Microwave Control and Measurement System at the KEKB Linac
Kazuro Furukawa, Norihiko Kamikubota, Hirofumi Hanaki, Hiroaki Katagiri,
Takao Urano, Shozo Anami and Kazuo NakaharaHigh Energy Accelerator Research Organization (KEK)
Oho 1-1, Tsukuba, Ibaraki, 305, Japan
Abstract
The Microwave System for the KEK electron/positronlinac is being rejuvenated for the KEKB project. Klystrons
are being upgraded and pulse compressors are also being
employed to accelerate electrons up to 8 GeV. Because of
the beam current and emittance requirements in the KEKB
accelerator complex, very stable operation of the microwave
source is indispensable.
Thirty VXI-based microwave-monitoring stations havebeen installed to maintain in a better operation condition.
PLC’s for basic controls are being adopted for new klystron
modulators and sub-boosters. A redundant optical switching
network is employed to accommodate a higher bandwidth
and to eliminate noise from the modulators.
Upper-layer software for device controls is being upgraded to enable transparent access to both old and new controllers. Not only the current values, but also statistical values, such as averages and standard deviations, will be served
for client programs. Advanced application programs, suchas feedback loops, are being developed to accomplish improved operation.
Although the simple RPC protocol is used for linac internal communication, an EPICS CA-server will be also prepared for global operation.
1 Introduction
In the KEKB project the stability of the linac beam is crucial
to achieve a higher experiment efficiency. Each componentof the linac accelerator should be monitored and controlled
to operate robustly.
Especially, the microwave system plays an essential andmost active role in linac-beam acceleration. The microwave
system consists of several sub-systems, and has many control parameters. Some of them are controlled in hardware
feedback loops, and should be routinely monitored. In thispaper, an overview of the KEKB linac controls is given first;
then, the microwave control and measurement system is described.
2 Linac control system and its network
The control system of the linac was rejuvenated in 1994
[1, 2]. In the new control system, international and de facto
standards, such as Unix, VME and TCP/IP, were employed,
while many of the old local device controllers should be continued to be supported. The control software was rewritten

so as to build layered equipment services utilizing a homemade remote procedure call (RPC) scheme.
2.1 Field controls
The computer network for controls comprises a FDDI and
about 50 Ethernet network segments, which are isolated
from the laboratory-wide network by a firewall. Although
the FDDI and Ethernet networks around the main control
room use twisted-pair cables, the connections to local field
controllers are now based on fiber-optic cables (10Base-FL
Ethernet) in order to eliminate noise from the high-power
klystron modulators in pulsed operation. A star-like topology was employed to localize any problems and to easetrouble-shooting.
Currently, the number of 10Base-FL nodes is just above
100, and may soon be doubled if the old controllers are
replaced. They are connected with one of 33 10Base-FL
repeater stations, which are spread along the 600-meterlinac building, and then concentrated into FDDI-10BaseFL
switches at the main control room. Although the 10BaseFL connection between the field controllers and repeater stations are single, those between the repeater stations and thecentral switches are made fault-tolerant by adopting redundant switches and transceivers, since any problem at thislevel is severe.
For local device controllers, no standard was defined.
Once it was considered to have VME computers as standard
device controllers. However, we are using many old controllers which are already over 15 years old, and every year
new technologies are revealed. Thus, from our experience,
it’s not practical to decide on a standard. Actually, it costs
much manpower to maintain a standard for 20 years.
Instead, we defined criteria, which require that each local
device controller should at least speak UDP protocol and be
diskless, if possible. If the controller is intelligent, the UDP
version of our RPC protocol is installed on it. Old controllers
are indirectly connected to the RPC network environment
through VME’s.
2.2 Central-control architecture
Unix computers consist of a computer cluster and isolated
computers, which are also operated to be fault-tolerant. They
are mainly DEC Alpha architectures, and a cluster software
called True Cluster is installed.
They carry most of the upper layer control tasks. Besides
running control-process software, they also support many
network services, such as file services (NFS, NetBIOS, Ap-pleShare), a network firewall, name resolutions (DNS, NIS),
remote booting (BOOTP, DHCP, TFTP), time synchronization (NTP), failure reports (SNMP, SMTP), routine reports(HTTP), printer services (lpd, AppleTalk) and office mail
(SMTP, POP3). Those services are utilized from a numberof control computers.
Control services on Unix computers are designed to beaccelerator-equipment oriented. Upper layer software serves
logical equipment controls hiding physical details. Since
several different controllers were developed over a period of
15 years for a kind of equipment, every effort was made tocarry hardware-dependent processes in the lower layer software. Most lower and upper layers communicate through the
UDP version of the RPC in order to recover failures reliably,
while the TCP version is used between the upper layers andthe application clients.
Each layer uses a simple memory-resident hasheddatabase to process controls. Depending on the responsetime of the underlying layer, a layer may cache information,
while commands to bypass the cache are also provided.

3 Linac upgrade and controls
For the KEKB project, the linac beam energy is being upgraded from 2.5 GeV up to 8 GeV, and 3.5 GeV positrons
are also to be generated [3]. In order to accomplish this, energy doublers (SLED) are employed and the length of linac
is extended by 50 percent; the number of devices is also to
be increased by roughly 50 percent.
Many old controllers for them, which were designed
about 20 years ago, could not be reproduced any more,
mainly because of the production discontinuance of theircomponents and the company closures. New functionalities
are also eagerly required. Thus, new controllers are designed
based on the criteria of a UDP connection and hard-disk-less.
New controllers are designed utilizing VME, VXI, CAMAC, PC and PLC technologies, depending on the needs
specific to the corresponding devices.
Most of newly designed simple controllers employ PLC’s(Programmable Logic Controller). Until recently, its performance and remote connectivity did not meet our requirements. Now, however, it just satisfies our needs for simple
controllers; further, its cost-performance is appealing. For
example, the response time of a remote control of several
input/output ports over a network is about 20 milliseconds.
Although this is 10-times slower than modern VME processors, if large data processing is not necessary, a PLC is adequate for simple controllers [4].
Upper layer software had been designed to be independent of the lower layers. It was, thus, relatively easy to integrate new lower layer software for new controllers. At least
the RPC interfaces between the upper layer software andclients are kept unchanged, although extensions of the protocol is independently planned to accommodate new needs.

Unix Server Computers
Network System (Redundant)
10Base-FL Repeaters / Switches / Router

PLC-based
Controller

VXI-based
Measurement
SystemHigh-Power
Klystron / SLED

PLC-based
Controller

High-Power
Klystron / SLEDFig. 1 New PLC-based controller attached to each of 20 new
high-power microwave sub-systems. Two sub-systems aregrouped and a VXI measurement station is installed. For
40 old sub-systems 20 new measurement stations are also
installed, but old controllers continue to be utilized insteadof PLC’s.
4 RF system upgrade and its controls
In order to accomplish the energy upgrade, the rf system
is being improved in both quality and quantity. The output powers of the high-power klystrons are being raised, and
SLED’s are being attached. Also, the number of high-power
klystrons are being increased from 40 to 60. At the sametime, related sub-systems, such as the low-power rf system,
vacuum system, and trigger system are being improved.
Old controllers for the klystrons [5] are connected with
VME’s through homemade fiber-optic networks. However,
because of the energy upgrade, they have suffered from noise
disturbance, and the failure rate of the communication has
become several percent. Although most of the errors are recovered by lower and upper layer software, clients see theperformance degradation.
The main reason for the noise perturbation seems to be
the absence of a grand plane in the circuit boards. Since they
were produced more than 15 years ago, multi-layer circuitboards were not chosen. It is also known that the noise depends on the operation points of the klystron modulators.
In order to fulfill the requirements from the beam quality for KEKB, extremely stable operation for the rf system
is indispensable. Also, many automatic functions and fastmeasurement capabilities are necessary, although the budget
is very limited.
In consequence, it was decided to install new PLC-based
controllers for new klystron modulators and new VXI-based
measurement stations for all klystron modulators, while
keeping the old controllers for old modulators. Communication between the upper and lower layer software was redesigned to hide the differences between the old and newcontrollers.
5 New controls for RF system
5.1 Basic controls with PLC
As already pointed out, PLC controllers are suitable for simple tasks. The control of a rf system, however, is not a simple
task, and the programming environment of the ladder pro-grams of the PLC’s is not ideal. However, if the fast data acquisition is separated, the hardware becomes relatively simple. Also, a simple architecture is often good for complicated tasks.
PLC is a kind of an industry standard, and robustly designed modules are commercially available. Also, recently
the programming environment and the connectivity to othersystems are much better. PLC-based controllers were, thus,
chosen.
It is required for PLC’s to have (1) a good TCP/UDP implementation on Ethernet, (2) a remote software installation
capability, and (3) a proper user interface for local operators.
To meet (1) and (2), an FA-M3 (Factory ACE) series PLC
of Yokogawa was chosen. Also, for (3) a V4 type panel of
Hakko Electronics was deployed.
The FA-M3 is small sized, and can fit into a space in therack where an old controller resided. Modules for digital
inputs, digital outputs, analog inputs, Ethernet and RS232C
have been installed. They are connected with local switches,indicators, interlock signals, slow analog signals, as well as
sub-controllers of an isolator/phase-shifter/attenuator (IΦA)
and a De-Q’ing trigger through RS232C.
The V4 (V4-t110j) is equipped with a 10.4-inch liquidcrystal display and a touch panel, and is linked with a PLC
through the RS232C. It can be easily configured to display
variables on the PLC in one of many formats. Also, a number of pages can be defined, which can be selected via atouch panel. Even a strip chart of PLC variables can be
drawn without any programs, which is very efficient to monitor the analog values.
An FA-M3 PLC and a V4 panel are programmed visuallyon a personal computer. A program module for the PLC canbe downloaded either via Ethernet remotely or locally via theRS232C. That for the panel can only be downloaded via theRS232C at present. Since it is not convenient to update software at many stations, we are asking the company to develop
firmware to transfer programs over the Ethernet through the
PLC.
The combination of an FA-M3 PLC and a V4 panel became a smart controller. It is three times as cost-effective 1
compared with the former controllers.
5.2 Measurement system with VXIAt the rf system, signal monitoring is also important. Such afunction was designed separately to be implemented on VXI
systems. One VXI system covers two high-power klystrons,and 30 systems will be installed in total to provide measurement facilities.
Several pieces of microwave measurement equipment will
be utilized, although the budget is not enough at the beginning. Before they were installed, it was not possible tomeasure the precise microwave power that is introduced forbeam acceleration. It was calculated by other means, while
those values are very important to transport linac beams.

Each VXI system contains a V743 controller and a waveform digitizer of 1 G sample/s from HP, and other modules,
like a digital I/O module. It also has a GPIB bus to othermeasurement instruments, such as a microwave power meter. Since the processor does not have a hard disk to avoid
problems, it uses an Ethernet connection to the boot servers
as well as control servers.
Its operating system is a HP-UX, which is capable of running the HP’s VEE (Visual Engineering Environment). The
VEE is used to prototype the measurement application programs. Actually, all applications are programmed on the
VEE presently, because its performance satisfies our current
needs. For example, 50 waveforms from the oscilloscope
can be transferred on to an X-terminal display over the network. 2
The programming environment of the VEE is well designed and new functionalities can be added visually. It isvery flexible to link with the existing facilities, such as thelinac control service. Even compared to other visual environments, like Labview, its feature seems to be mature andappropriate for our purposes.
However, this system consumes much network traffic bynature. Thus, the rf systems were moved to a separate subnet. Currently, the network bandwidth is consumed about
20 percent at most on a few segments. Network monitoring
tools survey the network, and no communication degradation has been observed up to now. 3
5.3 Interface to related systems
The rf system depends on other systems, such as the vacuum
and timing systems. Interlock signals from the vacuum system are connected in the hardware. The vacuum-pressure
values are also necessary in order to adjust the operating
point well. Thus, the pressure values are transferred every
second from the upper layer software of the vacuum system
on to PLC controllers. Each panel of a klystron controller
has a logarithmic strip chart which graphs the pressure atthree nearby ion pumps.
The new timing system, installed at the newly extended
part of the linac, consists of CAMAC digital delay modules and time-to-digital converters. The ECC-1365 crate
controllers of Hytec are attached to the UDP network directly. Precise timing information is important, especiallyfor SLED operation, and is transferred to the PLC controllers
through upper layer software of the timing system, including
the information from the old timing systems.
Since the KEKB ring where the linac beams are transported will be controlled by the EPICS system [7], information and control exchange is necessary between the ring andthe linac. For this purpose the EPICS channel access server(CA-server) has been developed [6]. The part for magnet
controls is almost completed, and now the part for klystrons
is under development. Using this link, the EPICS client sees
2 The VXI access is not normal message-based but register-based.

1 It costs about 8,000 dollars including the chassis and cable assemblies.

3 Several free SNMP software tools such as Scotty and MRTG are used on Unix servers.

linac microwave controls as a group of EPICS process variables emulated on the CA-server. For example, a slow, but
global, feedback system will be easily build for beam injection.
New PLC Controllers
Display Panels

VME

VXI Measurement
SystemVEE

Vacuum Control Sub-System
Timing Control Sub-System

Linac
Control
SystemChannel Access Server

Old controllers

Microwave
UpperLayer
Control
Software

Ring
EPICS
Control
SystemOther Control Sub-systems

Fig. 2 Layered microwave control sub-system exchanges
control information with other sub-systems, especially withthe vacuum and timing sub-systems, through linac upperlayer control software. They can be reached from the ring
EPICS control system as well as through the channel accessserver.
6 Applications
Many application programs are planned to be installed, but
not all of them are finished. Here, some of them are described.
In order to condition the klystron, SLED, wave guides andaccelerating structures, an automatic conditioning software
was developed at the central operator’s console system. Thistime, a simplified version of the software was implemented
at each PLC controller, which was found to be efficient. It
seems that operators found it comfortable to manipulate thesystem locally while viewing strip charts and other information.
If a fluctuation is found in the microwave measurements,
it may be due to a system disorder, and must be stabilized so
as not to affect the beams. It often has a connection with the
lifetimes of the microwave components as well. At the PLC
controllers, standard deviations of several analog points arecalculated internally. 4 Although the values are not yet being utilized much, it will soon help to produce stable system
operation.
Although fast measurements are carried on VXI’s, and results are displayed on X-terminals, sometimes it’s useful toview it locally. Thus, waveforms made possible to be transferred from a XVI station to the corresponding PLC panel.
Although the speed is as slow as once a second, it provides
good information for the local operators.
7 Conclusion
The communication to the new controllers is fast and reliable, although we had problems on old ones because of the
4 Modern PLC’s are powerful enough to carry such scientific calculations.

noise caused by the microwave system upgrade.
At the time of this writing, October 1997, about 20 PLC
controllers and 10 VXI systems had been installed, and effectively utilized. Actually, a part of a new linac sectionis under commissioning, and almost every day the software
for the PLC’s, the display panels and the VXI systems arebeing improved. A few klystron systems are used for test
beams, conditioning of the energy doubler cavities is carriedout at other systems, and the remaining systems are underconditioning of klystron themselves. In such multi-operation
modes, the system works without any large problems.
Using a well-designed software development environment, the cycle time of the new software to meet a new requirement is very quick both on the PLC’s and VXI’s. At thesame time, it shows its robust features, and the operators of
rf systems are almost satisfied.
The features available on old controllers are included on
the new one, and also are improved. The upper layer software hide the differences between them. Thus, clients canaccess the equipment transparently. Although new features
implemented on the new controllers should also be implemented on the upper layer to help the old ones, it’s underdevelopment.
Soon, more applications such as the automatic phaseadjustment system (phasing) and feedback system of the microwave power and phase may be implemented with some
improvements of the measurement instruments. This system
is expected to provide a firm and stable operation of the rf
system and the whole KEKB linac.
Acknowledgements
The authors would like to thank the linac staff for theirsupport and valuable discussions. They would also like tothank the ring control group and operators for their help inthe development of the CA-server.
References
[1]
[2]

[3]

[4]
[5]
[6]

[7]

K. Furukawa, N. Kamikubota, K. Nakahara and I. Abe,
Proc. ICALEPCS’91, Tsukuba, Japan, 1991, p. 89.
N. Kamikubota, K. Furukawa, K. Nakahara and I. Abe,
Proc. ICALEPCS’93, Berlin, Nucl. Instr. and Meth.
A352(1994)131.
A. Enomoto, Proc. of the XVIII International Linear
Accelerator Conference (LINAC96), Geneva, Switzerland, 1996, CERN96-07, p. 633.
A. Shirakawa et al., these proceedings.
T. Shidara, et al., Nucl. Instr. and Meth.
A245(1986)500.
K. Furukawa et al., Proc. ICALEPCS’95, Chicago,
1995,
FERMILAB-CONF96/069, p. 863.
Leo R. Dalesio et al., Proc. ICALEPCS’93, Berlin,
Nucl. Instr. and Meth. A 352, 1994, p 179.