C1-3 ULS

Instrumental Overview
    ULS (ULtra Small angle scattering) has been installed on the cold-source
beam-line C1-3 in JRR-3M.The instrument has been designed for experiments on
ultra-small angle scattering,neutron optics using multi-axis precision gonio
-meters, and interferometry.  Neutrons with a wavelength ranging from 4.3 to
5.1, monochromated by PG(002),are available in the beam-line. Unless special
requirement, the monochromator is set to select the wavelength of 4.73 A.
   A typical arrangement is illustrated in Fig.1. The instrument consists of
three high-precision goniometers and two neutron detectors mounted on a vib-
ration free table with a size of 1mx2m,all of which are installed in a hutch
whose temperature is controlled within a stability of 0.1. Two of the gonio
-meters,usually used in the double crystal arrangement, have rotary encoders.
One of them is   specially designed  so as to have double rotation mechanism
for theta axis:a piezo-electric driving mechanism with an angular resolution
of  less than 0.001 sec  is mounted  on a conventional stepping-motor driven 
mechanism.   The third goniometer  is used  as a sample table in ultra small
angle scattering experiment with an accessory for sample exchange.The perfor
-mance of the instrument  was tested using the (+,-) parallel setting in the
double crystal arrangement of Si 111.   The rocking curves were observed for
neutrons with a wavelength of 4.731  using two sets of crystals; plate crys-
tals and channel-cut crystals with five successive reflections.The experimen
-tal results are shown in Fig.2.
  The observed rocking curves agree well with the calculated curves.The FWHW
of the rocking curve  shown in Fig. 2(a)  was 6.0 sec for plate crystals and
4.4 sec for channel cut crystals.The tail part of the rocking curve as shown
in  Fig.2(b)  is strongly reduced  for the channel cut crystal.   The result 
suggests  that experiments  on ultra small angle scattering  with q-range of
from 10-5  to 10-2 will be done with a dynamic rage of 105.   The background
level is an order 0f 0.01 count/sec.

Contact person : Tosio TAKAHASHI
	Institute for Solid State Physics,
	University of Tokyo,
	Roppongi,Minato-ku,Tokyo 106

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