Ⅱ-8. Accelerator

RIKEN Accel. Prog. Rep. 53

Power supply backup system for injection and extraction magnets ofcyclotrons
K. Kumagai∗1 and N. Fukunishi∗1A large number of electromagnets are used to accelerate ion beams in the RIBF1) . For example, in the case of
the uranium-beam machine time, there are 500 electromagnets from RILAC2 to the end of SRC through RRC,
fRC, and IRC, each of which is excited by a DC power
supply with high current stability. As a high-quality
beam cannot be emitted unless all power supplies areavailable, it is important to perform the regular maintenance of power supplies and to consider how to handle
them if a failure occurs. In particular, in the case ofa failure during the machine time, it is necessary to restore the power supply as quickly as possible to minimize
downtime.
If any power supply fails, we attempt to repair it ﬁrst.
However, if the defective part cannot be identiﬁed immediately, the part is estimated to take time to repair,or a replacement is not at hand, it is necessary to consider whether another power supply can be used. As
power supplies with relatively low output current, suchas those for quadrupole magnets and steering magnets,
have relatively small chassis and are easy to handle, it iseasy to replace them with the same type of power supply
used for other beam courses. Since the output currentof the power supply for the trim coil and the dipole is
not very large, about 500 A at maximum, it is possible to substitute a power supply for other courses. On
the other hand, the main coil power supply for the four
cyclotrons (RRC, fRC, IRC, and SRC) typically has an
output of several hundred to several thousand amperes
and several hundred volts, and no power supply can bereplaced. Therefore, in the event of a failure, it is necessary to repair this power supply; therefore, we prepare
as many spare parts as possible.
Each cyclotron has 4 to 5 injection magnets and 3 to
5 extraction magnets. These magnets require extremely
high current of approximately 1000 A to 3500 A andvarious voltages ranging from 20 V to 120 V. Despite thelarge number of power supplies, the power supply chassis
are large and need many thick output-current cables;
therefore, it is diﬃcult to relocate the power supply after
a failure occurs. Therefore, a plan has been considered inwhich a power supply that can be replaced in the eventof a failure is arranged at an appropriate place and used
as a replacement for as many injection/extraction power
supplies as possible by adding partial temporary wiring.
The fRC-EBM power supply, a power supply for thefRC Extraction Bending Magnet manufactured in 2012,
was designed to be operated in the dual pattern of large
current-low voltage (2800 A–65 V) and medium currentmedium voltage (1500 A–100 V) in anticipation of use
as an alternative power supply. The thyristor rectiﬁcation part of the power supply is equipped with twounits, which can be connected in parallel or series, and∗1

RIKEN Nishina CenterFig. 1. Wiring layout of the backup power supply for theinjection/extraction magnets of RRC and IRC.

the voltage-current ratio can be changed. In addition,
the transistor driver is prepared in two patterns having
diﬀerent control constants. In 2014, we reassigned thepower supply as that for the DAKR magnet on the IRCE5 beam line, which is operated several times a year, andwired it so that it could be used as an alternative power
supply for injection and extraction magnets of the RRC
cyclotron (hereafter referred to as “backup power supply”). In 2019, the wiring was extended so that it could
be used as a substitute for the power supply for injectionand extraction magnets of the IRC cyclotron if a failure
occurs. Figure 1 shows the current wiring layout of thebackup power supply.
A malfunction of the RRC-EBM1 power supply occurred on November 13, 2019 during a preparation period for uranium machine time. It was caused by thefailure of a shunt made of zeranin, a low-resistance alloy
for high-precision current detection, immersed in cooling water and had been used since the power supply wasmanufactured in 1985. It was expected that it would
take about a week to remove the failed shunt, install
the DCCT, replace the accompanying control boards,
and make overall adjustments. Therefore, we immediately decided against repairing, switched the RRCEBM1 magnet to the backup power supply, and resumed
operation on the same day.
In addition, to enable the immediate use of the alternative power supply in case of trouble, we installed AC
400 V power receiving equipment, cooling water piping
for the alternative power supply, and wiring for the DC
current output in various places. In this manner we arepreparing to maintain the machine time.
Reference1) Y. Yano, Proc. PAC07, TUYKI02, 700 (2007).
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