plasmas // Phys. Rev. Lett. v.63, N20. 1989,
2232.
3. S.A. Prasad, J.H. Malmberg. A nonlinear diocotron
mode // Phys. Fluids 29(7) July 1986, 2196.
4. N.A. Kervalishvili. Rotational instability of the
charged plasma in crossed fields E┴H and electron
production with anomaliusly high energy // Sov. J.
Plasma. Phys. 15(2), February 1989.
5. V.D. Fedorchenko, Yu.P. Masalov, A.S. Bakai.
Regulation of the profile of potential waves in
multiflow plasma systems // Sov. j. Phys. JETP
76,107,1979.
6. A.A. Bizyukov, E.P. Volkov, K.H. Sereda, A.I.
Tarasov, I.K. Tarasov. Quasi-stationary self-
consistent electric fields in plasma beam discharge //
jornal of Technical Physics Vol. XL No.1,
Warszawa 1999, 237-240.
7. V.A. Bashko, S.M. Krivoruchko and I.K. Tarasov.
Experimental study of the mechanism for buildup
and confinement of a noneutral plasma resulting
from the injection of an electron beam into a uniform
magnetic field // Sov. j. Plasma. Phys. 17(8), August
1991.
dfTdphV ππ ==
Introduction
References
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| id | nasplib_isofts_kiev_ua-123456789-78539 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T18:18:16Z |
| publishDate | 2000 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Bizyukov, A.A. Volkov, E.D. Tarasov, I.K. 2015-03-18T18:39:41Z 2015-03-18T18:39:41Z 2000 Trapped particles influence on the electron production with anomalously high energy / A.A. Bizyukov, E.D. Volkov , I.K. Tarasov // Вопросы атомной науки и техники. — 2000. — № 6. — С. 106-108. — Бібліогр.: 7 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/78539 533.9 en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Plasma dynamics and plasma-wall interaction Trapped particles influence on the electron production with anomalously high energy Article published earlier |
| spellingShingle | Trapped particles influence on the electron production with anomalously high energy Bizyukov, A.A. Volkov, E.D. Tarasov, I.K. Plasma dynamics and plasma-wall interaction |
| title | Trapped particles influence on the electron production with anomalously high energy |
| title_full | Trapped particles influence on the electron production with anomalously high energy |
| title_fullStr | Trapped particles influence on the electron production with anomalously high energy |
| title_full_unstemmed | Trapped particles influence on the electron production with anomalously high energy |
| title_short | Trapped particles influence on the electron production with anomalously high energy |
| title_sort | trapped particles influence on the electron production with anomalously high energy |
| topic | Plasma dynamics and plasma-wall interaction |
| topic_facet | Plasma dynamics and plasma-wall interaction |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/78539 |
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