The project of a high-power FEL driven by an SC ERL at KAERI
The project of a high-power FEL at Korea Atomic Energy Research Institute and its recent status are described. The FEL is driven by a superconducting energy recovery linac. The first-stage machine will operate in the far IR region and its CW power is expected to be a few kW. Possible upgrade of th...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2006
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| Цитувати: | The project of a high-power FEL driven by an SC ERL at KAERI / S.V. Miginsky, A.V. Bondarenko, B.C. Lee, S.H. Park, Y.U. Jeong, Y.H. Han, S.C. Kim // Вопросы атомной науки и техники. — 2006. — № 2. — С. 37-39. — Бібліогр.: 6 назв. — англ. |
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irk-123456789-786972015-03-21T03:02:00Z The project of a high-power FEL driven by an SC ERL at KAERI Miginsky, S.V. Bondarenko, A.V. Lee, B.C. Park, S.H. Jeong, Y.U. Han, Y.H. Kim, S.C. Линейные ускорители заряженных частиц The project of a high-power FEL at Korea Atomic Energy Research Institute and its recent status are described. The FEL is driven by a superconducting energy recovery linac. The first-stage machine will operate in the far IR region and its CW power is expected to be a few kW. Possible upgrade of the machine is also considered. The upgraded machine will operate in the near IR region and its expected power is a few tens kW. Описан проект мощного ЛСЭ в Корейском институте атомной энергии, а также текущее состояние дел. В ЛСЭ будет использован сверхпроводящий линак-рекуператор. Машина первой очереди будет работать в дальнем ИК-диапазоне, ее ожидаемая средняя мощность несколько киловатт. Рассматривается возможная модернизация машины. Модернизированная машина будет генерировать десятки киловатт средней мощности в ближнем ИК-диапазоне. Описано проект потужного ЛВЕ в Корейському інституті атомної енергії, а також поточний стан справ. У ЛВЕ буде використаний надпровідний лінак-рекуператор. Машина першої черги буде працювати в далекому ІЧ-діапазоні, її очікувана середня потужність − кілька кіловат. Розглядається можлива модернізація машини. Модернізована машина буде генерувати десятки кіловатів середньої потужності в ближньому ІЧ-діапазоні. 2006 Article The project of a high-power FEL driven by an SC ERL at KAERI / S.V. Miginsky, A.V. Bondarenko, B.C. Lee, S.H. Park, Y.U. Jeong, Y.H. Han, S.C. Kim // Вопросы атомной науки и техники. — 2006. — № 2. — С. 37-39. — Бібліогр.: 6 назв. — англ. 1562-6016 PACS: 41.60.Cr http://dspace.nbuv.gov.ua/handle/123456789/78697 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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| topic |
Линейные ускорители заряженных частиц Линейные ускорители заряженных частиц |
| spellingShingle |
Линейные ускорители заряженных частиц Линейные ускорители заряженных частиц Miginsky, S.V. Bondarenko, A.V. Lee, B.C. Park, S.H. Jeong, Y.U. Han, Y.H. Kim, S.C. The project of a high-power FEL driven by an SC ERL at KAERI Вопросы атомной науки и техники |
| description |
The project of a high-power FEL at Korea Atomic Energy Research Institute and its recent status are described.
The FEL is driven by a superconducting energy recovery linac. The first-stage machine will operate in the far IR region
and its CW power is expected to be a few kW. Possible upgrade of the machine is also considered. The upgraded
machine will operate in the near IR region and its expected power is a few tens kW. |
| format |
Article |
| author |
Miginsky, S.V. Bondarenko, A.V. Lee, B.C. Park, S.H. Jeong, Y.U. Han, Y.H. Kim, S.C. |
| author_facet |
Miginsky, S.V. Bondarenko, A.V. Lee, B.C. Park, S.H. Jeong, Y.U. Han, Y.H. Kim, S.C. |
| author_sort |
Miginsky, S.V. |
| title |
The project of a high-power FEL driven by an SC ERL at KAERI |
| title_short |
The project of a high-power FEL driven by an SC ERL at KAERI |
| title_full |
The project of a high-power FEL driven by an SC ERL at KAERI |
| title_fullStr |
The project of a high-power FEL driven by an SC ERL at KAERI |
| title_full_unstemmed |
The project of a high-power FEL driven by an SC ERL at KAERI |
| title_sort |
project of a high-power fel driven by an sc erl at kaeri |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2006 |
| topic_facet |
Линейные ускорители заряженных частиц |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/78697 |
| citation_txt |
The project of a high-power FEL driven by an SC ERL at KAERI / S.V. Miginsky, A.V. Bondarenko, B.C. Lee, S.H. Park, Y.U. Jeong, Y.H. Han, S.C. Kim // Вопросы атомной науки и техники. — 2006. — № 2. — С. 37-39. — Бібліогр.: 6 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-07-06T02:46:07Z |
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| fulltext |
THE PROJECT OF A HIGH-POWER FEL DRIVEN BY AN SC ERL
AT KAERI
S.V. Miginsky, A.V. Bondarenko, B.C. Lee1, S.H. Park1, Y.U. Jeong1, Y.H. Han1, S.C. Kim1
Budker INP, Novosibirsk, Russia
1Korea Atomic Energy Research Institute, Daejeon, Korea
E-mail: S.V.Miginsky@inp.nsk.su
The project of a high-power FEL at Korea Atomic Energy Research Institute and its recent status are described.
The FEL is driven by a superconducting energy recovery linac. The first-stage machine will operate in the far IR re-
gion and its CW power is expected to be a few kW. Possible upgrade of the machine is also considered. The upgrad-
ed machine will operate in the near IR region and its expected power is a few tens kW.
PACS: 41.60.Cr
1. INTRODUCTION
The project of a free electron laser (FEL) driven by
an accelerator-recuperator (AR) was started at KAERI
in 1998. It is ever considered as a high-power CW
source of IR-FIR radiation. The first step was the com-
missioning of an electron injector very analogous to the
one of the Novosibirsk FEL [0] in collaboration with
BINP. Since then, the project has been revised several
times. Now a superconducting (SC) energy recovery
linac (ERL) is considered as the driver of the FEL.
2. INJECTOR
The source of electrons is a 300 kV DC electron gun
with a gridded thermionic cathode manipulated with a
controlled pulser. Electron bunches from the gun gain
the correlated energy spread in a bunching 176-MHz
normal-conducting RF cavity, are compressed due to
klystron-like bunching in a 2.5 m drift space, and gain
higher energy in a pair of analogous accelerating cavi-
ties. The latter also compensate the residual correlated
energy spread. Basic parameters of the gun are:
electron energy (kinetic)……300 keV;
average current:……………..12 mA;
charge of bunch……………..2 nC;
repetition rate………………..0...11 MHz;
pulse duration……………….1.1 ns;
normalized emittance………20π mm·mrad;
operation mode……………..CW.
The injection energy (full) is 2 MeV.
3. RF SYSTEM
The RF accelerating structure consists of two
352.2 MHz superconducting cavities embedded into one
cryostat [0], [0]. These cavities were previously used in
LEP, CERN. Each cavity has four π-type cells. The cav-
ities are fed by two 50 kW tetrode generator modules.
Maximum energy gain obtained for one cavity is
12 MeV [0].
The normal-conducting cavities of the injector are
very similar to the ones at BINP [0]. They were modi-
fied a little to decrease their resonant frequency from
initial 181 to 176.1 = 352.2/2 MHz. The accelerating
cavities of the injector are fed by two 100 kW tetrode
generator modules.
4. BEAMLINES
An injection beamline (Fig. 1) is intended to conduct
a 2 MeV electron beam from the injector to the SC cavi-
ties and control its parameters so that to avoid any loss-
es inside the cavities. The injection shift was provided
for future upgrade to ERL.
GUN
Bending
magnet
176 MHz
RF-cavity S
ol
en
oi
d
Quadrupole
P
ic
ku
p
352 MHz
superconducting
RF-cavity
Beam
current
monitor
Injector
900
900
300
300
450
450
1350
4600
3100
1700
1000
6900
Fig. 1. Current status of the SC linac at KAERI
___________________________________________________________
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2006. № 2.
Series: Nuclear Physics Investigations (46), p.37-39. 37
The extraction beamline conducts an accelerated
10 MeV electron beam to a scanning device to extract it
to the atmosphere. Beam losses in the beamline are van-
ishingly small.
The future ERL will be connected to the existing
machine without any modification. It consists of two
180º bents and two straight sections (Fig. 2): one is for
the FEL, another for Compton backscattering. One can
choose the regime controlling the lenses. The dispersion
function η is zero together with its derivative in one of
these sections, so one bent is achromatic, while the oth-
er is almost achromatic. Both bents are almost
isochronous, so that the total ERL is perfectly
isochronous to avoid any problems with longitudinal
beam instability. The ERL has enough degrees of free-
dom to control both betatron phase independently to
suppress regenerative transverse beam instability.
SC cavities
Undulator
Compton BS
Dump
Injection
Quadrupole Sextupole
160
12°
32°
32°
160
12°
32°
Fig. 2. Future energy recovery linac at KAERI
The beamline can be adjusted for the beam energy
10…22 MeV. As the electron-transit time depends on
the energy, the phase of the second (deceleration) pass
differs for different energies. It means that the extrac-
tion energy and the energy spread are varied. At 10 and
22 MeV the extraction energy will be 2.1 and 2.8 MeV,
and the energy spread 1.85…2.38 and 1.7…3.9 MeV,
respectively. It is without the energy spread added by
the FEL. To absorb such a wide-spectrum beam, the
dump is combined with the first dipole magnet in the
left bent (). The acceptance of the dump is 0.27…3.1
and 0.6…7 MeV for 10 and 22 MeV regimes, respec-
tively. So, the FEL may add ±0.7 and ±1.1 MeV energy
spread, respectively.
Fig. 3. Dump
The beamline was optimized for aberrations to mini-
mize emittance growth. An appropriate number of sex-
tupoles is added to suppress chromatic aberrations. Due
to that, from the cavity to the active section and from
the latter to the cavity 0/ =∂η∂ p and 0/ =∂η ′∂ p ,
while pxy ∂α∂ / and pxy ∂β∂ / are in compromise
with the strengths of the sextupoles, as both parameters
degrade the emittance. The emittance growth is
5.0/2 ≤εε∆ due to the aberration in sextupoles,
the same due to pxy ∂α∂ / and pxy ∂β∂ / , and
2.0/2 ≤εε∆ in quadrupoles. Thus, the total rela-
tive emittance degradation through the whole machine is
≈ 1.5. The sensitivity to the lenses gradients is moderate,
so the permissible relative PS instability is 8·10-3.
5. FEL
The conventional scheme of the FEL is considered.
It will consist of a 2 m helical in-vacuum undulator
made of permanent magnets. Its period will be 35 mm,
maximum K = 1.6 at the gap of 15.5 mm. One mirror of
the optical cavity is blind and made of copper, another
one, the outcoupler, is semi-transparent and made of
CVD diamond [0]. The expected average power is a few
kW, the tuning range 35…70 μm.
6. ATTAINED RESULTS
Recently, stable current of 6 mA at the energy of
10 MeV was obtained. At the higher current an instabili-
ty connected with the SC cavities occurs. It appears as
exponential rise of the beam losses at the extraction
beamline of the characteristic time ~ 1 s. Every time a
quench occurs in the cryostat.
The injector is capable to emit higher average cur-
rent. Its limitation is giant current pulses occurred at an
average current > 8 mA. After the cleaning procedure its
maximum stable current exceeds 12 mA.
7.6 and 7.8 MeV maximum energy gains were ob-
tained for the SC cavities. The limiting factor in our
case was not mechanical vibrations of the cavities as in
[0], but the reactive power in the feeders. After the up-
grade to feeders one can expect to achieve 12 MeV.
7. POSSIBLE UPGRADE
The most desirable upgrade is an addition of one
more pair of SC cavities. In this case the maximum
beam energy of the ERL will exceed 40 MeV. It will en-
able to make an FEL in the near-IR region. Of course, a
new beamline is to be designed in this case. The main
difference is that π/2 rotation in the longitudinal phase
space will be done, so the appropriate longitudinal dis-
persion will be in the bents. It is necessary as the peak
current is extremely critical for a shorter-wavelength
FEL, while the bunch duration does not limit the
linewidth. In this case higher harmonic linearization of
the accelerating voltage is extremely useful to minimize
the longitudinal emittance.
The FEL power is proportional to the average elec-
tron current, so any improvement of the injector is high-
ly helpful. Boost of the injection energy and the current
is also considered.
As the average power of the upgraded FEL can
reach several tens kW, its alternative schemes, like re-
generative amplifier [0] or electron outcoupling [0]
should be considered thoroughly. In other case its power
will be limited by the optical resonator mirrors.
2
8. CONCLUSION
The SC linac at KAERI operates successfully and
stably now. The design of the beamline for the ERL sat-
isfies all the requirements for successful operation to-
gether with an FEL. These facts together give a good fu-
ture prospect for constructing and commissioning the
whole machine in the nearest future.
REFERENCES
[0. V.P. Bolotin, N.A. Vinokurov, D.A. Kayran et al.
Status of the Novosibirsk terahertz FEL // Nucl. In-
str. and Methods. 2005, v.A543, №1, p.81-84.
[0. P. Bernard, D. Bloess, G. Cavallari et al. Supercon-
ducting RF cavities for LEP. Proc. of European Part.
Acc. Conf., Rome. 1988, v.2, p.958-960.
[0. D.Boussard, G.Cavallari, H.P.Kinderman et al. Fur-
ther results from the test of a 352 MHz supercon-
ducting cavity in the CERN SPS. CERN/EF/RF 88-3.
1988.
[0. A.V. Bondarenko, S.V. Miginsky. Simulation and
minimization of thermal deformation of mirrors in a
resonator of free electron laser // Nucl. Instr. and
Methods. 2005, v.A543, №1, p. 110-113.
[0. D.C. Nguyen, C.M. Fortgang, J.C. Goldstein et al.
Synchronously injected amplifiers, a novel approach
to high-average-power FE // Nucl. Instr. and Meth-
ods. 1997, v.A393, №1-3, p.252-256.
[0. G.N. Kulipanov, A.S. Sokolov, N.A. Vinokurov.
Coherent undulator radiation of an electron beam
microbunched for the FEL power outcoupling // Nu-
cl. Instr. and Methods. 1996, v.A375, №1-3, p.576-
579.
ПРОЕКТ МОЩНОГО ЛСЭ В KAERI НА БАЗЕ СВЕРХПРОВОДЯЩЕГО ЛИНАКА-
РЕКУПЕРАТОРА
С.В. Мигинский, А.В. Бондаренко, Б.Ч. Ли, С.Х. Пак, Я.У. Джонг, Я.Х. Хан, С.Ч. Ким
Описан проект мощного ЛСЭ в Корейском институте атомной энергии, а также текущее состояние дел. В
ЛСЭ будет использован сверхпроводящий линак-рекуператор. Машина первой очереди будет работать в
дальнем ИК-диапазоне, ее ожидаемая средняя мощность несколько киловатт. Рассматривается возможная
модернизация машины. Модернизированная машина будет генерировать десятки киловатт средней мощно-
сти в ближнем ИК-диапазоне.
ПРОЕКТ ПОТУЖНОГО ЛВЕ В KAERІ НА БАЗІ НАДПРОВІДНОГО ЛИНАКА-РЕКУПЕРАТОРА
С.В. Мигинський, А.В. Бондаренко, Б.Ч. Лі, С.Х. Пак, Я.У. Джонг, Я.Х. Хан, С.Ч. Кім
Описано проект потужного ЛВЕ в Корейському інституті атомної енергії, а також поточний стан справ.
У ЛВЕ буде використаний надпровідний лінак-рекуператор. Машина першої черги буде працювати в
далекому ІЧ-діапазоні, її очікувана середня потужність − кілька кіловат. Розглядається можлива
модернізація машини. Модернізована машина буде генерувати десятки кіловатів середньої потужності в
ближньому ІЧ-діапазоні.
___________________________________________________________
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2006. № 2.
Series: Nuclear Physics Investigations (46), p.37-39. 37
Проект мощного ЛСЭ в KAERI на базе сверхпроводящего линака-рекуператора
ПРОЕКТ ПОТУЖНОГО ЛВЕ В KAERІ НА БАЗІ НАДПРОВІДНОГО ЛИНАКА-РЕКУПЕРАТОРА
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