Proceedings of the 11th Annual Meeting of Particle Accelerator Society of Japan
August 9-11, 2014, Aomori, Japan

PASJ2014-SUP063

LARGE ANGLE PRECISION ROTATING TABLES FORSEXTUPOLE MAGNETS IN SuperKEKB
Ryuhei Sugahara A) , Mika Masuzawa A), Tatsuya Moriyama B)
A) High Energy Accelerator Research Organization (KEK)
1-1 Oho, Tsukuba-shi, Ibaraki, 305-0801, Japan
B) Tokyo Giken, Inc.
4-42-37 Higashi Yamada, Tuzuki-ku, Yokohama-shi, Kanagawa, 224-0023, Japan

Abstract
Beams have to be tuned precisely in the collision region in order to get the beam size as small as about 50nm
vertically in the SuperKEKB operation [1]. Large angle precision rotating tables have been fabricated as a tool to handle
this precision beam tuning. Rotating tables rotate precisely 24 sextupole magnets in the LER beam line in the collisionarea from -30 to +30 degrees. The fabrication of these large angle precision rotating tables is reported.

1. INTRODUCTION
Beams have to be tuned precisely in the collision
region in order to get the beam size as small as about
50nm vertically in the SuperKEKB operation [1]. Largeangle precision rotating tables have been fabricated as atool to handle this precision beam tuning. Rotating tables
rotate precisely 24 sextupole magnets in the LER beamline in the collision area from -30 to +30 degrees tochange the function of magnets from the sextuple to theskew-sextupole. The precision of the rotation is expected
to be 0.1mrad. The rotation is controlled from the KEKB
central beam operation room. The rotating tables have to
be made compact as the sp*ace in the accelerator tunnel isvery limited. The sextupole magnets to be rotated havebeen modified on the arrangement of the electric cables
and the cooling water horses in order for the magnets to
fit in these compact rotating tables. Figure 1 shows a
sextupole magnet mounted on a rotating table andinstalled in the accelerator tunnel.

2. THE MECHANISM
The fabrication drawing of the rotating table is shownin Figure 2(a) and (b). A helical gear is fixed at the bottomof the magnet support part, a straight worm gear is fixed
on the top of the support base, and these gears areengaged. The magnet support part is rotated by rotating
the straight worm gear with a pulse motor. The radius ofthe helical gear is 450mm. The extended view of thegear part is shown in Figure 3. The position of themagnets can be adjusted vertically and horizontally withadjusting screw bolts at the magnet mounting plates. Theposition of the whole system of the magnet and therotating table can also be adjusted vertically andhorizontally with adjusting screw bolts at the base plate.

3. ADJUSTMENT OF THE MAGNET
CENTER TO THE ROTATION CENTER

Figure 1: A rotating sextupole magnet installed in thetunnel.
* ryuhei.sugahara@kek.jp

The position of the magnet center has to be adjusted tothe center of the rotation. This adjustment was carried out
by observing the vertical and horizontal displacement of
the hair crosses in the close plane and in the far plane aswell with a theodolite telescope. The hair crosses wereprepared by stretching 0.1mm thick beryllium cupper wire
between the facing edges of the magnet pole pieces asshown in Figure 4. Three wires were stretched, and their- 1153 -Proceedings of the 11th Annual Meeting of Particle Accelerator Society of Japan
August 9-11, 2014, Aomori, JapanPASJ2014-SUP063

Figure 2(a): The front view of the rotating table.

Figure 2(b): The Side view of the rotating table.

Figure 3: The picture of the gear system.

Figure 4: Hair crosses stretched between facing
boundaries of pole pieces.

crossing point was referred as the center of the magnet.
Hair crosses were prepared in both sides of magnets.
First of all, a rotating magnet system is adjusted level by
watching a digital bubble level placed on the alignment
base on the back of the magnet. Then the theodolite
telescope is adjusted so that its optical axis is placed along
the line connecting the close and far hair crosses. Then themagnet is rotated 30 degrees, and the vertical andhorizontal displacements of the close and far hair crosses
are measured. Next the magnet is rotated -30 degrees, andthe displacements are measured. From thesemeasurements, the displacement of the magnet center iscalculated as follows:dX = (Y+ - Y-) / (2*sin(K))
dY = -(X+ - X-) / (2*sin(K))
where the origin of the coordinate system is arbitrary, andX and Y are the horizontal and vertical axis
correspondingly. The position (X+, Y+) is that for the haircross when the magnet is rotated +K degrees, and (X-, Y-)
when the magnet is rotated -K degrees. dX and dY are thedisplacements of the magnet center from the rotation- 1154 -Proceedings of the 11th Annual Meeting of Particle Accelerator Society of Japan
August 9-11, 2014, Aomori, Japan

PASJ2014-SUP063

Figure 5: Displacements of the magnet center from the rotation center after the adjustment, where dX and dY present
displacement in X and Y directions respectively. The suffixes F and B show those in the close and far plane.
center. These displacements are measured and correctedwith the adjusting screw bolts at the magnet mount for theclose and far hair crosses. This process is repeated until
all the displacements become smaller than 0.1mm.
Adjustment results are shown in Figure 5, where the final
values for the displacements are shown for 24 rotating
sextupole magnets.

D2 building. PLC modules of Keyence control directly
the rotating tables, which receive commands from andtransfer status signals to the KEKB central beam
operation room through Yokogawa PLC modules placedin the local control huts and the D2 building.

4. THE CONTROL SYSTEM AND THE
OPERATION
Sextupole magnets are placed on X-Y movers in theKEKB project [2]. These X-Y movers were controlledfrom the central KEKB beam operation room through 8
local control huts, LC1 to LC8, and the control room in
the D2 electric power building at Tsukuba area. The X-Ymovers for 24 sextupole magnets in the LER line in theTsukuba area were replaced by the precision rotatingtables. Control cables connecting the X-Y movers in thetunnel and the surface local control huts are re-used forthe rotating tables. Ten rotating tables in the left area,
looking from the accelerator ring center, are connected tothe LC8 local control hut, right ten rotating tables to theLC1, and the central four rotating tables to the control
room in the D2 electric power building. Control
electronics such as pulse motor drives and control PLC
modules are installed in the LC8 hut, the LC1 hut and theFigure 6: The tilting sensor installed to the rotating table.
Tilting sensors LCI-30 of Jewell Instruments areinstalled to each rotating table as shown in Figure 6.
These sensors can measure the tilt from 0 to 90 degrees.
Outputs from these sensors are fed to ADC modules in the- 1155 -Proceedings of the 11th Annual Meeting of Particle Accelerator Society of Japan
August 9-11, 2014, Aomori, Japan

PASJ2014-SUP063

Yokogawa PLC module systems. These outputs from theADC modules have to be read by the central control
system after some rotation is executed. If the value is notwithin the tolerance of 0.1 mrad, tables have to be rotatedagain reversely by the amount of the error. The backlashof the rotation can be cured with this process. Aimingrotation angle can usually be achieved in two or threetrials.

The authors would like to thank the people of Tokyo
Giken, Inc. for their effort in the fabrication of therotating tables. They also appreciate the cooperation of
the people of the control group of KEKB in theconstruction of the control system for the rotating
sextupole magnets.

REFERENCES
5. INSTALLATIONThe rotating sextupole magnets were installed in thetunnel after the adjustment of the magnet center to therotation center. Holding jigs were fabricated to hold andlift the whole system of the rotating sextupole magnet as
the magnet and the rotating table could not be separated
after the adjustment of the magnet center. These holding
jigs had to be strong enough to lift the weight of 700kg of
the magnet plus 700kg of the rotating table. These
rotating sextupole magnet systems were aligned to thebeam line and adjusted level by observing a bubble level
placed on the alignment base on the back of the magnet.
Fig.1 shows a rotating sextupole magnet installed in thetunnel.

[1] Y. Ohnishi et al., Prog. Theor. Exp. Phys. 2013, 03A011.
[2] KEKB B-factory Design Report 95-7, June, 1995.

SUMMARY
Large angle precision rotating tables have been
fabricated as a tool to achieve the precision beam tuningin the SuperKEKB operation. Rotating tables rotate
precisely 24 sextupole magnets in the LER beam line in
the collision area from -30 to +30 degrees at the precision
0.1mrad. Sextupole magnets to be rotated have been
modified on the arrangement of the electric cables and thecooling water horses in order to fit in the rotating tables.
The magnet center was adjusted to the rotation center at
the precision 0.1mrad before the magnets were installedin the accelerator tunnel. The rotation is controlled fromthe central KEKB beam operation room through the localcontrol hut LC1 and LC8 and the control room in the D2
electric power building. The tilt angles of magnets aremeasured with tilting sensors LCI-30 of Jewell
Instruments. Signals are fed to ADC modules placed in
the local control huts and the D2 building, and their
outputs are read by the central beam control system. If thevalue is not within the tolerance of 0.1 mrad after therotation, tables have to be rotated again reversely by theamount of the error. The backlash of the rotation is cured
with this process. Aiming rotation angle can usually beachieved in two or three trials.

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