Proceedings of the Second Asian Particle Accelerator Conference, Beijing, China, 2001

GROWTH OF CONTROL TRANSACTIONS OF THE KEK LINAC
DURING THE KEKB COMMISSIONING
N. Kamikubota∗ , K. Furukawa, T. Suwada and T. UranoHigh Energy Accelerator Research Organization (KEK)
1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan
Abstract

A simplified view of the control system is shown in Fig. 1.
The numbers of important control devices are summarizedin Table 1.

The number of control transactions handled by an accelerator control system and the load of control computers arefundamental parameters for long-term maintenance of thecontrol system. This article gives detailed information onsuch parameters of the KEK electron/positron linac. In addition, the growth of transactions and loads in recent years
is discussed with respect to the KEKB commissioning activities.

t::

1 INTRODUCTION
How many control transactions are handled by an accelerator control system ? How much computer load exist during accelerator operation ? Their amount and their changes
over several years are fundamental parameters for longterm maintenance of the control system.
In this article, we discuss the control transactions of theKEK electron/positron linac in recent years. As a partof the KEKB project during 1994-1998, the KEK electron/positron linac has been upgraded to provide singlebunch beams of 3.5-GeV positrons and 8-GeV electrons directly to the KEKB rings. It is worth noting that the period
covered by this report completely overlaps the period of theKEKB accelerator commissioning. The observed control
transactions and network traffic in recent years are given
in Section 2. The growth of the control transactions dueto the KEKB commissioning activities and the extensionof the control system to follow the growth are discussed inSection 3.

2))

Figure 1: Simplified view of the control system.
As shown in Fig. 1, all of the control transactions (monitor and/or control) from the application layer are managed
by device servers, i.e. no direct access from the application layer to the local-control layer is allowed. Thus, thenumber of transactions of each device can be deduced byanalyzing the access log-files of the device servers.

TRANSACTION STATISTICS

2.1 Control System Overview

Table 1: Devices at the KEK linac

The KEK linac has provided electron/positron beams to therings: a) 3.5-GeV positrons to the KEKB LER (KEK Bfactory Low-energy ring), b) 8-GeV electrons to the KEKBHER (High-energy ring), c) 2.5-GeV electrons to the PFring, and d) 2.5-GeV electrons to the PF-AR ring. The
present control system has been used since 1993 [1, 2].
The base of the control system comprises UNIX workstations, VME computers with the OS-9 operating system,
PLC (Programmable logic controller) controllers, and CAMAC interfaces with direct network ports. The home-made
RPC (remote procedure call), based on the TCP and/or
UDP protocols, are used for communication between them.
∗ E-mail: norihiko.kamikubota@kek.jp

109

Devicebeam-position
monitor (BPM)
klystron

total number
89

Front-end
19 x VME

69

69 x PLC

magnetpower-supplyvacuum(ion pump)
trigger-delay(timing signal)499

45 x PLC

284

17 x PLC

141

5 x VME11 x CAMAC

Proceedings of the Second Asian Particle Accelerator Conference, Beijing, China, 2001

2.2 Transactions in June 2001

from a change of the vacuum application. This application
sends vacuum data to 69 klystron controllers (PLC) at 2
second intervals. In the summer of 2000, the application
moved to a PC Linux in the local-control layer (see Fig. 1)
in order not to access the vacuum server, but to use local
cached data at the PC.

The total control transactions in June of 2001 were studied1 , and are given in Table 2. In 1999, we developed onmemory cache areas for the BPM, klystron, and vacuum(see Section 3). From that time on, read-only applications
use cached data, rather than accessing the device server.
The amounts of cache accesses are also shown in Table 22 .

Table 3: Total transactions in 1998-2001

Table 2: Transactions in June 2001
DeviceTotal[transactions/s](Cache)beam-position
monitor(BPM)
klystron

299 tr./s(257)27 tr./s(25)magnetpower-supply

23 tr./s(none)

vacuum(ion pump)

2.1 tr./s(2.1)

trigger-delay(timing)

1.6 tr./s(none)

Serverplum
lychee
grape
36
60
0.007
0.4
0.4
1010
3
0.0004
00
0.3
0.9
0.4

Device[transactions/s]
beam-position
monitorklystron

Client
KEKB-ring
Windows34
none

magnetpower-supply
vacuum2.5
0.1

trigger-delay
30.006

total
Jun.9832
tr./s5.3tr./s
63tr./snodata
0.028
tr./s

total
Jun.99158

total
Jun.00252

total
Jun.01
299

4.6

1827

70

24

23

nodata
0.035

45
tr./s
0.035

2.1
1.6

2.4 Network Capacity00

The network system for our control system, as shown inFig. 2, consists of the main backbone (FDDI, 100Mbps)
and about 50 local segments (10Mbps). Each segment islinked to the backbone; however, it is isolated from unnecessary network traffic by using switching-hubs.

0.004
0100 M bps

Actually, there are three server workstations (with nodenames plum, lychee, and grape). The plum has been usedas the primary server for miscellaneous transactions, while
the lychee has been dedicated to slow-feedback applications [3, 4]. The grape, the oldest workstation, (purchasedin 1993) has been used for transactions from the Windowsbased console system [5] and other supplementary controls.
The transactions for each workstation are separately given
in Table 2. In addition, the transaction requests from theKEKB-ring control and from the Windows-based consolesystem are also given in Table 2.

100 M bps
10 M bps

10 M bps

10 M bps

2.3 Changes of Transactions in 1998-2001
An analysis of the control transactions have been carriedout since 1998. Table 3 gives the control transactions from1998 to 2001.
A considerable growth of the BPM transaction is discussed in Section 3. A clear decrease in the magnet powersupply between 1999 and 2000 corresponds to an improvement of the surveillance program during the summer of1999. The monitoring method was changed from one-byone polling to event-driven base. Another obvious decreasein the vacuum transactions between 2000 and 2001 came

Figure 2: Network segments for the linac control.
In order to study the capacity of the control network, thenetwork traffic of typical local segments was measured inOctober, 1998. The results are given in Table 4. The observed network traffic in all four segments are 2–3 orders
smaller than the maximum capacity of the local segment.
The higher traffic observed at the RF-CB came from theklystron waveform monitor, which was occasionally running to observe a troublesome klystron.

1 In fact, the values are averages during June 10–16.
2 In Table 2, the Total counts include the Cache counts.

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Proceedings of the Second Asian Particle Accelerator Conference, Beijing, China, 2001

memory cache areas for BPM and vacuum data in addition to klystron. The total amount of control transaction
becomes 2–3 times larger in the recent 3 years (Table 3),
however, no problem on the CPU availability has occurred.

Table 4: Traffic of typical network segments
networksegment
RF-1A

network traffic
frames/s (Mbps)
29 (0.04)

RF-CB

170 (0.26)

VME-1B35 (0.05)

VME-CA26 (0.04)

3

devices
klystron(1sector 1st-half)
klystron(Csector 2nd-half)
BPM, mag, vac, etc.
(1sector 2nd-half)
BPM, mag, vac, etc.
(Csector 1st-half)

4 CONCLUSION
The number of control transactions at the KEK linac has
been studied. In June, 2001, the number of BPM transactions (klystron, magnet power-supply) was 299 (27, 23)
per second, respectively. The present network system witha FDDI backbone and several local segments has sufficient
capacity. Since 1998, the control transactions, especiallythe BPM transactions, have increased very rapidly, whichhave originated from the KEKB commissioning activities.
This increase caused a crisis of the CPU availability inDecember, 1998. However, by introducing on-memory
cached data on the server workstations, we succeeded tosuppress the total CPU consumption.

DISCUSSION

The KEKB commissioning started at the end of 1997 [8, 9].
The commissioning group includes both the linac and ring
staff members. The commissioning, even for the linac, hasbeen made by using ring-side Unix workstations. It was a
new experience for the linac to accept control transactions
from the KEKB-ring control workstations. Table 5 shows
the 4-year transition of the control transactions from theKEKB-ring workstations.
Various commissioning activities have produced a considerably greater amount of control transactions than before. A noticeable growth is found in the BPM transactions. The BPM has been newly developed in the KEKB
project as a key device for advanced beam studies of thelinac [6, 7]. The observed growth implies that the BPM
system has been successfully used in commissioning studies. It is worth noting that most of the BPM transactions
come from the KEKB-ring workstations.

5The authors acknowledge Prof. A. Enomoto and Prof.
K. Nakahara for kindly supervising our work. We thankthe KEKB commissioning group for various discussions
on the control system. We also thank the linac operatorsfor cooperative work to improve our control system.

6magnetpower-supply

total
Jun.9820 tr./s(57%)
3.5 tr./s(66%)
10 tr./s
(16%)

total
Jun.99134(85%)
1.8(39%)8(11%)

total
Jun.00
174
(69%)
2.5
(14%)
19(79%)REFERENCES[1] N. Kamikubota, K. Furukawa, K. Nakahara and I. Abe, Nucl.
Instr. Meth. A352(1994)131-134[2] N. Kamikubota et al., ”Improvements to Realize a Higher
Reliability of the KEK Linac Control System”, Proc.
ICALEPCS’95, Chicago, Oct.-Nov.1995, p.1052-1055

Table 5: Transactions from the KEKB-ring

Device[transactions/s]
beam-position
monitorklystron

ACKNOWLEDGMENT[3] K. Furukawa et al., ”Energy Feedback Systems at the KEKB
Injector Linac”, Proc. ICALEPCS’99, Trieste, Oct.1999,
p.248-250

total
Jun.0134(11%)2.5( 9%)3(13%)[4] K. Furukawa et al., ”Beam Switching and Beam Feedback
Systems at KEKB Linac”, Proc. LINAC2000, Monterey, CA,Aug.2000, p.633-635[5] N. Kamikubota, ”Introducing PCs to Unix-based Control
Systems”, oral presentation at PCaPAC 2000, Hamburg,Oct.2000, included in the CD-ROM Proceedings[6] T. Suwada, N. Kamikubota, K. Furukawa and H. Kobayashi,”New Data-Acquisition System of Beam-Position and WallCurrent Monitors for the KEKB Injector Linac”, Proc.
APAC98, Tsukuba, Japan, March 1998, p.531-533

In December, 1998, the CPU load of the plum reached100%. This is because many slow-feedback applications
were developed at plum in order to suppress various beam
instabilities. The analysis showed that the klystron server
consumed a very large fraction of the CPU resource. Wethus prepared on-memory cache areas to keep updated
klystron data in order to decrease the total CPU consumption by network communications. In addition, we introduced a new server workstation, lychee, in the summer of1999 to improve total CPU resources.
In the following years, we have proceeded to prepare on-[7] N. Kamikubota et al., ”Data Acquisition of BeamPosition Monitors for the KEKB Injector-Linac”, Proc.
ICALEPCS’99, Trieste, Oct.1999, p.217-219[8] Y. Ogawa and Linac Commissioning Group (LCG), ”Commissioning of the KEKB Linac”, Proc. LINAC98, Chicago,
Aug.1998, p.711-715[9] Y. Ogawa and Linac Commissioning Group (LCG), ”Commissioning Status of the KEKB Linac”, Proc. PAC’99, New
York, Mar.-Apr.1999, p.2984-2986

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