CONTROL SYSTEM BASED ON PCs FOR THE ISIR-FEL AT OSAKAUNIVERSITY
T.Igo, R.Kato, G.Isoyama, Institute of Scientific and Industrial Research, Osaka University,
8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan

Abstract

2

A control system composed only of personal computers(PCs) are being developed for the far-infrared freeelectron laser (FEL) at Institute of Scientific andIndustrial Research (ISIR), Osaka University. The system
is not only simple and flexible but also cost effective. All
the control devices are connected directly to PCs usinginterface boards in them and the PCs are connected withEthernet. The software for control consists of three layers;
the user interface layer, the database layer and the device
control layer. All data for control are transmitted throughdatabases, which are shared by all the PCs using the LAN.
Commercially available software is used for the databases
and the file sharing, so that it is easy to make and maintainthe control software.

1

INTRODUCTION

We have been developing a far-infrared free electron
laser (FEL) using the L-band linac at the ISIR, Osaka
University [1]. The linac and the FEL are operated with amanual control system consisting of helipots and meters.
Since reproducibility of setting values for the accelerator
components is crucial for operation of the FEL, we havestarted developing a computer control system for the FEL
beam line. Figure 1 shows the linac and the FEL system
schematically. The components to be controlled by thenew system are two bending magnets and five quadrupole
magnets in the FEL beam line and all steering magnets
shown in Fig. 1. The basic guidelines for development of
the new control system are as follows:
1. The control system should be simple and flexible.
2. Programming of control software should be easy.
3. Standard development tools for software should beused.
4. The control system should be easy expandable.
Based on these ideas, we are developing a control
system composed of some personal computers (PCs)connected with a small scale local area network (LAN). In
this paper, we will report of the control system and thepresent status of the development.

STRUCTURE OF THE SYSTEM

2.1 Hardware
The hardware structure of the control system is shown
schematically in Figure 2, where QM denotes aquadrupole magnet, BM a bending magnet, and ST asteering magnet.
There are two kinds of PCs in this system; PCs withcontrolled devices and those without them, which are used
for control and operator terminals. The controlled devices
at present are power supplies for bending magnets,
quadrupole magnets, and steering magnets in the FEL
beam line as well as a vacuum gauge. They are directly
connected to interface boards such as analog I/O boards,
digital I/O boards, and GPIB boards, which are inserted
into PCI or ISA buses. The power supplies have analog
input and output terminals for setting and reading theoutput current and are controlled with analog I/O boards.
The polarity of the steering magnets are changed using
relay units connected to a digital I/O board. The analog
output from the vacuum gauge is read using a digital
multimeter connected with GPIB. All the PCs areconnected with Ethernat (100Base-T).

2.2 software
The control software has the layered structure as shownin Figure 3. It is divided into three layers; the userinterface layer, the database layer and the device controllayer. The flow of data in the system is also shown inFigure 3. The databases have all the parameters of thecontrolled devices. Control panel programs in the userinterface layer read the output current data from thedatabases, and write setting values in them. Device
control programs in the device control layer check the
databases, and change the output current of power
supplies if the setting data in the databases are changed.
This software structure has some advantages. First, themaintenance of programs becomes easy. Secondly, The
system is flexible for expansion.

Figure 1. Layout of linac and FEL

Figure 2. Schematic drawing of hardware

The Microsoft file sharing service is used for sharing
database files. Since the databases are shared amongprograms, communication between them is easily madeby writing a few words in a user interface program as‘\\machine\folder\file’. Furthermore we can control
devices under the other computers in the network using a
Web browser [2]. Microsoft Visual Basic is used fordevelopment of these programs, so that we can easily
make control panel programs on Windows and also canuse device drivers for the interface boards provided byvendors.
Figure 3 shows control panels for the FEL. The layout of
FEL beam line is shown on the main window. A device iscontrolled from a corresponding dialog, which can beopened by clicking an open button on the main window.

Figure 3. Schematic diagram of data flow

Figure 4. Control panels for FEL line

3 THE PRESENT STATUS AND FUTURE
PLANS
The user interface programs and the device control
programs have been accomplished. The new control
system with one PC was used for FEL experiments
successfully. However, some problems are found:
1. The access speed to the databases from the userinterface programs is slower than expected.
2. The output currents shown on the control panels
fluctuate.
We plan to improve the control software as follows:
1. The programs will be debugged during FEL
experiments.
2. The software will be improved by operating the FEL
system during experiments.
3. The beam profile monitors in the FEL line will beincorporated in the control system.
4. The database will be expanded for logging data

REFERENCES[1] R. Kato, S. Okuda, Y. Nakajima, G. Kondo, Y. Iwase,
H. Kobayashi, S. Suemine, G. Isoyama, “Oscillation
at wavelengths from 21 to 126 µm on the ISIR FEL
at Osaka University, “Nucl. Instr. And Meth. A407
(1998) 157-160.
[2] R. Kato, T. Igo and G Isoyama, “Control panel madeon Web browser by using ActiveX Data Objects”,ibid.