The 9th Symposium on Accelerator &ience and Technology, Tsukuba, Japan 1993

SRRC CONSTRUCTION AND COMMISSIONING RESULTS
Y.C. Liu"l, J.R. Chenbl and C.C. Kuo
Synchrotron Radiation Research CenterNo 1. R&D Rd VI, Hsinchu Science-Based Industrial Park, Hsinchu, Taiwan, R.O.C.
•)Department of Physics, National Tsing Hua University,Hsinchu, Taiwan, R.O.C.
hlaJso Institute ofNuclcar Science, National Tsing Hua University, Hsinchu, Taiwan, R.O.C.
officially turned over to SRRC in July 1992. It took about ayear to install the BTS line and the storage ring, whichstarted in March 1992 and was completed in March 1993.
Beam tests in the BTS line started in August 1992 and werecompleted in January 1993. Up till now, the storage ring isin the final commissioning stage. The beam storage wasaccomplished in April 1993. We expect that the designed
beam current of 200 mA will be achieved after the vacuum
vessels have been baked out and cleaned by the synchrotron
radiation. The schedule of the civil construction is briefly
described in Sec. II. The design parameters and components
are described in Sec. III. The installation activities are givenin Sec. IV, and the early commissioning results are shown inSec. V.

Abstract
A 1.3 GeV third generation synchrotron radiation facility has
been constructed at the Synchrotron Radiation ResearchCenter (SRRC) located in Hsinchu, Taiwan, Republic ofChina. At this moment, the storage ring is in the final
commissioning stage. We had achieved a few mA stored
beam in April 1993 in a very short period and some machineparameters had been measured. The theoretical andmeasured values were in good agreement.
I. INTRODUCTION
To provide bright, continuous and tunable VUV and soft xray light sources for researches ranging over the fields ofphysics, chemistry, biology, medicine, material science, etc.,
a dedicated third-generation synchrotron radiation facility
was established in Taiwan. The SRRC accelerator complex,
as shown in Fig. 1, consists of a 50 MeVe· Iinac, a 1.3 GeV
synchrotron booster [1,2], a 70 m long BTS transfer line
[1,3], and a 1.3 GeV storage ring [1,4,5]. The injection
system including linac and booster synchrotron wascontracted out to Scanditronix AB, Sweden, and was0

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4II CIVIL CONSTRUCTION
The SRRC civil construction can be divided into threephases. The Phase I construction including theAdministration and Lab Building and the Machine shop wascompleted in May 1990. In June 1990, the entire staff moved
into the site. The Phase II construction included the Booster
and Storage Ring Buildings. By February 1991, the Booster

6B

10SCALE IN M(TO!SFig. I Layout of the SRRC accelerator complex: a 50 MeV Iinac, a 1.3 GeV booster and a 1.3 GeV storage rii1g.

-11-Building was ready in time for the delivery of the injector
components. In December 1991, the Storage Ring Building
was completed. The beneficial occupancy of the civil
construction was so smooth that no delay was caused in theinstallation and tests of the accelerator systems. The Phase
III construction is the Guest House and will be ready inAugust 1993.

III DESIGN PARAMETERS AND COMPONENTS
A. injector
A 1.3 GeV full energy injection system was contracted out toScanditronix AB, Sweden in August 1988. However, SRRC
was fully responsible for the RF system of the booster
synchrotron. Installation of the injector started in May 1991
and the beam tests began in January 1992. The performanceand reliability of the injector were demonstrated before it wasofficially turned over to SRRC in July 1992. The major
design parameters of the injector are listed in Table 1.
Table 1 Major Design Parameters of the Injector
Linac energy
Linac current(multibunch mode, averaged current)
Linac RF frequency
Booster energy
Booster circumference
Booster RF frequency
Booster natural emittance
Booster current (average)Multibunch mode
Single bunch mode
Booster repetition rate

6.6 104
Natural energy spread, rms
TunevJvy
7.18/4.13
Momentum compaction
0.00678
Radio frequency
500MHzRF cavity gap voltage (nominal)
800kV
1.15 I0-2
Synchrotron tune
18,48,24
Number of dipole, quad, sext
1.24 T
Bending field
10.691, 14.397, 8.708 ms
Damping time 'tx, 'ty, 'ts
Critical photon energy in dipole
1.39 keY
Beam size at insertion middle
Horizontal
0.45 mm
Vertical (10% emittance ratio)
0.024 mm
The dynamic aperture of the single particle dynamics and thecollective effects of the particle beam were studied in detail.
Fig. 3 depicts the dynamic aperture with and without thetypical multipole errors for a 1000-turn single particle
tracking which was obtained with the tracking code
RACETRACK [6]. The acceptable tolerances of the magnetic
properties and the alignment errors were given accordingly[1,3,4].

50 MeV
30mA
2997.9MHz
1.3 GeV
12m
500MHz1.2 10·7 m-rad

22

2.2

20

2.018

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1.4!. 1210

1.2'b.

5mA
0.3 mA
10Hz

ao.a .....,3I0.8•

0.40.220.000102015Length S

The injector has been operating satisfactorily since it wastaken over by SRRC. The machine parameters have beenmeasured and are in agreement with the design values [2].

-='1.0 ....-...

(m)Fig. 2 The betatron and dispersion functions of one cell of
the ring. The ring has six identical cells.

B. Storage Ring Lattice'?

The lattice structure is a combined-function triple-bendachromat (TBA) type with 6-fold symmetry [1,4,5]. Thereare six dispersion free long straight sections, each 6 m, forthe accommodation of the injection elements, RF cavities,undulators and wigglers. In Fig. 2, the lattice functions ofone period of the ring are shown. The major parameters ofthe storage ring are listed in Table 2.

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Table 2 Major Storage Ring Parameters
EnergyCircumference. Natural emittanceNominal current, multibunch
single bunch

2400

1.3 GeV120m
1.92 10·8 m-rad
200mA5mA

10203040

Horizontal Aperture (mm)Fig. 3 The dynamic aperture of the storage ring with andwithout the typical multipole field errors.

-12-C. Magnet and Power Supplies
There are 18 dipole magnets powered in series and fourfamilies of quadrupole magnets, each with 12 magnets
powered in series. The chromaticities are corrected with 2families of 24 sextupoles. In addition, there are 24 horizontal
and 30 vertical correctors for orbit correction. Moreover,several skew quadrupoles were used for coupling correction.
The magnets were designed, constructed, measured andanalyzed in the site with care. All the magnets installed inthe ring were within the acceptable tolerances in terms of themultipole errors and integrated fundamental field errors[1,7]. The pulsed magnets such as the septum and kickers
also met the specifications.
D. Vacuum

Most of the vacuum chambers were made of aluminum.
Much care was taken so as to provide an ultrahigh vacuum,
low impedance environment. The cleanness of the material,
the tapering of the chamber, the shielding of the bellows, thethermal load, the deformation, rigidity and flexibility of the
supporting frame, etc., were seriously considered in order tomeet the requirements. In the present, without turning on
the ion pumps, the vacuum pressure is about I0- 8 Torr
without beam and about 10·7 Torr with a few rnA stored
beam current. The bakeout of the vacuum chamber has been
carried out. After turning on the ion pumps, we expect thatthe vacuum pressure can reach I0- 11 Torr without beam.

sextupoles, the results were 0.20 mm rms and 0.15 mm rms
in the horizontal and vertical plane respectively. All thealignment results were within acceptable tolerances. The
measured closed orbit distortions were consistent with thesimulated results and will be described in Sec. V.

G. Beam Diagnostics
There were seven screen monitors for the first turn beamobservation in the ring. Among them, two were used for
injection launching adjustments in the first commissioning
stage. The number of the button type beam position monitors(BPM) was 47 in total. The processing electronic is shown in
Fig. 4. The dynamic range of the BPM electronic was from
50 J.l.A with resolution about 50Jlm to 200 mA with 10 Jlm
resolution. Two linear tapered stripline electrodes wereinstalled to measure the transverse motion and the ·bunchtime stmcture. One excitation electrode station could be used
for the tune measurements as well as for the transverse
instability damping if needed. The fast beam signal, such as
the filling stmcture, could also be measured using the fastcurrent transformer and the precise beam current wereobtained from the Bergoz's parametric current transformer(PCT) with resolution better than I J.l.A. Some other elements
such as the scraper, photon light monitor, etc., are describedin Ref. (8].

Be-1m Po!iftlon

RF Multlplrnr

IF moduleMonflor

E. RF system

In one of the long straight sections, two Doris I type cavities
purchased from DESY were installed. Each cavity is with 60
kW maximum RF power provided by individual transmitterpurchased from the Mountain Technology, USA. The lowlevel electronic control system was made in SLAC. The RF
system of the booster is identical to the ones in the storage
ring. The system can accelerate 1.3 GeV electron beam of
more than 200 rnA current in the presence of the insertion
devices. The nominal RF frequency is 499.654 MHz. The RF
systems, both in the booster and storage ring, have been
operating with incredibly reliable performance.

Fig. 4 The BPM processing electronic.

F Survey and Alignment· H. Control and Operation

Extremely tight requirements on the alignment of themagnets, especially the quadrupole magnets of the ring inboth transverse directions are necessary in order to reduceclosed orbit distortions. The acceptable alignment errors inboth planes are 0.15 mm rms and the rotation errors are 0.5
mrad rms. The quadmpole magnets were prealigned in thegirders and then moved into the tunnel. The final results of
the alignments for the dipoles and quadrupoles were 0.14
mm rms and 0.12 mm rms in the horizontal and verticalplane, respectively. The tilt errors were 0.2 mrad rms in thedipoles and 0.06 mrad rms in the quadmpoles. As for theThe control hardware architecture adopted was a two level
hierarchical system. Some VAX workstations mnning theVMS operating system were used for control computersystem. Between the database and the subsystem devices,intelligent local controllers (ILCs) wereseveralimplemented. Both level computers, including the booster
injector's, were linked via the Ethernet network. The control
software system was divided into 4 layers. They were thedevice access, network access, database access, and theapplications. A friendly graphical user interface (GUI)-13-operation panel was developed. It was very useful for themachine commissioning. The radiation safety interlock
system was a self-protected subsystem and was also linked tothe central control system [9].

magnet settings and RF frequency. The stored beam current
was a few rnA and beam lifetime was a few minutes undervacuum pressure of I0-7 Torr. A summary of the storage ringcommissioning milestones is given in Table 3.
Table 3. Commissioning Milestones

IV. INSTALLATION
The installation task of such a rather complicated system
indeed need well planning and full cooperation among all
subsystems involved. A cell of 20 m long mocked-up wasinstalled in the machine shop by end of 1991 and we gained
a lot of practical experience. The installation of the BTS
started in March 1992 and was completed in September 1992
except for the septum magnet. The installation of the ring
began in March 1992. By May 1992, the cabling work andmagnet stands installation were finished. The power supplies
and all the magnets, except for the pulsed magnets, wereinstalled by October 1992. Finally, the vacuum system
including the diagnostics elements, RF cavities and the RF
low level system were installed by end of 1993. In February
1993, we passed the full power test of the magnet power
supplies and the ring chambers were connected as a closed
form by then. Installation of the RF high power transmitterand the four kicker pulsers were finished in March 1993. The
alignment of the magnets reached the acceptable level inMarch. In the meantime, the subsystem tests with thecontrol computer and the development of the control systemsoftware were undenvay. The subsystem tests with beam
were carried out whenever necessary, The storage ringcommissioning started in April 1993 and we had beam storedvery soon.

First tum (on-axis injection at 1.3 GeV)First few turns
First beam stored
Closed orbit measured us~ng BPMs

Feb. 23, '93
Apr. 2, '93
Apr. 13, '93
Apr. 26, '93
B. Closed Orbit

We performed the closed orbit distortion measurements soonafter the BPM system was working and the orbit distortionwas corrected down to 0.5 mm and 0.3 mm rms in thehorizontal and vertical plane, respectively, using the on-line
application programs [10]. Further suppression of the orbit
distortions will be obtained as the BPM offset and nonlinear
calibration data are built into the .database. The preliminary
results of the closed orbit distortion measurements without
using the corrector were fairly consistent with the simulation
results using the existing alignment data and dipole fielderrors. Fig. 5 shows the closed orbit distortions before andafter correction and the simulated results as well.

E'V. COMMISSIONING!,MI8A. Milestones

We began the BTS beam tests in August 1992 when thelower level section of the transfer line was completed. By
September, the beam reached the septum entrance point.
After the pulsed magnets had been installed, the beam
passed through the septum and was injected into the ring inJanuary 1993. In Febmary 23, beam revolution, for the firsttime, was accomplished using one kicker for on-axisinjection. Beam was observed in each screen monitor \vithout
using any corrector. It showed that many subsystems werebasically in good condition. The beam sizes in the screen
were consistent with the theoretical values and the alignment
errors proved to be barely acceptable in the horizontal planeand extremely good in the vertical plane. Due to the long
half-sine base width of 1.6 J.l.S (400 ns revolution time) of the
kicker pulse and there was only one kicker available at thattime, the second tum observation was impossible. Soon after
all the four kickers were available in April, we had several
hundred beam revolutions using a few correctors without RF
power and beam was captured on April 13, 1993 after
turning on the RF power with minor adjustments of the-..- codbefore correction_.__cod

artcr correction-+- codsimulation before correction

Fig. 5 Closed orbit distortions before and after correction inboth transverse planes and the simulatedrorbit before
correction.

-14-C. Synchrotron Tune and Momentum Compaction Factor

F. Beam Energy and Circumference

The electron beam signal was picked-up with a striplineelectrode and analyzed with a spectrum analyzer. The
synchrotron sideband was measured and the momentum
compaction factor was extracted. The measured momentum
compaction factor was 0.00663 and was in good agreementwith the design value of 0.00678.

The injected beam energy was defined by varying the magnet
setting and RF frequency. From the closed orbit distortions,
one could obtain the energy deviation from the magnet
settings. The injected beam energy could be measured to a
precision of about 0.1 %. From the survey and alignment
data, the circumference deviated from the design value of
200 m was no more than 1 mm, which was consistent withthe closed orbit data.

D. Betatron Tune and Betatron Function

The tum-by-tum signal from one BPM electrode was FFf
analyzed after the electron beam was kicked using one of thekicker magnet with about 1 mrad in the horizontal plane.
The measured
The betatron sidebands were observed.
sextupolenominaltheathorizontal tune was Vx = 7.142
vy =tuneverticalThe
orbit.
strengths under the correctedverticalthewithchangesorbit
thefromobtained
was
4.170
corrector setting. We will measure the transverse tunes
using the tracking generator and spectrum analyzer systemat the second commissioning stage. The optimum working
point will be searched to get more beam storage current. Byvarying the quadrupole strength and measuring thehorizontal tune shift, we obtained the averaged betatronfunction at each family of the quadrupole location. The result
was in good agreement with the design value. From the orbitchange when a vertical corrector was excited, the verticalbetatron function was found to be in agreement with thedesign value [10].

E. Dispersion Function and Chromaticity
The dispersion function was deduced from the orbit
difference with different RF frequency setting. In Fig. 6 themeasured horizontal dispersion function as well as thedesigned value are shown. The vertical dispersion was verysmall. The horizontal chromaticity was measured byobserving the tune shift with the RF frequency change. The
horizontal chromaticity was corrected to about zero at thenominal sextupole strengths.

G. Bunch Length and Beam Size Measurement
The electron beam signal which was picked-up with thestripline electrode was analyzed with a fast digital sampling
oscilloscope to obtain the bunch length as shown in Fig. 7.
The measured bunch length at of 42 ps at 300 kV RF peakvoltage was in good agreement with the theoretical value of37 ps.
The transverse beam profile was measured from thesynchrotron light out of the bending magnet with theXCC77RR high resolution CCD camera. The video signal
was captured by a frame grabber and the transverse profile
information was extracted. Fig. 8 displays the preliminaryresult.
~.ACKNOWLEDGMENT

The authors would like to thank the entire SRRC staff
involved in the design, construction and commissioning ofsuch a delicate complex. Without their hardwork and fullcommitment, this early success would not have been possible.
Thanks are also extended to outside advisers for theirinvaluable guidance, advice and suggestions.

0.6

0.5

0.4

Iriii

0.3

0.2

0.1

__ eta-x m~::::uured -e-- eta-x design

Fig. 6 The measured and designed dispersion function.

Fig. 7 The bunch length measured using the Tekll801A
digital sampling oscilloscope. The signal was fromthe stripline electrode. The measured bunch length
was about 100 ps in FWHM with 300 kV RF gap
voltage.

-15-

VII. REFERENCES

Fig. 8 Preliminary result of the synchrotron radiation profile
measurement. Note that the depth of the field andthe diffraction effect are not corrected.

[l] "SRRC Design Handbook". SRRC, 1991.
[2] K.K. Lin, K.T. Hsu and T.S. Ueng, "Me<Jsurement on theSRRC 1.3 GeV Electron Booster Synchrotron Operation
Par<Jmeters and the Ramping Behaviour", PAC93,
W<~shington D.C..
[3) M.H. W<1ng, C.C. Kuo and C.S. Hsue, "The Booster toStomge Ring Transport Line for SRRC", IEEE PAC91, ·Vol. 5, pp. 2697-2699.
[4] C.S. Hsue, C.C. Kuo, J.C. Lee and M.H. Wang, "Lattice
Design of the SRRC 1.3 GeV Storage Ring", IEEE
PAC9l, Vol. 4, pp. 2670-2672.
[5] C.C. Kuo, C.S. Hsue, J.C. Lee. M.H. Wang and H.P.
Chang, "Beam Dynamics of the SRRC 1.3 GeV Storage
Ring", IEEE PAC91, Vol. 4, pp. 2667-2669.
[6) A. Wrulich, RACETRACK, DESY-84-07, 1984.
[7] C.H. Chang, H.C. Liu and G.J. Hwang, "Design andPerfonnance of the Dipole Magnet for SRRC Storage
Ring", PAC93, Washington D.C ..
[8] G. Jan and K.T. Hsu, "Diagnostic Instrumentation
System for the SRRC 1.3 GeV Synchrotron Radiation
Light Source", PAC93, Washington D.C ..
[9] J.S. Chen, C.J. Wang, S.J. Chen and G.J. Jan, "AGraphical User-Interface Control System at SRRC",
PAC93, Washington D.C ..
(10] P. Chang, C.H. Chang, C.C. Kuo, M.H. Wang, J.C. Lee,J.Y. Fan, H.J. Tasi and C.S. Hsue, "Machine Physics
Application Program for Control, Commissioning andError Findings for Storage Rings", PAC93, Washington
D.C ..

-16-