CONTROL SYSTEM STATUS OF SuperKEKB INJECTOR LINAC
M. Satoh#, I. Satake, H. Sugimura, Y. Seimiya, F. Miyahara, T. Natsui, Y. Enomoto, T. Suwada,K. Furukawa, KEK/ SOKENDAI, Tsukuba, Japan
Y. Mizukawa, K. Hisazumi, T. Kudou, S. Ushimoto, Y. Kuroda, S. Kusano, Mitsubishi Electric
System & Service Co., Ltd, Tsukuba, Japan
H. Saotome, T. Ohfusa, M. Takagi, Kanto Information Service, Accelerator Group, Tsuchiura,Japan
Abstract
The SuperKEKB injector linac provides the electronand positron beams of different properties for the fourindependent storage rings. The required beam energy isfrom 2.5 GeV to 7 GeV, and the amount of bunch charge
is from 0.3 nC to 10 nC. Especially, the injection beam toSuperKEKB electron and positron storage rings require
the low emittance and high intensity beams for the nanobeam scheme operation for aiming at the luminosity of8x1035 cm-2 s-1, 40 times higher than the luminosity recordof previous KEKB project. The Phase I beamcommissioning of SuperKEKB has been alreadyconducted from February to June in 2016. The injector
linac has successfully delivered the electron and positron
beams to the SuperKEKB main rings. The linac beamstudies and subsystem developments have also been
intensively going on together with the daily normal beam
injection to both rings of the SuperKEKB and two lightsources.
Towards Phase II and III beam commissioning ofSuperKEKB, the key issues are the fine beam control forthe low emittance beam transport, the high intensity
positron generation with the flux concentrator, the pulsed
quadrupole and steering magnets for the four ring
simultaneous top up injection, and the low emittancephoto cathode rf gun. For the stable beam operation with
the newly developed accelerator subsystems, the robust
control system is strongly required. In this paper, we
report the control system status of SuperKEKB injector
linac.

INTRODUCTION
The SuperKEKB injector linac is a linear electron
positron accelerator with the total length of about 600m [1]. Figure 1 shows the schematic layout of injector
linac. Two straight sections of 120 m long and 500 mlong are connected with the 180 degree bending
section. The both electron sources of thermionic andphoto cathode rf gun are situated at the most upstream
end. The thermionic electron gun is utilized for the lightsource injection with bunch charge of about 0.3 nC andthe primary electron of positron generation with bunchcharge of 10 nC. The photo cathode rf gun is required forthe low emittance electron beam injection to theSuperKEKB electron high energy ring (HER). Eventually,___________________________________________#masanori.satoh@kek.jp

the electron beam with the vertical normalized emittanceof less than 20 mm·mrad is required for getting the highpeak luminosity in Belle II physics experiment. The low
emittance electron beam transport without damping ringis one of key issues of injector linac operation. Both ofthe fine component alignment and the beam orbit
manipulation are crucial issues for the success ofSuperKEKB project. The beam studies related to theseissues are now on going. The main parameters requiredfor SuperKEKB operation are summarized in Table 1
together with ones for the former KEKB project [2, 3, 4,5].

Figure 1: Schematic layout of the SuperKEKB injector
linac. It comprises two strait sections of 120 m and 500m long. They are connected 180 degree bending
section. The both electron sources of thermionic andphoto cathode rf gun are situated at the most upstream
end of the injector linac.

PREVIOUS CONTROL SYSTEMAt the beginning of KEKB project, the injector linac
control system was based on the library softwaredeveloped in house. They have been implemented by C
language and conducted on the Tru64 UNIX server
computers. As the data storage system, the RAID system
has been used, and it was connected to the server
computer of HP DS20 alpha server via SCSI interface.
The operator interfaces (OPIs) were designed by theTcl/Tk scripting language and displayed on the X
terminals, Macintosh, and Windows PC via X serversoftware. For the local controllers of magnet, vacuum,and safety systems, the programmable logic controller(PLC) were utilized since its robustness are suitable forthe stable accelerator control. For the beam monitor ofbeam position monitor and profile monitor, the VME bus
based system were in operation. The timing delay
modules have been also developed as the VME bus
module board.

Table 1: Main Parameters of KEKB and SuperKEKB Injector Linac.
KEKB***ProjectSuperKEKB***

SuperKEKB****

SuperKEKB****(Phase I)(Phase II)(Phase III)

Beame-e+e-e+e-e+e-e+

Beam energy (GeV)

83.5

74

7474Stored current (A)

1.1

1.6

1

1-

-

2.6

3.6

Beam lifetime(min.)

200

150

100

100-

-

66

Bunch charge (nC)

11 (10*)10.4 (8*)

10.5(10*)44 (10*)

1200

150

40

20

15

1000

150

200

40

100

Normalized verticalemittance(mmmrad)

300
130**
310

1400

Normalized
horizontal emittance(mmmrad)

160
200**

Energy spread (%)

0.125

0.1250.5

0.5

0.1

0.16

0.07

0.16

Bunch length (mm)

1.3

2.6

1.3

2.6

1.3

0.7

1.3

0.7

# of bunch

222Maximum beamrepetition (Hz)50

2525 / 50

Top up injection

3 rings (HER,LER*****, PF)n/a

5 rings (HER, LER*****, DR, PF, PFAR)*: Primary electron beam for positron production.
**: Results with the photocathode rf electron gun.
***: Achieved values.
****: Design values.
*****: Low energy ring of KEKB and SuperKEKB.

The server computers, OPI, and local controllers wereconnected via Ethernet up to 100 Mbps data transfer
speed. For the high availability operation, we adopted theredundant network connection between the core and edge
network switches. Moreover, the core switch systemitself is also the redundant system since it is one of thekey component of the injector linac control system.

PRESENT CONTROL SYSTEMEPICS based Control System Software
In the middle stage of KEB project, the injector linaccontrol framework has been gradually migrated from thesystem developed in house to the experimental physics
and industrial control system (EPICS) based one [6]. TheKEKB and PF-AR ring control systems have been alreadydeveloped with the EPICS environment from thebeginning of the operation. Later, the PF ring control
system was also replaced by the EPICS based one. The
EPICS framework can provide the large number of driver
software, archiver tool, alarm software, and so on. It candrastically accelerate the development cycle of control

and commissioning software. In addition, it can also
provide the good affinity between the ring and injector
control system. Since we can conduct the quick and easy
data analysis to find some correlation between the ringand injector related parameters, it can eventually bring theTable 2: Number of EPICS IOCs for eachsubsystem.
Group# of IOCs
Safety2Monitor48

RF57

RF monitor

41

Magnet19

Vacuum1

Timing52

Utility2

Operation

3Table 3: Number of EPICS PVs registered to thechannel and CSS archivers.
Group# of IOCs
Beammonitor

29803

Injector

787

Timing8268

RF2206

RF monitor

9991

Magnet17204

Vacuum499

Operation

8977

Safetysystem940

Utility

324

Table 4: Number of local controllers for eachsubsystem.
Accelerator component#ofControll
type (# of accelerator
controler typecomponents)
lers
VME
64x

Event timing generator
Event timing receiverBPM (94)

450
94

PLC

DC magnet (363)
Vacuum (333)
Klystron (5)Profile monitor (116)

59
26
539

TDC (40)
Charge integrationinterlock (5)40
3Network
attached
power
supplyDC magnet (105)105

Embedded Linux

Klystron (66)66

Datalogger

Temperature and humidity
(720)

26

PXI
express

Pulsed magnet (74)Event timing receiver forpulsed magnet (13)1313concentrator and pulsed magnet. It is also effective for therapid OPI development.
Figure 2: Screen shot example of EPICS IOC runninginside of vncserver.
operators some useful information to fix the problem andimprove the beam quality. The beginning of migration in
the linac control system, the wrapper software for theexisting control software to EPICS has been developed
and deployed. After then, the whole system was migrated
to the pure EPICS control system. Table 2 and 3 show thenumber of EPICS IOCs and PVs registered to archiver,respectively. The total number of archived parameter isaround 70000, and the large parts of them are the beam
monitor and magnet parameters. The both of channel andCSS archiver systems record the large number of linac
parameters. As show in Fig. 2, the large parts of EPCIS
IOCs are conducted in the vncservers which are runningon two Linux virtual machines provided by the VMware
vSphere. Almost all OPIs are migrated from the Tcl/tk
based ones to the Python scripting language ones.
Recently, NI LabVIEW programming environment is alsoutilized to develop the control software for the flux

Control System Hardware
The previous server computers were replaced by thenew Linux based blade type server machines. The newservers are four ProLiant BL460c cards based on thec7000 enclosure. The utilization of blade type server
computers helps to increase the operational reliability
since the enclosure has the five power supply modules
and ten cooling fan units to make sure the redundancy.
The Linux distribution used in the injector linac is mainly
CentOS 6.8 x86_64 for the control system software. In
addition, the Linux CentOS 7.3 x86_64 is utilized for thebackend utility software like the LDAP, Web, andPostgreSQL services.
For the injector linac control network environment, thecore redundant network switch of Cisco C4506 wasreplaced by the Cisco C3750-X. Around fifteen edge
switches situated in the klystron gallery were migrated
from Cisco C2950 to C2960-S. The fiber link between thecore and each edge switch is also redundant connection
for the high operational availability. The replacement inthis time, the network speed is improved from 100 Mbps
to 1 Gbps. However, some local devices are still operated

via the 10 Mbps ethernet speed. In the future, they will bereplaced by the new high speed one since the such slow
speed network device has the low vulnerability to thelarge number of network packets. The core switch can be
upgraded to the 10 Gbps network transfer by replacing thetransceiver modules.
Table 4 shows the number of local controllers for eachsubsystem. The device types used as the local controllers
are mostly VME 64x and PLC based ones. It is a similar
situation with the former injector linac control system.
Recently, the PXI bus based system is also included forthe pulsed quadrupole and steering magnets controlsystems. In addition, the event receiver cards based on thePXI bus are also implemented for the pulsed magnet
timing system. Through the development of pulsed
magnet control system, we can get the much expertise
about the PXI bus system, and it is applicable to thefuture control system development or improvement.

SUMMARY AND FUTURE PLAN
The control system status of SuperKEKB injector linac
is summarized together with the former control systemoutline. Towards SuperKEKB Phase II and III
commissioning, the more advanced beam control software
will be developed to aim at the general search engine forfinding the optimized linac parameters by using themachine learning scheme. These machine study results
will be presented elsewhere in the near future.

ACKNOWLEDGEMENT
The authors thank to Jukka Pietarinen of MRF for thediscussion of event system. We also gratefully thank to Dr.
Brands Helge of PSI for giving us the Windows device
driver of cPCI based event system. It strongly helps ourdevelopment of the pulsed magnet timing control system.

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[3] M. Akemoto et al., “The KEKB injector linac”, Prog.
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[4] A. Akiyama et al., “Accelerator control system at
KEKB and the linac”, Prog. Theor. Exp. Phys. 2013,03A008.
[5] T. Abe et al., “Commissioning of KEKB”, Prog.
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[6] http://www.aps.anl.gov/epics/.