Ⅱ-8. Accelerator

RIKEN Accel. Prog. Rep. 52 (2019)

Updating control units around the AVF cyclotron
M. Komiyama,∗1 M. Fujimaki,∗1 N. Fukunishi,∗1 R. Koyama,∗2 M. Hamanaka,∗2 H. Mukai,∗3 T. Nakamura,∗2 andA. Uchiyama∗1
We report on the update of the control units aroundthe AVF cyclotron to reduce the diﬃculties caused by radiation and implement a new beam interlock system under construction (hereafter, AVF-BIS). The beam diagnostic equipment like a beam proﬁle monitor or a Faraday cup on the AVF cyclotron and its beam transportline has been controlled by DIM1) since 1989, and theequipment on the beam transport line around RILAC2
has been controlled by N-DIM2) since 2012. They wereinstalled in 19-inch racks (hereafter, rack) at two place:the ﬂoor on which the AVF cyclotron is placed (hereafter, AVF ﬂoor) and the ﬂoor that is one level below(hereafter, AVF-M2 ﬂoor). Recently, as the performanceof the AVF cyclotron has been improved and the beam
intensity accelerated by the AVF cyclotron has been increased, there have been frequent issues such as the control unit becoming unresponsive toward the remote control suddenly. In the most frequent case, it occurred
three times in 4 h while accelerating a 12 MeV/nucleon
deuteron beam with an intensity of 4 pµA at the C03
target. Because this frequently occurs during accelerating a deuteron in the AVF cyclotron, we speculatethat the cause of the trouble is the inﬂuence of radiation, especially the neutrons coming out from theAVF cyclotron and its beam transport line during beamtransport. Therefore, we measured the dose of neutron
around the installation location of the control unit using the TL badge. Figure 1 shows the measurement
locations and results of the two measurements. At theAVF-M2 ﬂoor, several racks are placed along the south
wall for the control unit. Among them, the control unit
where this issue frequently occurs is located at No. 1 inFig. 1. The results clearly show that the neutron doseat this point is higher than other places. This might beoccurring because No. 1 is close to the open hole underthe AVF cyclotron (No. 9). However, it has not been
speciﬁed yet. As the best measure at present, we moved
the control unit to a place where the neutron dose was
low based on the results.
Simultaneously, we updated the control unit from old
DIM to N-DIM. This update was made because the DIM
in use was old and the DIM-based existing beam interlock system for the AVF cyclotron needed to be renewed
along with its low-energy experimental facility to AVFBIS.3) AVF-BIS stops a beam by outputting signals toa beam chopper and Faraday cup for various interlock
signal inputs. In this system, the Faraday cup needs tobe controlled by N-DIM.
The updating work was conducted during the summer
maintenance period in 2018 as follows:∗1∗2∗3RIKEN Nishina Center
SHI Accelerator Service Ltd.
Japan Environment Research CorporationFig. 1. Neutron dose measurement. The AVF-B2 floor is onefloor below the AVF-M2 floor. The data written on theright side shows the average dose (integrated dose).

(1) To move one of the racks from No. 1 to No. 3 withthe N-DIM inside.
(2) To move some N-DIMs mounted on the rack next
to the rack to be relocated to the gap between theexisting racks near No. 3.
(3) To set up some new N-DIMs on the existing racks
near No. 3. Remove the signal and control cablefrom the DIM at No. 3 and AVF ﬂoor, and reconnect them to the newly set up N-DIMs.
Consequently, we moved and set up 28 N-DIMs in total. Currently, they control the beam diagnostic equipment on the beam transport line around RILAC2, andthe beam diagnostic equipment and vacuum system on
the beam transport line downstream of AVF cyclotron.
This indicates that approximately 60% of the DIMs under operation at the AVF and AVF-M2 ﬂoors have been
updated. Because DIM still controls the various equipment attached to the AVF cyclotron and the beam diagnostic equipment of the beam transport line in E7 experimental vault, we are planning to sequentially update
the control to N-DIM.
After the summer maintenance, the occurrence of thisissue in the control unit was reduced to 0% while accelerating the 12 MeV/nucleon deuteron beam with an intensity of 1.5 pµA at the C03 target for more than one
month. Thus, it is evident that this maintenance has
had certain eﬀect.
References1) K. Shimizu et al., Proc. Cyclotrons’84, pp. 392–395.
2) M. Fujimaki et al., RIKEN Accel. Prog. Rep. 37, 279(2004).
3) M. Komiyama et al., Proc. ICALEPCS2017, (2017),
pp. 427–430.

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