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

Magnetic Leakage Shield of Septum Magnet for SPring-8 Synchrotron
Hiroshi ABE, Tsuyoshi AQKI, Kenji FUKAMI, Souichiro HAYASHI*,
Naoyasu HOSODA, Takayoshi KANETA**, Shigeki OHZUCHI***, Kenji OKANISHI****,Yasushi SASAKI****, Hiromitsu SUZUKI, Norio TANI, Mitsugu TANIMOTO*,
Yasuo UEYAMA*****, Hideaki YOKOMIZO and Hiroto YONEHARA
Japan Synchrotron Radiation Research Institute,SPring-8, Kamigori, Ako-gun, Hyogo, 678-12, JAPAN*Japan Atomic Energy Research Institute,SPring-8, Kamigori, Ako-gun, Hyogo, 678-12, JAPAN**ISHIKAWAJIMA-HARIMA Heavy Industries, Ltd.,
1, Shinnakahara-cho, Isogo-ku, Yokohama, 235, JAPAN***TOSHIBA PLANT KENSETU Co., Ltd.,
3-3-21, Isogo, Isogo-ku, Yokohama, 235, JAPAN****SUMITOMO Heavy Industries, Ltd.,
5-2, Soubiraki-cho, Niihama, Ehime, 792, JAPAN*****HITACHI, Ltd.,
3-1-1, Saiwai-cho, Hitachi-shi, Ibaraki, 317, JAPAN
Abstract

This paper describes magnetic field measurementsof the prototype septum magnet and countermeasure for
reducing the leakage magnetic fields in the incidence andthe extraction parts of the SPring-8 synchrotron[!]. We
studied and developed "leakage magnetic shield" on thebasis of the tests data got in these measurements. Consequentially, it succeeded in reducing effects of the leakage
field to about 50% by installing the shield board in themagnet main body. Then, it was possible to manufacture the magnet which sufficiently held the effect of theleakage field for the electron and positron beam.
In this examination, we confirmed the reproduction
with the magnetic field distribution of the magnet measured in the manufacturer. We developed and producedof the septum magnets which were carried out determination of the shapes of the magnetic shielding.
1 Introduction

In the SPring-8 synchrotron, pulsed magnets[2] wererespectively installed at incidence division and extraction part. The fast pulse response of septum magnets[3]are also required at the microsecond order. The countermeasure of magnetic leakage field was examined on theseptum magnet with the characteristic structure. Consequentially, it succeeded in reducing effects of the magnetic field to about 50% by installing the shield board
in the magnet main body.
Therefore, all septum magnets has finished very
high-performance, and again, in the compact magnets.
2 Pulsed Magnets for Injection

Figure 1 shows the configuration of the magnets forthe injection system [2]. This system is composed of
two kicker magnets and two septum magnets. An electron/positron beams are accelerated from lGe V using
the linac to 8GeV by the synchrotron with through of
the injection system.

Fig. 1 The synchrotron injection system. It is a layout drawing of the magnet in the top. The bottom shows the horizontal orbit of the beam. Itshows the beam which came from the linac in
the continuous line, and shows incidence orbit.
The dotted line is reference orbit.
3 Pulsed Magnets for Extraction

The extraction system is composed of three kicker
magnets[4], four septum magnets and four bump magnets. The electron/positron beam accelerated to BGeV
by the synchrotron does be ejected in eleven pulse magnets to the storage ring. Figure 2 shows the configuration of the magnets for the extraction system [2].
4 Experiment

The third septum magnet which is prototype, it isnecessary to consider effect of the leakage field for thebeam orbit. The first septum magnet for the incidence
and the forth septum magnet for the extraction has done
the structure equal to the third septum magnet for extraction in a standard type ( cf.Table 1). It must be a
structural reason of the magnets. The magnetic fieldmeasurement was carried out on the third septum magnet. Then whether it might install "leakage magnetic-405-

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

Table 1
Characteristics of the septum magnets
Effective length [m]Number of turns
Current wave form
Septum [mm 2]
Pulse width [ms]Magnetic field strength [T]Leakage magnetic field [T]Deflection angle [mrad]
Shield Material
Resistance [mn]Inductance [JlH]*It is for the incidence part**It is for the extraction part

1st Septum*
1.00004
half-sinusoid
h30.9 x w7.8
2.5
1.000
3.0 X lQ- 5~7l(at0.9T)

uon
13.3
109

2nd Septum**0.40001
half-sinusoid
hll.3 x wl.5
0.1
0.344
3.0 X lQ- 54.95( at0.33T)
copper and iron
1.8
2.13rd Septum**1.11054
half-sinusoid
h30.9 x w7.8
2.5
1.225
2.0 X 10- 4
45.78(atl.lT)
iron
16.1
107

4th Septum**
1.40474
half-sinusoid
h30.9 x w7.8
2.5
1.440
4.0 X lQ- 5~3(atl.2T)

uon
18.6
147

Long Search CoilY-axis......

~-·····-······-···--····-·->

.....

··,

x-axh··-.... .. S-axis,· ..... ~~tractiOJ~---j----"-<;:-'':::::1.
'.f?{bitFig. 2 The synchrotron extraction system. The continuous line shows extraction orbit and bumporbit.
shield" of what kind of shape or installing existence wasdecided.

Bump Orbit(X=-69. 73 [rnrn])

Fig. 3 It is conceptual scheme of the search coil installation. The origin of the x, y and S axis
shows just outlet of the magnet. The arrow
direction of the axis is the positive direction.
extraction orbit.

4.1 set up

5 r.neasurer.nents
In the magnetic field measurement, we used short
search coil and long search coil [3]. Figure 3 shows ameasurement coordinate system. The setup of the longsearch coil was also installed in incidence orbit in themagnet gap or parallel position in it and reference orbit
and on the bump orbit. The search coil was respectively
set to the inlet and exit side of the magnet. This searchcoil used PEW line ( ¢ = 0.23[mm] ).
Figure 4 shows a picture of the installing shield andthe non-shield. By changing shape of the shield with
6 types, an effect of the leakage field is measured. We
chose the iron ( SPCC ) as a material of the leakage
shield with the conductivity. The iron is popular, andhandling is also a simple material. In the beam inlet side,
the reference orbit is x-36.2mm and x-69.73mmin the beam exit side from the incidence orbit. Then,
we measured the magnetic field of the incidence and the==The measurement contents are as follows, the current wave form, the pulse wave form of 1 pulse [/sec]
operation, the output differential wave form from thesearch coil and the magnetic field wave form which areintegral wave form ofthe search coil output voltage. The
oscilloscope is made to output 4 points of the above. Figure 5 shows the measurement wave form of the typical
septum magnet.
5.1 The effects of "leakage magnetic shield"

The BL product measurement of x axis direction
and bump orbit in the case that "leakage magneticshield" was installed and it is not added is carriedout in the leakage magnetic field region, y = Omm,
x = -35.0 ""' -69.73mm, in the x axis direction. In-406-The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997.........

-1.0000 ••!00

1.5000 ...
... /dl"

Fig. 5 The oscilloscope has 4 channels, 2GSa/ s and 8bits. The x axis is 500JJs/div, and the verticalline is 2.0V/div on C1 and C3. C2 is 5.0V/div,
The integral wave form is 1.2mV/div.

0.00180.00160.0014~ 0.0012~....l0.001~

0.00080.0006

Fig. 4 The beam exit side of the magnet, it is a photograph in the case in which the shield wasinstalled and case in which the shield is notdone. The photograph "A" is not installingthe shield, and the "B" is installing the shield.
The search coil has been attached to the reference orbit side of the magnet.

==-36.2 and -69.73mm
Omm, xthe bump orbit, ywere respectively measured. The shield size is 65mm x200mm x t2mm that time.

5.2 The leakage field of the shield shapes or sizes
The magnetic field distribution was measured on thebump orbit in the beam exit side. The measuring ranges
are x = -69.73mm, y = Omm, S = -30 and +40mm.
We measured the magnetic leakage fields distribution
using the shield of six types ( 65 x 200 x t2, 80 X 200
X t2, 80 X 3QQ X t2, 140 X 2QQ X t2, 140 X 300 X t2
and non-shield ) and the thickness of the shields. Theshield thickness is changed from t = 0, the shield is notinstalled, to 4mm. The thickness interval is t = lmm.

0.0004-70-65Figure 6 shows the result of magnetic leakage fieldmeasurement using the search coil. In the case in which
the magnetic shield was installed and it is not so, the-35-30

Fig. 6 The B L integral cloth of x axis direction (x = -35 "' -69.7mm ). It shows the peak-51.2mm. The reof the leakage field at x
duction in 50% leakage field was achieved in
the existence of the shield.

=reduction of the BL product of largest 50% was able toconfirm it.
Figure 7 shows how shapes or sizes of the magnetic
leakage shield are effective for the leakage field. Theleakage field does be saturated it in to some extent sizeon the magnetic shielding. However, it is possible tohold the leakage field quantity in 1/10, in the existenceof the shield. Therefore, the "type 2" shield size waschosen as a shielding material.
Figure 8 shows the relationship between thickness
and leakage field of the shield board. How much it could
reduce the leakage field, when the thickness of the shieldis changed, was examined. Consequentially, though theleakage field can be reduced even in t = lmm thickness.
However, the leakage field is not sufficiently held in the-30mm. It· is possible to hold thedistribution of S
leakage field, when the thickness of the board exceeds
t = 2mm, and it is well proven that the shield hoard
sufficiently reduces the leakage field, because the distribution becomes a saturation state. However, it may=

6 Results and Discussions-60 -55 -50 -45 -40
PositionofX-axis [mrn]-407-The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

0.0035~ 0.003t=:; 0.0025

I: non shield
2: 65 X 200 X t 2 mm
3: 80 X 200 X t 2 mm
4: 80 X 300 X t 2 mm
5: 140 x 200 x t 2 mm
6: 140 X 300 X I 2 mm

OJ

0.:::

-~

0.002

~

0.001

"e" 0.0015~""":10.0005

D

•

•

D

203

4

56

7

Magnetic shield type No.I to 6

Fig. 7 The leakage field distribution in using eachshields. By dividing the x axis many types ofthe shield to N o.l ~ 6, it is displayed. Therefore, the line was not connected, because eachplotting is separate.
interfere in the bump orbit, if t = 4mm thickness ofthe magnet it is structural are installed. Besides, themagnetic leakage shield was also decided in choosingt = 2mm thickness, because the shield already installedis the same thickness.
The calculated value of tolerance for the leakage fieldof the BL product is 2.1 x 1Q- 3 [Tm), and the leakage
field B is 1.9 x 10- 3 [T]. The experimental value is S.Sx 10- 4 [Tm] or less, maximum value of the graph whichshielded plots, in the BL product for it. The magnetic
field B got the result of 4.2 x 1Q- 4 [T] (see Figure S,
t = 2mm value of thickness at S = -30mm plotting ).
Actual leakage field considerably fell below the tolerance.
Realistically, it can be concluded that there is completely
no problem in kick broth to the injection orbit.

7 Conclusion
There were very few research in this field yet, veryrich data and worthwhile result were obtained.
Then, all pulsed magnets also makes the data except
for this paper to be a reference, and it carries out theadjustment.

-e-- S=-30mm:[ 0.003--0-- S=+40mm~il 0.0025
0.:::·€ 0.002~~ 0.0015
?.!'
0.001

30.00052341bickness of the magnetic shieldFig. S The thickness of the shield was made to change
to t = 0 ~ 4mm. Then, the effect of the leakage field by the thickness was viewed. The x
axis is thickness t mm of the magnetic shieldwhich uses iron ( SPCC:65mm x 200mmx tmm)

References[1] H. Suzuki et al., "Status of the booster synchrotronfor SPring-S", Rev. of Sci: Ins., 66, 1995, pp. 19641967.
[2] H. Yonehara et al., "Development of the Pulse Magnets for the Booster Synchrotron of SPring-S", Proc.
of the 1995 Particle Accelerator Conference, May 15, 1995, Dallas, Texas.
[3] Y. Sakamoto et al., "The Development of the Septum Magnets for TRISTAN Accumulation Ring Injection", KEK Report 94-6, September, 1994.
[4] Y. Sasaki et a!., "Development of the Kicker Magnetfor SPring-S", The 9th Symposium on Accelerator
Sci. and Tech., Tsukuba, Japan, 1993, pp. 255-257.

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