DESIGN AND PERFORMANCE OF THE NEW TIME-OF-FLIGHT SMALL ANGLE NEUTRON DIFFRACTOMETER SAND AT IPNS. P. Thiyagarajan, R.K. Crawford, J.E. Epperson, F. Trouw, R. Kleb, D. Wozniak and D. Leach. IPNS, Argonne National Laboratory, Argonne, IL 60439, USA.

A time-of-flight small angle neutron diffractometer SAND, which is capable of providing data in a wide q region of 0.0035 to 0.8 Å^-1 in a single measurement, has been commissioned at IPNS. This instrument has been built upon the more than 10 years experience with the proto-type time-of-flight SANS instrument SAD which has been serving the scientific user community during the past decade at IPNS. SAND has a fixed geometry but simultaneously uses neutrons with a wavelength region of 0.8 to 14 Å, thus producing data in such a large dynamic range in q. Some of the new features in the new instrument when compared to SAD are: a larger area detector, larger sample-to-detector distance, a frame elimination chopper to extend the wavelength range upto 28 Å, two sets of soller collimators and beam stops and a larger sample area. To widen the dynamic range in q even further as well as to improve the statistics in the high q data, an array of linear position sensitive detectors is being added. The design and perfomance of SAND along with the scientific opportunities provided by this instrument will be discussed.

Work supported by U.S. Department of Energy, BES, contract No. W-31-109-ENG-38. We also acknowledge the support received through a grant from National Science Foundation to Professor S.-H. Chen, MIT and another grant from Texaco Corporation.