Travelling wave deflector for free electron laser
For the measuring system of electron bunch length and emittance at free electron laser there were examined both the known configuration in the form of disc loaded waveguide with two holes for the wave polarization plane stabilization and the new versions of the deflector: with peripheral recesses (t...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2010
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| Cite this: | Travelling wave deflector for free electron laser / A.A. Anisimov, V.I. Kaminskij, M.V. Lalayan, N.P. Sobenin, A.A. Zavadtsev // Вопросы атомной науки и техники. — 2010. — № 2. — С. 56-59. — Бібліогр.: 5 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859749432855101440 |
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| author | Anisimov, A.A. Kaminskij, V.I. Lalayan, M.V. Sobenin, N.P. Zavadtsev, A.A. |
| author_facet | Anisimov, A.A. Kaminskij, V.I. Lalayan, M.V. Sobenin, N.P. Zavadtsev, A.A. |
| citation_txt | Travelling wave deflector for free electron laser / A.A. Anisimov, V.I. Kaminskij, M.V. Lalayan, N.P. Sobenin, A.A. Zavadtsev // Вопросы атомной науки и техники. — 2010. — № 2. — С. 56-59. — Бібліогр.: 5 назв. — англ. |
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| description | For the measuring system of electron bunch length and emittance at free electron laser there were examined both the known configuration in the form of disc loaded waveguide with two holes for the wave polarization plane stabilization and the new versions of the deflector: with peripheral recesses (two grooves in the cowling) and with the oval aperture.
Для системы измерения длины и эмиттанса электронного сгустка в лазере на свободных электронах рассмотрены как известная конфигурация в виде круглого диафрагмированного волновода с двумя отверстиями для стабилизации плоскости поляризации волны, так и новые варианты дефлектора: с двумя выемками в обечайке и с овальной формой отверстия связи.
Для системи виміру довжини і еміттанса електронного згустку в лазері на вільних електронах розглянуті як відома конфігурація у вигляді круглого діафрагмованого хвилеводу із двома отворами для стабілізації площини поляризації хвилі, так і нові варіанти дефлектора: з двома виїмками в обичайці і з овальною формою отвору зв'язку.
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| first_indexed | 2025-12-01T23:14:19Z |
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____________________________________________________________
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2010. № 2.
Series: Nuclear Physics Investigations (53), p.56-59. 56
TRAVELLING WAVE DEFLECTOR FOR FREE ELECTRON LASER
A.A. Anisimov, V.I. Kaminskij, M.V. Lalayan, N.P. Sobenin, A.A. Zavadtsev1
Moscow Physics Engineering Institute (State University);
1JSC “Nano-Invest, Ltd”
E-mail: sobenin@mail.ru
For the measuring system of electron bunch length and emittance at free electron laser there were examined both
the known configuration in the form of disc loaded waveguide with two holes for the wave polarization plane stabi-
lization and the new versions of the deflector: with peripheral recesses (two grooves in the cowling) and with the
oval aperture.
PACS 29.17.+w, 29.27.Eg
1. INTRODUCTION
The linear electron accelerators with the supercon-
ductive accelerating structures are base installations of
contemporary free electron lasers (FEL). The radiation
brightness of these lasers is very large because of the
high average power of the accelerated beam, which ge-
nerates coherent radiation. Radiation wavelength at FEL
can be essentially adjusted; in particular, FEL can work
in the X-ray range. Nowadays intensive development of
free electron laser of X-ray range (X-ray Free Electron
Laser, X-FEL) is conducted at scientific center DESY
(Germany) with the participation of a number of coun-
tries, including Russia. Maximum beam energy will be
20 GeV, the radiation wavelength 0.1 nm [1].
Installation must be equipped with the metrological
equipment, which ensures quality control of the acceler-
ated beam. Accelerating structure with traveling wave
and transverse deflection field is considered as tool for
bunch length measuring, and also as additional means
with the analysis of free electron laser phase space at X-
FEL project [1]. The prototype of this structure can be
disc loaded waveguide operating on E01 wave type with
two diametrically located holes in diaphragms for the
stabilization of wave polarization plane [2,3]. Usually
deflectors with travelling wave are designed for opera-
tion at S-band with 2π/3 mode and wave relative phase
velocity βph=vph/c=1.
2. ELECTRODYNAMIC CHARACTERISTICS
Table 1 includes requirements for three deflectors of
the X-FEL project. Main electrodynamic characteristics,
which are the basis of the selection of the deflector type,
include the following parameters: linear transverse shunt
resistance (rsh⊥), the relative group velocity (βgr), the elec-
tric field maximal gradient on the surface (ES max), the
microwave power attenuation factor (α). Important pa-
rameter is the frequency separation of main and neigh-
bor oscillation modes. Table 2 includes data of three
frequency differences Δfi=f0 − fi, (i = 1,2,3), which are of
interest at structure study. Here frequencies f0 and f3 are
oscillation frequencies at 2π/3 mode and π mode for
working polarization. Frequencies f1 and f2 are oscilla-
tion frequencies at 2π/3 mode and π mode respectively
for other polarization. In all calculations f0 =3000 MHz.
For obtaining the assigned deflecting voltage V⊥ at
any of three sections with the assigned adjusting lengths
and the input power indicated it is necessary to fulfill of
condition:
PE /0 λ⊥ >(220…240), Ω1/2.
Values |βgr|>0.016 ensure the section required filling
time with microwave power τ. For the exception of ex-
citation of mode with nonworking polarization at oper-
ating frequency f0 it is desirable to have frequency sepa-
ration Δf2 > 15 MHz.
In the process of deflector optimum version selection,
first of all, it is necessary to calculate dispersion charac-
teristics of the wave E11 with two polarizations. The lin-
ear transverse shunt resistance is the important parameter
of deflectors. It is calculated by the formula [4]:
( )
( ) Pl
V
Plka
dzzE
r
l
axz
sh
2
2
2
0 1 ⊥
=
=
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
=
∫
. (1)
Here x=a is distance from the axis, at which distribu-
tion of electric field longitudinal component along the
coordinate Ez(z) was calculated; P=ωU/Q, where U −
energy, stored up for the length l of the designed sec-
tion; k=2π/λ, where λ − oscillation wavelength.
Transverse deflecting voltage V⊥ is connected with
the transverse deflecting electric field E0⊥ with deflector
length l as follows:
( )
α
−
==
α−
⊥α−
⊥⊥ ∫
l
z
l eEdzeEV 10
0
0 . (2)
In calculations of deflector with travelling wave cha-
racteristics it is used normalized transverse field gradi-
ent [5]:
Q
r
P
E
gr
sh
β
πλ2λ .0 ⊥⊥ = . (3)
Table 1.
X-FEL deflector characteristics
Characteristics Deflector type
TDS1 TDS2 TDS3
Beam energy W, MeV 130 500 2000
Deflecting voltage V⊥, MV 1.7 14 27
Maximum base length l,
mm
0.7 1.6 3.6
Filling time with microwave
power τ, ns
<120 <320 <320
Input power Р, MW 2.5 26.3 2×20.7
57
a b c
d e
f
Fig.1. Deflecting structure variants
Researched structures are shown in Fig.1. Structure
characteristics were calculated and compared for selec-
tion of optimum profile of deflector section. Variants of
deflector structure are: a, b − with two stabilization
holes; c, d − with the oval aperture, e −with two periph-
eral recesses; f − rounding of the peripheral recesses and
the longitudinal cutting section of cells. Designation шn
the Fig.1 are: Rb − radius of cell; Ra − radius of aperture;
D=33.31 mm − period of structure; Rc = t/2 − radius of
rounding of aperture hole in the diaphragm
(t = 5.25 mm − thickness of diaphragm); Rst − radius of
the stabilization holes, L − radial position of stabiliza-
tion hole axes; h − distance between centers of two se-
micircles with a radius of Ra in the oval aperture; dr −
increase in the radius Rb on the angular dimension ϕ.
Fig.1,f is depicted fragment of structure drawing with
rounding of the peripheral recesses with indication of
lines of sharp boundary rounding, and also longitudinal
cutting of cells. Vector E shown in pictures in Fig.1 is
the direction of deflecting transverse component of elec-
tric field E11 for the working polarization.
3. DEFLECTOR
WITH STABILIZATION HOLES
It is known use of round disc loaded waveguides
with two circular holes for polarization plane stabiliza-
tion of wave E11 as the deflector (see Fig.1,a). It is im-
portant to study influence of hole size in diaphragm Ra,
radius size Rst and position L of stabilization holes to
deflector electrodynamic characteristics. Dispersion
curves at different values of hole radius in diaphragm Ra
are represented in Fig.2. Structure operates on the wave
E11 with the stabilization holes of radius Rst=8.5 mm,
located at distance from cell axis of L=Ra+13.5 mm.
This location of stabilization holes is accepted in the
works [2,3]. Character of dispersion curved on the wave
E11 changes depending on hole radius in diaphragm.
With Ra=23.0 mm the passage from negative dispersion
to positive one takes place.
a b
Fig.2. Dispersion curves of structure with Rst = 8.5 mm and L=Ra+13.5 mm at various Ra (а)
and dispersion curves of two polarizations at Rа=22 mm (б); θ − oscillation mode
3300
3200
3100
3000
0 60 120 180 θ°
f, MHz Ra=21.5 mm
Ra=18.5 mm
Ra=22.0 mm
Ra=23.0 mm
3300
3200
3100
3000
0 60 120 180 θ°
f, MHz
58
Stabilization holes can be positioned near cowling
(L=Rb−10.5 mm). Comparison of characteristics for two
cases of positioning of stabilization holes is given in
Table 2 (versions a, b). It must be noted, that with
L=Rb−10.5 mm the deflection field of the wave E11 is
located in the plane, passing through the axes of the
stabilization holes. Dispersion curves of working polari-
zation with different radii of hole in the diaphragm Ra
are given in Fig.2,a. Solid line in Fig.2,b depicts disper-
sion curve for the working polarization, and broken line
− for the perpendicular polarization.
4. DEFLECTOR WITH OVAL APERTURE
On the basis of structure with the oval aperture (see
Fig.1,c,d) it is possible the creation of deflectors with
the necessary characteristics with two values of distance
h between the centers of hole rounding radii in the dia-
phragm. Corresponding calculation data for the struc-
ture versions are shown in Table 2 (c,d). With h near
1.7 and 7.5 mm of the value of group velocity and given
gradient of transverse component of electric field corre-
spond to presented requirements.
5. DEFLECTOR
WITH PERIPHERAL RECESSES
For the structures with two peripheral recesses (see
Fig.1,e) it was researched influence of aperture angle of
the turning ϕ and its depth dr, first of all, to the separa-
tion of frequencies. Structure with the hole in dia-
phragm of radius Ra=21.5 mm was examined. Taking
into account requirements for the characteristics of de-
flector and production technology of structure with the
peripheral recesses, it is preferable to select depth of
peripheral recesses of small (dr=1 mm) and the angle of
its solution of ϕ = 65°. Corresponding characteristics for
this structure are presented in Table 2, variant e.
Table 2.
Geometrical and electrodynamical parameters of structure various variants
Structure variants, see Fig.1 Parameter a b c d e
L, mm 35.0 45.6 − − −
Rst, mm 8.5 8.5 − − −
h, mm − − 1.7 7.5 -
φ, degree − − - - 65
dr, mm − − - - 1
Ra, mm 21.5 22.0 20.5 21.5 21.5
Rb, mm 55.38 55.04 55.49 53.39 55.03
α, 1/m 0.153 0.150 0.148 0.153 0.147
βgr −0.017 −0.018 −0.017 0.018 −0.017
Rsh⊥, MΩ/m 19.17 18.60 21.07 18.00 19.84
Q 11804 11934 12190 11650 12272
1fΔ , MHz −23 −20 −30 −169 −27
2fΔ , MHz −12 −13 −27 −175 −17
3fΔ , MHz 11 12 12 −17 11
PE /0 λ⊥ , Ω1/2 242 235 252 232 242
Values of sensitivity functions (MHz/mm) for the
structure type e from Table 2 are given below. These
functions are the shift of oscillation frequency at 2π/3
mode with a change in structure dimensions. In the last
column sensitivity function to the aperture angle of
groove is shown.
df/dRb, df/dRa, df/dD, df/dt,
−48.5 −16.3 0.8 4.0
df/dRc, df/d(dr) df/φ, MHz/degree
−3.9 −28 −0.42
6. ELECTRIC AND MAGNETIC FIELDS
ON CELL SURFACE
For the evaluation of dielectric strength of structure
it is necessary to calculate electrical and magnetic fields
on the surface from the outlines, showed in Fig.3 by
bold lines. The results of calculations for the structure
with the peripheral recesses are shown bellow in Ta-
ble 3. Structure has following geometric dimensions:
D=33.31 mm, Ra=21.5 mm, t=5.25 mm, Rc=t/2,
dr=1 mm, ϕ=65°, Rb=55.03 mm.
Since to account field on the structure surface pre-
cisely is impossible, calculations were performed at
different distances from the surface. For determining the
maximum value of field on the surface the extrapolation
of calculation data was used.
а b
Fig.3. Outlines for field maximal value calculation
59
The results of the calculations of maximum field at
the deflecting structure are given in Table 3.
Table 3.
Calculation results of field maximal value
Emax2(0), MV/m
Р, MW At outline
in Fig.3,а
At outline in
Fig.3,b
Нmax2(0),
kA/m
2.3 13.29 0.035 44.03
2.6 14.12 0.036 46.82
22.0 41.10 0.107 136.2
24.0 42.93 0.111 142.2
26.3 44.94 0.117 144.5
7. THERMAL REGIME
The calculations of thermal regime of the deflecting
structures were carried out. Calculations of temperature
distribution in the deflecting structure with two and four
tubes of cooling with diameter 4 mm were carried out.
The power of losses composes approximately 9.5 W to
the cell with the average transmitting power of 812 W.
Pulse power is 26.2 MW, pulse duration is 3.1 μs, pulse
repetition rate is 10 Hz.
With the use of four cooling channels with rectangu-
lar cross-section and flow speed of the cooling water
1.22 m/s temperature maximum change in the structure
is equal 1.67°C. For the structure with the peripheral
recesses temperature change is 1.5 times less than for
the structures with two s stabilization holes at the same
speed of cooling water flow.
CONCLUSIONS
All versions of the deflecting structure, given in Ta-
ble 2, principally can be used for X-FEL. All versions
can be realized technologically. Versions c, d and e (see
Table 2) have greater electric strength (the smaller value
ES max), because of the absence of the stabilization holes
in diaphragms. These structures also have 1.5 times
smaller gradient of temperature. In the version a (see
Table 2) for L=35.0 mm the thin wall between the aper-
ture and stabilization hole is obtained. In the version b
(see Table 2) for L=45.6 mm the stabilization holes are
located closely to the wall of cowling, which compli-
cates the production of roundings on the edges of these
holes. The fulfillment of oval aperture completely actu-
ally technologically, but will require the additional time
and means for its production. Version e is preferable,
since it satisfies all requirements for the deflecting
structures X-FEL and it is most simple technologically.
For this version of the deflecting structure the calculated
maximum values of electrical and magnetic field gradi-
ent on the surface are 14 mV/m and 47 kA/m, respec-
tively, with the input power of 2.6 MW.
The authors express gratitude to L.V. Kravchuk,
V.V. Paramonov, M. Huening and F. Stephan for the
useful discussions.
REFERENCES
1. M. Altarelli, R. Brinkmann, M. Chergui, et al. XFEL
Technical Design Report// DESY 2006-097. 2006,
p.11.
2. R. Akle, B. Lentson, P. Emma, et al. A Transverse
RF Deflecting Structure for Bunch Length and Phase
Space Diagnostics // SLAC-PUB-8864. June, 2001,
p.3.
3. D. Denisenko, V. Paramonov. The Transverse De-
flection Structure for X-FEL Numerical Simulation?
Analysis and results // Proc. RuPAC 2008. Russia,
Zvenigorod. 2008, p.37.
4. N.P. Sobenin, B.V. Zverev. Electrodynamic Charac-
teristics of Accelerating Cavities. London: “Founda-
tion for International Scientific and Education Co-
operation”, 1999, p.98.
5. O.A. Valdner, N.P. Sobenin, B.V. Zverev,
I.S. Shchedrin. Disc loaded waveguides. Manual.
M.: “Energoatomizdat”, 1991, p.87.
Статья поступила в редакцию 07.09.2009 г.
ДЕФЛЕКТОР НА БЕГУЩЕЙ ВОЛНЕ ДЛЯ ЛАЗЕРА НА СВОБОДНЫХ ЭЛЕКТРОНАХ
А.А. Анисимов, В.И. Каминский, М.В. Лалаян, Н.П. Собенин, А.А. Завадцев
Для системы измерения длины и эмиттанса электронного сгустка в лазере на свободных электронах рас-
смотрены как известная конфигурация в виде круглого диафрагмированного волновода с двумя отверстиями
для стабилизации плоскости поляризации волны, так и новые варианты дефлектора: с двумя выемками в
обечайке и с овальной формой отверстия связи.
ДЕФЛЕКТОР НА ХВИЛІ, ЩО БІЖИТЬ, ДЛЯ ЛАЗЕРА НА ВІЛЬНИХ ЕЛЕКТРОНАХ
А.А. Анісімов, В.І. Камінський, М.В. Лалаян, Н.П. Собенін, А.А. Завадцев
Для системи виміру довжини і еміттанса електронного згустку в лазері на вільних електронах розглянуті
як відома конфігурація у вигляді круглого діафрагмованого хвилеводу із двома отворами для стабілізації
площини поляризації хвилі, так і нові варіанти дефлектора: з двома виїмками в обичайці і з овальною фор-
мою отвору зв'язку.
|
| id | nasplib_isofts_kiev_ua-123456789-15686 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-01T23:14:19Z |
| publishDate | 2010 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Anisimov, A.A. Kaminskij, V.I. Lalayan, M.V. Sobenin, N.P. Zavadtsev, A.A. 2011-01-31T15:07:47Z 2011-01-31T15:07:47Z 2010 Travelling wave deflector for free electron laser / A.A. Anisimov, V.I. Kaminskij, M.V. Lalayan, N.P. Sobenin, A.A. Zavadtsev // Вопросы атомной науки и техники. — 2010. — № 2. — С. 56-59. — Бібліогр.: 5 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/15686 For the measuring system of electron bunch length and emittance at free electron laser there were examined both the known configuration in the form of disc loaded waveguide with two holes for the wave polarization plane stabilization and the new versions of the deflector: with peripheral recesses (two grooves in the cowling) and with the oval aperture. Для системы измерения длины и эмиттанса электронного сгустка в лазере на свободных электронах рассмотрены как известная конфигурация в виде круглого диафрагмированного волновода с двумя отверстиями для стабилизации плоскости поляризации волны, так и новые варианты дефлектора: с двумя выемками в обечайке и с овальной формой отверстия связи. Для системи виміру довжини і еміттанса електронного згустку в лазері на вільних електронах розглянуті як відома конфігурація у вигляді круглого діафрагмованого хвилеводу із двома отворами для стабілізації площини поляризації хвилі, так і нові варіанти дефлектора: з двома виїмками в обичайці і з овальною формою отвору зв'язку. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Физика и техника ускорителей Travelling wave deflector for free electron laser Дефлектор на бегущей волне для лазера на свободных электронах Дефлектор на хвилі, що біжить, для лазера на вільних електронах Article published earlier |
| spellingShingle | Travelling wave deflector for free electron laser Anisimov, A.A. Kaminskij, V.I. Lalayan, M.V. Sobenin, N.P. Zavadtsev, A.A. Физика и техника ускорителей |
| title | Travelling wave deflector for free electron laser |
| title_alt | Дефлектор на бегущей волне для лазера на свободных электронах Дефлектор на хвилі, що біжить, для лазера на вільних електронах |
| title_full | Travelling wave deflector for free electron laser |
| title_fullStr | Travelling wave deflector for free electron laser |
| title_full_unstemmed | Travelling wave deflector for free electron laser |
| title_short | Travelling wave deflector for free electron laser |
| title_sort | travelling wave deflector for free electron laser |
| topic | Физика и техника ускорителей |
| topic_facet | Физика и техника ускорителей |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/15686 |
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