JAERI-Conf 95-021

1p-2

Construction of SPring-S injector system
H. Yokomizo, H. Abe, T. Aoki, K. Fukami, S. Hayashi, T. Hori, H. Hosoda, M. Ichihara, Y. Itoh,T. Kaneda, M. Kodera, H. Kotaki, A. Kuba, A. Mizuno, K. Okanishi, T. Oku, S. Ohzuchi, H. Oyatani,
H. Sakaki, H. Suzuki, S. Suzuki, N. Tani, T. Taniuchi, K. Yanagida, H. Yonehara, H. Yoshikawa
JAERI-RIKEN SPring-S Project Team
Kamigori, Ako-gun, Hyogo, 67S-12, JAPANAbstract
The SPring-S injector system composed of a linac
and a booster synchrotron is under construction onschedule. The performances of the linac preinjector were proved to satisfy the requirements. Many
components were fabricated and tested their performances. Construction of the injector building wascompleted in April 1995 and installation of the accelerators was started from May 1995.

1INTRODUCTION

The SPring-S is a third generation synchrotron radiation X-ray facility with a main accelerator of S GeV
storage ring. The injector [?] for SPring-S consistsof a lGev linac and a S GeV booster synchrotron,as shown in Fig. ??. The positrons are used for theoperation particle in the storage ring as well as theelectrons. Fabrication of the accelerator components
began in 1990. Construction ofthe injector building
began in 1992 and was completed in 1995. Installation of the accelerator was started in 1995. Generalfeature of the injector system will be explained in
section 2, and status of the linac and the. booster
synchrotron will be presented in sections 3 and 4.

2

GENERAL FEATURES

The lGeV linac consists of a 250MeV high current
linac and electron/positron converter, and a 900MeV

main linac. The electron beam is able to be accelerated up to 1.15GeV by means of extracting the target of the electron/positron converter from the beamline. The linac is able to produce various kind of thepulse width from lnsec to lpsec, which are requestedby the storage ring operation modes; a multi-bunch
operation and a single-bunch operation. The linac rffrequency is 2S56MHz and its operation rate is 60Hz
at the maximum. The tatollength from the electron
gun to the end of the linac is 140m followed by a 39m
long beam transport line to the synchrotron.
The booster synchrotron is able to accelerate thebeam injected from the linac from lGeV to SGeV
which is the operation energy of the storage ring.
The operation rate is 1Hz. The synchrotron has
a racetrack shape with a FODO lattice containing
40 cells, which consists of 30 normal cells and two
straight sections including 5 cells each. This straightsection has 3 dispersion-free cells and 2 dispersionsuppressing cells with missing bending magnets. One
cell is --lOrn long, and circumference of the synchrotron is 396.12m. The natural emittance is2.3xlo- 7 m·· rad at SGeV, and that is expected to besatisfactory for subsequent injection into the storage
ring. The horizontal and vertical tunes are 11. 73,
and S~S7, and the natural chromaticities are -14.4
and -11.5 for the horizontal and vertical direction,
respectively. The beam transport line between thesynchrotron and the storage ring is 310m in length,
climbing up by 9m in height.

3GUN

HL

3.1

Figure 1: Layout of the SPring-S injector system.

LINAC STATUS

Preinjector

The preinjector of the linac consists of the electron
gun, two prebunchers, a buncher, several beam monitors, etc. This was fabricated in 1992 and temporarily installed in Tokai site to examine its performances. The performances of a thermionic cathodeassemble were observed in many cases of changing
parameters such as the high-voltage, grid-voltage,heater-power. The maximum beam current was obtained 22A at the condition of the high voltage of
200kV. The stability of the beam current was measured to be less than ± 1.5%. The pulse shape wasadjusted by changing the three different types of thegrid p.ulsers. The pulse width less than lnsec wasachieved by means of using a 4kV rapid rise-time-14-JAERI-Conf 95-021

These magnets were all fabricated and quadupole
magnets were already installed in the machine room.

2 (degree)

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Figure 2:
methodPhase Deviation by Nodal Shiftpulser with a short circuit. The pulse transmission
line between grid pulser and the electron gun was designed to have an impedance matched with the 1nsec
grid pulser to prevent deformation of the 1nsec pulse.
The bunching efficiency of the prebunchers and thebuncher were 65% which is agreed with the calculation. The beaq1 energy is 9Me V at the exit of thebuncher and the energy spread was obtained to beless than ± 2%. The normarized emittance was measured to be about 130mm · mrad at the exit of thebuncher.

3.4 Klystron
13 klystrons are used for high power microwave amplifiers [2]. The klystron used in SPring-S has. thecapabilities of the output-power 80MW, the pulse
width ·4p;sec, the repetition rate 60pps. The klystronnormally operates at the beam condition of 391kV
and 474A. One klystron feeds the microwave to two
accelerator columns. The fabication of klystrons areunder way and now 8 klystrons were completed.

3.5 Modulator
The 190MW pulse modulator has a line type PFN
with 4 parallel and 14 series condensors and inductors [3]. The ratio of the pulse transformer is 1:16,
so that this modulator is required to produce thehigh-voltage pulse with 49kV. The voltage fluctuation was achieved to be less than ± 0.5% during theflat-top of 2p;sec among the full width of 5p;sec. The
reproducibility of the output voltage was obtained tobe good within ± 0.5%. The thyratron was selected
F351; peak voltage 55kV and peak current 10,000A
after the careful examination of several candidates.

4 SYNCHROTRONSTATUS

3.2 Accelerator column
The linac has 26 accelerator columns. One accelerator column is 2.835m long containing 81 cells, and211' /3 traveling-wave constant-gradient type. They
have three· different type in a borediameter of anexit iris, which are 20.0mm, 20.5mm and 20.95mm,respectively. They are arranged in a manner to prevent multisection beam-breakup. The rf power is
fed 26MW to each column, so that the average accelerating field is ""'16MVfm, and the energy gain
per each column becomes ""'45MeV. The accelerator columns are designed to operate in the constanttemperature of 30 'C. The water cooling system isplanned to have a capability of adjusting the temper, ature within an accuracy of ± 0.1 'C. The disks andsylinders of the accelerator column are carefully machined with high precision and brazed in the vacuumfurnace. The phase deviation of each cell, as shownin Fig. 2, are low enough within the specification of2 degrees. The whole of the accelerator columns are
already fabricated and stored on site enclosed withthe dry nitrogen.

4.1.Magnet

The magnets of the synchrotron are 64 dipole magnets, 80 qudrupole magnets, 60 sextupole magnets
and 80 correction magnets. The core of these magnets is stacked with 0.5mm thick, silicon steel laminations. The dipole magnet has C-type core. The pole
length is 2.870mm, and the maximum field strengthis 0.9T. The pole width is 140mm with lateral shims
7.5mm wide by 1mm high. The good field region
was obtained in the area of ± 40mm as shown inFig. 3. The dipole magnets were all fabricated andstarted to be installed in the synchrotron tunnel sinceAugust 1995. The bore radius and the length are
70mm and 0.57m for the quadrupole magnets, andthe maximum field strength is 15Tfm. The bore radius and the length are 100mm and 0.15m for thesextupole magnets, and the maximum field strengthis 200T /m 2 • These magnets were all fabricated andmeasured their performances [4].

4.2 RF cavity
3.3 Magnet

508.58MHz RF system for the synchrotron includes
The beam focusing magnets are composed of triplettwo 1:MW klystrons and eight 5-cells cavities. The requadrupole magnets, which are placed in between
quiered RF voltage is 8MV at injection and 18.7MV
accelerator columns. The steering magnets are utiat extraction, and the maximum RF power islized for beam position adjustment, which are used
1.69MW. The effective RF voltage is changed by conwith the combination of the beam position monitors.
trolling the microwave phases between two klystrons-15-JAERI-Conf 95-021

quadrupole magnet by using a set of four button electrodes(BPM) mounted on the vacuum chamber. The
signals from each BPM are transmitted through lowloss, high-frequency responce cables to the detector
circuits via fast pin-diode switches. For real timemeasurements of the beam position during ramping,
4 electric circuits are independently processing datafrom 4 electrodes. BPMs were calibrated to obtain
the exact beam position using the rf-antenna simulating the beam current [5].

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Positiou aloug z-azi• (. .)Figure 3: Cross sectional field distribution.
Circles at 1 Ge V and rectangulars at 8GeV.

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The integrated timing system is necessary to operate the accelerator complex such as SPring-8. Since
the time width of each RF bucket is 2nsec, the timing accuracy required for beam transfer between two
accelerators must be less than lOOpsec to suppress
the beam loss due to the synchrotron oscillation atinjection. Optical fiber of the transfer line, EO/OE
transmitter and reciever and other compoments arerequired to be low jitter and low temperature dependence [6]. Several components were tested andthe jitter of the electron beam produced by the linac
preinjector was achieved tobe less than 30psec using
the high performance timing system.

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IS cellTiming system

5The construction of the SPring-8 injector system is inprogress, and many components were fabricated andtested to confirm their ferformances. The installation of the machine was started in the accelerator
tunnel from May 1995.

6Figure 4: Electric· field distribution.
from 131 degrees to zero degree, keeping the output power of the each klystron constant:845kW. The
5-cells cavity was selected to realize a high shunt
impedance to reduce the wall losses. The effectiveshunt impedance was obtained to be ---21M 0/m.
The cavity has inductive coupling slots. A large coupling factor is required to stabilize the accelerating
field against disturbances of the temperature rise.
The total length 1640mm and the outer diameter is492mm. Each cell of the cavity has a fixed tuner anda movable tuner to adjust the resonant frequency.
The field distribution of 5 cells was adjusted to beconstant as shown in Fig. 4.

4.3

CONCLUSIONREFERENCES

T.Harami,
K.Fujita,
T.Aoki,[I] H.Yokomizo,
S.Hayashi, et al., "Injector system for SPring-S", inproceedings of the XVth Int. Con£. on High Energy
Accelerators, (Hamburg, 1992)p55S.
[2] S.Suzuki et al.,"RF system ofSPring-Slinac", in thisconference.
[3] A.Mizuno et al., "Modulators for SPring-S linac" ,in this conference.
[4] K.Fukami et al.," Manufacture and arrangement ofbending magnets of SPring-S synchrotron", in thisconference.
[5] T.Aoki et al.,"Calibration of beam position monitor
for SPring-S synchrotron", in this conference.
[6] T.Miyaoka et al.,"High accurate timing system forSPring-S synchrotron", in this conference.

Beam monitor

The synchrotron has several kinds of beam monitors; 3 current monitors, 80 position monitors, 14
screen monitors, a photon monitor, a RF-KO, 5 loss
monitors. The beam position is measured at every-16-