Simulation of electron bunch shaping and accelerating in two-section technological linac
The paper presents the results of electron dynamics computing in the powerful resonance electron accelerator. The accelerator consists of two accelerating structures with a variable geometry and an injector including a diode electron gun, klystron type buncher and accelerating cavity. The wave phase...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2000
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| Cite this: | Simulation of electron bunch shaping and accelerating in two-section technological linac / N.I. Aizatsky, I.V. Khodak, V.A. Kushnir, V.V. Mitrochenko, S.A. Perezhogin // Вопросы атомной науки и техники. — 2000. — № 2. — С. 69-71. — Бібліогр.: 7 назв. — англ. |
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nasplib_isofts_kiev_ua-123456789-822802025-02-23T18:28:41Z Simulation of electron bunch shaping and accelerating in two-section technological linac Численное моделирование формирования и ускорения частиц в двухсекционном ЛУЭ технологического назначения Aizatsky, N.I. Khodak, I.V. Kushnir, V.A. Mitrochenko, V.V. Perezhogin, S.A. Тheory and technics of particle acceleration The paper presents the results of electron dynamics computing in the powerful resonance electron accelerator. The accelerator consists of two accelerating structures with a variable geometry and an injector including a diode electron gun, klystron type buncher and accelerating cavity. The wave phase velocity in structures is equal to the light velocity. The electron motion in the accelerator was simulated using the PARMELA code. With the 11 MW RF power supplying accelerating structures and the 1 A current at the accelerator exit the beam energy is up to 20 MeV. 2000 Article Simulation of electron bunch shaping and accelerating in two-section technological linac / N.I. Aizatsky, I.V. Khodak, V.A. Kushnir, V.V. Mitrochenko, S.A. Perezhogin // Вопросы атомной науки и техники. — 2000. — № 2. — С. 69-71. — Бібліогр.: 7 назв. — англ. 1562-6016 PACS: 41.85 https://nasplib.isofts.kiev.ua/handle/123456789/82280 en Вопросы атомной науки и техники application/pdf Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Тheory and technics of particle acceleration Тheory and technics of particle acceleration |
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Тheory and technics of particle acceleration Тheory and technics of particle acceleration Aizatsky, N.I. Khodak, I.V. Kushnir, V.A. Mitrochenko, V.V. Perezhogin, S.A. Simulation of electron bunch shaping and accelerating in two-section technological linac Вопросы атомной науки и техники |
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The paper presents the results of electron dynamics computing in the powerful resonance electron accelerator. The accelerator consists of two accelerating structures with a variable geometry and an injector including a diode electron gun, klystron type buncher and accelerating cavity. The wave phase velocity in structures is equal to the light velocity. The electron motion in the accelerator was simulated using the PARMELA code. With the 11 MW RF power supplying accelerating structures and the 1 A current at the accelerator exit the beam energy is up to 20 MeV. |
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Article |
| author |
Aizatsky, N.I. Khodak, I.V. Kushnir, V.A. Mitrochenko, V.V. Perezhogin, S.A. |
| author_facet |
Aizatsky, N.I. Khodak, I.V. Kushnir, V.A. Mitrochenko, V.V. Perezhogin, S.A. |
| author_sort |
Aizatsky, N.I. |
| title |
Simulation of electron bunch shaping and accelerating in two-section technological linac |
| title_short |
Simulation of electron bunch shaping and accelerating in two-section technological linac |
| title_full |
Simulation of electron bunch shaping and accelerating in two-section technological linac |
| title_fullStr |
Simulation of electron bunch shaping and accelerating in two-section technological linac |
| title_full_unstemmed |
Simulation of electron bunch shaping and accelerating in two-section technological linac |
| title_sort |
simulation of electron bunch shaping and accelerating in two-section technological linac |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2000 |
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Тheory and technics of particle acceleration |
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https://nasplib.isofts.kiev.ua/handle/123456789/82280 |
| citation_txt |
Simulation of electron bunch shaping and accelerating in two-section technological linac / N.I. Aizatsky, I.V. Khodak, V.A. Kushnir, V.V. Mitrochenko, S.A. Perezhogin // Вопросы атомной науки и техники. — 2000. — № 2. — С. 69-71. — Бібліогр.: 7 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-11-24T10:52:05Z |
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| fulltext |
SIMULATION OF ELECTRON BUNCH SHAPING AND
ACCELERATING IN TWO-SECTION TECHNOLOGICAL LINAC
N.I. Aizatsky, I.V. Khodak, V.A. Kushnir, V.V. Mitrochenko, S.A. Perezhogin
National Science Center "Kharkov Institute of Physics and Technology",
"Accelerator" R&D Production Establishment, Kharkov, Ukraine
The paper presents the results of electron dynamics computing in the powerful resonance electron accelerator.
The accelerator consists of two accelerating structures with a variable geometry and an injector including a diode
electron gun, klystron type buncher and accelerating cavity. The wave phase velocity in structures is equal to the
light velocity. The electron motion in the accelerator was simulated using the PARMELA code. With the 11 MW
RF power supplying accelerating structures and the 1 A current at the accelerator exit the beam energy is up to
20 MeV.
PACS: 41.85
1. INTRODUCTION
Powerful linear electron accelerators with the energy
up to 20 MeV can be applied for radiation technologies,
for instance, for radionuclide production using (γ,n)
reactions [1]. Such performances as the electron
efficiency, accelerator length, probability of
accelerating structures and beamline to be damaged by a
beam and the reliability of a whole facility are important
for a technological accelerator. The present paper is
devoted to electron beam dynamics simulation in the
one of such accelerator. Basing on a long-term
operational experience the KUT accelerator [2] was
selected as a prototype for the accelerator design. This
accelerator consists of an injector and one accelerating
section with the variable geometry and constant phase
velocity. The injector includes diode electron gun,
klystron type buncher and accelerating cavity. The
length of the accelerating section is 1.2 m, the
oscillation mode is Θ=2π/3 at a frequency of
2797.2 MHz. The electron energy at its exit with the
beam current 1 A can reach 10 MeV. It is supposed to
use one more the same section to get the electron energy
gain up to 20 MeV.
The purpose of simulation was the optimization of
electron dynamics in the injector, calculation of beam
parameters at the accelerator exit and calculation of
operating performances, in particular, the dissipating
power caused by lost particles.
2. SIMULATION METHODS
As the operating of the accelerator is supposed with
long enough current pulse duration (~4 µs) the only
steady-state mode was considered on this stage of
researches. Beam parameters at the gun [3] exit were
calculated using the EGUN code [4]. The longitudinal
and transverse beam dynamics in the accelerator was
simulated using the PARMELA code [5]. This code
computes the electron dynamics in the given
electromagnetic fields. The space distribution of
magnetic field in axial focusing magnetic elements of
the accelerator (three lenses and a short solenoid on the
first section) and the space distribution of
electromagnetic fields in the buncher and the
accelerating cavity were computed using the
SUPERFISH/POISSON code [6]. This code was also
used for the space harmonics computing in the
piecewise uniform structure (11 harmonics were taken
into account). The calculation of amplitude and phase
distribution for the fundamental space harmonic in the
non-uniform structure, with taking into account the
current loading, was performed using a self-consistent
one-dimensional model [7] by dividing the interaction
region into an arrange of uniform sites matching to each
other on an operating frequency. The energy and the
bunch phase length at the structure input were
calculated using results of the injector PARMELA
simulation. Results of the self-consistent problem
calculation were used to evaluate the amplitude and
phase of fundamental space harmonic in each cell of the
travelling wave (TW) accelerating structure as it is
needed for PARMELA simulations. According to the
code the travelling wave accelerating structure is
represented by an arrange of cells which would be if the
structure to be cut along transverse planes at the middle
of disks except the first cell. The first cell has a length
equal to half a length of the next cell. Therefore the
structure begins from the half a cell that makes it
possible to take into account field penetration in the
input coupler. According to this, the input coupler is
divided in two regions. The first region is the first TW
cell. The second one is the cavity completing this cell to
the real coupler. As the field at the structure exit in
operating mode is small enough the output coupler is set
as a simple cell of the structure. Fig. 1 indicates the
instantaneous electric field distribution along the axis of
the first structure proceeding from spatial harmonics
computing for 10 MW input power and 1 A beam
current.
To take correctly into account the space charge
forces the beam is set as a bunch having the length 5βλ,
where β is the initial normalized velocity of particles, λ
is the operating wavelength.
3. SIMULATION RESULTS
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2000, № 2.
Серия: Ядерно-физические исследования (36), с. 69-71.
69
The simulation has been carried out in several steps.
During the first step there was investigated beam
parameters at the injector exit depending on the phase
shift between the buncher and accelerating cavity and
on the field amplitude in the accelerating cavity under
different magnetic field configurations and positions of
elements of the injector. Based on simulation results the
injector layout was optimized. Fig. 2 and 3 indicate
some simulation results of particle dynamics in the
upgraded injector.
-20
-15
-10
-5
0
5
10
15
20
3
0
5
0
7
0
9
0
11
0
13
0
15
0
17
0Z, (cm)
E
z,
(M
V
/m
)
Fig. 1. Instantaneous electric field distribution
along axis of the first section
Fig. 2. Bunch phase length at the injector exit
(of 70 particles).
Fig. 3. Beam diameter at the injector exit (95% of
particles)
The phase length of the bunch containing 70 % of
particles and the beam diameter (95 % of particles) are
shown as a function of a phase shift and average field
strength in the accelerating cavity. Proceeding from the
obtained results and accessible 1 MW RF power the
best values of phase shift and field amplitude in the
accelerating cavity are selected (ϕ=150° and Е =
10 MV/m).
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 00
1
2
3
4
5
6
7
Z , c m
R
b,
m
m
(9
5%
o
f p
ar
tic
le
s) ← 3 6 °
← 0 °
← 1 8 °
← 0 ° s c h = 0
← 0 ° (B = 5 0 0 G )
Fig. 4. Beam envelope along the accelerator
In the next step the first accelerating section was
added to the injector and the phase shift between them
giving the maximum energy gain was computed. Then
the second section was added and the same procedure
was carried out for the phase shift between sections.
Fig. 4 shows the envelope of the beam containing 95 %
of particles along the accelerator with different phase
shifts between sections. The solenoid was turned off in
this case. The curve marked "0°" corresponds to the
maximum energy gain of a bunch. The curve marked
"sch=0" corresponds to the simulation without taking
into account the space charge forces. The curve marked
"0° (B=500 G)" is obtained in the case when the
solenoid was turned on with a 500 G field. One can see
that the section has a RF focusing. The beam diameter is
less than the minimum aperture of the section (∅
=19 mm) even though the solenoid is turned off. It
should be noted that it is necessary to be careful
choosing the solenoid field on the first section of such
two-section accelerator because the beam overfocusing
can damage elements of a target part of the accelerator.
70
∆ϕ
,
°
0 1 0 0 2 0 0 3 0 0 4 0 0
0
5
1 0
1 5
2 0
A
v
e
ra
g
e
p
o
w
e
r
(W
)
Fig. 5. Average dissipating power distribution along
the accelerator
Fig. 5 shows the average dissipating power
distribution along the accelerator (duty factor was equal
to 0.1%). Such dissipating power does not represent a
danger to the accelerator elements. The main part of
particles (26 %) is lost in the injector, 10 % of particles
are lost in the first section and 1 % is lost in the second
section. Therewith the main energy loss falls at the first
diaphragm of the subsection with a minimum aperture
magnitude. The average power released in it will be
18 W.
Table 1
Parameters Out
cav.
Incoming
section
Pin , MW (Igun=1,54А) 1 --
Iout , А 1,18 1.14
εx rms ,π⋅mm⋅mrad (norm) 54 86
εy rms ,π⋅mm⋅mrad (norm) 53 90
4σx , mm 6.6 10
4σy , mm 6.3 10
∆ϕ for 70% of particles 26 39
∆W/W, % for 70% of particles 20 19
Wmax , MeV 0.61 0.61
Wav , MeV 0.49 0.51
W max probability , MeV 0.55 0.6
∅x , mm for 70% of particles 2.6 4.5
∅y , mm for 70% of particles 2.6 4.4
Table 2
Parameters Section
#1
Section
#2
Pin, MW 11 11
Iout, A 1,04 1,0
εx rms, π⋅mm⋅mrad (norm.) 48 46
εy rms, π⋅mm⋅mrad (norm.) 48 45
4σx, mm (B=0) 8.9 (13) 8.8
(10,7)
4σy, mm (B=0) 8.9 (13) 8.8
(10,7)
∆ϕ for 70 % of particles 22 21
∆W/W, %
for 70 % of particles
5 3
Wmax , MeV 10.1 19.8
Wav , MeV 9.4 18.9
Wmax probability , MeV 10 19.8
∅x , mm (B=0) for 70 % of
partiсles
3.6 (6) 3.4 (5)
∅y , mm (B=0) for 70 % of
partiсles
3.3 (6) 3.4 (5)
Analysis of the transverse beam profile at the
accelerator exit showed the beam has a brightly
expressed core. The beam parameters at the injector and
at the exit of sections are given in Table 1 and Table 2,
respectively. The beam FWHM is 2.5 mm in diameter
(beam sizes for 70 % and 95 % of particles are indicated
in Table 2). Therewith the beam has a halo limited by
the aperture of the accelerator. The average power of
258 W (178 W in the first section with the injector and
82 W in the second section) will dissipate in the
accelerator because of halo particle losing. It will be
about 1 % from the average power of the accelerated
beam.
4. CONCLUSION
The fulfilled beam dynamics simulation showed the
availability of the chosen accelerator design. Simulation
results allowed chan the injector and electron gun layout
for improvement of the beam parameters at the
accelerator exit. According to the simulation the capture
ratio in the accelerator will be up to 66 % with the
average beam power about 20 kW.
Therewith the questions concerned with dynamics in
unsteady-state mode and in axial nonsymmetrical
electromagnetic fields require the further researches.
REFERENCES
1. A.N. Dovbnya, G.D. Pugachev, D.G. Pugachev et.
al. Obtaining power photon beams for medical
radionuclidous production // VANT, “Nuclear
Physics Research” series, 1997, v. 4,5(31,32),
p. 154 – 156 (in Russian).
2. N.I. Aizatsky, Yu.I. Akchurin, V.A., Gurin et. al.
KUT-industrial technological acceleretor //
Proceedings of XIV Workshop on charged particles
accelerators, Protvino, 1994, v. 4, p. 259-263 (in
Russian).
3. I.V. Khodak, V.A. Kushnir, V.V. Mitrochenko et. al.
Electron gun for technological linear accelerator //
VANT,this issue, p.86-88.
4. W.B. Herrmannsfeldt. EGUN: Electron Optics
Program, Stanford Linear Accelerator Center,
SLAC-PUB-6729, 1994.
5. L.M. Young. PARMELA. –Los Alamos, 1996, p. 93
(preprint) / Los Alamos National Laboratory, LA-
UR-96-1835).
6. J.H. Billen and L.M. Young. POISSON/
SUPERFISH on PC compatibles // Proc. 1993
Particle Accelerator Conff., Washington (USA),
1993, p. 790–792.
7. N.I. Aizatsky, L.A. Makhnenko. About current
loading of the bunching section of a linear
accelerator, GTF, 1982, v. 52, Ser. 4, p. 680-683 (in
Russian).
71
REFERENCES
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