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<title>Progress at X-ray Diffuse Scattering Station</title>
<h1>Progress at X-ray Diffuse Scattering Station</h1>

    During the dedicated synchrotron radiation operation of BEPC storage 
ring, substantial progresses were made in    
upgrading of beamline itself and its experimental instrumentation
 at Diffuse Scattering Station. 
4WIC beamline, a  branch of 4W1B beamline, is split from 4W1B  and can 
operate independently. With the splitting done,   beam  hour is increased 
 several times, which enables 
us   to carry out  feasible research on grazing 
incident X-ray diffraction (GID) in amorphous multilayers and crystalline 
material. Meantime, the users can also perform systematic 
researches.<p>
    The key point in splitting  4W1B and 4WIC beamlines is to lower the   
triangular monochromator  from the normal position in a purpose of 
guiding part of 
synchrotron beam pass through the hypotenuse of the triangular crystal 
to  4W1B, while the other part  be  reflected to  
4WIC. A wider flat pipe (30mmX100mm) was built to replace the 
 former one (30mmX60mm) in order to extract all the 4mrad beam, 
and a bellow was inserted into the pipe for easy adjustment; down and up 
movement of the crystal was controlled by a gear system driven by a 
step-motor. The beam performance was measured  under the conditions of 
4W1C independent operation. Results show that effects of beam-splitting 
on energy resolution and focusing performance are less than 10%, while 
that  on intensity of the beam was obviously, the latter affected quite 
 a few  of the experiments.<p>
    The GID method was studied on the 5-circle diffractometer with fine 
movable table and position-sensitive detector. Scattering patterns  from 
lateral amorphous structure of W/C and Fe/Mo multilayers were observed,  
and its intensity varied with the change of  grazing incident angle of 
X-ray. The 
ratio of peak/background became worse with the increasing of incident 
angle, which consisted with the principal of GID that the X-ray penetrated 
deeper at larger angle. Further development is focused on the fabrication 
and adjustment of the apparatus.<p>
    Satisfactory results were obtained in users' experiments. The 
structures of $\delta$-doped epitaxy films 
with different doping doses and annealing 
temperatures were systematically researched with X-ray reflection by users 
from Fudan University; in the measurement of 
domain orientation in ferroelectrics 
films, very interesting phenomena were observed by the group from Nanjing 
University, which provided reliable proofs 
on the model of domain orientation; 
the atomic composite in epitaxy semiconductor film were measured by users 
from Institute of Semiconductor. Researches carried out by our group also 
went on  smoothly. For instance, 
the nonspecular X-ray scattering from films 
prepared under different conditions will provide experimental evidence for 
 kinetic process and mechanism of film formation; expected results were 
also obtained in nonspecular scattering measurement of 
amorphous multilayers.<p>
<address>Jiang Xiaoming</address>
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June 1995 BEPC News<p>