Paramagnetic states of high-current electron beams in a beam-plasma system
Results of computer simulation of low-energy high-current electron beam generation in a low-impedance system show that high-current beams shape in paramagnetic states. Low-impedance system consists of a diode with a long plasma anode, just siding with an explosive emission cathode and an auxiliary...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2006
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| Цитувати: | Paramagnetic states of high-current electron beams in a beam-plasma system / A.V. Agafonov, V.P. Tarakanov // Вопросы атомной науки и техники. — 2006. — № 6. — С. 169-171. — Бібліогр.: 6 назв. — англ. |
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irk-123456789-822932015-05-28T03:02:15Z Paramagnetic states of high-current electron beams in a beam-plasma system Agafonov, A.V. Tarakanov, V.P. Plasma electronics Results of computer simulation of low-energy high-current electron beam generation in a low-impedance system show that high-current beams shape in paramagnetic states. Low-impedance system consists of a diode with a long plasma anode, just siding with an explosive emission cathode and an auxiliary thermionic cathode. The long plasma anode plays simultaneously the role of the transport channel providing charge neutralisation of high-current beam. Usually, a beam in an external magnetic field behaves as a diamagnetic and forces the magnetic field out of its volume. Earlier it was shown that for some systems it is possible to realise conditions under which the magnetic field is increased inside the volume occupied by the beam. It is accompanied by considerable increase of the magnetic field as compared as external field. The behaviour of beam-plasma system is discussed under different conditions. Computer simulation was performed using PIC code KARAT. 2006 Article Paramagnetic states of high-current electron beams in a beam-plasma system / A.V. Agafonov, V.P. Tarakanov // Вопросы атомной науки и техники. — 2006. — № 6. — С. 169-171. — Бібліогр.: 6 назв. — англ. 1562-6016 PACS: 52.40.Mj http://dspace.nbuv.gov.ua/handle/123456789/82293 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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DSpace DC |
| language |
English |
| topic |
Plasma electronics Plasma electronics |
| spellingShingle |
Plasma electronics Plasma electronics Agafonov, A.V. Tarakanov, V.P. Paramagnetic states of high-current electron beams in a beam-plasma system Вопросы атомной науки и техники |
| description |
Results of computer simulation of low-energy high-current electron beam generation in a low-impedance system
show that high-current beams shape in paramagnetic states. Low-impedance system consists of a diode with a long
plasma anode, just siding with an explosive emission cathode and an auxiliary thermionic cathode. The long plasma
anode plays simultaneously the role of the transport channel providing charge neutralisation of high-current beam.
Usually, a beam in an external magnetic field behaves as a diamagnetic and forces the magnetic field out of its volume.
Earlier it was shown that for some systems it is possible to realise conditions under which the magnetic field is
increased inside the volume occupied by the beam. It is accompanied by considerable increase of the magnetic field as
compared as external field. The behaviour of beam-plasma system is discussed under different conditions. Computer
simulation was performed using PIC code KARAT. |
| format |
Article |
| author |
Agafonov, A.V. Tarakanov, V.P. |
| author_facet |
Agafonov, A.V. Tarakanov, V.P. |
| author_sort |
Agafonov, A.V. |
| title |
Paramagnetic states of high-current electron beams in a beam-plasma system |
| title_short |
Paramagnetic states of high-current electron beams in a beam-plasma system |
| title_full |
Paramagnetic states of high-current electron beams in a beam-plasma system |
| title_fullStr |
Paramagnetic states of high-current electron beams in a beam-plasma system |
| title_full_unstemmed |
Paramagnetic states of high-current electron beams in a beam-plasma system |
| title_sort |
paramagnetic states of high-current electron beams in a beam-plasma system |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2006 |
| topic_facet |
Plasma electronics |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/82293 |
| citation_txt |
Paramagnetic states of high-current electron beams in a beam-plasma system / A.V. Agafonov, V.P. Tarakanov // Вопросы атомной науки и техники. — 2006. — № 6. — С. 169-171. — Бібліогр.: 6 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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AT agafonovav paramagneticstatesofhighcurrentelectronbeamsinabeamplasmasystem AT tarakanovvp paramagneticstatesofhighcurrentelectronbeamsinabeamplasmasystem |
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2025-07-06T08:48:08Z |
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2025-07-06T08:48:08Z |
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1836886723794042880 |
| fulltext |
Problems of Atomic Science and Technology. 2006, 6. Series: Plasma Physics (12), p. 169-171 169
PARAMAGNETIC STATES OF HIGH-CURRENT ELECTRON BEAMS
IN A BEAM-PLASMA SYSTEM
A.V. Agafonov1, V.P. Tarakanov2
1P.N.Lebedev Physical Institute of RAS, Leninsky Prosp. 53, Moscow, GSP-1, 119991, Russia,
e-mail: agafonov@sci.lebedev.ru;
2Institute for High Energy Densities of RAS, Izorskaya 13/19, Moscow, 125412 Russia
Results of computer simulation of low-energy high-current electron beam generation in a low-impedance system
show that high-current beams shape in paramagnetic states. Low-impedance system consists of a diode with a long
plasma anode, just siding with an explosive emission cathode and an auxiliary thermionic cathode. The long plasma
anode plays simultaneously the role of the transport channel providing charge neutralisation of high-current beam.
Usually, a beam in an external magnetic field behaves as a diamagnetic and forces the magnetic field out of its volume.
Earlier it was shown that for some systems it is possible to realise conditions under which the magnetic field is
increased inside the volume occupied by the beam. It is accompanied by considerable increase of the magnetic field as
compared as external field. The behaviour of beam-plasma system is discussed under different conditions. Computer
simulation was performed using PIC code KARAT. Work supported by RFBR under grant 05-02-16442.
PACS: 52.40.Mj
1. INTRODUCTION
Plasma-filled diodes with explosive cathodes are used
for the generation of high-current low-energy electron
beams for surface modification [1 - 3]. The main idea of
high-current beam generation is based on the origin of a
thin double-layer between a cathode and adjoined anode
plasma just after the beginning of accelerating voltage
pulse. The full voltage is localised across this layer
making possible the beginning of the explosive emission
from a cathode surface. The plasma serves as the “liquid”
anode preventing the system from collapses of impedance
from one side and as the channel to guide a high-current
beam from another side making sure charge neutralisation
of the beam and its transport to a target. In our
experiments to create well-defined plasma channel we use
a residual gas ionisation by additional pulsed low-energy,
low-current electron beam guided by longitudinal
magnetic field [2 – 3].
2. SOME PECUILARITIES OF BEAM-
PLASMA DYNAMICS
Generation and transportation of low-energy high-
current beams in such system is conditioned by several
peculiarities: exceeding Alfven’s limiting current,
prevalence of transverse dynamics of beam electrons,
different time scales and multistage of processes, and
comparable density of the plasma and generated electron
beam. Behaviour and the main characteristics of the beam
depend on the external magnetic field. The system as a
whole can be characterised as multi-component one with
alternating number of particles and can’t be described by
regular theoretical methods.
Results of computer simulation of plasma anode
formation in residual gas by an auxiliary electron beam
and the generation of high-current beams was described in
[3]. Diameter of the explosive emission cathode was
chosen equals to 1 cm. At initial time the plasma column
of the same diameter along the system fills completely
space in longitudinal direction between explosive
emission cathode and anode placed instead of auxiliary
gun. The density of plasma is homogeneously distributed
along longitudinal z and radial r co-ordinates and was
varied from 1×1013 cm-3 up to 7×1013 cm-3. Initial
temperature of the plasma was changed from several to
tens electronvolts. Applied voltage has the given form. It
rose up to 20 kV for different time (1, 5, 10 ns) and was
constant further. Output of electrons was permitted from
the field-emission cathode and surfaces into plasma if
accelerating field exceeds a given value. Calculations
were performed for hydrogen, nitrogen and xenon
plasmas for different values of external longitudinal
magnetic field and for two different length of the plasma
diode (2 and 10 cm).
2.1. INFLUENCE OF EXTERNAL MAGNETIC
FIELD
Calculations were carried out for different levels of
external magnetic field: 0, 500 and 5000 Gs. The behavior
of the beam does not differ significantly for the first two
cases and for diodes of different length excepting the
duration of the beam current. In small magnetic fields
pinched state of the beam-plasma system is formed very
likes to Bennett’s pinch. Beam electrons force plasma
electrons out to electrodes in longitudinal direction, beam
electrons are pinched to the axis of the system by self
magnetic field exceeding significantly external one, and
near axis ion pivot is formed. Such metastable state of
beam-plasma system exists for 10…20 nanoseconds and
further it goes to annular configuration of plasma ions and
electron beam and emission of electrons from central area
of the cathode is depressed. Fig. 1 shows radial
distributions of beam electrons and plasma ions densities
in pinched state for short diode and for external magnetic
field B = 0 and initial plasma density is 7x1013 cm-3
(pressure of xenon 2x10-3 Tor). A half of the beam current
reaches the anode electrode out of the marked area of the
collector of 1 cm diameter.
mailto:agafonov@sci.lebedev.ru
170
Fig.1. Radial distributions of beam electrons (upper part)
and plasma ions (bottom part) in pinched state of beam-
plasma system at different position along the system
Fig.2. Trajectories of several beam electrons in pinched
state
Corresponding trajectories of several beam electrons
emitted from the field-emission cathode are shown in
Fig. 2 for 2 ns time interval. The current of the beam at
the moment is about 10 kA.
If external magnetic field is high enough to prevent
beam electrons from focusing to the axis of the system
then pinched state is not reached at all. Plasma ions leave
pre-axis area under influence of self space charge and
annular distributions of beam electrons and plasma ions
are formed. Such state slowly expanding in radial
direction with decreasing beam current can exist for tens
nanoseconds. Radial densities distributions of beam
electrons and plasma ions for B = 5 kGs are shown in
Fig. 3. Results are given for long diode and initial plasma
density of 7x1013 cm-3.
Fig.3. Radial distributions of beam electrons (upper part)
and plasma ions (bottom part) in annular state of beam-
plasma system at different position along the system
2.2. PARAMAGNETIC STATES OF THE BEAMS
Usually, a beam in an external magnetic field behaves
as a diamagnetic and forces the magnetic field out of its
volume. In [4, 5] it was shown that for some systems, e.g.
for inverted coaxial magnetic isolation diodes, it is
possible to realise conditions under which the magnetic
field is forced out inside the volume occupied by the
beam and is increased considerable as compared as
external field. About similar situation is realised in the
beam-plasma system under consideration. In this case the
role of the internal electrode plays near axis ion pivot.
The reasons of the creation just of paramagnetic state of
the beam are not clear enough. It can be assumed that the
main role plays fast forced escape of plasma electrons to
the electrodes and exceeding of Alfven’s limit. As the
result a “clear” system consisting of slow plasma ions and
fast beam electrons is formed. This system has many
commons with so-called coupling state in moving quasi-
neutral medium [6] and can be considered as polarised
one.
The degree of magnetic field amplification depends
on the value of the external magnetic field, plasma
density, rise time of applied voltage and transverse
dimensions of the system. In high external magnetic field
the amplification is small. Fig. 4 shows longitudinal
distribution of complete longitudinal field at different
radii. Naturally, the field reaches its maximum value on
the axis of the system. For the case of external field
B = 5 kGs magnetic field on the axis exceeds 12 kGs.
171
Fig.4. Longitudinal distributions of complete magnetic
field at different radii for the B = 5 kGs
Fig.5. Longitudinal distributions of magnetic field at
different radii for the B = 500 Gs
In low magnetic fields the amplification of the field
can exceed 20. No special attempts to find conditions of
maximum amplification were done. The example of field
amplification for low magnetic field is shown in Fig. 5.
REFERENCES
1. G.E. Ozur, D.S. Nazarov, D.I. Proskurovsky.
Generation of low-energy high-current electron beams in
plasma anode gun// Izvestija VUZov. Physics. 1994, N 3,
p. 100-107 (in Russian).
2. A.V. Agafonov, V.A. Bogachenkov, E.G. Krastelev.
High-current low-energy electron beam generation in
plasma system// Problems of atomic science and
technology. Series “Nuclear Physics Investigations” (47).
2006, N 3, p. 43-45.
3. A.V. Agafonov. Electron beam generation in a low-
impedance system// Problems of atomic science and
technology. Series “Nuclear Physics Investigations” (46).
2006, N 2, p. 55-57.
4. A.V.Agafonov. Charged E-layer// J. Tech. Phys.
Letters. 1975, N1, p. 918-922 (in Russian).
5. A.V.Agafonov. High-current electron beam
equilibrium of theta-pinch type inside inverse coaxial
isolation diode// J. Plasma Physics. 1982, N 8, p. 925-930
(in Russian).
6. A.V.Agafonov. Coupling states in moving quasi-
neutral medium.// Problems of atomic science and
technology. Series “Plasma Physics” (11). 2005, N 2,
p. 49-51.
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