Present Status of UVSOR-II
Masahiro Katoh, Eiji Shigemasa, Shin-ichi Kimura and Nobuhiro Kosugi
UVSOR Facility, Institute for Molecular Science, Myodaiji-cho, Okazaki, 444-8585 Japan
Abstract. A 750 MeV synchrotron light source, UVSOR-II, is routinely operated for users with emittance of 27 nm-rad,which is the world smallest among the operational synchrotron light sources of relatively low energy below 1 GeV. Eightbending magnets and three undulators provide synchrotron light to totally 13 beam-lines. Two of the undulators are of invacuum type and another is of variable polarization type. A high performance monochromator for the beam-line, BL3U,
and a high-resolution photoelectron energy analyzer for the end station at BL5U have been successfully installed, both ofwhich utilize undulator radiation. The IR beam-line, BL6B has been upgraded by introducing a so-called magic mirror as
the first mirrors and the world-highest intensity has been successfully achieved. Fourth undulator of variable polarization
type and its beam-line are under construction. The energy upgrade of the injector is in progress, to realize the top-up
operation within a few years. The wavelength of the free electron laser has come into the deep UV region, thanks to thelow emittance of the ring. Some users’ experiments are in progress. A Ti:Sa laser for the laser-bunch slicing experiments
was installed. Intense coherent terahertz radiation produced by the laser e-beam interaction has been successfully detected.
Keywords: emittance, storage ring, undulator, beam-line, monochromator.
PACS: 07.85.QeINTRODUCTION
The first light on UVSOR was in 1983. Since then, this 750 MeV synchrotron light source has been providing
synchrotron radiation in a wide wavelength range from far-infrared to soft X-rays. After the successful 15 year
operation, it had come to be noticed that the facility must have been upgraded to survive for the next one decade as anational facility among the newly constructed 3rd generation light sources. In 2000, a new magnetic lattice wasproposed which would have much smaller emittance and more straight sections available for insertion devices [1].
To realize this lattice, all the quadrupole and sextupole magnets and their beam pipes must have been replaced.
Replacements of the insertion devices and some old components of the injector were included in the upgrade plan.
Fortunately, this plan was soon approved and funded. In 2003, the reconstruction of the accelerators was carried out.
It took about three months to complete the reconstruction works and took about two months for the commissioning
including the vacuum conditioning [2]. An old undulator and an old super-conducting wiggler were replaced with
two in-vacuum undulators during the upgrade [3]. Even after this upgrade, the accelerators and the beam-lines havebeen being upgraded continuously. Recent progress will be described in this paper. Latest results from the researcheson the light source developments will be also described.

STATUS OF ACCELERATORSThe UVSOR-II accelerator complex is composed of a 15 MeV linear accelerator, a 600 MeV booster synchrotron
and a 750 MeV electron storage ring. The ring is routinely operated for users with a small emittance of 27 nm-rad,which is the world smallest among the operational synchrotron light sources of relatively low energy below 1 GeV.
The main machine parameters are summarized in Table 1. The ring is equipped with three undulators as shown in
Table 2. Two of them are of in-vacuum type and one is of variably polarized type. The latter is used not only to
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CP879, Synchrotron Radiation Instrumentation: Ninth International Conference,edited by Jae-Young Choi and Seungyu Rah© 2007 American Institute of Physics 978-0-7354-0373-4/07/$23.00

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Following the major upgrade in 2003, the main RF accelerating cavity of the storage ring has been replaced in2005 [4]. The new cavity can provide three times higher accelerating voltage than before, which was necessary tokeep the lifetime long against the strong Touschek effect. The control system which was constructed in 90’s basedon mini-computers and CAMAC interfaces has been replaced part by part with new system based on personal
computers. In 2006, the replacement has been completed.
The accelerator complex is operated for about 40 weeks in a year. Weekly, the machine is operated for users
experiments from Tuesday to Friday and for machine studies on Monday. Daily, the machine is operated for 12hours, from 9 a.m. to 9 p.m. The beam injection interval is 6 hours. UVSOR-II is normally operated under multibunch mode with partial filling. The single bunch operation is also conducted about two weeks per year. Initial beam
currents stored under multi-bunch and single-bunch modes are 350 mA and 100 mA, respectively.

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5GRVWOFIGURE 1. Configuration of UVSOR-II Storage Ring. The undulator between B6 and B7 will be installed in October 2006.
TABLE 1. Main Parameters of UVSOR-IIParameters
Electron Energy
Circumference
Straight Sections
Bending Radius
Natural EmittanceNatural Energy Spread
Natural Bunch Length
RF Frequency
RF Voltage
Filling Beam Current (Multi-bunch Mode)(Single-bunch Mode)

Values
750 MeV53.2 m4 m x 4, 1.5 m x 4
2.2 m
27.4 nm-rad
4.2 x 10-4
160 psec
90 MHz
100 kV350 mA
100 mA

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TABLE 2. Insertion Devices of UVSOR-IIInsertion Devices
BL3U In-vacuum Undulator

Parameters
Number of Periods
Period Length
Pole LengthMax. Deflection Parameters
Polarization
Number of Periods
Period Length
Pole LengthMax. Deflection Parameters5038 mm
1.9 m
2.0Linear
BL5U Variably Polarized Undulator
21110 mm
2.35 m
4.6 (Helical)
8.5 (Linear)
Polarization
Linear/Helical
Number of periods
26BL6U In-vacuum Undulator(1)Period Length
36 mmPole Length
0.94 mMax. Deflection Parameter
2.8Polarization
LinearNumber of periods
38
BL7U Variably Polarized Undulator(2)Period Length
76 mmPole Length2.95 mMax. Deflection Parameter
5.4 (Horizontal)
3.6 (Vertical)
3.0 (Helical)
Polarization
Horizontal/Vertical/HelicalNote) (1) This undulator is now at the straight section between B6 and B7 and will be moved to the section between B5 and B6 insummer 2006. (2) This undulator is under construction and will be installed in summer 2006.

LIGHT SOURCE DEVELOPMENTS
The free electron laser (FEL) at UVSOR has a long history. By introducing a helical optical klystron in 1990’s,
the laser wavelength of 239 nm was achieved, which was once the world shortest [5]. After the upgrade of theaccelerators in 2003, the FEL has come into a new phase. Thanks to the smaller emittance and the shorter bunch
length of UVSOR-II, the FEL gain in the deep UV region has been greatly improved. Now the FEL can be oscillated
at 215 nm with the output power exceeding 100 mW. Some users’ experiments are in progress by using the deep UV
FEL.
Laser bunch slicing is a method to produce density structures on electron pulses by using an ultra-short laser [6].
At UVSOR-II, a Ti:Sa laser which could be synchronized with the electron pulses was commissioned in 2005. The
laser pulses could be introduced to the ring by utilizing a part of the optical system for the FEL without any
modification on the accelerator. The undulator for the FEL can be tuned to the wavelength of the Ti:Sa laser(800nm). This enables the energy exchange between the laser field and the electron beam, which is essential to thistechnology. We have successfully observed an intense terahertz radiation which indicated the occurrence of the lasere-beam interaction [7]. The intensity per pulse of the terahertz radiation is 105 times higher than that of the normal
synchrotron radiation in the same wavelength region.
Even after the replacement of the RF cavity, the typical lifetime in users’ operation is 6 hours at 200 mA and thebeam is injected every 6 hours. To solve this problem completely, we are going to introduce the top-up injection
scheme. The energy of the booster synchrotron, which is currently 600 MeV, will be increased to the full energy,
750 MeV, in summer 2006 by replacing the 20 year old magnet power supply. Some parts of the beam transportsystem will also be replaced. The top-up operation will be introduced to the users operation within a few years.

STATUS OF BEAM-LINES
Eight bending magnets and three undulators provide synchrotron light to totally 13 beam-lines, at present. Thebending magnet with its radius of 2.2 m provides SR, whose critical energy is 425 eV. The undulators cover theenergy range from UV to soft X-rays. The 13 beam-lines can be classified into two categories. Nine of them are socalled "Open beam-lines", which are open to scientists of universities and research institutes belonging to thegovernment, public organizations, private enterprises and those of foreign countries. The rest of the 4 beam lines are194
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so-called "In-house beam-lines", which are dedicated to the use of the research groups within Institute for MolecularScience.
We have 1 soft X-rays (SX) station equipped with a double-crystal monochromator, 7 EUV and SX stations witha grazing incidence monochromator, 3 VUV stations with a normal incidence monochromator (1 VUV station
BL7U with an undulator is under construction), 1 infrared station equipped with FT interferometers, 1 nonmonochromatized stations for the irradiation of white-light. A high performance monochromator for BL3U [8] and ahigh-resolution photoelectron energy analyzer for the end station at BL5U [9] have been successfully installed, bothof which utilize undulator radiation. The IR beam-line, BL6B has been upgraded to be capable of providing
powerful far-infrared radiation [10]. This was realized by introducing a so-called magic mirror as the first mirrors.
The world-highest intensity has been achieved in the wavelength range from sub-milli to near IR region.
The new beam line, which will utilize the variably polarized light provided by the new undulator, is underconstruction at BL7U [11]. The commissioning will start in October, 2006.
TABLE 3. List of Beam-lines
Beam Light
Monochromator/Spectrometer
Energy Range
Experiments
LinesSource
1A
bending
Double-Crystal
600 eV – 4 keV
Solid (Absorption)
1B
bending
1m Seya-Namioka
1.9 – 40 eV
Solid (Reflection/Absorption)
2B
bending
18m Spherical Grating
20 – 200 eV
Gas (Photoionization/Photodissociation)
3U
undulator
Varied-Line-Spacing Plane Grating
40 – 600 eV
Gas, Liquid, Solid(Photoelectron/Photon Emission)(Monk-Gillieson)
4A1
bending
Multi-Layered Mirror
50 – 95 eV
Irradiation
4A2
bending
None
Irradiation
bending
Varied-Line-Spacing Plane Grating
80 – 800 eV
Gas (Photoionization/Photodissociation),
4B(Monk-Gillieson)
Solid (Photoemission/Absorption)
5U
undulator
Spherical Grating (SGM-TRAIN)
5 – 250 eV
Solid (Photoemission)
5B
bending
Plane Grating5 – 600 eVCalibration, Solid (Absorption)
undulator(under consideration)
40 – 600 eV(Surface Science)
6U(1)6B
bending
Martin-Puplett FT-FIR, Michelson
0.25 meV
Solid (Reflection/Absorption)
FT-IR– 2.5 eV
7U(2)undulator
10m Wadsworth
6 - 40 eV
Solid (Photoemission)
7B
bending
3m Normal Incidence
1.2 – 30 eV
Solid (Reflection/Absorption)
8B1
bending
15m Constant Deviation Grazing
30 – 600 eV
Gas, Solid (Absorption)
Incidencebending
Plane Grating
1.9 – 150 eV
Solid (Photoemission)
8B2Note) (1) The undulator is now at the straight section between B6 and B7 and will be moved to the section between B5 and B6 insummer 2006. (2) This undulator and the beam-line is under construction and will be installed in summer 2006.

ACKNOWLEDGMENTS
The authors wish to give thanks to all the staff members of the UVSOR facility, for their efforts on the operationand maintenance of the facility.

REFERENCES
1. M. Katoh et al., Nucl. Instr. Meth. Phys. Res. A 467-468, 68-71 (2001)
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American Institute of Physics, Melville, NY, 2004, pp.49-52
3. A. Mochihashi et al., ibid., pp.259-262
4. A. Mochihashi et al., in UVSOR Activity Report 2004, Institute for Molecular Science, 2005, p. 35
5. H. Hama et al., in FreeElectron laser and its Application in Asia, edited by T. Tomimasu et al., IONICS Publishing Co., Ltd.,Tokyo, pp. 17-24
6. A. Zholents and M. Zolotorev, Phys.Rev.Lett. 76, 912 (1996)
7. M Katoh et al. (in these proceedings)
8. T. Hatsui, H. Setoyama, E. Shigemasa, N. Kosugi, J. Electron Spectrosc. Relat. Phenom.,144-147 , 1059 (2005)
9. H.J. Im, T. Ito, J.B. Hong, S. Kimura, Y.S. Kwon, Phys. Rev. B 72, 220405(R) (2005)
10. S. Kimura et al., in Synchrotron Radiation Instrumentation, edited by T. Warwick et al., AIP Conference Proceedings 705,
American Institute of Physics, Melville, NY, 2004, pp.416-419
11. S. Kimura et al., (in these proceedings)

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