The Application of Personal Computer in Topography Experimental
Station at the BSRF
G. Wang J. Jiang Y. Tian Y. Han Z. Wang
BSRF, Institute of High Energy Physics, Chinese Academy of sciences
P.O. Box 918 (2-7), Beijing 100039, P.R. China
Abstract
The topography experimental station is part of theBeijing synchrotron Radiation Facility (BSRF). Two PCs
are used to build its control and data acquisition system, of
which one is used for beamline and experimental station
on-line control, while the another is used for x-ray
topographic image capture and treatment.
1 Introduction
The x-ray topography station and attached 4W1A
beamline[1] are part of the Beijing Synchrotron Radiation
Facility (BSRF) to employ the synchrotron radiation fromthe Beijing Electron Positron Collider (BEPC). The 4W1A
is a 45m long white/monochromatic wiggler beamline.
When the BEPC is operated at the energy of 2.2 GeV andthe magnetic field of the wiggler at 1.8T, the photon flux at
1.54 Å is 6×1010 photons/s/mA/mrad2/0.1%BW and themaxim beam size at the specimen point is 45(H) ×13(V)mm2. The topography station situated at the end of thebeamline 4W1A is mainly used for the study of theperfection of single crystals, high resolution multi-crystal
diffraction and x-ray standing wave research. The mainequipment of the station consists of a white radiation
topography camera, three environmental sample chambers,
an x-ray video imaging system and a four crystal
monochromatic camera. These are installed inside aninterlocked hutch of 3m wide and 6m long. We built its on-line control and data acquisition system by using two
personal computer and some plug in cards, of which one
PC is served as beamline and experimental station on-linecontrol, while the another is mainly used for topographic
image on-line and off-line treatment. The schematic of thewhole system is shown in Fig.1.
2 Beam line control
The 4W1A beamline is equipped with two water cooled
tunable slits driven by four-phase stepping motors to define
the incident beam size, equipped with a double crystal
monochromator to chose the x-ray at any energy. After the
monochromator, an ion chamber is set to measure theincident beam intensity. The signal of the x-ray intensityfrom the ion chamber through the amplifier anddiscriminator become the standard TTL pulse, then into theon-line computer or NIM scalar for display.
Considering the scale of beamline, We developed amultifunctional ISA interface specially used for beamline
control, which has one channel timer, three channels scalarand eight channels stepping motors controller. The motors
can be used in open loop control or feedback mode, whenin feedback mode, the rotating encoder can be readout byinterface’s scalar to correct the missed steps automatically.
Currently, we use only one interface for slits control,
monochromator control and ion chamber readout, but twoor more interfaces can be used simultaneously if necessary.

SRBeamline
Control

FCCWRCmotorsmotors

ISA Board

On-line Control PC

Si(Li)
Detector

GPIB

P/100

CCD

MonitorControl/amplify

VideotaperecorderMCA

Image Card

Windows95

Image Treatment PC

Fig.1 The schematic of control and data acquisition system at BSRF topography station.
FCC: Four Crystal Camera; WRC: White Radiation Camera; CCD: directly x-ray imaging CCD.

3 Experimental system

3.3 X-ray standing wave research system

The topography station consists of three different
experimental set-ups, so the control system is the combination of three independent programs. These programs run
on Windows95 platform respectively.

The x-ray standing wave (XSW) research system
consists of the double crystal diffractometer (ref.3.2), aEG&G Si(Li) detector, a ISA bus EG&G multichannel(MCA) buffer and attached electronics. The commercial
Windows based software attached with the MCA is used
for fluorescence signals acquisition.

3.1 White radiation dynamic topographic system
The white radiation topography camera and three environmental sample chambers are used for the dynamic
topographic experiments with change of temperature,stress, electric field or other parameters[2]. The whiteradiation camera[3] has five axes to rotate the specimen to
any orientation with the incident beam and to rotate thedetector to collect the any diffracted beam. All axes are
driven by stepping motors and run in open loop control. An
GPIB stepping motor controller and a plug-in GPIB
interface are used for motors control.
Three environmental sample chambers, including two
high temperature sample chambers and one lowtemperature chamber, are used for different experimental
requirements. One of the high temperature chamber (“ heavy”) is multifunctional but difficult to align, which isused for temperature over than 1000°C; while the another(“ light”) is simple but easy to handle, which is used for
medium temperature range. A digital control power supply
can ramp the electric current smoothly when starting toheat. The temperature control system is based on theEurotherm controller (model 818) and solid state relay(SSR). By using PID control and time proportion method,
the temperature stability is about 0.05°C when holding
and 0.1°C when ramping. The on-line PC can set andmonitor the temperature via RS-232 interface.
3.2 Four-crystal camera system
The four crystal camera[4] consists of the monochromator mounted at the end of the beamline and a double
crystal diffractometer.
The double crystal monochromator comprises a pair ofparallel Si perfect crystals which can be rotated to fit theBragg angle by a Huber goniometer. The second crystal
can be finely adjusted by two ways to ensure the parallelwith the first crystal. The first crystal can be moved down
to let the white radiation pass when the white beam
experiments are performed.
The main body of the double crystal diffractometer is a
precise two-axis diffractometer. A Si reference crystal oran asymmetrically cut Si standard crystal is set on the firstaxis; while the specimen is set on the second axis. Besides
the θB rotating, a set of rotating system is used to align thediffractometer, including two ways rotating of the standard
crystal, three ways rotating of the specimen and the wholebody rotating around the incident beam. These rotating
system are controllable and measurable by on-line PC via
GPIB. A scintillation counter mounted at the detector axis
is used to measure the intensity of the diffraction beam,
which is readout via GPIB too.

4 Topographic image treatment system
The topographic image treatment system is based onanother P/100 personal computer and a new developed PCI
bus plug in card, which is used for modest resolution, realtime display and treatment during dynamic experiments.
The x-ray sensitive CCD(Siemens XQ1177) is used todirectly convert the topographic image (x-ray diffractionpattern) into electrical signal with the spatial resolution of25µm. The CCD control unit output three channels ofstandard video signal, of which one to high resolution
monitor for real-time display, one to VHS recorder forrecording, while the another to PC for on-line image
treatment.
The schematic of the image capture/treatment card isshown in Fig.2, which can digitalis the image by standard
BMP or TIF file up to rate of 25 frames/sec with themaximum digital image resolution of 768×576×8 bits. The
treatment of image can be performed either on-line or postacquisition. Some simple functions, such as contrast
reverse or noise reduction by rolling integration method,
can be performed by on-line treatment; while a wide rangeof filters is used by post-acquisition treatment to improve
the quality of images recorded on VHS videotape or x-ray
film. Moreover, the image can be transferred into popularcommercial software such as Photoshop or Photofinish forfurther processing. A substantial improvement on theimage quality can be achieved after the image treatment
system having been used.

5 Physical results

Gen Lock

Video inFilter

Trig

A/DBuffer

Interrupt
control

PCIBusFig.2 The sketch of image capture/treatmentboard.
Many physical experiments have been performed on
the topography station at the dedicated time of SR. Forexample, the orthorhombic-tetragonal phase transition ofKNbO3 (a non-linear optical crystal) near 498K[5] and themetal-semiconductor phase transition of blue bronze
K0.3MoO3 (a typical model charge-density-waves material)
near 180K have been studied by ourselves. The wholeprocess of the phase transition has been performed andrecorded by the video imaging system, and the result isexcellent[2].

6 Conclusion
In summary, we have built the PC based control anddata acquisition system at the BSRF topography station.
Instead of using CAMAC or VME, we just use some PC
plug in cards and GPIB to build the system. This is thecheapest way and usually effective in small or medium
scale experimental system. Currently, the whole system

is only the simple combination of independent programs,
we will rewrite the software next step on a suitableenvironment, such as LabVIEW or EPICS, to make it morefriendly and standard.

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[2] Wang G.L., Jiang J.H., Tian Y.L., et al. (1998).
Journal of Synchrotron Radiation, to be published.
[3] D.K.Bowen, G.F.Clark, S.T. Davies, et al. (1982).
Nucl. Instru. and Meth. 195, 277-284.
[4] Jiang J.H. Tian Y.L. Wang G.L. et al. (1998).
Journal of Synchrotron Radiation, to be published.
[5] J.Y. Zhao, P. Yang, S.S. Jiang, et al. (1991). Appl.
Phys. Lett. 59, 1952-1954.