Research of high-current electron beam transport and convergence onto a common bremsstrahlung target
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| Дата: | 2001 |
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| Формат: | Стаття |
| Мова: | English |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2001
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| Назва видання: | Вопросы атомной науки и техники |
| Онлайн доступ: | http://dspace.nbuv.gov.ua/handle/123456789/79232 |
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| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Research of high-current electron beam transport and convergence onto a common bremsstrahlung target / V. Chornyi, I. Zaliubovskyi, G. Tsepilov, O. Frolov, A. Chornyi, V. Dubina, V. Solovyov // Вопросы атомной науки и техники. — 2001. — № 3. — С. 47-49. — Бібліогр.: 1 назв. — англ. |
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irk-123456789-792322015-03-31T03:02:02Z Research of high-current electron beam transport and convergence onto a common bremsstrahlung target Chornyi, V. Zaliubovskyi, I. Tsepilov, G. Frolov, O. Chornyi, A. Dubina, V. Solovyov, V. 2001 Article Research of high-current electron beam transport and convergence onto a common bremsstrahlung target / V. Chornyi, I. Zaliubovskyi, G. Tsepilov, O. Frolov, A. Chornyi, V. Dubina, V. Solovyov // Вопросы атомной науки и техники. — 2001. — № 3. — С. 47-49. — Бібліогр.: 1 назв. — англ. 1562-6016 PACS nambers: 29.27.Eg http://dspace.nbuv.gov.ua/handle/123456789/79232 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| language |
English |
| format |
Article |
| author |
Chornyi, V. Zaliubovskyi, I. Tsepilov, G. Frolov, O. Chornyi, A. Dubina, V. Solovyov, V. |
| spellingShingle |
Chornyi, V. Zaliubovskyi, I. Tsepilov, G. Frolov, O. Chornyi, A. Dubina, V. Solovyov, V. Research of high-current electron beam transport and convergence onto a common bremsstrahlung target Вопросы атомной науки и техники |
| author_facet |
Chornyi, V. Zaliubovskyi, I. Tsepilov, G. Frolov, O. Chornyi, A. Dubina, V. Solovyov, V. |
| author_sort |
Chornyi, V. |
| title |
Research of high-current electron beam transport and convergence onto a common bremsstrahlung target |
| title_short |
Research of high-current electron beam transport and convergence onto a common bremsstrahlung target |
| title_full |
Research of high-current electron beam transport and convergence onto a common bremsstrahlung target |
| title_fullStr |
Research of high-current electron beam transport and convergence onto a common bremsstrahlung target |
| title_full_unstemmed |
Research of high-current electron beam transport and convergence onto a common bremsstrahlung target |
| title_sort |
research of high-current electron beam transport and convergence onto a common bremsstrahlung target |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2001 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/79232 |
| citation_txt |
Research of high-current electron beam transport and convergence onto a common bremsstrahlung target / V. Chornyi, I. Zaliubovskyi, G. Tsepilov, O. Frolov, A. Chornyi, V. Dubina, V. Solovyov // Вопросы атомной науки и техники. — 2001. — № 3. — С. 47-49. — Бібліогр.: 1 назв. — англ. |
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Вопросы атомной науки и техники |
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| fulltext |
RESEARCH OF HIGH-CURRENT ELECTRON BEAM TRANSPORT AND
CONVERGENCE ONTO A COMMON BREMSSTRAHLUNG TARGET
V. Chornyi, I. Zaliubovskyi, G. Tsepilov, O. Frolov, A. Chornyi, V. Dubina, V. Solovyov
Kharkiv National University, Ukraine
E-mail: chorny@pht.univer.kharkov.ua
PACS numbers: 29.27.Eg
1 INTRODUCTION
One of the approaches to creation of new generation
super-power bremsstrahlung sources is based on con-
struction of multi-modular systems, whose every mod-
ule is to generate pulse power beams of 1012-1013 W. To
realize this concept the Defense Threat Reduction
Agency, USA, finances the design of the DECADE sys-
tem, which in its final version will consist of 16 mod-
ules. Each of the DECADE modules is designed to
transfer a beam with energy of about 1 kJ and pulse du-
ration of ≈ 10-7s to the bremsstrahlung radiation convert-
er. To increase the radiation source intensity the elec-
tron density on the target should be increased, what may
be achieved by combining the beams from the modules
into a single beam, as well as by compressing the com-
bined beam cross-section. Realization of such a scheme
assumes some space available for the beams to be trans-
ported to the point of their overlapping and for the
bremsstrahlung target to be installed. To transport the
beams (with allowance for their currents exceeding con-
siderably the Alfven current (>106А)) efficiently, virtu-
ally full compensation of the beams’ self-fields is re-
quired. To solve this problem a lot of physical research-
es are to be carried out.
Kharkiv National University in close collaboration
with DTRA and Naval Research Laboratory, USA,
studies the beam transport using the method of electron
gradient drifting in an azimuthal magnetic field created
by the linear conductor current. In this beam transport
method the magnetic fields are compensated by plasma
which is generated when the beam is injected into some
rarefied gas the transport channel is filled with [1].
2 TRANSVERSAL COMPRESSION
OF A BEAM
For effective capture of electrons, leaving the diode,
by an azimuthal magnetic field, the beam should have
tubular form and small wall thickness. It requires cre-
ation of special diodes capable to generate annular elec-
tron beams of terawatt power at the output windows.
The outer beam diameter may be reduced by devel-
oping drop of the azimuthal magnetic field along the
drift chamber axis.
As the computer simulation has shown the negative-
going gradient of the magnetic field along the drift the
chamber axis is more expedient to be set just behind the
diode output window, with the transition area between
high and low magnetic field zones having the shape of a
cone, with its vertex facing inward the drift chamber
along the beam trajectory, and the cone base not going
beyond the beam inner diameter, see Fig. 1 a).
a)
b)
Fig. 1. The effect of the magnetic field gradient along
the drift chamber axis: (a) Example of motion of the
electrons injected into the azimuthal magnetic field with
a negative-going gradient along the axis; (b) Experi-
mentally observed radial beam profiles in case the
beams are injected into an uniform (along their motion
axis) azimuthal magnetic field (the beam was injected at
the radius of 7.0 cm), as well as in case of the spoke
generated gradient field.
In this case, apart from the beam compression in di-
ameter, range extension of the drift captured electron
energies (in the direction of low energies) is achieved as
well, what improves the efficiency of energy transfer to
the target. Practically achievable, like that, factors of the
beam diameters compression are 1.4 - 1.5 that corre-
sponds to the beam density increase by a factor of about
2 (see. Fig. 1 b).
3 BEAMS CONVERGENCE
The technology of consistent propagation of a
megaampere beam along a linear current carrying con-
ductor is not completely studied for today because of
complex dynamics of physical processes occurring
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №3.
Серия: Ядерно-физические исследования (38), с. 47-49.
47
mailto:chorny@pht.univer.kharkov.ua
within the beam-plasma dynamic system placed in the
applied magnetic field. The processes of the beam self-
field compensation need a special study. To achieve
high level of the beam charge compensation by plasma
generally does not call any problems, while provision of
the beam current compensation requires some supple-
mentary theoretical and experimental researches to be
conducted. Within the electron energy range of
1.0-2.0 MeV the Alfven currents vary from 48 up to
80 kA. To provide the effective transport the residual
uncompensated currents are to be much lower than the
Alfven current is. This implies that for a megaampere
beam the under-compensation of its current should not
exceed 1 - 2 %. This requirement becomes stronger in
case of several beams convergence, as in the region of
their convergence the beam residual magnetic fields are
combined, and the total field structure becomes weakly
predicted.
Overlapping of several beams propagating by gradi-
ent drift is feasible in case they are biased from the
guide conductor axis and are made to drift aside. Such
propagation conditions may be provided by bending the
guiding conductor. In this case, the electrons are ejected
over the radius curvature to the lower field zone due to
azimuthal heterogeneity of the magnetic field. Should
we create the conditions for bringing the biased beams
closer, like this, we may obtain a combined beam with
cross-section not much exceeding that of a single beam.
Fig. 2 illustrates such a scheme of the beam conver-
gence.
Fig. 2. Scheme of beam convergence with guiding con-
ductors bending.
3 EXPERIMENTAL ARRANGEMENT
AND PRELIMINERY RESULTS
a) Beam Generator. The experiments were performed
at Kharkiv National University on «Nadia» electron ac-
celerator, which provides voltage pulse of up to 1 MV
with a 7 Ω load, the radix pulse width – 90 ns.
b) One-Beam Experiment was carried out to check the
numerical calculation results. For this purpose a double
diode generating three beams on 140-mm diameter with
total current of up to 100 kA was used. At the distance
of 200 mm from the diode output windows the beam
took an uniform structure over azimuth and was com-
pressed to 100 mm in diameter due to the negative-go-
ing gradient of the azimuthal magnetic field (see Fig.1
b). On passing 45 cm the beam turned away from the re-
gion of injection into the drift chamber. The experiment
scheme is shown in Fig. 3.
Fig. 3. Scheme of one-beam experiment.
To determine the beam shape and position in the re-
gion of the conductor curvature, a thin tantalum target
was placed in this region. The beam X-ray trace on this
target was registered by a pinhole camera.
The beams positions relative to the guide conductor
in the place of its curvature are presented as an X-ray
image of Ta target in Fig. 4 (a). Distribution density
along the indicated direction is also presented in
Fig. 4(b).
a) b)
Fig. 4.
As a whole, its behavior agreed with the computer
simulation forecasts.
The beam bias relative to the guide conductor de-
pends sufficiently on the particles angular spread: the
greater the spread is the larger portion of electron drifts
around the conductor without biasing to one side.
c) Two-Beam Convergence Experiment
The geometrical dimensions of the experimental de-
vice were adjusted to satisfy operation conditions of the
four-module Decade facility.
The shape of the injected beams was specified by the
diode output windows (10×25 mm). The beams were
injected at a distance of 2 cm from the outside of the
conductors producing an azimuthal magnetic field. The
distance between the beams in the injection region was
34 cm, the mean angle of the beam injection – 22o out-
wards the transport channel axis. The two-beams trans-
port channels had square cross-section 100×100 mm,
the length of transport to the point of the beams conver-
gence – 40 cm, angle between the channels axis – 44o.
The guiding magnetic field was generated by the
current pulse in the conductors, 40 kA in each.
To make the X-ray images of the drifting electron
beams the transport channels were filled with Xenon at
about 110 Torr pressure.
To make more accurate measurement of the beam
cross-section dimensions the transport channels were
filled with air at 30 Torr pressure. The beam was visual-
48
ized in X-rays with the help of three 13-µm Ta strips,
(see Fig. 5.)
According to the chosen conditions of the beam in-
jection and transport its diameter on the regular section
of transport was 65-70 mm (determined at the half-
height of the bremsstrahlung radiation intensity of its
trace in the underground gas and on Tantalum foil
placed across the beam).
a) b)
Fig. 5. Beam traces on thin Ta strips made in X-rays:
(a) strips image made by a pin-hole camera; (b) digi-
tal image processing in the place of the beams conver-
gence.
In Fig. 5 an example of the combined beam traces
and numerical processing results of the experimental
data are presented. Here, two quite different versions of
the beams overlapping were studied:
1. When the magnetic fields of the two conductors are
not combined, see Fig. 6. In this case the space be-
tween the guiding conductors was partitioned by a
plate with welded copper wires so that the reverse
current flow prevented combining of the azimuthal
magnetic fields.
2. The conducting plate between the guiding conduc-
tors was moved away. In this case the magnetic
field between the conductors decreased strongly
and the nature of the particles movement changed:
In the space between the conductors the electrons
suffer some betatron oscillations, and in case they
emerge outside, where magnetic fields from the two
conductors are combined, the electrons move at a
farther distance from the conductor. The image pre-
sented in Fig. 7 corresponds to this case.
conducting
plane
Fig. 6. Two beams convergence with the guiding
magnetic fields separated over the whole transport
length.
Fig. 7. Variant of the beam convergence with com-
bining the fields from the guiding conductors.
The size of the combined beam in the first case
made approximately 1.5 of a single beam diameter. In
the second case the beam had more blown up bound-
aries and increased electron loss on the transport system
walls in the region of mutual reduction of the guiding
magnetic fields.
4 CONCLUSIONS
Grad-B drift method of beam transport has been
shown to be capable of converging power from modular
systems.
Decrease of the converged beam size can be
achieved by increasing the portion of electrons passing
into the space between the conductors. For this purpose
the initial angular spread of electrons during their injec-
tion into the guide field should be decreased.
REFERENCES
1. James R. Lee, Robert C. Backstrom, John. A. Hal-
bleib, et al. // J. Appl. Phys. 1984. v. 56, # 11,
p. 3175-3181.
This work is supported by the Defense Threat Re-
duction Agency, USA, through the Science and Tech-
nology Center in Ukraine, Project # 2093.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №3.
Серия: Ядерно-физические исследования (38), с. 49-49.
49
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