Control System for the 6T Superconducting Wiggler at NSRL
Shouming Hu, Jiaming Chen, Daxiang Pan, Zhe Wu, Zhan ChenHefei National Synchrotron Radiation Laboratory
University of Science and Technology of China
P.O. Box 6022, Hefei, Anhui 230029, China
Abstract
The control system for the 6T superconducting wiggler
at Hefei National Synchrotron Radiation Laboratory isdescribed. The system comprises a personal computer anda Industrial control PC. A multithread program runningunder Windows and a local embedded real-time
application on the IPC are developed, to provide both theremote and local functions for controlling thesuperconducting wiggler and other related devices.
1 Introduction
The 6T superconducting wiggler provides the required
value of the magnetic field on the beam orbit by using
superconducting coils. It consists of a superconducting
magnet, Nitrogen and Helium system, vacuum system,
power supplies, and a measurement and protection system.
In normal operation, the wiggler system needs a group ofpower supplies, which consists of one main P.S., two
auxiliary P.S., one heat P.S. and four compensation
quadrupole P.S. [1]. These P.S. are cooperated andsynchronized especially during ramping process[2].
Meanwhile the LHi and LN2 system should be monitored,
the temperature and magnetic field should be measured
on-line. The quench protection is incredibly important.
M .P.S. 600A/6V
Local
Control
CentreControl
RS485

centreA.P.S.1 20A/5V
A.P.S.2 20A/5V
H.P.S. 1A/30V
Q.P.S. 120A/5V #1

M .P.S.: Main
Power Supply
A.P.S. : Auxiliary
Power Supply
H.P.S. : Heat
Power Supply
Q . P.S. : Q u a d r u p o l ePower Supply

Q.P.S. 120A/5V #4liquid He , liquid N2
Temp.& Field Measure
ProtectionFig. 1 The block diagram of control system
Consider the remote and local operation, the control
system for the 6T superconducting wiggler is a centralized
distribution system. It comprises two major parts: a remotecontrol computer in the control room, and a local control
IPC in the area near the wiggler. The communication path
between the two parts is through a RS485 field bus.
A multithread program running in Windows and a local
embedded real-time application on the IPC cooperate toprovide the remote and the local functions, which control
and measure the superconducting wiggler and other relateddevices. The block diagram is presented in Fig 1.
2 Remote control
The remote control unit is an operator interface. Itprovides the following functions: Devices status display,
P.S. ON and OFF control, current setting, current monitor,
ramping control, liquid level monitor, field measurement,display and Alarm. Remote control unit gets the control
through the local IPC.
2.1 Hardware
The computer for remote control is a PC, including amouse and a RS485 card installed.
2.2 software
The remote program is a multithread program runningunder Windows. It has a friendly operator interface, and
it is visual programmed, flexible, and easy to use.
The program includes four threads total. The mainthread manages the whole program, accesses andmanipulates the data files. Another thread is the Timing
thread. It sends the request to read the concerned devices
in fixed intervals. When the answers coming from the IPC
reach the computer, the main thread will analyze them andshow coresponding information on screen. Through themain thread, the operator can also send control instructions
to the local IPC if necessary. The other two threads, theinput thread and the output thread, do the fundamental
work for transmitting information through the RS485 serialport.
2.3 Develop environment
There are two versions of remote control program. One
is developed in LabWindows/CVI and another is in Delphi.
They are both running on Windows platform.
2.4 Communication protocol
The communication protocol of the system accords with
the NSRL communication protocol[3]. It is simplified, thelength of the data package is non-fixed.
3 Local control
The local control unit is the kernel of the control system.
It accepts the assignment from control center andimplements concrete operation. Major real-time functionsof the local control unit are: Power Supplies Switch ONand Switch OFF, Current Setting and Checking, Devices
Status Inspecting and Protecting, Temperature andMagnetic Field Measuring, and Synchronize the Operatingof Power Supplies. These functions are thus useful not only
for remote operation, but also for local operation andmaintenance.
3.1 Hardware-10v~+10v+15v

Local control unit includes an IPC based on X86
processor and several function modules. The IPC has agood effect on electric and magnetic shielding, which isparticularly suited to this environment.

R S 485

Nitrogen.
Schematic diagram of the 16 Bits A/D convert is shownin Fig. 6.
from IPC
to power
supplyIP C

16-channel
16 bits A /D

Isolated
C ircuit

9-channel
16 bits D /AIsolated
C ircuit+15v
analog(power supply)-15v

0 ~ +10v

analog(control)m agnetprotector

AmplifierFig. 4 Isolated Circuit 1+15v

24-channel
digitaloutputs

ISO100-15v(to IPC)

24-channel
digitalinputsIR Q

analog(control)High
Resolution
Isolation
Amplifier

HighResolution
IsolationAmplifier
ISO100DCCT+15v

Frompower
supplyanalog(power supply)
-15v

-15v

Fig. 3 Schematic of the Industrial PC
3.1.1 Isolated Circuit
To ensure the precision and safety of the devices frommutual interference, the isolated circuit should be used.
We use high precision isolated circuit ISO100 and AD202.
They are commercial products shown in Fig. 4 and Fig.5.
Circuit 1 is for current setting . Circuit 2 is for monitoringand measuring.

Fig. 5 Isolated Circuit 2Multiplex
In0In13.1.2 16-Channel 16 Bits A/DThe targets of main power supply of the superconducting
wiggler:

In15

Select one
from16-channel
inputsCurrent resolution 1 × 10-4 (100% FSR)
Current stability

1 × 10-4(20% ~ 100% FSR)

It is evident the current measurement must have enoughprecision. We use 16 Bits A/D converter, its resolution is1 × 10-5 .
The voltages come from Isolated Circuit are converted to16 Bits data. These voltages are reference voltages of thecurrent, they are acquired from the DCCT. The 16 Bits
A/D converter is used for monitoring the currents of power
supplies, measuring the temperatures and magnetic fields,
checking the levels of the liquid Helium and liquid

A B C D(select)Fig. 616 bits
Serial A/D
Serial toParallel

to IPC

16 Bits A/D converter

3.1.3 9-channel 16 Bits D/A
The D/A converter acts as an adjustable, high precisionreference voltage source to set the current in power
supplies. There are three D/A boards, each board contains
3 D/A channels. The DC power supplies for the D/A areisolated.

²

3.1.4 24-channel Digital Output Card
There is a relay for each channel, which is used for
isolation and TTL to +15V adaptation.

u

3.1.5 24-channel Digital Input Card
We designed an adapter and comparator circuit for eachchannel to transform various signals into TTL level.
D ata
B u ffe r-10 v — + 10 v
( to i s o l a te d c i rc u it )+5v

G N D -5 v

+15v

G N D -5 v

G N D -15 v

IR Q

D C -D C

D C -D C+5v

Voltage Detector Circuit

A m p li fie r

1 6 b i ts D /A

Wiggler Magnet

D 0-D 15
( fr o m IP C )Communication with the control center.

Fault tolerance:² Use watchdog to reset soft faults, use Flash
Memory instead of using disk to ensure thereliability.
² Add some protection code to avoid error ofoperation to protect the equipment.

+15v

Fig. 8 Protection Circuit

G N D -1 5v

Fig. 7 9-Channel D/A converter
3.1.6 Protection system
The protection system is necessary for safe operation
with the magnet system a wiggler. The main idea of theprotection is to avoid a high voltage if a quench happens. It
consists of a group of Diodes and a precision Voltage
Detector Circuit. In the case of a quench, or other situation,the voltage on a coil exceeds normal, the Voltage Detector
Circuit will generate an interrupt to the local control IPC to
cut off the supply current immediately, so that, quench may
be avoided and the power supply will be protected from thevoltage damage. During the charging or discharging
process, current is not allowed by the protection system[4].
3.2 Software
Local control software must control all devices in highspeed and real-time, we designed the application in
embedded environment, using Microsoft C/C++7.0.
u Main functions of the local application:² Turn on/off all power supplies simultaneously;² Programmed current value setting;² Read actual current value;² Check safety of power supplies;² Monitor the height of LHe. and LN2;² Magnetic temperature and field measurement;² Ramping control;² Protection;

4 Conclusion
The control system for the 6T Wiggler is already being
used in the field. It controls devices correctly in high speed
and real-time. The designed targets of the wiggler isreached and the magnetic field is measured. It is evident
that the system is a successful control system.
In the phase II project of NSRL[5], this system will be
modified to be brought into EPICS.
Acknowledgments
We would like to thank the staffs of wiggler group andother colleagues of NSRL for their commendableassistance.
References
[1]

[2]

[3]

[4]
[5]

N.Liu, Y.Jin, Z.Liu, “The Influence ofSuperconducting Wiggler on HLS Storage Ring”,
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C.Yao et al., “Ramping Magnet P.S. Control forHESYRL Ring”, Proceeding of Conference. on S.R.
Application, 1989.
S.Liu “Software for Local control and Data
Communi-cation.”, Proc. of Conf. on S.R.
Application, 1989.
RRC ‘Kurchatov Institute’ , “ 6T Superconductingwiggler”, Moscow, 1997.
W.M. Li, et al, “Upgrade Plan for the NSRL ControlSystem” , This proceeding.