CONSTRUCTION OF THE SAMPLE HOLDER AND SMALL-ANGLE X-RAY-SCATTERING MEASUREMENT FOR SUPERCRITICAL WATER

A high-temperature and high-pressure sample holder suitable for water under supercritical conditions was constructed for small-angle X-ray s cattering experiments, which was designed to endure the temperature up to 750 K and the pressure up to 40 MPa. By use of the holder, prelimi nary experiments for supercritical water were carried out along the is otherm at 663 K with pressures from 22.5 to 29.5 MPa. Isothermal chang e of the correlation length obtained from the scattering data showed m aximum near the critical isochore. The tendency is similar to other su percritical fluids, e.g., carbon dioxide, trifluorometane and ethylene .