TIME-RESOLVED SWAXS MEASUREMENTS OF EFFECTS INDUCED BY VARIATION OF PRESSURE

Miloš Steinhart, Manfred Kriechbaum, Martin Horký, Josef Baldrian, Heinz Amenitsch, and Peter Laggner

1Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague, Czech Republic
2Institute of Biophysics and X-Ray Structure Research, Austrian Academy of Sciences, 8010 Graz Austria
3Faculty of Nuclear Science and Engineering, Czech Technical University, 1800 00 Prague 8, Czech Republic

Keywords: SAXS, SWAXS, high-pressure, pressure-jump, time-resolved mesurements

An instrument to facilitate small- and wide-angle X-ray scattering measurements of phenomena induced in samples by elevated hydrostatic pressure as well as by pressure variations including jumps was constructed [1] and is being used for several kinds of experiments [2].

A pressure range from atmospheric up to 0.35 GPa (3.5 kbar) can be employed. The pressure is transferred by means of pressurising liquid to an X-ray sample cell. The cell has two Beryllium windows with total transmission of 0.4 (for X-rays of 8 keV) and low background scattering. Scattering curves can be observed at angles up to 30o. The sample consistency can range from solid to liquid with a minimal volume less than 30 ml and an irradiated volume up to 3 ml with an optical path-length of 1.6 mm. The pressurising medium can be separated from the sample by Teflon pistons thereby providing suitable environment for the particular sample.

The device is fully PC controlled and is capable of being integrated into a channel control and data acquisition system at a high-flux synchrotron facility. Static measurements at elevated pressures and in addition time-resolved experiments with the time resolution in the milliseconds range can be performed.

Parallel to this hardware setup, a data-reduction system for the treatment of huge amounts of data arising from these kind of time-resolved measurements is being developed.

At the recent time, two kinds of problems are being studied by the system described above using the SAX beamline at the synchrotron Elettra in Trieste, Italy. These are barotropic phase transitions in lipid/water systems (DOPE, DPPC) and pressure/temperature induced crystallizations of polymer systems (POE) at ambient/elevated pressures.

Some important details of the measuring system as well as of the novel data-reduction procedures will be presented in the talk. Also interesting results of the concrete studies will be given.

 

  1. K. Pressl, M. Kriechbaum, M. Steinhart, and P. Laggner, Rev. Sci. Instrum. 68, 4588-4592 (1997).

  2. M. Steinhart, M. Kriechbaum, K. Pressl, H. Amenitsch, P.Laggner, and S. Bernstorff, Rev. Sci. Instrum., (submitted in May 1998)