The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October2001

PRESENT STATUS OF UVSOR ACCELERATORS
M. Katoh\ M. Hosaka, A. Mochihashi, Y. Hori*, T. Kinoshita, J. Yamazaki, K. Hayashi,
Y. Takashima, Institute for Molecular Science, Myodaiji, Okazaki, Japan
S. Koda, Saga University, Honjo-machi, Saga, Japan

Abstract

UVSOR Multi-bunch Operation ('00.06.08)

UVSOR has been successfully operated for 18 years, asa synchrotron light source opened for nation-wide users.
The aged accelerator components have been replaced one
by one, year by year, to keep the performance of themachine as high aspossible.
To compete with the 3'd generation synchrotron lightsources, we are proposing an upgrade plan, in which thenumber of straight sections for insertion devices will be
doubled and the emittance will be reduced by a factor of 6.
The lattice design was completed and the hardware
developments are in progress.
This year, we have started a users experiment by using
the free electron laser on UVSOR. We have found that thestorage ring FEL is a very powerful tool for pump-probe
experiments because of its high average power and naturalsynchronization with synchrotron radiation.

300

250:;('!

200~=150

u.e"

100I

1-seam Current I

1\~v;t"'fi?"' f\J.

~~ 0-.

600sBeam Lifetimev I\ _, ~.......

.... /. ~500..

~

400"a300ii:t200!'3

.§:

~

100

50

Time [hh:rnm:ss]

Fig. I Typical beam current history in multi-bunch mode

2 RECENT DEVELOPMENTS
2.1 New Beam Position Monitor System

1 MACHINE OPERATIONUVSOR, a 750 MeV synchrotron light source, has beensuccessfully operational since 1983. Although this is arelatively small light source, whose circumference isabout 53m, it has totally 20 synchrotron radiation (SR)beam lines. About half of them are dedicated for in-houseusers and the remainders are opened for nation-wide users.
The UVSOR accelerator complex consists of a 15 MeV
linac, a 600 MeV booster-synchrotron and a 750 MeV
storage ring. Three insertion devices are installed in thering. To keep the performance of the machine as high as
possible, the aged components have been replaced one
bye one, year by year. In 2000, the UVSOR accelerator
complex was operated for about 43 weeks (includingmachine tunings) without serious troubles.
Typical operation pattern in a week is as follows.
Monday and Saturday morning (from 9 to 13 o'clock) are
assigned for machine tunings and machine studies. From
Tuesday to Friday, the machine is operated for users. The
beam is injected twice a day, at 9 and 13 o'clock. The
beam is stopped at 18 o'clock. It can be extended until 21o'clock if requested by users. On Thursday, the beam isinjected additionally at 17 o'clock and is stopped at 21o'clock. A typical beam current history in multi-bunchmode is shown in Figure 1. The machine is operated
normally in multi-bunch mode and, only for a few weeks
in a year, in single bunch mode.

The beam position monitor (BPM) system was replaced
this spring. Since mechanical switches are used in the oldsystem to accumulate the signals from the pick-up
electrodes, it took about one minutes to measure an orbit.
In addition, the attenuator control of the BPM signals was
not automated.
The new system comprises 16 signal-processing
modules, which are commercial products of Bergoz Co.
[1]. These modules give the beam position in horizontal
and vertical as DC voltages. They are AD-converted andaccumulated in a PC. The new system can measure one
orbit in a second with resolution of a few microns. The
detail of the new system is described elsewhere in theseproceedings [2].

2.2 High Current Operation
The filling beam current in multi-bunch mode has been
250 rnA in these years. As requested by some users, last
winter, multi-bunch operation at 300 rnA was tested. Thebeam stability, the temperature rises of the vacuum
chambers and the radiation level of the experimental floor
were observed and no problem was found. The users
operation with 300 rnA will be started soon. Higher
current would be challenged after improving beam
lifetime, which would be realized by some improvementson the RF cavity and the vacuum system.

2.3 In-vacuum Undulatort mkatoh@ims.ac.jp* a guest scientist from KEK-PF

We have started developing an in-vacuum short period
undulator in collaboration with the insertion device group-181-

The 13th Symposium on Accelerator Science and Technology, Suita, Osakn, Japan, October 2001of SPring-8. This type of device can produce highbrilliance SR in the energy region higher than IOO eV,
which cannot be produced by the existing unduiators atUVSOR. In the upgrade project described later, this typeof devices will play important roles.
The construction of the undulator will be finished until
the end of this year. It will be installed at the place of thesuper-conducting wiggler, which was recently decided tobe shutdown. The performance and its influence on theelectron beam, such as resistive wall effects [3], will bechecked. After finishing the performance test, an SR
beam-line will be constructed and will be opened forusers. Main parameters of the undulator are listed inTable I. The expected undulator spectrum is shown inFigure 2.

of the FEL beam to a SR beam-line, as shown in Figure 4,
was successfully demonstrated and the synchronization
between FEL pulses and SR pulses was confirmed.

Polarization

1.2500~ 0.8400 Q)CD

Ill3~()

300Q)

ff 0.6><(...Ja!

200 3.2::

0.4

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Q)

Pure Permanent (Nd-Fe-B)
1.17 Tesla
36 mm26936 mm
1.4 m
I 0 mm for low-~ optics
20 mm for present optics
2.77 for low-~ optics
1.15 for present optics
linear (horizontal)

Max. K-parameter

600I

Table I. Parameters of In-vacuum Undulator
Magnet type
Remanent Field
Period Length
Number of Period
Magnetic Length
Overall Length
Minimum Gap

1.4020406080

1000120Time (min)Fig. 3 Average output power of UVSOR-FELUVSOR Storage ring
5 10 1--1i~,.;f+·;···.,.-·· ;·;·':.

UVSOR Short Period Undulator -····;{L=Im,1u=3.6cm)

4 10 14~~~

3 10 1.t~=e="'

2 10 14~~~

Om

1 10145m10m...

..l300400500Fig. 4 FEL Transport LineThe FELis transported to an undulator beam-line(BL3A I) by using a set of mirrors. The path length isadjusted so as to realize the synchronization between SRandFEL.

61!0ENERGY [eV]Fig. 2 The expected SR spectra from the in-vacuum
undulator

2.4 Recent Progress in Free Electron Laser
The UVSOR free electron laser (FEL) has successfully
oscillated in wide spectral range from 590 nm to 240 nm.
Last winter, a users experiment was started, whichutilized the natural synchronization between FEL and SR.
The detail of this experiment was described elsewhere [4].
Towards the experiment, many efforts have been made torealize stable oscillation and high average power.
Recently, we have achieved an average power of 1.2 W,
which is the world highest record of a storage ring FEL,
as shown in Figure 3. The beam lifetime was successfullyincreased by optimising the XY -coupling, without
reducing the average power significantly. Transportation

3 UPGRADE PLANWe are proposin§ an upgrade plan of UVSOR, tocompete with the 3r generation light sources in the next
decade. We have designed a new lattice [5], which has
four new short straight sections and much smaller
emittance (27nm-rad). The magnetic lattice and theoptical functions are shown in Figure 5 and 6. Tracking
simulations proved that the new lattice has sufficiently
large dynamic aperture for injection and storage. The
vertical betatron function at each straight section is small
and optimised for installing narrow-gap insertion devices,such as a short-period undulator described in the previous
section.

-182-

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

All the quadrupoles and sextupoles will be replacedwith combined function magnets, which have capabilities
of producing both quadrupole and sextupole fields.
Construction of a prototype was completed and fieldmeasurements are in progress. The design of the vacuum
system is in progress. The details of these works aredescribed elsewhere in these proceedings [6].
To keep the beam lifetime long against the stronger
Touschek effect on the low emittance optics, we are going
to increase the RF accelerating voltage. We have toremove the heat problem of the input-coupler of the cavity,
which is currently limiting the input power. We are goingto replace the coupler in next spring.

25,-.,-~,
X

f='

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X

0010

2030s [m]25.......
e20
X

f='

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Table 2. Main Parameters of UVSOR
Present
53.2m
Circumference
DBA
Lattice Type
4
Number of Cells
3mx4
Straight Sections
750MeV
Beam Energy
165 nm-radEmittance
4.2 X ]0'4Energy Spread(3.16, 1.44)
Betatron Tunes(-3.4, -2.5)
Nat. Chromaticity-10%
XY Coupling
0.026
Mom. Comp. Factor
90.115 MHz
RF Frequency
16Harmonic Number
46kV
RF Voltage
0.74%
RF Bucket Height
250mA
Max. Beam Current
Beam Lifetime (200mA) -6 hr-~,

20eextended DB( A)
44m x 4, 1.5m x 4

1510>
X

c:c.

0027.4 nm-rad

20

30s [m](3.75, 3.20)(-8.1, -7.3)

Fig.6. Optical functions of present (lower) and upgraded(upper) lattice

0.028

4SUMMARY

>80kV
>1.1%
::> 250mA> 6hr

UVSOR is a relatively small synchrotron light source,which was built early in 1980's. Although this is a typical2"~ generation light source, a moderate change of themagnetic lattice will convert this old machine to a highbrilliance light source that can compete with the 3"'
generation light sources in next decade. A new lattice wasdesigned. The hardware developments are in progress. We
are waiting for the budget.
We have started users experiments using the storage
ring FEL on UVSOR. We have found that its high average
power and its perfect pulse-to-pulse synchronization withSR make the FEL a very unique and powerful tool forpump-probe experiments.
We are confident that, as upgrading the machine andpromoting the application of the storage ring FEL,UVSOR will survive in next decade among many
synchrotron light sources as a unique facility dedicatedfor molecular science.

5 REFERENCES
Fig. 5. Lattice modification
The lower is the present configuration and the upper isthe upgraded one. One quadrant of the ring is shown.

[1] http://www.bergoz.com[2] K. Hayashi et al, in these proceedings[3] K. Bane and S. Krinsky, Proc. 1993 PAC (1994), 3375
[4] M. Hosaka, submitted to Nucl. Inst. Meth. (2001)[5] M. Katoh et al., Nucl. Inst. Meth. A467-8 (2001), 68[6] J. Yamazaki et al., in these proceedings-183-