JAERI-Conf 95-021

PA33
Design of Magnet Power Supplies for KEKB Accelerator
Tadashi KUBO, Masato YOSHIDA, Hitoshi FUKUMA
Atsushi KABE, Shinichi YAMAMOTO*National Laboratory for High Energy Physics
1-1 Oho, Tsukuba-shi, Ibaraki-ken 305, Japan*ATC Co., Hachioji, Tokyo, Japan

Abstract
A number of rnagnet power supplies ( for Bending,Quadrupole, Sextupole and Wiggler magnet ) and about
1800 Steering magnet power supplies will be prepared
for KEKB Accelerator. The required specifications forthese power supplies, especially the specification for thecurrent stability is very severe. Various measurements
have been carried out and in progress at present to try
to realize these specifications. In consideration withthe results of the measurements the design of power
supplies has also been going on.

1. Introduction
There are 4 small and 4 large power supply stationsin TRISTAN. 90 main and 520 steering magnet power
supplies have been installed in these stations. These
existing power supplies will be recycled as far as
possible for KEKB Accelerator. Especially almost allof the main magnet power supplies in 4 large power
supply stations will be utilized again. But the numberof power supplies which have to be prepared for KEKB
Accelerator is quite larger than TRISTAN case. Thus
4 new power supply stations for the installation areasof new power supplies will be reserved in the floor of
the existing buildings or experimental hall of
TRISTAN. The design of power supplies has been put
into account in consideration with the room condition of
12 power supply stations which are different with eachother.
To investigate the recycling method of the power
supplies we altered a power supply of TRISTAN lastyear which is not in use. We are going to fabricate
typical R&D magnet power supplies as well. One isfor the 20kW class and the other is for the steering
magnet power supplies. We will adopt the switchingmode power supplies in both cases.
In this report the design process and its plan will bediscussed taking into account the results from thevarious measured data.

ripples will be smaller than current ripples because themagnet field ripples will be reduced by eddy current
effect of vacuum chamber.
Thus how to realize such high current stability is amost important problem for the design of magnet power
supplies.
Table 1.
Required Current Stability and Field Ripple
Content(P-P).
Magnet Power Current Stability Magnetic Field
Supplies forRipple ContentRate(P-P)
QCS(Superconducting
Quadrupole Mag.)
Quadrupole Mag.
1xi0-4/year(Curved Section)
1x10-4/year
Bending Mag.
5x10-4/year
Sextupole Mag.
5x10-4/year
Correction Mag.

1x1o-51x1o-51x1o-55x1o-45x1o-5To estimate the power supply design parameters
many kind of measurements have been carried out toattain these current stability and . Later these problems
will be discussed in detail.
Table 2 shows the list of power supplies to prepare.
Table 2.
The list of magnet power supplies required at KEKB.
RingMagnet
TypeLER

Dipole

1400
250
130
120
7070
4030

Wiggler400

2. Required Specifications for the PowerSupplies
Table 1. shows the required current stability andmagnetic field ripple content rate of the power supplies.
In the Cu vacuum chamber actual magnetic field-118-

Voltage Current Number of Total
(V)
(A)
Units
Units
1250
1100
1100
1250
1250
1100
1100
1250
1250
550
1100

1222222252830

JAERI-Conf 95-021

Quadrupole 700
6004001301008070504030
Sextupole

5040500
500500500500
500500500500500
425425425

3221322123556
2Fig. 1
Temp. Measurement of small
Power Supply Station 950822-24

120

448
254886886

Ai~Temp.
2o-l--+-r-+~-+-""'t":::---~
1081223020408123

5060

812~

Time (hour)

Steering
HER

Dipole1400
4020

Quadrupole 900
500400300
100603020
Sextupole

6050
Steering

840
840
840
840

1439500500
500
500
500500500500

1163101246291109425425242852886886

500

It will be able to keep the room temperature in therange of 20 to 40 degrees in all the year only by on/off
control of ventilation fan. Consequently it became clearthat to guarantee the specification given in Table 1 thedesign of KEKB magnet power supplies must be carriedout by taking account of the room temperature changeof 20 degrees .

17

4. Configuration Plan of KEKB Magnet
Power Supplies

3. Measurement of the Room Condition ofthe Power Supply Station
The room temperature of the existing 8 power supplystations have not been controlled. But the existing
magnet power supplies satisfy the specification ofTRISTAN because the control circuits of the power
supply have been kept in constant temperature box. We
are planning to install all new Sextupole, Steering andseveral Quadrupole magnet power supplies in 4 existingsmall power supply stations, and the other newBending, Quadrupole and Wiggler magnet power
supplies in 4 new power supply stations. But in bothcases the constant temperature box will not be used byreason of the cost performance. Therefore we measured
the room temperature variation at the time of power
supply operation. Fig.l shows the measured data on
this summer. As can be seen the room temperature issame as the air outside when the ventilation fan has
been operating.

The KEKB magnet power supplies will be separated
into two parts because of the reason mentioned in theprevious sections. Namely one is a hardware part notaffected by the temperature variation comes fromsurroundings. The other is a control part which is mostimportant part to satisfy the specification and easily
affected by the temperature drift. So the latter part has
to be kept in air-conditioned room. Fig.2 shows theconfiguration plan of the KEKB magnet power supply.
All the control units of power supplies will be put
together in same air-conditioned room. The temperature
coefficient of the head of DCCT will be ignored
normally. So it will be installed in hardware part. On
the other hand the control circuit of DCCT will beinstalled in air-conditioned room. In case of steering
magnet power supplies the current sensors will beprobably kept in air-conditioned room to reduce thecost.

5. Measurement of altered TRISTAN magnet
Power Supply
Various measurements have been carried out with theconfiguration shown in Fig.3 by using alteredTRISTAN magnet power supply. DCCT of HOLEC
company has been used as the external monitor. 20m
length of connection cable between DCCT head and .
control circuit is guaranteed by the company. So weused it to confirm the specification.

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Fig.2
B, Q and Sx Power Supply Plan for B-FActoryr------------,Contorol Unit

Power Supply Hardware Unit

16blt Digital

Slgnal-+-t---J=~DA~c=J20m

DCCT Control Unit

DCCT Head Unit

1-------------agne

Air Connditioned Room 25±2 "CFig.3
Block Diagram of Current Stability Measurement
Altered Puwer Supply

GND 0.7Smm square cable
Air-<:onditioned Container

Ma netFig.4 shows a typical measured data. Large drift ofDCCT output at warming up was perhaps caused bytemp. drift of the resistors which have been used for thedifferential amplifiers in the current .feedback loop.
The temp. coefficient of resisters is 100 ppm/ degree.
Fog.4
CUrrent Stabllty Measurement of alterlld Power SUpply
t. OAC 8'ld error anp. drcUt tlOads are placed 1n air conditiOned room
apat from altered powS' Sl.PP'Y with 25m Clista'lce.
2. Olly OCCT signal transfer is orrerendal type a'ld d!iver dro..lt is· in temp. consta1t box at th•s test.
3. OCCT moritor drO.it is tmproved to observe correct signet

6. R&D Magnet Power Supplies
It proved to be clear that the configuration shown inFig.3 has been applicable to KEKB magnet power
supplies on the basis of the measurement described inprevious sections. Accordingly by this way thefabrication of 20kW class and low power bipolar
steering magnet power supplies has been going on as
R&D at present. Recently in Europe and USA
switching mode power supplies have been introduced
for almost all of the power supplies of these classes.
For example nowadays it is not difficult to use
semiconductor component like IGBT. In Japanswitching mode magnet power supplies for accelerator
are not so popular. So we would like to adopt
switching mode power supplies in both cases whichhave many merits like very small sizes, high powerfactor etc.

117. Magnet Power Supplies for KEKB
Accelerator
Time (hour)
Auctuation-(Ciutp.Jt(V)-CMput(V)(n"'t))/CMput(V)(fim)Test suns after it.lol.l 1 hcu idling with SOA ( 1096) output.

600SEP-6 Flue. max.-min.... 6.7 10-s

The current stability of this power supply is within
10 ppm after warming up. This value is enough for thespecification of KEKB magnet power supplies.

As pointed out in this report it wiil be surely possible
to fabricate KEKB magnet power supplies which
satisfy the given specifications. But here we point out
again that how important are the selection of electricparts and the design of electric circuits.
We arenow drawing up a detail construction scheduleof the magnet power supplies toward KEKB
Accelerator operation.

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