II-8. Accelerator

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Deployment of a beam interlock system driven by changes in magnet
current (Curs-BIS) at the RI Beam Factory
K. Kumagai∗1 and A. Uchiyama∗1The beam intensity has been gradually increasing at
the RI Beam Factory. To prevent accidents such as
melting of the vacuum chamber due to the beam orbit change, a system to detect the current change ofthe magnets due to unknown causes or noises during
the beam operation and to stop the beam is required.
The beam interlock system driven by changes in magnet current (Curs-BIS) was developed in 2019.1) The
developed system could detect the current values of 24
magnet power supplies per unit, and now it can detect
the current values of 48 power supplies. One unit of
the Curs-BIS is shown in Fig. 1. Various improvements
have been made to the sequence and web-based monitoring programs. The interlock signal is not erroneously
when the power supply is set from 0 A, and the inactivity time of the interlock signal was adjusted according
to the energizing characteristics of each power supply.
It is now possible to directly link the monitoring screen
to a table of power supply speciﬁcations and a graph ofﬂuctuations in the current value of each power supply.
Three units of the system are currently installed in
IRC and SRC, four units in the beam transport line of
the RIBF, eight units in the RARF (the old facility)and fRC, three units in RILAC2 and AVF, three units
in RILAC. The sequence program is the same for allunits, and each unit can be operated independently bysimply changing the parameter ﬁle for magnet power
supply speciﬁcations, upper and lower limits of current
values, etc.
Accelerators have various types and ages of magnet
power supplies, and the current value of the magnet
power supply is detected in three main ways. Powersupplies with a very high current stability, such as cyclotron main power supplies, usually have a DCCT formonitoring in addition to the DCCT for power supply control; therefore, the monitor output is used fordetection. For power supplies that do not have a highprecision DCCT for monitoring, an inexpensive external DCCT is installed to detect the current, although
the output accuracy is poor at ±1% of full scale. For
some power supplies, the signal from the feedback circuit is branched oﬀ and the signal through the isolation
ampliﬁer is detected. The Curs-BIS system is set toemit an interlock when the power supply current value
ﬂuctuates by more than ±1% of the rated current as
the initial value, but it can be changed. For the power
supply for steering magnets, the value is ±5% of therated value.
The system is also used for the early detection of supply current oscillation in scenarios in which the feedback∗1Fig. 1. Picture of a unit of the beam interlock system driven
by changes in the magnet current (Curs-BIS).

control of the power supply is not operating properly.
A beam interlock system for detecting EIC and EDC
discharges was also build using the same method as theCurs-BIS. The EIC and EDC are electric-ﬁeld beam deﬂection channels used for beam injection and extractionof the cyclotron. The beam is deﬂected by applying ahigh voltage of approximately 100 kV to an electrodeplate placed in the beam orbit. Because a high electricﬁeld is applied between the plates of ten and several
millimeters, discharges often occur and the beam orbit
is changed. Therefore, the beam should be stopped assoon as the discharge occurs.
Discharges were detected using only the actual voltage change with an analog type circuit. Now, a system
similar to the Curs-BIS can stop the beam by detecting
the change in the actual voltage and current replenishment due to the discharge. The system was installedin the cyclotrons of the SRC and IRC in parallel usage with the analog circuit. Since the RRC and fRC
cyclotrons did not have a discharge detection system,
this system was newly installed. With the system, theallowable value can be changed on the monitor screen,
which was previously changed on site using the analogcircuit. The system can also stop the beam under a sudden change in the set voltage and maintain a log of thenumber of discharges per hour, which can be monitored
on the Web.
Most of the power supplies in the RIBF are now being monitored using Curs-BIS, but a few 10% of thepower supplies on the RARF remain to be set. We areplanning to increase the number of registered powersupplies.
Reference1) K. Kumagai et al., RIKEN Accel. Prog. Rep. 52, 115(2019).

RIKEN Nishina Center- 64 -1