The lith Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

Beam Transport for SPring-S Linac Future PlanKenichi YANAGIDA, Shinsuke SUZUKI, Akihiko MIZUNO, Tsutomu TANIUCHI,Hiroshi YOSHIKAWA, Hiroshi ABE, Toshihiko HORI, Takao ASAKA,
Hironao SAKAKI, Atsushi KUBA * and Hideaki YOKOMIZO
Accelerator Division, Japan Synchrotron Radiation Research Institute
Kamigori, Hyogo, 67S-12 JAPAN*Japan Atomic Energy Research Institute
Kamigori, Hyogo, 67S-12 JAPAN
Abstract
A triple bends and a double bends nondispersivemagnet systems are designed for beam transport lines tothe assembly hall and to the New SUBARU storage ring.
The triple bends system can be tuned as im isochronoussystem.

construction of the New SUBARU building will be completed in fiscal 1997. However the construction of L3and L4 beam transport building has not been started in
September 1997. Figure 1 shows a schematic layout of
the SPring-S linac facility complex. And Fig. 2 is thephotograph of present status. The L3 and L4 transportbuilding has extra room for klystrons and modulators
which will be used for bunch compressors in the future.

1 Introduction

3 Beam OpticsThe 1.2Ge V SPring-S linac was completed in August 1996 as the injector for the large synchrotron radiation facility and now provides the electron beam to thebooster synchrotron. In October 1997, the use of public
beamline of the storage ring will be. started. Then thelinac will be operated twice a day for the beam injection
to the booster synchrotron. In the rest of the time, there
are some future plans of linac utilization for various applications. For example, a New SUBARU storage ring [1)beam injection, an inverse Compton scattering [2), aparametrix X-ray generation and a slow posjtron generation are planned using present linac electron beam.
After the improvement of beam characteristics, a single
pass FEL operating i~ the Self Amplified SpontaneousEmission (SASE) [3) mode will be challenged. This paper describes the present and preliminary design of beamtransport line where "'1.2GeV electron or positron beam
can be utilized~

On designing a beam transport line it is necessary
to assume the beam characteristics. In the case of
the present linac whose electron gun is a conventional
thermionic gun, absolute 90% emittances and an energydeviation will be properly assumed as l7rmm·mrad and±0.5% respectively. Absolute 90% emittances x and ywere measured as 0.1"'0.77rmm·mrad at the end of thelinac. Therefore the value of assumption, 17rmm·mrad,
has appropriate margin compared with the actual emittance. If we require a better emittance beam, we canscrape the beam halo using a slit at the nondispersive
point. On the other hand an energy deviation will bephysically restrained within ±0.5 % using another slit
at the dispersive point. This slit will be installed atthe large dispersive section where its value of dispersion
function is "'2m.

3.1 L3 Beam Transport Line
2· Buildings
Three buildings are being constructed in order toutilize the electron beam of the linac. One is a machine experimental building where the "'250MeV electron beam can be utilized. The others are an assembly
hall and the New SUBARU building where the "'1.2GeV
electron beam can be utilized. The beam transport line
to the assembly hall is called L3 beam transport (L3BT)
line, and the one to the New SUBARU storage ring iscalled L4 beam transport (L4BT) line.
·The walls have the thickness of 3m for the L3BT line
and the thickness of 1m for the L4BT line respectivelyfor radiation protection. The difference of wall thickness is due to the beam duty. The duty for the L3BT
line is average current of 1.6nA (1.2GeV-1ns-1.6A-lpps)
with total beam time of 22 minutes per week. While theduty for L4BT line is average current of l2J.LA (1.2GeV2J.ts-100mA-60pps) with total beam time of 17 hours perweek.
'The construction of the machine experimental building and the assembly hall have been completed. TheThe L3BT line is designed as a triple bends nondispersive magnetic system. There are three identical 30°
bending magnets, and the total bending angle is 90°.
These three bending magnets are excited in series. The
reason for the triple bends nondispersive magnetic system is to obtain the various characteristics of the electron beam when we utilize the electron beam in the assembly hall. The figure of merit is that we can choose
various compression factors. If we want a high peak current beam, this system tuned as a bunch compressor.
While if we want small energy deviation beam, this system tuned as an energy compressor.
At present this system is tuned as an isochronous
nondispersive system. Its betatron and dispersion functions from the end of the linac to the beam dump areshown in Fig. 3. In this figure the dispersion function x
takes negative value around the second bending magnet.
And the dispersion function y takes finite value at thebeam dump because the electron bearri is bent to thebeam dump which is installed under the floor.
The magnetic parameters in the dispersive section-528-The II th Symposium on Accelerator Science and Technology, Harima Science Garden City, I997

Assembly HallMachine
Experimental
BuildingLinacSynchrotron''\).'

Fig. 1 Schematic layout of the SPring-8 linac facility complex
3.2 L4 Beam Transport Line50-~.

-11,--·-·[\-----lly

2
1.5

0.5
100 '-'--~~~.........~~-'--"-~.._J..._~~c.........~....L....~.......J -0.5w~~~w w
0w

Length from End of Linac (m)Fig. 3 Betatron and dispersion function of 13 beamtransport line

are shown in Table 1. As a principle the magnetic parameters are determined not to exceed more than 30m
in betatron function. However in Fig. 3, the value of betatron function exceeds more than 30m. Because a 15°
switching bending magnet to the booster synchrotron
exits, there is no place to install quadrupole magnets formatching of twiss parameters. The length of this drift
space becomes -2. 75m. The bending radius is 4.85m.
We apply the maximum magnetic field of 1.25T for thisbending magnet, therefore maximum magnetic rigidity
becomes 6.07T·m.

The L4BT line is designed as a double bends nondispersive magnetic system. There are two identical 30°
bending magnets, and the total bending angle is 60°.
These two bending magnets are excited in series.
On the way of the L4BT line there are a reference
point and a border point. The border point is called
P-point. The reference point is the optically connecting
point between the linac and the New SUBARU storage
ring where a., and ay are set as 0 (double waist point)
and the values of betatron function x and y are ..... sm.
On the other hand the border point is the mechanicalconnecting point between the linac and the New SUBARU storage ring. There is a ceramic break for electric
insulation. All elements on the upstream of the border
are under control of the linac system, and all elementson the downstream of the border are under control of
the New SUBARU system. The this system is designed
under following concept. One is the stable and apparent
connection point. And one is easy operation for parameter survey when the electron beam is injected into theNew SUBARUstorage ring.
The betatron and dispersion functions from the endof the linac and to the reference point are shown in Fig. 4.
And its magnetic parameters in the dispersive section arealso shown in Table 1. In order to reduce the numberof quadrupole magnets, the dispersion function becomes
relatively large.

-529-

4 Conclusion

The preliminary design of the L3BT and the L4BT

The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

fig. 2 Present stat.us of around th~ L3 and Ju4 beam tr~~sport building-~.

40

4Table 1
Magnetic parameters for L3BT and L4BT lines in thedispersive section----- ~y-11.

303Element
10OL........__._j._--'--'-~....,_,~_._._~~L........~__L_,_......uL.l.__.~_.__jo0w

w

~~~w

w

Length from End of Linac (m)Fig. 4 Betatron ancJ.. dispersion function of L3 beamtransport linelines were determined. The construction of this transport line will be started soon. Because of the budget
problem or things like that, there may be change of thedesign. However we will construct these beam lines along
the concept described in this paper.
neferences[1] A. Ando et al., Proc. Particle Accl. Conf. (1997) tobe published.
[2] A. Mizuno et al., "Studies of Laser-Beam Interaction
at SPring-8 Linac", Proc. of the 11th Sympo. on Accel. Sci. and Tech., Harirna Sci. Garden City, (1997)
to be published.
[3] K. Yanagida et al., "SPring-8 linac single pass FEL",
Proc. of the 18th Int. Free Electron Laser Conf.,
Rome 1996, to be published.

-530-BM
Drift
QDl
Drift
QFl
Drift
QD2
Drift
BM
Drift
QD2
Drift
QFl
Drift
QD1
Drift
BMDrift
QD2
Drift
QF2
Drift
QF2
Drift
QD2
Drift
QFl
Drift
QDl
Drift
BM

L3BT
Element
Length(m)2.5400.640
0.300
1.700
0.300
1.700
0.300
4.725
2.540
4.725
0.300
1.700
0.300
1.700
0.300
0.640
2.540

L3BT
p (m)
K (m- 2 )4.851
-0.3001.801

L4BT
Element
Length(m)
2.540
0.640
0.300
1.700
0.300

L4BT
p (m)
K (m- 2 )4.851
-1.2001.065-0.9004.851-0.9001.801-0.300
4.851
9.520
0.300
1.700
0.300
14.422
0.300
1.700
0.300
9.520
0.300
1.700
0.300
0.640
2.540

-0.9000.595
0.595-0.9001.065-1.2004.851