JAERI-Conf 95-021

PA34
MAGNETS FOR THE HIGH BRILLIANT CONFIGURATION
AT THE PHOTON FACTORY STORAGE RING
Yukinori KOBAYASHI, Masahiro KATOH, and Toshio Kasuga

Photon Factory, National Laboratory for High Energy Physics, Tsukuba, Ibaraki 305, Japan
Abstract
The quadrupole and sextupole magnets have been
fabricated for the high brilliant configuration at thePhoton Factory Storage Ring. The field measurement ofthese magnets is now in progress. The shape andthickness of the end-shims in both of the quadrupole andsextupole magnets were determined to correct the higher
multipole fields, whose effects were less than ±lxlo- 4
for the quadrupoles and ±2xlo-4 for the sextupoles at a
position of 36 mm from the magnetic center.

1. Introduction
The emittance upgrade for the high brilliant
configuration is made by doubling the quadrupole andsextupole magnets in the normal cell section [1]. Severe
conditions are however required to these magnets. The
space to place the double magnets is limited and they areinterfered with the photon beam lines because thebending magnets are fixed. Moreover, they are rather
strongly excited than the existing ones; twice for thequadrupoles and ten times for the sextupoles atmaximum. Under such conditions the magnets havebeen designed and fabricated, and the field measurement isnow going.

2. Design and Fabrication
2-1. Quadrupoles
Two types of the quadrupoles for QF and QD in thenormal cells were designed. Their principal parameters
are summarized in Table 1. The schematic drawing isshown in Figure 1. They have same cross-sectional view
and are different in core length. The cores are made ofsoft iron. The coils are water-cooled. Because of thespace limitation, not only the core lengths but also themechanical lengths including coils were made as short aspossible. The bore radius (40 mm) is smaller than thatof the present quadrupoles (55 mm) to produce field
gradient strong enough to realize a 3 GeV operation withthe smallest emittance optics. Not to disturb the SR
extraction to the existing beam lines, the cores areCollins types. The cores are supported by SUS blocks
to keep the field symmetry. The outer SUS supports
have several types of shape to fit several types of the SR
extraction ports.

prevent mechanical deformations, which have several
types of shapes as in the case of quadrupoles. The
sextupoles have auxiliary windings for vertical steering
to save the spaces for correcting magnets. They also
have auxiliary windings to correct the field asymmetry
which arises from the core shape.
Table 1 Specifications of the magnets
TypeCore Length
Bore Radius
Max Field GradientMax. Current
Turns/CoilPower Dissipation
WaterFlow

QF
0.40 m
40mm
24T/m
900A
19 turns
17kW
9.4 1/min

SX
0.20 m
45 mm
600T/m2
450A
17 turns
6kW
4.0 1/rnin

QD
0.25 m40mm
24T/m
900A
19 turns
13kW
7.2 1/min

3. Field Measurement
The field measurements of these magnets are now inprogress using a harmonic coil method [2], which is astandard technique to obtain the main field and the higher
multipole components precisely. In this method, theinduced voltage is represented as a function of an angular
position since a coil is rotated in a magnet. Then theharmonic content of the magnet is directly given as theFourier components of the induced voltage.
Fig.l Schematic drawing of the quadmpole magnet

2-2. Sextupoles
The core of all the sextupoles are same. Theirprincipal parameters are summarized in Table 1. The
schematic drawing is shown in Figure 2. The cores are
made of soft iron and are C-shaped for the SR extraction.
The coils are water-cooled. The lengths and the bore
radius are small because of the same reason on thequadrupoles. The cores are supported by SUS blocks to- 121-

550

r--1
I
I

I
I
r---

1
I
I

L---

1I
I
I
I"-----,I

L - - - - - - - - - - - - - - - - -~

JAERI-Conf 95-021

CD Harmonic Coil@ Chackill'il Collet@Gorder

VerticalSteering~+-_c_oi,_,l~@ Operation Boord@ Anguklr Encoder

IIIII0~aoI.J

1600

r--- ---, r-L.._..J _ _ _r--J

Fig. 3 sc·hematic view of the harmonic coil measurement
system

Fig.2 Schematic drawing of the sextupole magnets
3.1 Measurement System
Figure 3 shows the schematic view of ourmeasurement system. The system is designed so that we
can measure two magnets simultaneously; for example, apair of quadrupole and sextupole magnets. The length ofthe coil is within 1 m in consideration of a distortion ofthe bobbin made of glass-epoxy resin, in which the coil
is winded. The bobbin is packed in the rotating cylinderThe
which is fixed by two chacking collet.
reproducibility of the cylinder position is less than ±50J.Lm. The cylinder is rotated by a DC motor whose speed
is available to change from 10 to 100 rpm. During
rotation an angular encoder mounted in one side of thecylinder outputs an angular position signal, which isused as a trigger of the integration of the induced voltage.
The alignment between the geometric center of themagnet and the coil axis is made using a level scope andtargets whose center position is marked. Two digital
integrators employing a voltage-to-frequency converter(VFC) and a precise amplifier are used in data acquisition.
They are controlled by on-line computer through GP-IBinterface. The specification of the system are listed inTable 2.
Table 2 Specifications ofthe harmonic coil measurement
systemGuardermaterial

iron

methodsignal output

chacking collet
4 pin rotary connector

Coil Support

DC Motor
10- 100 rpm
6000 pulse/tum:

pdi5025]i[METROLB3f] I t:~[AC200V_ _ _ .JI______-------J•-,r-J~----------------~

rotating speed
Angular Encoder
resolution

L..-.J--.,

1 Power Supply 1 : Digital Int1!9rator

3.2 Rotating Coil Probe
Two different set of the rotating coil probe are usedin the measurement; one is a radial coil set, and the otheris a tangential. The radial coil set is located in the planeof one axis, while the tangential is installed on thecylinder surface.
The radial coil set consists of two separate coils; oneis a long coil for measuring the integrated field gradientand the other is a short for the point field gradient, whoseparameters are listed in Table 3. The purpose of theradial coil is to measure a precise main field gradient anda deviation of the magnetic center from the geometriccenter.
Table 3 Parameters of the radial coil set
ShortLong
Coil
20
Length (mm)
1000
29.5
29.9
Radius (mm)50
Tum Number
10On the other hand, the tangential coil set iscomposed of six different coils; <j>4, 7t4, 1t/2, and 3/27t
coils for the quadrupole magnets and <j>6, 1t6, 7t/2, and3/27t for the sextupole magnets are connected. The crosssection view of coil geometry is shown in Fig. 4. All
are long coils to measure the integrated field. Since themain field components reduce with proper angles and tum
numbers of the coils listed in Table 4, the higher
multipole components should relatively enlarge. For
example, the measured data are shown in Figs. 5 for QD
and SX types. While the main field components reduced
in both magnets, the higher multipole ones are clearlyobserved; the dodecapole component (n=6) is dominant
for QD and the 18 poles (n=9) for SX without a end-shimcorrection.

- 122-JAERI-Conf 95-021

Table 4 Parameters of the tangential coil set
n/2 3/27t'n6n4<j>6<j>4Coil925 925 925
925 925 925
Length (mm)36.0 36.0 36.0 36.0 36.0 36.0
Radius (mm)0.57t 1.57t
1t
0.206 0.148 1t
Angle (rad)22621410Tum Number

cp<r-coilcp4-coil

3.3 End-Shim Correction
Since large higher multipole fields are undesirable inreal operation, it is hopeful to reduce them as possible.
In general it is available using a proper end-shim
implemented on the magnetic poles. So one of theimportant purpose in the field measurement is to searchparameters of the end-shim. Figures 6 show a field
gradient ratio of the dominant higher multipole fieldcomponent to the main field one. Data were measured by
I 00 A step of an excitation current and 2 mm step of a
thickness using a tangential coil. Since the higher
multi pole effect depends on the thickness of the end-shim
we could easily determine the best thickness to reduce
them; 4 mm for QD and QF, and 3 mm for SX. As aresult the higher multipole effects were reduced less than±lxio-4 for QD and QF and ±2xlo-4 for SX at aposition of 36 mm from the magnetic center.

.
''Fig.4 Cross section view of the tangential coil geometry~.......-;=::r::::::::::::c:::::::r;.......1

3.0 10' r~;~~i"..".

10"50.15

10-5·3.0 10-5060

120

180

240

300

360

co.,;

Fig.5-a The integrated induced voltage as a function of anangular position at an excitation current of 900 A on QD

2.0 10'!!"1.0 10.

~~~

400

600

BOO

1000

,.--,-r-r-,--r-T-r-..,......,,.-....-,.....,..,-r-rr=======n--+- t=O(mm)

:~:
~
~

0.10

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

0.05••••••••••••••••·r•····•••••••·••••+....... ..

'E

.§.

Angular position (deg)

"..

'•

;

•

Fig.6-a The field gradient ratio of the dodecapole field tothe quadrupole field on QD

f!

"' ·2.0.!!
.5!

___ _,. _____________ _Excitation Current (A).!!

..."' 0.00
-.
~

-0.05

-<>-t=2(mm)---- t=4(mm)-<>-t=6(mm)-+-t-8(mm)•••••••-uT • ~ • ~ • + •-·--·············:------------------:-------------------1···················;------------------------······---~---··-·····-------:.

•••••.•.......... .!.. _________________ ;_ _______________ _ill

~ SX Type

1=450 (A)Without end shims-0.10----------------r----------------r ..................r.. ---------------r----------------0.15
1000.,>

200300400500

Excitation Current (A).,".5., ·1.00.0 10°

Fig.6-b The field gradient ratio of the 18 pole field to thesextupole field on SX:I.;;,~OOOOOOOUOOU000+ 0000 0000U0"''00-f'"''0000"00000+ooOOoOUOOOUOUtOOOO~'"OOOO

2000u-0.02--------~--------------0.03:I"'---------~"' 1.00>.,
0.0 10".,"u.,.5 ·1.0 10'~·0.01•900 (A)Without end shims!!

~.................

~ QD type I =2.0 1Q·5'''i'''""'"''"""!""""'"''"''f"

0.00

1Q•5!

!
.5References·2.0 1Q·5·3.0 1Q·&
060

120

180240300

360Angular Position (deg)Fig.5-b The integrated induced voltage as a function of anangular position at an excitation current of 450 A on SX[1] M. Katoh and Y. H01i, " Status of the Emittance Upgrade
Program at the Photon Factory storage Ring", in thisproceedings.
[2] L. W alckiers, "The Harmonic-Coil Method", CERN 9205, p.138- 123-