The stability of magnetized non-neutral plasma flow with a broad velocity distribution
The stability of the magnetized non-neutral plasma cylindrical flow was studied experimentally. The flow is injected into the drift tube and spreads along its axis. The radial motion of the charged particles is limited by longitudinal magnetic field. During the experimental study the influence of su...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2010
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| Zitieren: | The stability of magnetized non-neutral plasma flow with a broad velocity distribution / M.I. Tarasov, I.K. Tarasov, D.A. Sitnikov, V.K. Pashnev // Вопросы атомной науки и техники. — 2010. — № 6. — С. 85-87. — Бібліогр.: 4 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860221308288106496 |
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| author | Tarasov, M.I. Tarasov, I.K. Sitnikov, D.A. Pashnev, V.K. |
| author_facet | Tarasov, M.I. Tarasov, I.K. Sitnikov, D.A. Pashnev, V.K. |
| citation_txt | The stability of magnetized non-neutral plasma flow with a broad velocity distribution / M.I. Tarasov, I.K. Tarasov, D.A. Sitnikov, V.K. Pashnev // Вопросы атомной науки и техники. — 2010. — № 6. — С. 85-87. — Бібліогр.: 4 назв. — англ. |
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| description | The stability of the magnetized non-neutral plasma cylindrical flow was studied experimentally. The flow is injected into the drift tube and spreads along its axis. The radial motion of the charged particles is limited by longitudinal magnetic field. During the experimental study the influence of such factors as the magnetic field strength and the average flow velocity on stability of the flow fluctuations was investigated.
Экспериментально исследована устойчивость замагниченного цилиндрического потока заряженной плазмы. Поток инжектировался в трубку дрейфа и распространялся вдоль ее оси. Радиальный дрейф частиц потока ограничивался продольным магнитным полем. Исследовалось влияние на устойчивость системы таких факторов как напряженность магнитного поля и средняя скорость частиц потока.
Експериментально досліджено стійкість замагніченого потоку зарядженої плазми. Потік інжектувался до трубки дрейфу та поширювався вздовж її вісі. Радіальний дрейф частинок потоку обмежувався повздовжнім магнітним полем. Досліджувався вплив на стійкість системи таких факторів як напруженість магнітного поля та середня швидкість частинок потоку.
|
| first_indexed | 2025-12-07T18:17:55Z |
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THE STABILITY OF MAGNETIZED NON-NEUTRAL PLASMA FLOW
WITH A BROAD VELOCITY DISTRIBUTION
M.I. Tarasov, I.K. Tarasov, D.A. Sitnikov, V.K. Pashnev
Institute of Plasma Physics NSC “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
The stability of the magnetized non-neutral plasma cylindrical flow was studied experimentally. The flow is injected
into the drift tube and spreads along its axis. The radial motion of the charged particles is limited by longitudinal
magnetic field. During the experimental study the influence of such factors as the magnetic field strength and the
average flow velocity on stability of the flow fluctuations was investigated.
PACS:52.27.Jt
INTRODUCTION
The stability of low-frequency electrostatic
fluctuations in cylindrical non-neutral plasma flow with
relatively broad distribution of the particle velocities
injected into a longitudinal magnetic field represents an
attractive subject for both theoretical and experimental
study. The results of such studies are not only important
for physics of charged particle beams but also may be
exploited in the field of plasma physics and controlled
fusion.
Studied fluctuations are observed in cylindrical flow
of non-neutral (electron) plasma. They have a pronounced
azimuthal component. Thus under certain conditions they
may interact with the flow particles which are drifting
azimuthally (ExB - drift) with the velocities Vdr ≈ Vph.
Such particles are usually called ‘resonant’. Depending on
the resonant particles distribution by velocities the
fluctuations amplitude may be stimulated or damped. In
the first case the fluctuations become unstable. This may
cause the distortion of the flow profile and forming of the
density bunches which are shifted from the symmetry axis
of the system (diocotron instability). The bunches are
moving azimuthally with the wave phase velocity.
In most cases, the wave-particle interaction for such
type of fluctuations provides damping of the oscillations
[1,2]. The reason of this lies in decreasing electron
density profile which is characteristic for the most of
cylindrical electron beams. In this case the waves with the
azimuthal wave number l = 1 are observed. Such waves
are usually excited due to interaction of the flow
fluctuations with the drift tube walls or with the resonant
ions.
In this work we study the influence of such parameters
as the longitudinal magnetic field strength and the
acceleration voltage on dynamics of the diocotron
instability. Special attention is paid to the effect of the
probe insertion into the flow which is really noticeable
under certain experimental conditions.
Heating current
Injection pulse
Entrance grid Exit grid
Capacity
probe
Capacity
probe
Electrostatic
Langmuir
probe
Vacuum
chamber
Particles
collector
Magnetic
field coils
Fig.1. Schematic of the experimental device
EXPERIMENTAL SETUP
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2010. № 6. 85
Series: Plasma Physics (16), p. 85-87.
The experimental device (Fig. 1) represented a brass
drift tube (L = 150 cm, R = 2 cm) placed into vacuum
chamber (p = 5×10-7 Torr) at longitudinal magnetic field
(H = 920…2100 Oe). The charged electrons flow was
formed using the particles injector consisted of indirectly
heated cathode and grounded anode grid. The injection of
the flow was performed by applying of a negative
potential pulse to the cathode. In the framework of the
experimental study the pulse amplitude (UACCEL) did not
exceeded a value of 30 V. The flow density at the drift
tube entrance was ne = 2×107 сm-3. The flow radius was
rfl = 1 сm. The width of the flow particles distribution by
velocities was 20 eV.
The drift tube consisted of two azimuthal segments.
Such construction allows carrying out the measurements
of the fluctuations azimuthal dynamics. The
measurements of longitudinal distribution of potential
were performed by a moveable Langmuir probe.
EXPERIMENTAL RESULTS
Variation of the magnetic field intensity and the
acceleration voltage
The fluctuations dynamics was investigated without
the Langmuir probe insertion into the flow.
a
b
c
H = 920 Oe
U = 30 V
ACCEL
U = 30 V
ACCEL
Fig.2. The averaged depth of the amplitude modulation (a
and b), the averaged frequency and the width of the
frequency band (c) depending on UACCEL and Н
The main attention was paid to the current fluctuations
detected in the drift chamber walls. The behavior of such
fluctuations usually displays the azimuthal dynamics of
the flow fluctuations. In the framework of the
experimental study the analysis of nonlinear effects
observed in the fluctuations dynamics was carried out.
In particular, the averaged depth of the amplitude
modulation ( MODA ) was measured for different
experimental conditions.
It was shown that MODA grows (Fig.2) together with
increase of the magnetic field intensity (H) or the
acceleration voltage (UACCEL). In the first case MODA
grows intensively while H is increasing from 920 to
1200 Oe. Further increase of H results in MODA growth
with smaller rates.
The dependence of the frequency characteristics
(averaged frequency - f and frequency band width - df)
on H correlates with those of MODA
Increase of the acceleration voltage gives a
pronounced MODA growth in the range of
UACCEL=27…30V. At lower values of UACCEL the
amplitude modulation is much weaker and the frequency
band width is negligibly small.
Probe measurements
The measurements of the longitudinal potential
distribution (Fig. 3,c,d) have shown the presence of a
pronounced potential maximum at z = 20...70 cm. (the
coordinate of the maximum point depended on the
experimental parameters). In our configuration such
phenomena may be explained by influence of spatial
charge of the electron flow.
One of the most interesting results of the probe
measurements consisted in a noticeable influence of the
probe insertion into the flow on the electrostatic
fluctuations behavior. In particular the most intensive
reaction of MODA , f and df on the probe introduction was
observed at increased values of H and UACCEL (Fig. 3,a,b).
a
e
b
f
c
g
d
h
Fig.3. The amplitude modulation depth (a – for different Н values, e – for different UACCEL values), the probe current
(b – for different Н values, f – for different UACCEL values), the average frequency (c– for different Н values, g – for
different UACCEL values) and the frequency band width (d – for different Н values, h – for different UACCEL values)
dependencies on the probe longitudinal coordinate
As one could see from the experimental data the
current level in the probe circuit reduces together with
increasing of H. At the same time, the most pronounced
reaction on the probe introduction was observed at higher
values of H. Thus the effect of the probe immersion is not
proportional to the rate of interaction between the probe
and the flow particles. However, the probe insertion may
distort the distribution of the resonant electrons (or ions)
by their velocities and so it may cause noticeable changes
in the fluctuations dynamics. It is useful to note that the
86
87
injector is placed outside the magnetic field coil. So the
flow is injected into spatially inhomogeneous magnetic
field at the coil edge. Thus the magnetic field intensity
variation affects strongly on the flow radius. In particular,
the increasing of H should lead to the flow radius
decreasing. This suggestion allows to conclude that the
instability is much more sensitive to the probe immersion
if the probe is inserted into the edge of the flow.
CONCLUSIONS
It was shown experimentally that the increase of the
magnetic field strength leads to intensification of the
unstable processes. This fact contradicts with the classic
pattern of diocotron instability development in pure
electron plasma. It was also estimated that the
acceleration voltage rising leads to more intensive
development of the instability which also leads to the
question about the influence of ionization processes on
the system stability [3,4]. The dynamics of the frequency
characteristics has shown a good correlation with that of
the average depth of the amplitude modulation.
The probe measurements have shown that the resonant
particles may be concentrated at the flow edge.
REFERENCES
1. R.H. Levy // Phys. Fluids.1965, v. 8, N 7, p. 1288.
2. R.C. Davidson. Theory of Nonneutral Plasmas.
Massachusetts: “Benjamin, Reading”, 1974, chap. 2.
3. A. J. Peurrung, J. Notte and J. Fajans// Phys. Rev. Lett.
1993, v. 70, p. 295.
4. G. Bettega, F. Cavaliere, M. Cavenago, A. Illiberi,
R. Pozzoli and M. Rome // Plasma Phys. Control.
Fusion. 2005, v. 47, p. 1697.
Article received 5.10.10
УСТОЙЧИВОСТЬ ПОТОКА ЗАМАГНИЧЕННОЙ ЗАРЯЖЕННОЙ ПЛАЗМЫ С ШИРОКИМ
РАСПРЕДЕЛЕНИЕМ ЧАСТИЦ ПО СКОРОСТЯМ
М.И. Тарасов, И.К. Тарасов, Д.А. Ситников, В.К. Пашнев
Экспериментально исследована устойчивость замагниченного цилиндрического потока заряженной
плазмы. Поток инжектировался в трубку дрейфа и распространялся вдоль ее оси. Радиальный дрейф частиц
потока ограничивался продольным магнитным полем. Исследовалось влияние на устойчивость системы таких
факторов как напряженность магнитного поля и средняя скорость частиц потока.
СТІЙКІСТЬ ПОТОКУ ЗАМАГНІЧЕНОЇ ЗАРЯДЖЕНОЇ ПЛАЗМИ ІЗ ШИРОКИМ РОЗПОДІЛОМ
ЧАСТОК ПО ШВИДКОСТЯХ
M.I. Тарасов, I.К. Тарасов, Д.A. Сітников, В.К. Пашнєв
Експериментально досліджено стійкість замагніченого потоку зарядженої плазми. Потік інжектувался до
трубки дрейфу та поширювався вздовж її вісі. Радіальний дрейф частинок потоку обмежувався повздовжнім
магнітним полем. Досліджувався вплив на стійкість системи таких факторів як напруженість магнітного поля та
середня швидкість частинок потоку.
|
| id | nasplib_isofts_kiev_ua-123456789-17466 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T18:17:55Z |
| publishDate | 2010 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Tarasov, M.I. Tarasov, I.K. Sitnikov, D.A. Pashnev, V.K. 2011-02-26T21:26:44Z 2011-02-26T21:26:44Z 2010 The stability of magnetized non-neutral plasma flow with a broad velocity distribution / M.I. Tarasov, I.K. Tarasov, D.A. Sitnikov, V.K. Pashnev // Вопросы атомной науки и техники. — 2010. — № 6. — С. 85-87. — Бібліогр.: 4 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/17466 The stability of the magnetized non-neutral plasma cylindrical flow was studied experimentally. The flow is injected into the drift tube and spreads along its axis. The radial motion of the charged particles is limited by longitudinal magnetic field. During the experimental study the influence of such factors as the magnetic field strength and the average flow velocity on stability of the flow fluctuations was investigated. Экспериментально исследована устойчивость замагниченного цилиндрического потока заряженной плазмы. Поток инжектировался в трубку дрейфа и распространялся вдоль ее оси. Радиальный дрейф частиц потока ограничивался продольным магнитным полем. Исследовалось влияние на устойчивость системы таких факторов как напряженность магнитного поля и средняя скорость частиц потока. Експериментально досліджено стійкість замагніченого потоку зарядженої плазми. Потік інжектувался до трубки дрейфу та поширювався вздовж її вісі. Радіальний дрейф частинок потоку обмежувався повздовжнім магнітним полем. Досліджувався вплив на стійкість системи таких факторів як напруженість магнітного поля та середня швидкість частинок потоку. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Фундаментальная физика плазмы The stability of magnetized non-neutral plasma flow with a broad velocity distribution Устойчивость потока замагниченной заряженной плазмы с широким распределением частиц по скоростям Стійкість потоку замагніченої зарядженої плазми із широким розподілом часток по швидкостях Article published earlier |
| spellingShingle | The stability of magnetized non-neutral plasma flow with a broad velocity distribution Tarasov, M.I. Tarasov, I.K. Sitnikov, D.A. Pashnev, V.K. Фундаментальная физика плазмы |
| title | The stability of magnetized non-neutral plasma flow with a broad velocity distribution |
| title_alt | Устойчивость потока замагниченной заряженной плазмы с широким распределением частиц по скоростям Стійкість потоку замагніченої зарядженої плазми із широким розподілом часток по швидкостях |
| title_full | The stability of magnetized non-neutral plasma flow with a broad velocity distribution |
| title_fullStr | The stability of magnetized non-neutral plasma flow with a broad velocity distribution |
| title_full_unstemmed | The stability of magnetized non-neutral plasma flow with a broad velocity distribution |
| title_short | The stability of magnetized non-neutral plasma flow with a broad velocity distribution |
| title_sort | stability of magnetized non-neutral plasma flow with a broad velocity distribution |
| topic | Фундаментальная физика плазмы |
| topic_facet | Фундаментальная физика плазмы |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/17466 |
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