The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

LATTICE COMPONENTS FOR UPGRADING UVSOR
J. Yamazaki, M. Katoh\ Y. Hori*, M. Hosaka, A. Mochihashi, T. Kinoshita, K. Hayashi,

Y. Takashima, Institute for Molecular Science, Myodaiji, Okazaki, Japan
S. Koda, Saga University, Honjo-machi, Saga, Japan

Abstract
In the upgrade plan proposed for UVSOR, the original
magnetic lattice will be modified to reduce the emittanceand to increase the number of straight sections forinsertion devices. We have completed the lattice design.
We are designing and developing the lattice components,
such as quadrupole/sextupole magnets and the vacuum
chambers. Because of the space limitation, sextupoles will
be integrated in quadrupoles. We have constructed a
prototype of the combined-function magnets. Field
measurements are in progress. It has been shown that themagnet is capable of producing required field strengths.
Fig. 1. Lattice modification. The lower is the present
configuration and the upper is the upgraded one. One
quadrant of the ring is shown.

1 INTRODUCTIONUVSOR, a 750 MeV synchrotron light source, has beensuccessfully operational since 1983. During these 18years, many efforts have been made to keep theperformance and reliability of the machine as high aspossible. The aged accelerator components have been
replaced one by one, year by year. As a result, forexample, there were only a few minor troubles during
FY2000. However, as for the basic properties of themachine, such as the beam emittance or the number of
insertion devices, UVSOR cannot stand comparison withthe 3'd generation light sources.
Recently, some of the 2"d generation light sources wasor are planned to be reconstructed towards high brilliance[1, 2]. As stimulated by these works, we also havedesigned a new lattice, which will give a smaller
emittance by a factor of 6 and more straight-sections for
insertion devices [3]. We have proposed an upgrade plan
based on this new lattice and are waiting for the budget.
In this paper, we will describe the magnetic lattice andsome results from the recent R&D's on the latticecomponents.

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We are going to modify the magnetic lattice ofUVSOR,
as shown in Figure 1. The optical functions are shown inFigure 2. The original lattice consists of four DBA cells.
There is a triplet between two bending magnets.
Dispersion function has non-zero value between the twobending magnets and becomes zero in the straight-

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00s [m]Fig.2. Optical functions of present (lower) and upgraded(upper) lattice (one quadrant of the ring is shown)tmkatoh@ims.ac.jp*.a guest scientist from KEK-PF-280-

The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

sections. In the new lattice, the triplet is replaced with two
doublets and there is one short straight section between
them. The dispersion function is not eliminated in thestraight sections. This is effective to reduce the emittance.
The vertical betatron function at each straight section issmall and optimised for installing narrow-gap insertion
devices, such as in-vacuum short period undulators.
To make the newly created straight sections as long as
possible, all the quadrupoles and sextupoles will be
replaced with combined function magnets, which arecapable of producing both quadrupole and sextupole
fields. The details of the magnets are described in the next
section.

o50100mm

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Quadrupole Coil
Sextupole Coil

Table 1. Main Parameters of UVSOR
UpgradedPresent
53.2m
Circumference
extended DB(A)DBA
Lattice Type44
Number of Cells
4m x 4, 1.5m x 4
Straight Sections
3mx4
750MeV
Beam Energy
165 nm-rad
27.4 nm-rad
Emittance
4.2 X 10'4
Energy Spread(3.16, 1.44) (3.75, 3.20)
Betatron Tunes(-3.4, -2.5) . (-8.1, -7.3)
Nat. Chromaticity~10%
XY Coupling
0.028
Mom. Comp. Factor
0.026

Fig.3 Combined-function (quadrupole/sextupole) magnet(cross-sectional view)

3MAGNETIn the new lattice, the space limitation is very severe. In
some of the modem light sources, sextupoles areintegrated in the quadrupole magnets, to save the spaceand reduce the cost [4, 5]. They are successfullyoperational. We decided to introduce this type of magnet.
There are several types of configuration. We have adopted
the configuration as shown in Figure 3. The shape of theiron core is same as ordinary quadrupoles. The auxiliary
coils on the pole face (sextupole coils) produce dipole
field and sextupole field. Other auxiliary coils on thepoles (dipole correction coils) eliminate the dipole field.
The main parameters of the magnet are summarized inTable 2.
A prototype was constructed as shown in Figure 4.
Field measurements are in progress. Some results fromthe field measurements are shown in Figure 5 and 6. It
was proved that the quadrupole and sextupole fieldrequired from the lattice could be achieved well below themaximum excitation current. It was also proved that thedipole field could be eliminated by exciting the dipole
correction coils, for the typical operational currents ofquadrupole and sextupole. However, at around themaximum excitation of quadrupole and sextupole where
the iron core is saturated, it was found that the dipole field
could not eliminated even with the maximum excitationof the dipole correction coils.

Fig.4 Prototype of the combined function magnet(Constructed by Mitsubishi Electric Co.)

Table 2. Parameters of focusing magnets
0.2 m
Core Length
94 mmBore Diameter
625A x 24 turns
Quadrupole Coil
400A x 4 turns
Sextupole Coil
40A x 21 turns
Dipole Correction Coil
15 TimMaximum Quadrupole Field
35 T/m2
Maximum Sextupole Field-281-

The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

At present, pickup electrodes for beam position
monitors (BPM) are mounted only on the bending magnet
chambers. Since these chambers are not mechanically
fixed to the magnets, the BPMs can be moved relative tothe magnets. To prevent this, we are going to install aBPM on each beam pipe at the quadrupole doublets. They
will be mechanically fixed to the magnets.

Quadrupole Field
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B100

200300 400
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500

600

B700

Figure 6 Layout of the vacuum components at a shortstraight section
A chamber for in-vacuum undulator is also shown.

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Fig.5 Excitation curve of quadrupole fieldTypical operational current will be around 400A.
Sextupole Field
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Fig.6 Excitation curve of sextupole fieldTypical operational current will be around 200A.
The dipole correction current is shown for the quadrupole
excitation at 300A.

4 VACUUM SYSTEM
The design work on the vacuum system is in progress.
As an example, the layout of the vacuum components at ashort straight section is shown in Figure 6. The crosssection of the beam pipe is basically kept same as that ofthe present ones, which is a racetrack shape. In thetentative design, because of the space limitation, thechambers are pumped by NEG pumps, which aremounted on the side room of the pipe as shown in Figure
7. There is installed a water channel on the other side,preparing for future high current operation. Sputter ionpumps and NEG pumps are installed on the undulatorchamber.

UVSOR is a relatively small synchrotron light source,which was built early in 1980's. Although this is a typical2"d generation light source, a moderately small change ofthe magnetic lattice will convert this old machine to ahigh brilliance light .source that can compete with t~e 3'dgeneration light sources in the next decade. C~mbmed­
function (quadrupole/sextupole) magnet was designed. A
prototype was constructed. The field measurement provedthat the required magnetic field could be achieved. The
design study on the vacuum system is in progress.

6 REFERENCES(1] M. Katoh et al., J. Synchrotron Rad. 5 (1998), 336(2] S. Brennan and R. Hettel, Synchrotron Radiation
News, Vol.11, No. 1 ( 1998), 25(3] M. Katoh et al., Nucl. Inst. Meth. A467-8 (2001), 68(4] M. Barthes et al., Proc. 9'h International Conference on
Magnet Technology (Zurich, 1985), p.114(5] M. Eriksson, Proc. Of 5'h European Particle Ace. Conf.
(Sitges, 1996), 72-282-