Chapter 7
Magnet System
In this chapter, we describe designs of magnet system including the parameters forSuperKEKB. Special magnets in the near beam collision points are also discussed.

7.1

Magnets in the Arc and Straight Sections

The basic design concepts for SuperKEKB are:• Use the KEKB tunnel,• Use the components of KEKB as much as possible;– Preserve the present cells in the HER,
– Replace dipole magnets, keeping other main magnets in the LER arcs.
While utilizing existing resources, we also have major upgrade plan to achieve newlow emittance beam optics for both LER and HER.
• Replace dipoles and change the wiggler layout for LER,
• Install wiggler magnets in HER,
• Increase number of quadrupole magnets in HER.

7.1.1

LER

To achieve a few nm in emittance, there are two steps to be taken. First, bending
magnets in the arc have to be from 0.9-m types to 4.0-m types, which allow to decrease
field strength. And, the number of quadrupole magnet is increased. Second, shortening216

Llam orLef f (m)B,
B’(T/m),B”(T/m)current
× turns/ poleNumberofmagnets

57 (min. 55)

2.23

0.22

1000A × 24
or 1000A × 24

11

55

3.99

0.17

55
55

4.19
4.19

0.22
0.18

57 (min. 54)
Bs
57 (min. 54)
Bv2
55
Quadrupole magnets
Qrf
83
83

0.89
0.43
1.4

0.42
0.21
0.2

860A × 10
860A × 10
or 1100 × 10
860A × 10
200 – 1250A
× 32
500A × 20
500A × 18

0.58
0.58

7.2
7.2

Qarc

55

0.46

55
Sextupole magnets
SL
56
SF, SD
56
wiggler magnets
double pole55
single pole55
half pole
55

Half gap orbore radius
Designation(mm)
Dipole magnets
Blc

Barc

Usage

new
or
reuse

5

local
correction
local
correction

14
100

normalnormal

new
new

20
1
4

normaltransIR
vertical

reuse
reuse
reuse

600A × 35
500A × 35

10
37

new
reuse

9.0

500A × 25

120

0.46

7.5

500A × 25

271

RF section
RF sectionarc,straight
arc,
straight

0.3
0.3

98.83
327.6

425A × 21
425A × 21

8
100

focus
defocus
f,d

reuse
reuse

0.75
0.75
0.75

0.77
0.77
0.77

1400A × 36
1400A × 36
1400A × 36

112
56
56

wiggler
wiggler
wiggler

new
new
new

Table 7.1: LER (e+) Magnet types.

217

reuse
new

reuse
reuse

Half gap orbore radius
Designation(mm)
Dipole magnets

Lam.
length(m)B,
B’(T/m),B”(T/m)current
× turns/pole

Numberofmagnets

Usage

new
or
old

Blc
Barc

4
5.9
0.76
1.14
1.14

0.20
0.2
0.22
0.02
0.2

860, 880
or 1100A × 10
840A × 10
500A × 32
500A × 12
1000A × 24

11
113
1
1
2

local
correction
normal
arc
arc
arc

new
reuse
reuse
reuse
reuse

0.46

5.0

500A × 25

4

50
50

0.56
1.12

13.6
14.2

700A × 27
700A × 27

33
2

50

0.55

14.2

500A × 26

80

50

0.83

8.7

500A × 17

195

50

0.83

8.7

500A × 26

8

50

1.0

6.9

500A × 17

97

50
83

0.82
1.0

8.9
4.35

500A ×26
500A ×35

4
31

Qwig
55
Sextupole magnets
SL
56
56
SXabort
56
SF
56
SD
56
Wiggler magnets
55
help

0.46

9.7

500A ×25

7

0.6
0.5
0.3
0.3
1.0

353
322
322
304
316

600A ×22600A ×22600A ×22425A ×21
425A ×21

4
4
2
52
48

normalnormalabort
focus
defocus

0.77

800A × 36

36

wigglerrecycle55
35 (33.15)
57 (54)35 (33.15)
35 (33.15)
Quadrupole magnets
Qarc
55

Qx
Qrf

arc
reuse
arc,
straight
new
arc
new
arc,
straight
reuse
arc,
straight
reuse
arc,
straight
newarc,
straight
reuse
arc,
straight
reuse
RF section reuse
wigg.
sectionreuse

see details for recycled magnets KEKB design report.
Table 7.2: HER (e-) Magnet types.

218

new
new
new
reuse
reuse

Dipole magnets
Quadrupole magnets

Tolerance at 50mm radius
B3 /B1 < 0.12%
B5 /B1 < 0.45%
B6 /B2 < 0.12%
B10 /B2 < 0.14%

Table 7.3: Tolerances of systematic multipole errors.
the wiggler period by half is also eﬀective for lower emittance. Wiggler magnets, which
are usually installed as synchrotron radiation sources, deflect the electron (or positron)
beam in alternate directions, producing an angular excursion of the beam and emitting
electromagnetic radiation. However, the electrons leave the magnet in the same way
they would if the magnet were turned oﬀ, that is, they produce no net deflection or
displacement of the beam orbit. We will discuss details of about Wiggler magnets laterin this section.
Table 7.1 summarizes the magnets the magnets that required for the LER. Fourtypes of dipole bend magnets are needed in the LER:Barc , Blc , Bs and Bv . Two typesof quadrupole magnets (Qarc and Qrf ), and three types of sextupole magnets (SL, SF
and SD) are presented. In addition to them, wiggler magnets are also presented.
Dipole Magnets
The LER requires 155 dipole magnets except near IR region. They include 119 newmagnets. Cross section view of Barc and Blc are same and shown in Figure 7.1.
Quadrupole Magnets
There are 438 quadrupoles in the LER. The 391 will be used for the arc and thestraight sections, except for the beam line that includes RF cavities. For the RF
sections, 47 which have larger aperture will be used. Cross section view of Qrf iw
shown in Figure 7.2.
Table 7.3 depicts the tolerances on the multipole field errors for the dipole andquadrupole magnets. These values have been determined from studies on the expected
dynamic aperture and emittance coupling. We should emphasize that these requirements are well met by existing magnets in the KEKB Main Ring.

219

LER

HER

Vertical steering
Number of Magnets
195
215
Bore radius
133
133
Lamination core length
0.2m
0.2m
Current × turns/pole
5A × 162 5A × 162
Table 7.4: Parameters of the vertical steering magnets for the LER and HER.
Wiggler Magnets
The wiggler magnets will be used to control the radiation damping time. Figure 7.4
depicts a double pole wiggler, called a ”KEKB wiggler”. The type of electromagnetic
radiation produced depends on how quickly the beam wiggles. The role of the wiggler
magnets in KEKB and Super KEKB is to control the emittance of the beam. Therefore,
we shorten the wiggler period by half and increase the peak field from 0.77 T to 0.98 T.
We expect emittance to decrease to one-fifth that of KEKB. As shown in Figure 7.3, thisnew wiggler system design requires two new H-type magnets (single-pole wigglers (WS)and half-pole wigglers (HS)), and they are interleaved between the existing ”KEKB
wigllers”.
Vertical steering Magnets
Table 7.4 depicts parameters of the new vertical steering magnets. They include 225
new magnets. The maximum kick angle of 1 mrad is assumed for the vertical steering
magnets. Almost same number of horizontal steering magnets are needed as well, which
are reuse of KEKB horizontal steering magnets.

7.1.2

HER

Table 7.2 summarizes the magnets the magnets that required for the HER. The HER
emittance can be decreased to 5 nm by preserving the KEKB cell structure andreducing the electron beam energy down to 7 GeV (24 nm at 8GeV in KEKB). But
there is one major change in the HER. A wiggler section is newly installed in one of thestraight sections, which the KEKB HER did not have. In the current design, the restof the ”KEKB” wigglers are installed. In case of full wiggler installation, we expect
emittance reduction down to 4 nm.

220

Figure 7.1: Cross section view of the design of a LER dipole magnet (Blc and Barc ).

Figure 7.2: Cross section view of the design of a LER quadrupole magnet (Qrf ).

221

Figure 7.3: New wiggler system. Pole size of ”KEKB”, ”single-pole” and ”half-pole”
types are 250mm, 280mm and 150mm, respectively.

Figure 7.4: Left: Picture of double-pole wiggler magnet ”kekB wiggler”. Right: Field
strength for left and right poles calculated by OPERA-3D.

222

Half gap orbore radius
(mm)

Lam.
length(m)B,
B’(T/m),B”(T/m)current
× turns/pole

Numberofmagnets

112
112

1.59,2.13
2.13, 3.5

0.2232
0.117

1000A × 10
500A × 10

2
4

66

0.2

0.048

10A × 25

2

133

0.2

0.136

20A × 720

8

55
134

0.5, 0.54
0.3

2.04
2.04

500A × 6
10A × 20

2
17

Designation
Dipole magnets
BLC1LP1, BLC1RP
other BLC typevertical steering bend
BC1RP, BC1LP
BC∗ E, BC∗P,(∗=1 – 4)
Quadrupole magnets
QLC2LE,QLC2RE
QK∗E, QK∗P

Table 7.5: Summary of new near IR Magnets.
Dipole Magnets
The HER requires 128 dipole magnets except near IR region. They include 11 new
magnets for local correction. But we reuse most of magnets from KEKB.
Quadrupole Magnets
There are 461 quadrupoles in the HER. They include 54 new magnets. For the RF
sections, 31 of Qrf which have larger aperture will be used. Seven of Qwigg are installedat wiggler section.

7.1.3

Magnets in the near Interaction Region

Figure 7.5 and figure 7.6 depict the beam lines in the very near IR region for SuperKEKB. To achieve a few nm in emittance, the new design of beam line in the nearinteraction region is completely changed from KEKB. Crossing angle of the LER andthe HER changes from 23 mrad to 83 mrad. Some magnets get closer to the interaction point. It turns out that distance between the LER and the HER beam lines canbe 340 mm in the smallest case (BC1LP and QKALE in figure 7.5, and BC1RP and
QKARE in figure 7.6). Therefore, magnets in the near interaction region should be
carefully designed taking in to consideration of their alignment and installation procedure. Table 7.5 depicts parameters of the magnets in the near interaction region,
which are newly fabricated for SuperKEKB.

223

Figure 7.5: ”D2” side of the near IR beam line

Figure 7.6: ”D1” side of the near IR beam line

224

Figure 7.7: Design of vertical steering magnet (BC1LP and BC1RP).

Figure 7.8: Design of skew quadrupole magnet (QK type).

225

7.2

Cooling water system for the magnets

Most of the SuperKEB magnets are water-cooled resistive magnets of hollow copper
conductor. The number of water-cooled magnets is increasing from ∼ 1600 in KEKB
to ∼ 2000 in SuperKEKB, mainly in the Oho and Nikko straight sections where newly
fabricated wiggler magnets are installed. The water to the ∼ 1600 magnets was supplied by the four pumping systems located near the Tsukuba, Oho, Fuji and Nikko
experimental halls for KEKB. Each pumping system is capable of supplying pure water at up to 4000 liters/minute. New utility buildings are to be built at four locations
in between the existing experimental halls to meet the needs of the increased numberof water-cooled magnets for SuperKEKB. Modifications to the water distribution systems, including the addition of pipes from the new utility buildings to the tunnel, will
also take place. The water system for the SuperKEKB main ring magnets follows thatof KEKB. For example, flow rates to the individual magnets will be measured using
ultrasonic flow meters, and the flow rates are adjusted by closing/opening the globe
valves if needed. Each magnet is equipped with a flow switch and the interlock level
will also be adjusted.

7.3

Alignment

The alignment tolerance is of the same order as that for KEKB. The KEKB magnet
positions would have provided excellent reference points for aligning new magnets in
the Tsukuba straight section had it not been for the eﬀects of the Great East Japan
Earthquake on March 11th, 2011. The earthquake created considerable damage inthe tunnel area with large movements and changes in alignment being observed, particularly on either side of expansion joints. This is not surprising, as the expansion
joints completely decouple the adjacent concrete structures so that they will moveindependently of each other in the event of an earthquake. This created very large
misalignments where the beams and magnets crossed these expansion joints. The locations of all the expansion joints are easily seen when looking at the post-earthquakealignment measurements. Several types of earthquake-related damage occurred within
the tunnel complex, including: cracking of platforms and concrete structures, liquefaction in places, surface soil disruption cracks, floor movement, cracks (both structuraland superficial), and large shifts in magnet and equipment stands. The environmental
conditions could no longer be controlled in the tunnel after the earthquake, and thetemperature variation is ±7 degrees of the nominal operating temperature. Precisionalignment of the magnets is therefore planned to be carried out once the environmental

226

controls and temperature stability of the tunnel have been re-established.

7.4

Magnet Power Supplies

The main issues of the upgrade from KEKB to SuperKEKB related to the magnet
system are as follows:
1. full rearrangement of the magnets in the Tsukuba straight section, including
superconducting magnets and correction coils in the interaction region,
2. replacement of the LER main bending magnets by longer ones,
3. increase of LER wiggler magnets in magnet type and number, and new installation of wiggler magnets in HER.
4. higher precision of magnetic fields, particularly of the main bending magnets andthe superconducting quadrupole magnets in the interaction region.
The tasks on the magnet power supplies are hence set as bellow:
1. R&D to attain high stability of output current and precision of current setting,
2. fabrication of new power supplies,
3. maintenance of existing power supplies,
4. management of cables and power-supply stations,
5. upgrade and maintenance of the control system.

7.4.1

Improvement of Output-Current Stability and CurrentSetting Precision

At KEKB, the typical specifications of the power supplies were as follows:
output-current stability : ≤ 100 ppm/month, ≤ 20 ppm/day
magnetic-field ripple : ≤ 10 ppm
precision of current setting : ±50 ppm
In SuperKEKB, the power supplies for the main bending magnets and the superconducting quadrupole magnets should have higher performance:
output-current stability : ≤ 10 ppm/month, ≤ 2 ppm/day
current ripple : ≤ 1 ppm (rms)
precision of current setting : ≤ 1 ppm
temperature coeﬃcient of output current : ≤ 0.1 ppm/K

227

In order to regulate the output current with high stability, the followings are important: (1) electronic parts with small temperature coeﬃcients should be used, andif necessary, they will be contained in a thermostatic box; (2) the devices for current
monitoring and setting should have high resolutions; (3) the current-control circuit
should be elaborately designed and fabricated.
Our current-control circuit should have two feedback loops: a major loop and aminor one. The former, having fast response, shares coarse control, and the latter,having slow response, shares fine control. Since an analogue feedback loop of a standard current-control circuit has fast response, it will be applied to the major feedback
loop. It will work eﬃciently in a transient stage, where the current-setting valuechanges, and will suit also reduction of low-frequency components (< a few kHz) of
current ripple. The analogue feedback will, however, fail in fine regulation, because ananalogue circuit is inherently noisy. A digital feedback loop shall hence take over thefine regulation. The output current is measured on a high-performance DCCT (DCcurrent transformer) and an 8.5-digit digital multimeter. The measured current value iscompared with the reference value; the both values are digital. The diﬀerence between
them is fed back into the input of a DAC (dig ital to analog converter). The DCCT
electronics and the multimeter will be installed in a thermostatic chamber beside thepower supply.
The DAC should have a resolution of more than 20 bits, the current measurement in
the feedback loop should be accurate. Since high-performance 20-bit DAC’s are commercially available, we will develop a 24-bit DAC circuit by combining 20-bit DAC’s.
For instance, 20 bits of one DAC are used for coarse setting and 4 bits of another forfine setting. Another idea is to divide the full range into 16 and allot one division to
one 20-bit DAC.
Noise suppression is another key issue for a switch-mode power supply. The switching, of which the typical frequency is a few kHz or higher, generates noises with highfrequency components below a few MHz. Because the analogue feedback loop is not
eﬀective at all in such high frequencies, proper passive filters should be prepared.

7.4.2

Fabrication and Maintenance of Power Supplies

In KEKB, the number of power supplies for normal-conducting magnets was about
2300: 28 large-size power supplies (rated output power ≥ 135 kW), 374 middle-size ones
(6 ∼ 105 kW), and ∼1900 small-size ones (325 ∼ 700 W). Most of them shall operatein SuperKEKB. Overhaul is planned to the large- and middle-size power supplies to bereused. Old electronic parts, such as electrolytic capacitors, variable resistances, DC
power supplies, circuit breakers, and IGBT’s (Insulated Gate Bipolar Transistors) are
228

Ring
HER
LER

Rated
current
860 A
860 A

voltage1100 V
1100 V

Number of
PS’s
1
1

power
946 kW
946 kW

Number ofmagnets/PS
105
100

DAC
resolution
24 bits
24 bits

Table 7.6: The power supplies (PS’s) for the main bending magnets.

HER
LER

Rated
current
800 A
1400 A

voltage
500 V
350 ∼ 750 V

power
400 kW
490 ∼ 1050 kW

Number ofPS’s
1
8

Number ofmagnets/PS
36
26 ∼ 52

DAC
resolution
24 bits
24 bits

Table 7.7: The power supplies for the wiggler magnets
to be replaced. Overhaul of small-size power supplies hinge on budget.
In SuperKEKB the number of power supplies for normal-conducting magnets isabout 2400, and about 60 for superconducting magnets. About 400 new power supplies
are to be fabricated.
Power Supplies for the Main Bending Magnets
In each of the KEKB rings, two power supplies operated for the main bending magnets. Their rated outputs were 840 A, 590 V (HER) and 1250 A, 770 V (LER). The
power modules were thyristors. The four power supplies were too old to be used in SuperKEKB, because they had worked not only in KEKB but also in TRISTAN. As listed
in Table 7.6, the new power supplies are two identical ones (1 power supply/ring) with
rated outputs of 860 A and 1100 V. The power modules are IGBT’s, and the resolutionof the DAC’s are 24 bits.
Power Supplies for Wiggler Magnets
There were 76 identical wiggler magnets in each of the Oho and Nikko straight sectionsof KEKB LER. Four identical power supplies with rated outputs of 1000 A and 700 V
excited them (38 wiggler magnets per power supply). Except for rated outputs, they
were same as the power supplies for the main bending magnets. Replacement by newones is hence necessary. In SuperKEKB, most of the KEKB magnets are reused, andtwo diﬀerent types of magnets are added. Moreover, a set of wigglers are to be installedin the Oho straight section of HER. The number of new power supplies is accordingly
nine: 1 in HER Oho, 4 in LER Oho, 4 in LER Nikko (see Table 7.7). The power
supplies are same as those for the main bending magnets, except for rated outputs.

229

Ring
HER
LER

Rated
current
500 A
500 A

voltage
270 ∼ 930 V
440 ∼ 800 V

power
135 ∼ 465 kW
220 ∼ 400 kW

Number ofPS’s
77

Number ofmagnets/PS
22 ∼ 48
22 ∼ 48

DAC
resolution
20 bits
20 bits

Table 7.8: The power supplies for the main quadrupole magnets.
Power Supplies for the Main Quadrupole Magnets
There were seven sets of main quadrupole magnets in each of LER and HER of KEKB.
The magnets were excited by fourteen 500-A power supplies. They shall work in
SuperKEKB after being overhauled and improved (see Table 7.8). For more precise
regulation of the tune values of betatron oscillation, the resolution of the DAC’s for
current setting, which was 18 bits in KEK HER and 16 in LER, is to be increased to
20 bits. The current-monitor signals were so noisy that circuits and cable paths areto be improved. The cabinets of the power supplies lie in contact with the floor. For
better grounding, the cabinets will be isolated from the floor and the water pipes.1
Middle-Size Power Supplies
There were 374 middle-size power supplies for local bending, quadrupole, and sextupole
magnets in KEKB. In SuperKEKB, 335 out of them will be used, and 39 will be kept
as spare. Reused power supplies are listed in Table 7.9.
The number of power supplies to be fabricated is 92 (see Table 7.10); 53 out ofthem are for magnets in the Tsukuba straight section. The specifications of the 92
power supplies (> 10 kW) are as follows.
output-current stability : ≤ 100 ppm/year, ≤ 20 ppm/day
current ripple : ≤ 10 ppm (peak-to-peak)
DAC resolution : 20 bits
temperature coeﬃcient of output current : better than ±0.6 ppm/K
Small-Size Power Supplies
In KEKB, the number of small-size power supplies was about 1820: ∼1220 were used forsteering magnets, auxiliary coils, and skew sextupole magnets, and ∼600 for solenoids,
which suppressed the electron-cloud eﬀect in LER. The power supplies are bipolar
ones with rated output current of ±5 A and ±10 A. Most of them are to be used1

The cabinets of the power supplies were not isolated from floors in KEKB. In SuperKEKB, the cabinets of large- and middle-size power supplies will be isolated.

230

Ratedcurrent
voltage
1250 A
30 V
1000 A
105 V
840 A
15, 30 V
600 A
15 ∼ 60 V
500 A 10 ∼ 120 V
425 A 35 ∼ 80 V
300 A
60 V
200 A
40 V
Lambertson magnet (HER)†
230 A
80 V
†
Lambertson magnet (LER)
200 A
70 V
‡
Auxiliary coils±30 A±200 V† for beam abort. ‡ for beam-based alignment.
Magnet, coil
Local
bending, quadrupole,
sextupole magnets

power
38 kW
105 kW13, 25 kW
9 ∼ 36 kW
5 ∼ 60 kW
15 ∼ 34 kW
18 kW
8 kW
18 kW
14 kW
6 kW

Number of
PS’s
3
2
4
16
198
104
1
1
1
1
4

Table 7.9: Middle-size power supplies to be overhauled for SuperKEKB

MagnetLocal
bending, quadrupole,
sextupole magnets

Rated
current
1100 A
1000 A
880 A
860 A
700 A
600 A
500 A

voltage30 ∼ 45 V
30 ∼ 45 V
35 V
25 ∼ 35 V
40 ∼ 60 V
38 ∼ 75 V
35 ∼ 75 V

power
33 ∼ 50 kW
30 ∼ 45 kW
31 kW
22 ∼ 30 kW
28 ∼ 42 kW
23 ∼ 45 kW
18 ∼ 38 kW

Number of
PS’s
6
3
2
11
17
11
42

Table 7.10: Middle-size power supplies to be fabricated231Magnets, coils
Steering magnets
Steering magnets
Vertical bending magnets
Auxiliary coils on bending magnets
Auxiliary coils on chicane magnets
Skew quadrupole magnets
Skew sextupole magnets
Correction coils on quadrupole
Skew quad. coils on sextupole magnets
Skew quad. coils on sextupole magnets
Bump magnets in interaction region (DC)
Bump magnets in interaction region (AC)Vertical bending magnets

Rated
current
±5 A
±5 A
±10 A
±10 A
±5 A
±10 A
±10 A
±5 A
±10 A
±10 A
±60 A
±60 A
20 A

voltage±65 V±100 V
±50 V
±50 V
±65 V
±50 V
±50 V
±65 V
±50 V
±80 V
±50 V
±50 V
120 V

power
325 W
500 W
500 W
500 W
325 W
500 W
500 W
325 W
500 W
800 W
3,000 W
3,000 W
2,400 W

Number of
PS’s
439
385
2
80
2
16
10
546
169
47
12
16
10

Table 7.11: Small-size power supplies
Rated
current
10 A
5A

voltage
300 V
300 V

power
3,000 W
1,500 W

Number of
PS’s
∼160
∼80

Table 7.12: The power supplies for solenoids to suppress electron cloudin SuperKEKB, where about 1700 small-size power supplies are necessary, as listed inTable 7.11. The number of reused power supplies is so large that implement of overhaul
hinges on budget. We need about 320 power supplies of ±10 A, but we have only 120
in stock. It is necessary to fabricate 140 power supplies of ±10 A, ±50 V and 60 onesof ±10 A, ±80 V. For vertical bending magnets placed near the interaction region, we
will fabricate ten 20-A unipolar power supplies.
Power supplies for Solenoids against Electron-Cloud
During the KEKB operation, power supplies prepared for LER steering magnets were
utilized for solenoids that suppress the electron-cloud eﬀect in LER. The rated outputs
were ±5 A, ±65 V and ±5 A, ±100 V. In SuperKEKB, unipolar power supplies withhigher rated voltages shall replace the bipolar ones, as shown in Table 7.12.
Power Supplies for Superconducting Magnets and Correction Coils
Superconducting magnets are installed in the interaction region. In KEKB, the numberof power supplies was 9: 1 (rated output current was 4000 A), 6 (50 A), and 2 (650 A).
232

Magnet, coil
Quadrupole magnets
Solenoids
Correction coils

Ratedcurrent
1000 ∼ 2000 A
200 ∼ 500 A±60 A

voltage
10 V
15 V
±5 V

power
10 ∼ 20 kW
3 ∼ 7.5 kW
0.3 kW

Number of
PS’s
8
4
∼45

DAC
resolution
24 bits
20 bits
16 bits

Table 7.13: The power supplies for superconducting magnets in the interaction region.
The 4000-A power supply was for quadrupole magnet. The 50-A ones were connected
to correction coils for beam steering and skew-quadrupole correction. A pole-changer
was attached to each of the power supplies. The 650-A power supplies excited solenoids,
which canceled the magnetic field produced by the Belle solenoid.
In SuperKEKB, about 60 power supplies are necessary, as listed in Table 7.13. Allof them are to be newly fabricated. The power supplies for quadrupole magnets are
diﬃcult in their circuit design for the following reasons: 1) high performance is requiredin stability, precision, and ripple; 2) the inductances of the superconducting coils arevery small (0.9 mH at minimum); 3) the output current has to fall to zero immediately
after quench (in 20 ms or less). We plan to fabricate first a prototype power supply;
we will be thereby able to solve the technical problems.

7.4.3

Management of Cables and Power-Supply Stations

Every power supply of KEKB connects with cables for AC input, DC output, interlock,
output-current monitor, and control. In SuperKEKB the existing cables will be used
for as many as possible. In the Tsukuba straight section, where the magnets are to be
fully rearranged, we will remove the power cables between the magnets and the power
supplies and lay new cables. An estimated cable length is 50 km or longer.
The earth-leakage circuit breakers and molded-case circuit beakers in AC lines (100V, 210 V, 420 V) are so old that they should be replaced with new ones. In the D2
power station, where power supplies for the magnets in the Tsukuba straight section
are installed, the circuit-breaker boards are to be rearranged in accordance with theincrease of power supplies. Compact arrangement of the power supplies is required inD2 because of its limited area. The power supplies for superconducting magnets stoodby those for normal conducting magnets in KEKB. In SuperKEKB, another area isnecessary for the new power supplies.

2337.4.4Upgrade and Maintenance of the Control System

The network system for the control of the power supplies from the central control room
will be ARCNET in SuperKEKB as well as in KEKB. The interface boards, which areslotted into the power supplies, are so old that they will be replaced with new ones.
Since some electronic parts on the board are unavailable today, we must design new
interfaces. Three types of interface are necessary in accordance with the three DAC
resolutions: 16, 20, and 24 bits.
The current monitor system for measuring output currents of the power supplies
and transferring them to the data-logging system in the central control room will not
be changed. In the system, one digital multimeter is connected to several tens power
supplies via a switching circuit. These devices will be overhauled, and a few will bepurchased.
A power supply is forced to stop by external interlock in a case of insuﬃcientwater-flow in a magnet coil, increase of coil temperature, turning oﬀ of warning lights,
and emergency stop from the central control room. The PLC (Programmable Logic
Controller) system that controls these interlocks will be renewed for two reasons: oneis that the KEKB’s PLC is old, and the other is that its capacity is insuﬃcient for theincrease of power supplies.

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