The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

BENDING MAGNET AND QUADRUPOLE MAGNETFOR JKJ 50-GEV PROTON SYNCHROTRON
M. Muto, K. Egawa, Y. Mori, K. Niki and E. Yanaoka
Accelerator Laboratory,
High Energy Accelerator Research Organization (KEK),
Oho 1-1, Tsukuba, lbaraki 305-0801, Japan.

Abstract
A bending magnet and a <padupole magnet of the 50GeV proton synchrotron for the JAERI-KEK Joint project(JKJ), the very high-intensity proton accelerator project,
have been designed The 50-GeV main ring consists of 96bending magnets, 216 quadrupole magnets, 72 sextupolemagnets and 192 steering magnets. The bending magnet
is of a modified winoow-frame type, whose maximum
field is 1.9 T. Field gradient of the quadrupole magnet is
18 T/m in peak and the bore radus is 65 mm, which waschanged from the previous design of 63 mm.
This year, full-size prototype bending magnet andquadrupole magnet were constructed for R&D study.
This paper shows the design features and preliminary
results of field measurements of both bending andquadrupole magnets.

150-GEV MAIN RING MAGNETS

The principal parameters of the bending magnet and thequadrupole magnet are summarized in Table 1.
Table 1. Main Parameters of JKJ 50-GeV Main Ring
Magnets
Bending Magnet (BM1524)
Magnetic Rigidity
Bending Radius
Field

12.76- 170 Tm
89.381 m
0.143 T (for 3 GeV)
1.9 T (for 50 GeV)
Useful Aperture (horizontal) 120 mm(S ± 5 x 10"4 at injection)
Gap Height
106 mmCore Length
5.85 mQuadrupole Magnet (11 families) (QM2102)
Field Gradient1.35 T/m (for 3 GeV)
18 T/m (for 50 GeV)

The bending magnet was designed with the code ofPOISSON. The maximum ampere-tum is 93617 AT for
the field of 1.9 T. The tum-number of the coil is 30
turns/pole. The coil resistance and indlctance are 45 mohm and 101 mH, respectively.
The maximum field gradient and its ampere-tum of thequadrupole magnet are 18 T/m and 38600 AT,respectively. The tum-number of the main coil is 24
turns/pole. In ad:li.tion to this, a correction coil is also
equipped to each pole, whose ampere-tum is equivalent to5 % of that of the main coil. The 216 quadupole
magnets, having the same cross sectional shape, aredivided into 7 groups according to the length.

2 DESIGN FEATURE OF MAGNETS
The bending magnet and the quadupole magnet areexcited up to very high field region and used in theenvironment of very high radiation level during operation.
Then, the special cautions are paid on choosing a corematerial and insulation resin of the coil.

2.1 Bending Magnet
The cross sectional view of the bending magnet(BM1524) is shown in Fig. 1. The type of magnet is of
winoow-frame and sector type with the bending radius of89.381 m.

JHF 50-GeV R!n£ (BM-15-24,1Aperture
130 mm<l>
Useful Aperture (horizontal) 132 mm(S ± 5 x 10"4 at injection)
Core Length
0.86 m - 1.86 m(7 kinds)

I.

vrrrrrrrrru·rlOSO mmFig. 1. Cross sectional view of the bending magnet-277-

The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

The magnet core is mare of laminated silicon steel withinorganic insulation, whose core name is 65A1600 in JIS
standard The thickness is 0.65 mm. This core material
is chosen from the view points of the high stacking-factorof magnet core, the high permeability at the high fieldregion of about 2 T in the iron and the high resistivity
abainst radiation.
Using this material, the field computation results showthat the good field region (B/Bo ~ 0.1 %) at 1.9 T isremarkably improved and the total electric power loss isred!ced by about 6% (- 1 MW or more for 50-GeV mainring), comparing to the case of using a usual material
such as 50A800.
The magnet ends are cut with the Rogowski curve being
approximated with 8 steps. The Rogowski curve is
rescribed as z/d = 1+(211t)exp(1tx/2d), where dis the half
length of the gap and x is the position of the longitudinal
direction of the magnet.
For the insulation material of the coil, pre-impregnatedtape with polyimire resin and boron-less glass is chosen
instead of epoxy-resin, because polyimire resin shows
very high resistivity against radiation, namely a few-ten
times stronger than epoxy resin.

cut with the straight slope being approximated with 7steps. The repth and height of each step is 2.6 mm and 5mm, respectively.

3R&D STUDY OF THE MAGNETS3.1 Bending Magnet

Figure 3 shows the full-size R&D bending magnet
being unrer field measurement. Total length and weightare 6.3 m and 32.4 tons, respectively.

2.2 Quadrupole Magnet
The cross sectional view of the quadrupole magnet(QM2102) is shown in Fig. 2.

Fig. 3. R&D bending magnet under field measurement
The stacking factor of the magnet core was achieved tobe 0.995 with the stacking pressure of 20 kgf/cm2.
Figure 4 shows the excitation characteristics measured
with an NMR probe. The measurement result is very
consistent with the calculation result (open circle).

1 - - - - - - - - 9 2 0 mm - - - - - - - 1

BM1524 Excitation Curve(65EF1600, sf=0.995)

15G'l
1!

~ 10"'---------~----------t--------·-j·-------·-i··

The core material and the insulation material of thequadrupole magnet are also adJpted the same ones as thoseof the bending magnet. The magnet ends of each pole are

j!l:l;l! ! i i i !
!

iFig. 2. Cross sectional view of the quadrupole magnet:~l········-i---·------i----···· -i----------i---------·i---···----i---······iJHF 50-GeV Ring QM2102

11------r----------r--------·

r :::::: : r
.

.

.

.

l-o-B-cal.-2 (kG)iltm

0 o~~50~0~1~00~0~1~50~0~2~00~0~2~5o7
o~30~o7o~35o·o(A)

Fig. 4. Excitation characteristics of the bending magnet-278-

The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

Figure 5 shows the measurement results of the field
distribution up to 1.15 T (corresponding to 30 GeVoperation) measured with a Hall probe.
Field Distribution(BM1524, 65EF1600, sf-0.995)

0. 2

0' 1l

~0.0rr-,.......,....,.......,..,..,...,.....,...,..,...,.,..,..............,...,....,..,..,...,....,..,....,........,..,·······-r········-r········t········t········t········t········j········:li ! i : l·0.1---···r---------r------··t········t·-----··t--------r------··i··----0.2

1 l ! l l ~ l--------r---------r--------r--------r------··t··-···-·t········i··------<>-- B/Bo (96) 3GeV! i !

-0.3
-0.4

At present, field measurement of the R&D quadrupole
magnet is oone with temporary system, whose rotating
coil radius is only 46.5 mm. New rotating coil system
for the 50-GeV quadrupole magnet is under construction.
Figure 7 shows the saturation curve normalized at thecurrent of 724 A.

····· -<>-- B/Bo (96) 1OGeV-<>-- 8/Bo (96) ZOGeV-<>-- B/Bo (96) 30GeV

QM2007 Excitation(65EF1600)

0.9······+······+······+······
!
!
!
!

!

.........................

j"""'""'"""''""''j''""'

j~ '·" ..... ~:::.~=~:.:.

!

······r·····r·····-r······-0. 5 ....................~........_.._._......._._._....J.....o._._._..w..............................~.......,-80-60-40·20
020406080x(mm):: •••••••••• . r•••••••• : r••••••••••••••••

Fig. 5. Field distribution of the bending magnet

O.S o!-.__..__..__...._,.50i.,0--'---'---'---'-1,...,0l..00--'---'---'---'-1....J500

The measurement results also agreed with thecalculation results very well. As seen from the figure, thegood field region (B/Bo !5: ± 5 x 104 ) more than ± 60 mmof the radial direction is obtained.
Measurement of field distribution up to 1. 9 T is now inprogress.

I(A)Fig. 7. Saturation curve of R&D quadrupole magnet
Figure 8 shows the multipole component of the R&D
quadrupole magnet.

3.2 Quadrupole Magnet
Mullpole Component ofR&D Quadrupole Magnet

Figure 6 shows the full-size R&D quadrupole magnet.
The total length of the magnet is 1.2 m, which is theshortest one in 7 groups. The bore radius of the R&D
magnet is 63 mm basing on the previous resign(QM2007).
Now, it has been changed to 65 mm,described above.
The stacking factor of four magnet core blocks were0.993-0.994 with the stacking pressure of 15 kgf/cm2.

..

....

.

'0o~ooi" " " " " " ' " " " " " " f " " " " " " ' ' " " " " ' " 1 " " " " 1 1..............

0.001

0.0008c;.a0.0006

0.00040.0002

.
•.••
0b.3

b.4
b.SD0b.6

Db.9
b.10
b.11
b.12

"b.7

---~-------------------------~---·--------.•-··----------~··············· -----------·---- ----------···-- ------

b.8---,------·--------- ---------,------------·---------------------------------~----.--------------------l-----------------------'
!
Dci
I[A]

Fir. 8. Multipole component of R&D magnet
The figure shows that the sextupole component (b.3) isconstantly higher than others regardless of the level ofexcitation current. This suggests that it is due to somemechanical errors, not due to electrical reason. The retailed
cause is now under investigation.

4 ACKNOWLEDGEMENTS
Fir. 6. R&D quadrupole magnet under field measurement

The authors would like to thank the KEK-B fieldmeasurement group for their help to oo field measurementof the quadrupole magnet.

-279-