Ⅱ-8. Accelerator

RIKEN Accel. Prog. Rep. 51 (2018)

Magnet power supplies for GARIS-II
K. Kumagai,∗1 K. Morimoto,∗1 and D. Kaji∗1∗1

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fRC/BT and GARIS-II magnets.
Table 1. Speciﬁcations of power supplies for GARIS-II magnets.
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The superheavy element production team at RIKEN
Nishina Center is planning to produce the elements withatomic numbers z = 119 and 120. For early implementation of the project, we planned to relocate GARIS-II1)from RILAC to the downstream of RRC. The production of new elements will be accelerated by irradiationin parallel with GARIS-III, which will be newly built
in RILAC in FY2018. The GARIS-II was relocated tothe E6 experimental room. The vanadium beam accelerated by RILAC2 and RRC is guided to GARIS-II after
passing through the RIPS-Q6 magnet.
The magnets of GARIS-II consist of two bending magnets and three quadrupole magnets. Two quadrupolemagnets and a set of steering magnets were placed upstream of GARIS-II magnets for beam transport. Since
the power supplies used in RILAC have been used for
GARIS-III, other power supplies had to be prepared.
Table 1 summarizes the requested speciﬁcations of thepower supply for the GARIS-II magnets and their current and voltage speciﬁcations. The detectors used inGARIS-II are susceptible to noise. When a power supply using thyristors as a pre-regulator was used for exciting a dipole magnet in GARIS-I, which was installedin RILAC, the noise aﬀected the detectors in some cases.
We decided to apply existing power supplies which use
a saturable reactor as a pre-regulator as power supplies for ﬁve GARIS-II magnets. The four power supplies used for the RIKEN Projectile-fragment Separator(RIPS) and a power supply used in the past for the E2
dipole magnet were used. These supplies are alreadyused not only for RIPS magnets but also for the injection/extraction magnet for the fRC cyclotron and amagnet for beam transport to the E5 experimental room.
The connection between the power supply and the magnets for each beam course could be switched using theswitching board placed in the E4 experimental room.
Since the switching board was able to switch only to
two courses (RIPS or fRC/BT), the switching sequencein the board was modiﬁed so that it could be switched tothree courses (RIPS, fRC/BT and GARIS-II). Figure 1
shows the switching sequence of power supplies.
The maximum current of the power supply connected
to GARIS2-D1 is nearly 2 times larger than the allowablecurrent of the magnet. To prevent operational errors,a voltage sensor is planned to be installed in February
2018 on the load terminal to turn oﬀ the power whenthe voltage is higher than the allowable voltage of themagnet. It will be installed.
The power supplies that excite the double quadrupole
magnets and a set of steering magnets placed upstreamof GARIS-II were switched from the triplet quadrupole(QTD17) and a set of steering magnets (STH16) on thebeam transport line to fRC. The switching board was" :; */.+&: ; : ;!!  : ; :; 

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/&$*'*$"3*.-25)&-3)&,"(-&325&1&/+"$&%*-relocated from the E4 experimental room, where it wasused previously, to a place near the beam transport linein the D room.
After the wiring and the protection interlock test,
the current output test for GARIS-II magnets was performed. It is necessary to adjust the power supplies
so that stable current can be fed to both magnets onRIPS, fRC and GARIS-II. Most power supplies could
feed stable current without matching adjustment of thefeedback circuit. For the E2 dipole magnet power supply, the output current was stabilized by replacing the3-terminal regulator that generate voltage of ±15 V DC
for the error ampliﬁer and the capacitors around it in
the feedback loop circuit.
The commissioning of GARIS-II started in December
2017. The power supplies performed satisfactorily. InFY2018, DC current transformers will be installed tomeasure the precise current of power supplies.
Reference1) D. Kaji, K. Morimoto, The Japan Society of Nuclear andRadiochemical Sciences 34, 12–23 (2016).

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