The 9th t'rymposium on Accelerator Science and Technology, Tsukuba, Japan 1993

Present status of SPring-S project
N.Kumagai and JAERI-RIKEN SPring-S Project TeamJAERI-RIKEN SPring-S Project Team
2-2S-S,Honkomagome,Bunkyo-ku,Tokyo,ll3,JAPAN

Abstract
SPring-S (Super Photon ring- S GeV) is thefacility of a Qthird generation" synchrotron
radiation source in the X-ray region. The facility
consists of an accelerator complex and 61 photon
beamlines, and is under construction in Harima
Science Garden City, Hyogo Prefecture, Japan. The
commissioning of the storage ring is expected inspring 1997 and 10 beaml ines wi 11 be installed byFY 1998. The present status is described in thispaper.
Review of SPring-S Facility
The accelerator complex[l] consists of an injector system and a storage ring. The main
parameters are shown in table 1. The injector system is composed of a 1 GeV linac and an S GeV
synchrotron to realize the stable operation of thestorage ring by full energy injection system andto supply the beam to future applications such as
beam injection into a VUV storage ring, a highpower FEL storage ring and the production of slow
positron beam. The linac consists of a 250 MeV
high-current linac, an electron/positron converter, and a 900 MeV main linac. The electron is
to be accelerated up to an energy of 1.15 GeV byremoving the converter from the linac beam line.
The maximum repetition rate of this linac is 60
Hz. The synchrotron is a race-track type with
two-fold symmetric lattice composed of 40 FODO
cells. RF cavities and the devices for injectionand extraction are installed in two straight sections. The maximum repetition rate is 1Hz. The
natural emittance is 2.3xlo-7 mrad at S GeV. The
storage ring has a fourfold-symmetric lattice composed of 44 Chasman-Green cells and 4 straightcells. The circumference is 1436 m to realize thelow emittance of 5.6 nmrad at S GeV. The ChasmanGreen cell consists of two bending, 10 quadrupoleand 7 sextupole magnets. The straight cell composed of the Chasman-Green cell with its two bending magnets removed. Each cell has a straight section for installation of insertion devices. The
storage ring has 61 photon beamlines. Among thebeamlines, 3S beamlines are available for highbrilliance or high-flux radiations from insertion
devices (undulators and wigglers) and 23 beamlines
for high-flux and high energy radiation from bending magnets. In the future, the four straightcells are to make the magnet free space of 30m
by the rearrangement of the quadrupole and sextupole magnets. In the free space, very long unto obtain higher brildulators are installed
liance and an improvement in the coherence oflight source.

-17-Table 1 Main Parameters of Accelerator Complex
1. The storage ring
electron/positronParticle
Energy8 GeV1435. 94S m
Circumference
Chasman-Green
Lattice
4/4S
Superperiods/No. of cells
5.55 nmrad
Natural emittanceStored current
100 mA/5 mA
multi bunch/single bunch
Harmonic number2436
rf frequency
50S.6 MHz
53.22/20.16
Betatron tune( {3 xl {3 y)Synchrotron tune
0.0101
1. 46xlo-4
Momentum compaction
1. 01x1o-3
Energy spread ( a E)
Damping time(msec)
8.3/8.3/4.15
C-c x!T: y! -c s)
Number of ID sections
38
standard(--4 m)/long(--30 m)
34/4
Critical photon energy
28.9 keV
2. The injectors
1) linac
Energy(electron/positron)
1. 15/0.9 GeVEmittanceelectron/positron <: 1 mmmrad/<: 1.5 mmmrad
Beam current
electron
100mA(1 fLS), 300mA(1ns)
positronlOrnA
Repetition
60 Hz
rf-frequency
2856 MHz
No. of accelerator sections
26
Accelerator section
Traveling wavestructuremode
2 n: /3
length
2.S35menergy gain
45 MV
No. of accelerator section
26
No. of klystron
26
Klystron output power
35 MWmax.
2) synchrotron
Energy( injection/extraction)
0.9GeV/8GeV
Circumference
396.12 m
Lattice
FODO
Superperiods/No. of cells
2/40
222 nmrad
Natural emittanceBeam current
10 mA
rf frequency
508.6 MHz
Repetition
1 Hz
Betatron tune( {3 xl {3 y)11. 73/S. 7S
1. Olxro-2
Momentum compaction
Storage Ring
The overall design of the storage ring has
been almost completed. The magnet, vacuum and rfsystem are now under fabricatio n. By the end of
this year, one cell of the storage ring will beassembled at the SPr ing-8 construct ion site, tocheck the interfere nce between the magnet andvacuum systems before the whole vacuum system 1s
manufactured.
Magnetic measurements of pilot magnets
Four magnets, one bending, 2 quadrupole and 1
sextupole, were built as pilot models. The field
profile, multipole strength and excitation curve
were measured by a hall prove for the bending magnet, a twin flip coil for the quadrupole magnets
and a harmonic coil for the sextupole magnet. On
the bending and sextupole magnets, the measured
multipole field strength(e xcept for fundamentalcomponent) satisfied field tolerance required fromorbit analysis. On the other hand, for quadrupole
magnets, the strength of the integrated dodecapole
component was several times larger than the field
tolerance required from orbit analysis. The
dodecapole component, therefore, was corrected byattaching an iron shim of 9.1 mm thick to the end
plate of both sides of the magnet core. The resultis shown in fig.l. The real line is the profile
measured with the shim, while the dotted line is
the profile without the shim. A useful aperture ofabout 30 mm was obtained over a wide range of excitation levels by this end shim technique.
x.(mm)

were obtained. Frequencies of higher order modes
are affected by positions of plungers set on thecavity qnd one of the suppressing methods forcoupled bunch instabili ties is shown in thisconference [3].
Beam Dynamics
To obtain a higher brillianc e of lightsource, we must correct a betatron coupling as
small as possible.The design goal of the coupling
coefficient is less than 1 %. The coupling is induced from a skew quadrupole component along thering, whose component is generated from the tilt
error of quadrupole magnets, the alignment errorof sextupole magnets and a residual COD. The coupling behavior varies along the storage ring, andis not constant or uniform, because the rotation
angle between the eigen axis of normal mode andthose in the laboratory flame vary according to
the distributio n of the skew quadrupole component.
It is ,therefore, difficult to realize the vertical emittance of less than 1% to the horizontal
one at any position of the storage ring. For thiscorrection, we found the good correction scheme tokeep the maximum vertical emittance less than 1%of the horizontal one at any position as shown 1nfig.2. The details will be given elsewhere.
70~060>(-30-20-3020

10-10~-o,,II'o,,,>.c:u'qc\\·n\\''\\\0.99

Jg(x)dxjJg(xzo )dx'bJle0I0I0..

With end shim of 9.1 mm 1\thickness
Without end shim:;:l20
100IIuIII

00.00

II

0.98

30

.S

II'Iu\\IIII

80'I'''I'~\9400)

\I

50

01.57

3.14

4.71

6.28

Azimuthal Position 8 [rad]Fig .. l Radial profile of integrate d field
gradients with and without end shim.

Fig.2 Maximum vertical emittance. Real lines anddotted lines show before and after corrections,respectively. Each shape of symbols corresponds toa different case of sextupole alignment errors.

RF system
The new power supply[2 ] for the 1 MWklystron, which has no crowbar circuit to protect
the klystron, was designed and its small sizemodel was fabricated as a pilot model. This power
supply is a primary rectifier controlle d by SCR
with a primary filter inductor. The SCR rectifier
can control the klystron voltage close loop byphase control with a regulation of better than0.1%. The real type is now under fabricati on.
Field profiles of resonant dipole modes of a R&Dcavity(bell shaped cavity) were measured with abead perturbat ion method and coupling impedances
over the Q-factor for coupled bunch instabili ties

Beam Monitor
The first stage of the R&D for BPM(Beam Position Monitor) is successfu lly finished. Button
electrode s are to be directly welded to the extruded Al alloy vacuum chamber to avoid any
problems on vacuum leakage in many cycles ofbaking process. The electrode is made of stainlesssteel with lOmm in diameter and is screwed andwelded to the central conductor. The electric center is calibrate d by a moving antenna. Thecalibratio n system is now in operation at theHarima site. The BPMs have their own reference
planes(ho rizontal and vertical planes) outside-18-

the vacuum chamber. The pos1t1on of thesereference planes are precisely calibrated to themagnetic center of sextupole magnet after themagnetic alignment and the vacuum baking.
Injector System
Test of the prein.iector
A pre injector of the l inac, shown in fig. 3,
was constructed in Tokai(JAERI) for test operation. The preinjector consists of an electron gun,2 prebunchers, 1 buncher and a beam monitoring
system to observe the beam quality. The beamenergy is 9 MeV at the exit of the buncher. It is
to be operated in two modes. One is a high current
mode for positron production and the other a low
current for electron use. The el~ctron gun(modelY796 with a cathode area of 2 cmZ) is designed toproduce a 200 keV pulsed beam with a peak currentof 20 A and a width of 1nsec. As the result ofbeam tests, the beam current was obtained in therange of several tens rnA to 20 A, by varying theemission current from the gun and physicallydefining the beam size using iris. Three types ofgrid pulsers were tested to generate different
pulse lengths and stable operated. Two prebunchers
were operated with a gap voltages of 20kV and 30
kV, respectively. Each buncher is a type ofstanding-wave structure with 13 gaps. The bunchingefficiency obtained was about 65 %. The energy
spread at the maximum energy was within ±2%,which was measured by an energy analyzer locatedbehind the buncher.

Fig.3 Preinjector of linac
Control System
As the accelerator complex and experimental
equipments are distributed geographically andfunctionally over the SPring-8 site, a distributed
computer control system is adopted. The designconcept of SPring-8 control system is to use
standard hardware and software. The control system

consists of a operating system located in acentral control room, several control system foraccelerators and beamlines ,and a computer systemfor program development. Each system is linked bya high speed computer networks such as FDDI. Thecontrol system is composed of a host computer andseveral front end processors(FEP) such as VME andprogrammable logic controller, which are connectedwith each other by sub networks. As for theoperating system, an UNIX is used for upper levelcomputers, and a real time OS' s, which conform toIEEE POSIX standard, will be used for FEP's. C
and C++ are used as languages to describe application programs for machine control, since many application programs developing tools are preparedby C library functions. FORTRAN is useful forlarge numerical calculation programs, such as COD
correction and a calculation of beam dynamics.
Beamline
The SPring-8 Project Team plans to construct
10 beamlines by FY 1998, of which 6 are assumed
to have insertion devices as light sources and therest from bending magnets. To make the standardization of beamline components in the front-end
channel and optics and of the control system of
the beamlines, two beamlines are designed and constructed as pilot beamlines from this year.
R&D of Insertion Device
Two kinds of prototype devices have been fabricated. One is a wedged-pole-hybride undulator, andthe other is a variable polarized undulator embodying a new concept[4]. The wedged-pole-hybride
undulator has a magnetic period of 33mm long, 123
magnetic poles and a peak magnetic field of 5.87kG
at the minimum gap of 13. 5mm. The magnetic
measurement was performed. By using the data obtained, the radiation intensity expected by thisundulator was estimated. The variable polarized
undulator consists of two pairs of planar permanent magnet arrays above and below the horizontal plane. Therefore, the device has no magnetic
structures in the horizontal plane and no conflictwith a vacuum chamber. The on-axis magnetic field
generated by this device, the strongest among existing planar helical devices, induces helical andsinusoidal beam orbit motions by shifting therelative positions of a pair of magnet arrays. It
leads to the generation of circularly and linearlypolarized undulator radiation. The test of thisnew undulator has been performed by using JSR in
Tokai(JAERI) and its performance confirmed.
References[1] M. Hara et al., "Status of the SPring-8 Project(storage ring)", IEEE,
Particle Ace. USA, p2646 (1991)[2] R.Cassel,private communication[3] H. Ego et al., "Higher Order ~lodes of theSingle Cell Cavity for the SPring-8", in thisconference[4] S. Sasaki et a!.," A New Undulator for
Generating Variably Polarized Radiation", JJAP,vol31, Ll794, 1992

-19-