Parallel coupled cavity structure with constant magnets focusing system
Accelerator for intensive electron beam (average current up to 2 A) from energy 50 keV up to energy 3-5 MeV is offered. Accelerating structure consist of a few resonators fed parallel from one waveguide. Focusing system contains constant radial magnets located between accelerating resonators and cre...
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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 |
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| Цитувати: | Parallel coupled cavity structure with constant magnets focusing system / V.M. Pavlov, S.V. Shiyankov, V.I. Ivannikov, Yu.D. Chernousov, I.V. Shebolaev // Вопросы атомной науки и техники. — 2001. — № 5. — С. 74-76. — Бібліогр.: 11 назв. — англ. |
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irk-123456789-789902015-03-25T03:01:53Z Parallel coupled cavity structure with constant magnets focusing system Pavlov, V.M. Shiyankov, S.V. Ivannikov, V.I. Chernousov, Yu.D. Shebolaev, I.V. Accelerator for intensive electron beam (average current up to 2 A) from energy 50 keV up to energy 3-5 MeV is offered. Accelerating structure consist of a few resonators fed parallel from one waveguide. Focusing system contains constant radial magnets located between accelerating resonators and creating the axial alternating-gradient focusing magnetic field. Geometry and results of beam dynamics calculation such kind accelerator are presented. 2001 Article Parallel coupled cavity structure with constant magnets focusing system / V.M. Pavlov, S.V. Shiyankov, V.I. Ivannikov, Yu.D. Chernousov, I.V. Shebolaev // Вопросы атомной науки и техники. — 2001. — № 5. — С. 74-76. — Бібліогр.: 11 назв. — англ. 1562-6016 PACS number: 29.17.+w http://dspace.nbuv.gov.ua/handle/123456789/78990 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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English |
| description |
Accelerator for intensive electron beam (average current up to 2 A) from energy 50 keV up to energy 3-5 MeV is offered. Accelerating structure consist of a few resonators fed parallel from one waveguide. Focusing system contains constant radial magnets located between accelerating resonators and creating the axial alternating-gradient focusing magnetic field. Geometry and results of beam dynamics calculation such kind accelerator are presented. |
| format |
Article |
| author |
Pavlov, V.M. Shiyankov, S.V. Ivannikov, V.I. Chernousov, Yu.D. Shebolaev, I.V. |
| spellingShingle |
Pavlov, V.M. Shiyankov, S.V. Ivannikov, V.I. Chernousov, Yu.D. Shebolaev, I.V. Parallel coupled cavity structure with constant magnets focusing system Вопросы атомной науки и техники |
| author_facet |
Pavlov, V.M. Shiyankov, S.V. Ivannikov, V.I. Chernousov, Yu.D. Shebolaev, I.V. |
| author_sort |
Pavlov, V.M. |
| title |
Parallel coupled cavity structure with constant magnets focusing system |
| title_short |
Parallel coupled cavity structure with constant magnets focusing system |
| title_full |
Parallel coupled cavity structure with constant magnets focusing system |
| title_fullStr |
Parallel coupled cavity structure with constant magnets focusing system |
| title_full_unstemmed |
Parallel coupled cavity structure with constant magnets focusing system |
| title_sort |
parallel coupled cavity structure with constant magnets focusing system |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2001 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/78990 |
| citation_txt |
Parallel coupled cavity structure with constant magnets focusing system / V.M. Pavlov, S.V. Shiyankov, V.I. Ivannikov, Yu.D. Chernousov, I.V. Shebolaev // Вопросы атомной науки и техники. — 2001. — № 5. — С. 74-76. — Бібліогр.: 11 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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| first_indexed |
2025-07-06T03:07:07Z |
| last_indexed |
2025-07-06T03:07:07Z |
| _version_ |
1836865267306594304 |
| fulltext |
PARALLEL COUPLED CAVITY STRUCTURE WITH
CONSTANT MAGNETS FOCUSING SYSTEM
V.M. Pavlov, S.V. Shiyankov, V.I. Ivannikov1, Yu.D. Chernousov1, I.V. Shebolaev1
Budker Institute of Nuclear Physics,
630090 Novosibirsk, Russia, Lavrentiev av., 11
e-mail: Pavlov@inp.nsk.su
1 Institute of Chemical Kinetic and Combustion
630090 Novosibirsk, Russia, Institutskaya str., 3
e-mail: Chern@catalysis.nsk.su
Accelerator for intensive electron beam (average current up to 2 A) from energy 50 keV up to energy 3-5 MeV is of-
fered. Accelerating structure consist of a few resonators fed parallel from one waveguide. Focusing system contains
constant radial magnets located between accelerating resonators and creating the axial alternating-gradient focusing
magnetic field.
Geometry and results of beam dynamics calculation such kind accelerator are presented.
PACS number: 29.17.+w
The development of an electron accelerator on low
energies β ≅ (0.4-1) with pulse current more than 0.1 A
represents some difficulties due to influence of the
space charge on beam dynamics. To retain a beam the
magnetic field of the order 0.05 - 0.2 T is necessary.
The weight a focusing solenoid is significant, the DC
power sources and cooling system are necessary. All
these essentially increase the weight and cost of such
kind of accelerators.
The focusing of a beam by a sign-alternating mag-
netic field allows reducing the weight and cost of the fo-
cusing system [1]. Permanent magnets with a large re-
manence are attractive for producing strong magnetic
fields. The focusing of a beam, for example in powerful
klystrons, is carried out by Sm-Co permanent magnets
keeping on axes of beams an alternating field with max-
imum induction 0.1-0.2 Т [2]. However such fields, ca-
pable of retaining a beam current of several ampere, in
making injector -accelerators are not utilized. The rea-
son is simple: due to the construction of usual accelerat-
ing structure, in which the accelerating cavities are lo-
cated close to each other, or the intervals are occupied
by coupling cavities [3-5].
In parallel coupled structure [6] the creation of an al-
ternating magnetic field on the axis of a beam with the
help of radially magnetized magnets is possible. In such
a structure the accelerating cavities are located sequen-
tially one after another and are excited from a wave-
guide through a common wall [6, 7]. If for excitation a
rectangular wave-guide is used, the condition of a trav-
elling wave with the phase velocity vϕ > c is fulfilled.
The cavities should be installed at the distance
( )gvcL Λ+= /// 00 λλ apart, where 0λ , gΛ - wave-
lengths of the accelerating field in free space and in the
wave-guide respectively. The direction of particle mo-
tion in the structure must be opposite to the direction of
the wave-guide phase velocity. Under these conditions
the synchronous acceleration of particles with variable
velocity v is possible. The intervals between accelerat-
ing cavities are free and can be used for installation of
focusing magnets.
The sizes of cavity coupling slots become consider-
able even if cavity quality-factor is equal to 105 [8]. That
can result in the appearance of asymmetric field compo-
nents in the accelerating cavity. In our case at quality-
factor of accelerating resonators Q ≅ 104 the sizes of
coupling holes can be essentially reduced by exciting
accelerating cavities through the transmission-type cavi-
ty.
The scheme of such a structure with built-in magnets
is shown in Fig. 1. The accelerating cavities (1) are ex-
cited from the transmission-type cavity (6) through cou-
pling slots (3) in the common wall. Excitation of the
whole system is carried out through a coupling hole (7).
The cavity (6) represents a cut of the rectangular wave-
guide, operated on H104 -mode. The wave-guide is load-
ed by capacity protuberances (2) to reduce the wave-
length.
In the transmission-type cavity (6) the standing wave
with a period L = λ o/2 is settled. The distance between
the neighboring coupling holes (3) is also λo/2. There-
fore accelerating cavities are exited by the transversal
component of the magnetic field of cavity (6) with a
phase shift π.
The wave-guide-fed slots of all cavities (1) are in
identical conditions. They are connected in series and
can be considered as one equivalent cavity. Thus the
structure can be described as a system of two coupled
cavities [9, 10].
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №5.
Серия: Ядерно-физические исследования (39), с. 74-76.
74
mailto:Pavlov@inp.nsk.su
mailto:Chern@catalysis.nsk.su
Fig. 1. Scheme of the accelerating structure.
1 – accelerating cavity, 2 – capacity protuberance, 3 – coupling slot, 4 – symmetrized magnetic circuit, 5 – mag-
nets, 6 – transmission-type cavity, 7 – input coupling hole.
In such a system the coupling coefficient between
cavities (final and intermediate) can vary over a wide
range. The ratio of stored energies in final cavity W1 and
intermediate cavity W2 depends on coupling coefficient
k between the cavities and the quality-factor of the final
cavity Q1: W1/W2 = k 2Q1
2. The system is matched, if the
entering coupling coefficient is chosen from the require-
ment: k o = 1 + k 2Q1⋅Q2.
Thus, increasing the amplitude of the field in a trans-
mission-type cavity with keeping the input matched re-
duces the coupling coefficient between the cavities and,
hence, decreases the sizes of the coupling holes. This re-
duces the influence of coupling slot on the distribution
of fields in the accelerating cavity.
To create radially magnetized system four rectangu-
lar Nd-Fe-B magnets (5) are used. The aperture magnet-
ic field is symmetrized by Fe- bushes (4) with a round
hole. Magnets (5) are located inside the intervals be-
tween cavities (1). The magnets are magnetized alter-
nately - from axis and to axis of structure. This produces
an alternating longitudinal magnetic field on beam axis.
The adjusting accessories of magnets are demountable,
that allows to remove them if the structure must be heat-
ed.
The optimum sizes of accelerating cavities depend
on the current of the beam and power input. When a
large current is accelerated, the influence of longitudinal
wake fields becomes essential. The voltage variation of
the beam U on an single cavity with length L and effec-
tive shunt impedance Z taking into account radiation is
determined by the expression: U = (PZL)1/2 - IZL/2,
where P – input RF power and I – average accelerating
beam current. At given P and I, U as the function of
(ZL) has maximum at (ZL)0 = P/I 2, and is equal to zero
at ZL = 4(ZL)0 and unsignificantly (about 20 %) varies
when changing ZL from (ZL)0 up to 2(ZL)0. The power
P is always restricted by employed RF source, therefore
ZL should be chosen from the requirements: (ZL)opt.=1.5⋅
Pmax/I 2
max. In this case at a variation of a power level the
effective acceleration of currents up to Imax is possible.
As an example one of the variants of beam dynamics
calculation is presented. Basic data:
Operate frequency 2856 MHz,
Injection energy 50 kV (input
energy spread
2%),
Average beam current 1.95 A ,
Number of particles in bunch 0.36⋅1010,
Pulse duration of input current is according to π injec-
tion,
Diameter of input beam 4 mm,
Phase shift between cavities equal to π,
Input RF powers (without current load) 0.025, 0.15,
0.25, 0.35 and 0.45 MW respectively.
The distribution of accelerating field of Е010 cavities
and its parameters were calculated previously using pro-
gram SLANS [11]. The diameter of aperture is equal to
10 mm. Cavity diameter 80 mm, (operating frequency
2856 MHz). Length of cavities: 18, 22, 32, 36 and
36 mm respectively. Cavities are assumed not coupling.
The magnetic field of radially magnetized perma-
nent magnets was modelled by the field of thin close lo-
cated solenoids with opposing current [1]. The lengths
of magnets located between the cavities are 8 mm.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №5.
Серия: Ядерно-физические исследования (39), с. 75-76.
75
The results of calculations are shown in Fig. 2.
Fig. 2. The results of calculation.
There one can see the distributions of focusing mag-
netic field, relative amplitude of accelerating RF field in
the cavities and results of calculation:
Average output energy 3.6 MeV,
root-mean-square deviation of energy ±0.7 %,
Electrons capture 100 %.
Calculated normalized emittance of accelerating parti-
cles is less than 33 π⋅mm⋅mrad for both x and y axes.
At present time the model of accelerator on parallel
coupled cavity is in progress.
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