Ⅱ-8. Accelerator

RIKEN Accel. Prog. Rep. 51 (2018)

Renewal of control system and driving mechanism of cavity tuning
devices for RILAC Rebuncher
K. Yamada,∗1 T. Ohki,∗2 K. Oyamada,∗2 K. Suda,∗1 and N. Sakamoto∗1
The RIKEN Linear Accelerator (RILAC) is used
as an injector to the RIBF accelerator complex forheavy-ions up to krypton. For example, 48 Ca beamis accelerated by a cascade of the RILAC, RIKEN
Ring Cyclotron (RRC), Intermediate-stage Ring Cyclotron (IRC), and Superconducting Ring Cyclotron(SRC). The rebuncher called X5-REB and located at
the beam transport line from the RILAC to the RRC
is required for this operation to adjust the longitudinal bunch length because of the long distance of thebeam transport line.1) The rebuncher system was built
approximately 30 years ago2,3) and showed problems
such as low stability of rf voltage and phase becauseof old low-level (LL) circuits; less reproducibility ofthe driving mechanism for frequency tuning devices;
and insuﬃcient usability of local and remote control.
Therefore, the control system as well as the driving
mechanism of cavity tuning devices were upgraded toovercome these problems.
We replaced the old control system with a new system using a programmable logic controller (PLC), as
shown in Fig. 1. The right side is a controller cabinet
including the PLC, and the other side comprises the LL
circuits and a transistor wide-band ampliﬁer (WBA).
The LL circuits were newly fabricated with rf voltage
stability of ±0.1% and phase stability of ±0.1◦ . Thesecircuits are compatible with the standard LL circuitsof the RIBF. The frequency of the LL circuits ranges
are from 36 to 76.4 MHz. The WBA was not new butunused with a maximum output power of 500 W andfrequency range of 34–90 MHz. The local operation
was performed using a graphical touch panel similar to
those used in other rf devices of the RIBF. The remote
operation was integrated into the operation terminal of
the RILAC2 by using SCADA software of Wanderware
InTouch.
A cavity of the X5-REB has ﬁve driving devices:
two side tuners (L and R) for the coarse tuning of resonant frequency, a shorting plate for the coarse tuningof resonant frequency, a trimmer for the ﬁne tuning offrequency, and an rf power coupler. The old driving
mechanism, except for the shorting plate, used a linear actuator with a rack and pinion-geared reversible
motor, the amount of rotation and driving speed ofwhich were impossible to control. In addition, the actuator had a large backlash. Thus, we modiﬁed thefour sets of driving mechanism excluding the shorting plate to use as a stepping motor and a trapezoidal
screw. The reversible motor of the shorting plate was∗1∗2

RIKEN Nishina Center
SHI Accelerator Service Ltd.

- 136 -replaced with a new one because of deterioration. Figure 2 shows the cavity and the part of driving devicesof the X5-REB after the modiﬁcation. Tuner L andpower coupler cannot be seen in the ﬁgure.
Owing to these modiﬁcations, the stability of therf voltage and phase, the reproducibility of position
for each tuning device and the usability were greatlyimproved; this contributed to the stabilization of beamduring the RIBF experiment.

Fig. 1. New control system after the upgrade. Motordrivers are mounted on the backside of the PLC.

Fig. 2. Cavity and frequency tuning devices of the X5-REB
after the modification.

References
1) A. Goto et al., RIKEN Accel. Prog. Rep. 18, 184 (1984).
2) A. Goto et al., RIKEN Accel. Prog. Rep. 19, 184 (1985).
3) A. Goto et al., RIKEN Accel. Prog. Rep. 20, 176 (1986).