DESIGN AND STATUS OF THE SUPERKEKB ACCELERATOR CONTROLNETWORK SYSTEM
M. Iwasaki#, K. Furukawa, H. Kaji, K. Mikawa, T. T. Nakamura, T. Obina, M. Satoh, KEK, Ibaraki,JapanT. Aoyama, M. Fujita, S. Kusano, T. Nakamura, N. Tanaka, K. Yoshii, Mitsubishi Electric System& Service Co. Ltd, Japan
Abstract
We have upgraded the accelerator control network
system for SuperKEKB, the next generation B-factory
experiment in Japan. The designed network system has
the higher performance based on the wider bandwidth
data transfer, and more reliable and redundantconfiguration. For the SuperKEKB beamline construction
and accelerator components maintenance, we haveinstalled the new wireless network system consists withthe Leaky Coaxial (LCX) cable antennas and collinearantennas into the 3 km circumference accelerator tunnel.
In this paper, we describe the design and current status of
the SuperKEKB accelerator control network system.

DESIGN OF THE SUPERKEKB CONTROLNETWORK SYSTEM
Fig. 1 shows the schematic view of the SuperKEKB
accelerator main ring. The accelerator control networksystem employs a star network topology. The mainnetwork switch (core switch) is located at the SuerKEKB
control room. All network switches (edge switches)
located at 26 sub control rooms along the SuperKEKB
main ring, the SuperKEKB injector linac (Linac), and AR,
are connected to the core switch in the SuperKEKB
control room with optical cables.

INTRODUCTION
SuperKEKB, the upgrade of the KEKB asymmetricenergy electron-positron collider for the next generation
B-factory experiment in Japan, was approved and iscurrently under construction [1]. The designed luminosity
is 8×1035 cm-2s-1, 40 times higher than the world highest
luminosity record at KEKB. For SuperKEKB, we haveupgraded the accelerator control network system.
For SuperKEKB, the accelerator control network
system with the higher performance of the wider
bandwidth data transfer, and more reliable and redundantnetwork configuration is required, to ensure the robust
network under the 40 times higher luminosity operations.
We have designed the SuperKEKB control network basedon the 10 gigabit Ethernet (10GbE) for the wider
bandwidth data transfer. Optical cable installation is also
on going to construct the redundant network.
We reconfigure the network design to connect theSuperKEKB accelerator control network and the KEK
network. It enhances the security of the accelerator
control network.
It is also important to provide the convenient network
environment for the efficient accelerator construction andmaintenance of it. We install the new wireless network
system based on the Leaky Coaxial (LCX) cable antennas
and collinear antennas into the SuperKEKB 3 km
circumference beamline tunnel.
This paper describes the design and status of theSuperKEKB accelerator control network system.

___________________________________________#masako.iwasaki@kek.jp

Figure 1: Schematic view of the SuperKEKB accelerator
main ring. Red star indicates the SuperKEKB controlroom. Blue circles are the sub control rooms, locatedalong the SuperKEKB main ring, Linac and AR
In KEKB, the network bandwidth of the edge switchesat the sub control rooms were 100MbE or 1GbE. For
historical reasons, there exist several 10MbE media

convertors in the network line. Fig.2 shows the network
connection between the KEKB control room and D1 andD2 sub control rooms, as an example. The 10MbE media
convertor restricted the network bandwidth up to 10 MbE.

Figure 2: Network connections from KEKB control roomto D1 and D2 sub-control rooms at KEKB. Yellow solid,
blue dots, and black solid lines indicate the connection
with a single-mode optical cable, a multi-mode opticalcable, and a LAN cable, respectively.
For SuperKEKB, we’re going to install the edge
switches having both 1GbE and 10GbE connections into
the all sub-control rooms along the SuperKEKB main
ring and Linac. We have installed the single-mode opticalcables to assure the 10GbE data transfer. As shown in theFig.2, in the KEKB case, the KEKB control network andthe Belle detector DAQ network at Tsukuba experimentalbuilding was not connected directly. For SuperKEKB,
we’ll install the 10GbE edge switches at Tsukuba B3 andB4 floors, and install the single mode optical cables toTsukuba so that the SuperKEKB accelerator control
network can be directly connected with the BelleII
detector DAQ system located at B3, the SuperKEKB
Superconducting final focusing Q-magnet system (QCS),
the beam position monitors (BPM) for the interaction
regions, and the cryogenic system for detector solenoid
and QCS located at B4.
The SuperKEKB control network system is designed tohave the redundant structure, where all edge switches areconnected to the core switch via both 10GbE and 1GbElines, employing the active-standby configuration. Herethe 1GbE line will be active if the 10GbE one loses link.
The 10GbE edge switch installations and the opticalcable laying to Tsukuba will be completed within this JFY.

In SuperKEKB, the number of the controlled devices,which have the Ethernet interface to connect with theIOCs, increases, and these devices also receive the UDP
broadcasts in the accelerator control network. Several
devices cannot properly operate under the high rate UDP
broadcast environment.
To prevent such UDP broadcast effects to theaccelerator components, we apply the VLAN-based
network segmentation to the SuperKEKB control network.
Here IOCs and the accelerator components with Ethernet
interfaces are in the different VLANs. The core switch of
the SuperKEKB control network takes care of the routing
task among the VLANs.
We have tested the VLAN segmentation, and confirm
that the device with an Ethernet interface in the different
VLAN operates properly in the new segmented VLAN
configuration.

Network reconfiguration to connect with theKEK network
We reconfigure the network design, on the connection
between the SuperKEKB accelerator control network andthe KEK network. The new network design enhances thereliability and security of the SuperKEKB accelerator
control network.
In KEKB, there were many computers, including theSAD computers, the accelerator control computers, andconsoles, connecting to both KEK and KEKBaccelerator-control networks. Here the account system for
SAD computers and the KEKB accelerator control
computers were common, and all SAD account folders
including the non-collaborators of KEKB could access toVLAN segmentation for the SuperKEKB control
NetworkIn the KEKB operations, we used EPICS [2] as themain software to control the accelerator components.
Based on the experience of the KEKB operations, wehave continued to employ the EPICS software tools tocontrol the SuperKEKB accelerator. In EPICS, the UDP
broadcast is used to communicate between Operator
Interfaces (OPIs) and Input/Output Controllers (IOCs).
Therefore, there are many UDP broadcast packets in theaccelerator control network.

Figure 3: New configuration for the SuperKEKB
accelerator control network and the KEK network
connection.

the KEKB control network.
For SuperKEKB, we have changed the network
configurations as shown in Fig.3. Here all computers inthe accelerator control network do not connect to theKEK network. We also change the account system, andthe only SuperKEKB collaborators logged into thecomputers in the accelerator control network. Thissummer, we changed and applied the new network
configuration.

INSTALLATION OF THE WIRESS LANSYSTEM INTO THE ACCELERATOR
It is important to provide the convenient network
environment for the efficient accelerator components
construction and maintenance of them. We install thenew wireless network system based on the Leaky Coaxial(LCX) cable antennas and collinear antennas into theSuperKEKB accelerator tunnel.
As we described in the previous section, there are many
UDP broadcast packets in the SuperKEKB accelerator
control network. To chose the access point which can be

operate under our network environment, the network
speed was measured using the installed test 200m-length
20D-type LCX antenna, with the electric characters of acoupling loss of 70dB and a transmission loss of7(dB/100m), in the SuperKEKB tunnel.
Figs 4 and 5 show the results of the network speedmeasurements in the SuperKEKB tunnel, for the accesspoint A and B, respectively. As shown in the Fig. 4, thenetwork speed in the SuperKEKB control network (greenlines) is 10-30 kbps for the access point A. While, in theFig. 5, there is little difference of the network speed
between with (purple lines) and without (red lines)
connecting to the SuperKEKB control network for theaccess point B. We then select the access point B for ourwireless LAN system. In the area of >150m from theaccess point, the network speed degradation is observed.
Then we design the length of the LCX antenna to 125m
for our system. We also optimized the electric charactersof the LCX antenna.
Fig.6 shows the layout of the wireless LANcomponents, access points, LCX antennas and collinear
antennas. The figure is for the 1/4 of the SuperEKKB
main ring. The 16 125m-length 20D-type LCX antennas,
2000m length in total, are installed into the 4 arc sections,and 16 collinear antennas are installed into the 4 linear
sections covering 1000m length area.

Figure 4: Measured network speed for access point A
using a LCX antenna, with (green) or without (blue)
connecting to the accelerator control network.

Figure 6: Layout of the wireless LAN components in theSuperKEKB tunnel. Blue lines, yellow circles, green
squares indicate the LCX antennas, access points for
LCX, and collinear antennas, respectively. The figure isfor the 1/4 of the SuperKEKB main ring.

Figure 5: Measured network speed for access point B
using a LCX antenna, with (purple) or without (red)connecting to the accelerator control network.

The installed 20D LCX has the electric characters of acoupling loss of 65dB and a transmission loss of9(dB/100m). The gain of the collinear antenna is 6dBi.
There are little power supplies in the arc sections. Thenpower supply for the access points at the middle of the arcsections is provided from the PoE modems at power
equipment buildings.
For SuperKEKB, we have selected the LCX andcollinear antennas which have good radiation hardness ofmore than 1MGy. Figs 7 and 8 show the installed LCX
antenna and collinear antenna into the SuperKEKB arc
section and the straight section, respectively. As shown inthe figures, all access points, as well as PoE modems forpower supply in the accelerator tunnel are installed within
the lead boxes. All connector connections are wrappedwith lead sheets and fixed with cable ties made with
polyetheretherketone (PEEK).

After the installation, we tested the wireless LAN
system. Fig. 9 shows the measured effective transmission
rate for LCX antennas in the arc section between Tsukubaand Oho. We obtain the good performance of about
18Mbps effective transmission rate in the SuperKEKB
tunnel. In the figure, the performance degradation isfound around Tsukuba area. It is due to the interference
from the other wireless networks.

Figure 9: Effective transmission rate for LCX antennas inMbps measured in the arc section between Tsukuba andOho. Performance degradation around Tsukuba area isdue to the interference from the other wireless networks.
Figure 7: An access point and a 125m length LCX
antenna installed at the SuperKEKB arc section. The
access point is located in a lead box.

In addition to the 32 access points installed in theSuperKEKB main ring, we also install the access points
into AR, Linac, SuperKEKB sub control rooms, andpower equipment rooms at the power equipment buildings.
Total 70 new access points are controlled by an accesspoint controller.

SUMMARY
We have upgraded the accelerator control network
system for SuperKEKB. The designed network system
has the higher performance based on the wider bandwidth
data transfer, and more redundant configurations. Wechange the network configuration on the connection of
the KEKB network to enhance the security.
For the SuperKEKB beamline construction andaccelerator components maintenance, we have installed
the new wireless network system consists with the LCX
antennas and collinear antennas into the 3 km
circumference accelerator tunnel. The wireless LAN
system has the sufficient effective transmission rate over
the whole accelerator area.

REFERENCES

Figure 8: An access point and a collinear antenna installedat the SuperKEKB straight section. The access point islocated in a lead box.

[1] SuperKEKB Task Force, Letter of Intent for KEK
Super B Factory, KEK-REPROT-2004-4, Jun. 2004.
Belle II Collaboration, KEK-REPORT-2010-1, Nov.
2010.
[2] EPICS, http://www.aps.anl.gov/epics/