Possibilities of LU-50 linear electron accelerator modification
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irk-123456789-815112016-11-15T14:43:41Z Possibilities of LU-50 linear electron accelerator modification Zavyalov, N.V. Telnov, A.V. Khokhlov, Yu.A. Shorikov, I.V. 1999 Article Possibilities of LU-50 linear electron accelerator modification / N.V. Zavyalov, A.V. Telnov, Yu.A. Khokhlov, I.V. Shorikov // Вопросы атомной науки и техники. — 1999. — № 4. — С. 5-7. — Бібліогр.: 10 назв. — англ. 1562-6016 http://dspace.nbuv.gov.ua/handle/123456789/81511 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Zavyalov, N.V. Telnov, A.V. Khokhlov, Yu.A. Shorikov, I.V. Possibilities of LU-50 linear electron accelerator modification Вопросы атомной науки и техники |
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Possibilities of LU-50 linear electron accelerator modification |
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Possibilities of LU-50 linear electron accelerator modification |
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Possibilities of LU-50 linear electron accelerator modification |
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Possibilities of LU-50 linear electron accelerator modification |
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Possibilities of LU-50 linear electron accelerator modification |
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possibilities of lu-50 linear electron accelerator modification |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Possibilities of LU-50 linear electron accelerator modification / N.V. Zavyalov, A.V. Telnov, Yu.A. Khokhlov, I.V. Shorikov // Вопросы атомной науки и техники. — 1999. — № 4. — С. 5-7. — Бібліогр.: 10 назв. — англ. |
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Вопросы атомной науки и техники |
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2025-07-06T06:30:04Z |
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2025-07-06T06:30:04Z |
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POSSIBILITIES OF LU-50 LINEAR ELECTRON ACCELERATOR
MODIFICATION
N.V. Zavyalov, A.V. Telnov, Yu.A. Khokhlov, I.V. Shorikov
Russian Federal Nuclear Center – All-Russia Scientific Research Institute of Experimental
Physics, Sarov, Russian Federation
INTRODUCTION
The most significant trends of accelerator
development are efficiency increase and widening of the
designed installation functional possibilities. LU-50
accelerator was designed in the late seventies when
there existed an acute necessity in measuring nuclear
constants; for this purpose it was needed to generate
short electron pulses (10ns) with maximum permissible
current (up to 10A) to insure the technique of time-of-
flight neutron spectroscopy [1]. On LU-50 there was
obtained a 2⋅1013neutr/s fluence of neutrons at the
electron beam average power of 10kW. Now there arise
new physics tasks requiring high values of the beam
average current, they are: investigation of a process of
neutrons multiplication in media for the purpose of
creating a sub-critical frequency two-cascade power
blanket [2]; neutronography of materials at the
investigation of phase transitions in solid states on the
basis of neutron wave properties at the energies of ≈
0.01eV; radiation resistance investigations. Thus, it was
proposed to perfect LU-50 accelerator [3] for their
effective solution.
The most characteristic accelerators for neutron
researches are as follows: GELINA (150MeV, IRMM,
Geel), ORELA (140MeV, ORNL, Oak Ridge), CLIO
(50MeV, LURE, Orsay) [3] and a new 100MeV
accelerator (PAL, Korea) [4]. All these installations
except for ORELA (1969) operate both in the mode of
stored energy and on a long pulse; as injector there are
used grouping sections, and AS with a long-time filling
by microwave power (more than 1µs) are applied.
1. ANALYSIS OF LU-50 ELECTRON
DYNAMICS
To determine possible ways of the accelerator
perfection and to reveal the reasons of LU-50 beam
current losses there were performed numeric
calculations of electron dynamics in the mode of stored
energy. It assisted in testing the program of calculation
and made it possible to compare the results with the
calculations performed in MEPhI [5,6]. The operation
of LU-50 accelerating structure is based on the principle
of using microwave energy stored in a circular iris
waveguide (CIW). The accelerating guide consists of
two similar accelerating sections (AS) with varied
geometry and long time of filling with microwave
power (≈0.94µs). AS operates on the wavelength of
16,5cm with 2π/3 oscillation type. A 50-kV diode gun
with a cylindrical resonator excited on E010 wave is used
as an injector. A microwave generator consists of MI-
328 magnetron (exciter) and MIU-34 magnetron with
30MW pulse power and 100kW average power. The
output power of the amplifying magnetron is divided
into two similar channels (arms). The first arm of
microwave generator feeds the first AS, some share of
power (about 10%) is fed through a directed coupler and
phase-shifter to a grouping resonator. The second arm is
connected to the second AS through a waveguide phase
shifter of trombone type.
In the calculation program there is applied an
algorithm of one-particle approximation at which each
particle corresponds to the charge injected over the time
of microwave phase change by 10°. To describe the
formation of one bunch (360°) there were used in the
calculation 35 particles uniformly distributed over the
whole period of accelerating field and discretely
describing phase motion of continuously injected
electrons. The calculations were performed for 21
electron bunches what corresponds to 11.5ns pulse
duration.
It follows from the calculations that one can get a
well-grouped bunch of 25% of the particles injected. Its
nucleus will be as long as 15°, i.e. 22.9ps. The process
of bunches grouping is completed at the beginning of
the first section, during the second section there only
takes place the acceleration.
The analysis of the results of numeric simulation
of LU-50 electrons dynamics demonstrated that basic
current losses fall on the initial stage of acceleration –
resonator (50%) and on the output to the first section
(25%). The resonator in which any slight deviation in
the field strength leads to the deviation from the
optimum phase of bunches flight into AS turned out to
be of particular criticality for the sustain of the
operation mode. As a whole, the calculation parameters
coincided well with the experimental data and with the
calculations performed before in MEPI. This points out
to a sufficiently high degree of the chosen calculation
model approximation to reality. The bunches duration
experimentally determined through Cherenkov radiation
registration in air constitutes 27ps [7], what corresponds
to the phase duration of ~18°.
2. INVESTIGATION OF LU-50 PERFECTION
POSSIBILITY
The researches on initiation of nuclear power
two-cascade blanket and radiation resistance of
materials formed premises for the LU-50 transfer to a
more economically efficient operation mode with high
average beam power.
There were performed before the numeric
calculations of the versions of bunches grouping
optimization for the purpose of increasing the LU-50
current pulse up to 20 A at 10ns duration. They
demonstrated that such possibility does exist /5, 6/ and
can be realized with no replacement of the available AS
through:
the addition of buncher with the supply power up to
15MW and constant loading factor equal to 0.1154.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. № 4.
Серия: Ядерно-физические исследования (35), с. 5-7.
5
the introduction of additional accelerating resonator
(klystron grouping) with pulse power not less than
100kW. This method is elaborated in theory and
design.
The increase of LU-50 beam power can be also
achieved by its transfer to the mode of the long-pulse
current of accelerated electrons. The principle of using
microwave energy stored in CIW when the current pulse
duration (10ns) is by far shorter than the duration of
microwave pulse (1.5µs) and filling time, is efficient
only in the case of accelerating short pulses of high
charge. In modern accelerators aimed at neutron
researches the work requiring high average beam power
is carried out in a more economically efficient mode of
long current pulse (>1µs) acceleration when the power
carried away by a microwave beam has time to be
compensated by the generator.
At the analysis of initiated by the beam non-
symmetric waves that are the reason of occurring the
effect called “pulse break” there were obtained for AS
of LU-50 the limitation by current of ~1,4A at the
increased duration of the pulse up to 1µs [8]. The
limitation by pulse that was found from the data of
report [6] is of the same order.
B AS3EG
е- е- е- е-
MIU-
34
е-
1-st arm 2-nd arm
Р
Р/2 Р/2
Р
Р/2 Р/2
AS4AS2AS1
е-
MI-
328
MI-
328ML
Р/20
ML
Fig.1. Structural scheme of the third version of
modification: ML – matched load, EG – electron gun,
B - buncher, AS – accelerating section.
From this it follows that there exists the
possibility of increasing the average beam power by a
factor of 2 both through the improvement of electron
bunches grouping and through the transfer to the mode
of current long pulse acceleration with no change in the
accelerating structure. The more than double growth of
the beam average power can be achieved through
modification of the accelerating structure and (or)
microwave supply. The scheme of a microwave
generator used nowadays demonstrated its reliability
under the condition of twenty-four-hour work. Thus, it
is supposed that its basic assemblies will remain
unchanged, the existing MIU-34 magnetron being taken
as a basis.
In a new accelerating structure it is supposed to
use a traveling wave buncher with 2π/3 mode to
eliminate disadvantages caused by one-resonator
grouping. In the first version considered a half of the
first magnetron arm power was separated out for it.
Then, at the left half release to the second traveling
wave 2π/3-mode section one would manage to unify
AS. For this purpose the second arm power can be split
into two equal parts to feed the third and the fourth
sections fully identical to the second one. The AS
shortening assists in weakening the effect of “pulse
break”, thus, there is considered the creation of a large
number of waveguides but of shorter length (~2m).
Basic disadvantages of the first method consist in
the increased supply power released to the buncher.
This affects negatively to the phase grouping of bunches
and to the capture coefficient at the acceleration mode.
In this version one can succeed in implementing the
capture of only 40% of particles at 15° phase extent of
bunches.
Thus, there was considered the second version
characterized by reduced microwave power fed to the
buncher input. While considering different power
splitting relations of the first magnetron arm there was
found the most suitable proportion to meet the following
criteria:
minimum difference in power level;
satisfactory phase grouping of particles;
good phase capture to acceleration;
equal filling time of bunching and accelerating
sections.
At microwave supply of the buncher with 5MW
(9MW for the second section) power, the above-
mentioned criteria were satisfied best of all.
In the second version there were obtained at the
accelerator output well-grouped bunches with the basic
part phase extent not less than 8° at comparatively low
scattering by energy of the order of 2MeV (4%). The
disadvantages of this version consist in differences of
AS by length and cell size and the differences of the
corresponding guide components aimed at releasing
microwave power. This will make it more difficult to
produce and adjust the accelerator. Among the
advantages of this method one can separate a good
coefficient of phase capture to acceleration and
grouping of electrons into bunches of short extent.
In the third version there were combined design
advantages of the first two versions and the MI-328
magnetron-based microwave generator was added
(fig.1). It is required to separate by power the bunching
part of the accelerator from the accelerating one.
This will make it possible to flexibly implement
the tuning to optimum beam parameters and to fully
unify the production of AS. The power of each MIU-34
accelerating magnetron arm will be separated into two
equal shares. It will be released to four absolutely
identical sections whose aim is to accelerate the grouped
bunches. Phase motion of bunches in these sections
does not practically exist, thus, having once established
the sections one must not reconstruct them even at
microwave supply power change. Having separated by
power the accelerating part one can adjust the buncher
more accurately.
The main difficulty in realizing the third version
consists, in comparison with the previous ones, in the
system of microwave feeding with two generator
magnetrons synchronization. Possible methods of
magnetrons synchronization were described in several
papers [9-11], through whose analysis there was chosen
the system proposed.
In version 3 the buncher is fed from the MI-328
magnetron-based generator with the pulse power up to
6MW, while its synchronization is insured through the
mechanism of pulling the frequency along with mag-
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. № 4.
Серия: Ядерно-физические исследования (35), с. 5-7.
5
netron coupling through a circulator. MIU-34 will be a
master oscillator, its main function consists in providing
four AS with power (by 7 MW). The second magnetron
MI-328 will serve as a modulator as it does now.
Phase portrait of a accelerated electron bunch
on the accelerator output (ver. No 3)
56
57
58
59
60
-15 -10 -5 0 5 10
Accelerating wave phase, degree
E
le
ct
ro
n
en
er
gy
, M
eV
Fig. 2.
In this version electron bunches can be
accelerated up to the energy of 58.3MeV, the scattering
of the basic part of a bunch will constitute at 8° phase
extent 1MeV (Fig.2). The calculation time of AS filling
is equal to 0,67µs. The average beam power at operating
in the long-pulse (2.5µs) mode is equal to 60.9kW.
3. CONCLUSION
A high-current accelerator applied to achieve in
the first cascade a neutron flux of the order of 1014–1015
per pulse is supposed to be used in the development of
experiments in simulating two-cascade nuclear power
boosters with unilateral coupling.
There exists the possibility of increasing the
average beam power of LU-50 several times through a
more efficient use of microwave energy. In the report
there are analyzed different trends of LU-50
modification basing on the available microwave
generator whose assemblies are well elaborated over a
long period of its operation. It is shown that to increase
the average beam power several times it is required to
modify the LU-50 accelerating system as a whole.
Among the modification versions most promising is the
one that is more complex by the microwave feeding
system consisting of a grouping section and four similar
accelerating sections. This version makes it possible to
considerably increase beam energy and to unify AS.
At the application of different methods of
suppressing lateral oscillation modes, such as shortened
AS and radial cuts on diaphragms one can operate more
efficiently both in the mode of stored energy and on a
long current pulse with the average beam power higher
than 50kW. Such beam power allows to achieve the
required fluence of neutrons and to carry out physics
investigations requiring high intensity of electron,
bremsstrahlung or neutron radiation fluxes.
4. REFERENCES
1. G.P.Antropov et al. VANT, 1985,.2/3/.-p.3-5.
2. Clendenin J. et al. Compendium of Scientific Linacs.-
CERN.-XVIII Intern. Linac Conference.- Geneva, 1996.
3. Kim G.N. et al. \Proposed Neutron Facility Using
100-MeV Electron Linac at Pohang Accelerator
Laboratory. -Conf. Proc. Nuclear Data for Science and
Technology.-Trieste.-1997.-P.556.
4. Zavyalov N.V., Kolesov V.F. and Yu.A.Khokhlov
On the Possibility of Experimental Testing for the
Conception of Cascade Electronuclear Facilities Using
237Np\ II Intern. Workshop: Nuclear Fission and Fission-
Product Spectroscopy, Seysins, France. – 1998.
5. Majorov Ju.K., Zavyalov N.V., Khokhlov Yu.A.et al..
Particle dynamics in LU-50 accelerator and
determination of the possibility of increasing the
intensity of accelerated beam // XI All-Union Workshop
on Linear Accelerators of Charged Particles (Kharkov,
June 6-8, 1989) – Abstracts, p. 43 (in Russian).
6. Zavyalov N.V.,Ivanin I.A., In′kov V.I., Sitnikov N.P.
et al // PTE.-1990 .-№3 .-p. 56-58.
7. Burshteyn E.L., Voskrecenskiy G.V. Linear electron
accelerators with intensive beams. Moscow, Atomizdat
Publ., 1970 (in Russian).
8. Khlopov Yu.N. Basics of magnetron usage. Moscow,
“Sovetskoe Radio” Publ., 1967 (in Russian).
9. Vikulov V.F., Vinogradov K.A., Milovanov O.S. //
Accelerators. - Moscow, Atomizdat Publ., 1968, v. 10,
p.181 (in Russian).
10. Thal H.L. and Lock R.G. Locking of magnetrons by
an injected RF signal.-IEEE Trans.-1965.-Nov.-
MTT-13.- #6.-P.836.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. № 4.
Серия: Ядерно-физические исследования (35), с. 5-7.
5
1.ANALYSIS OF LU-50 ELECTRON DYNAMICS
2.INVESTIGATION OF LU-50 PERFECTION POSSIBILITY
3.CONCLUSION
4.REFERENCES
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