High-pressure instrument for small- and wide-angle x-ray scattering. II. Time-resolved experiments

An instrument to facilitate small- and wide-angle x-ray scattering measurem ents of samples under elevated hydrostatic pressures or exposed to pressure jumps is described. Pressure from atmospheric up to 0.35 GPa is produced b y a motor-driven, piston-type generator and transferred through a network c ontaining pressurizing liquid to a sample cell. The cell, with the optical path length of 1.6 mm, has two Beryllium windows with a total transmission of 0.4 (for x rays of lambda = 0.154 nm) and low background scattering. Sca ttering can be observed at angles up to 30 degrees. Samples can be solid or liquid with a minimal volume less than 30 mu l and the irradiated volume u p to 3 mu l. Separation of the samples from the pressurizing medium is acco mplished by Teflon pistons. The high-pressure network has two sections sepa rated by a pneumatic valve. The inner section is connected permanently to t he cell and the outer one to the pressure generator. For pressure jumps, th e outer section is brought to a different pressure level than the inner one and the jumps are accomplished by opening fast the connection between both sections. At the same time a trigger signal is sent to the data acquisitio n electronics. All functions of the instrument are PC controlled. To illust rate the performance characteristics of the instrument, time-resolved small -angle x-ray scattering measurements of phase transitions in liquid crystal line phospholipid, dioleoylphosphatidylethanolamine are shown. Pressure-jum p experiments with 5 ms time resolution as well as temperature scans at a c onstant elevated pressure are presented. (C) 1999 American Institute of Phy sics. [S0034-6748(99)00102-1].