Abstract
Microwave spectroscopy that can be applied to study the dielectric relaxation of various fluids under high temperature and pressure has been developed in the frequency range up to 40 GHz. By utilizing this new technique the dielectric relaxation in water has been measured in the temperature and pressure range up to 750°C and 120 MPa, which corresponds to a density range between 0. 05 and 1 g/cm3. The static dielectric constant ε (0) is deduced from the time required for microwave signal to travel through the sample by means of the time domain analysis. The dielectric relaxation time τ is obtained by fitting the experimentally observed microwave transmission rate to the value calculated using the Smatrices on the assumption that the dielectric constant obeys the Debye relaxation. It is concluded that the most relevant parameter determining τ is the temperature at lower temperatures or higher densities, and is the density at higher temperatures or lower densities.
