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A needle-type coaxial probe for the measurement of radio frequency and microwave permittivity of biological samples is studied both theoretically and experimentally. The probe is obtained by a slanted cut, and therefore the radiation aperture is elliptical. Both theoretical analysis and experiments show that the measurement sensitivity is improved with the increased bevel angle of the probe. Calibration results using water and air at low frequencies are in agreement with theoretical calculations. Measurements on three biological samples (sonicated DNA macromolecules, water solutions of protein (the protamine), and in -aminocaproic acid) were made from 1 MHz to 1 GHz. All the measured results are in very good agreement with similar tests obtained from the same materials using a standard probe. The theoretical and experimental results show that the probe improves measurement sensitivity and it facilitates insertion into some test samples. >

This paper presents a modified theory for the measurement of the surface resistivity of thin films, deposited on either thin or thick dielectric substrates; in addition the formulations for the measurements of thin dielectric substrates is derived. The reflection coefficient of a probe in contact with the surface is used to calculate the surface resistivity of the film or else the dielectric constant of the dielectric substrate. The expression giving the reflection coefficient in terms of the surface resistivity of a film on a thin substrate is developed by matching the electromagnetic fields at the aperture of the coaxial line. Experimental results of conductive thin films on thin substrates (indium tin-oxide thin film deposited on polyethylene substrates) and dielectric substrates without films are reported from DC to 4 GHz. The experimental results calculated with the derived expressions and the measured reflection coefficients are in agreement with surface resistivity values quoted by the manufacturer of the various test samples used.

This paper examines the edge effects of introducing a dielectric test cylinder with a test material into a cavity via a metallic support tube extending outside the cavity. A first-order perturbation theory is used for this metallic hole containing two different concentric dielectric materials. The Galerkin method is used to determine the amplitudes of numerous evanescent modes which exist in such composite hole geometries. Comparisons are made with the effects produced by a simple hole in which a single dielectric is postulated inside the metallic support tribe. The effects of the composite hole on the measurement of the dielectric properties of materials are given.

Very little work has been done in the past on the use of microwave plasmas for the desulfurization of oil products. This paper presents the measured desuffurizaiion levels on a diisopropyl disulfide oil solution containing 5.2% by weight of sulfur. Complete desulfurization was obtained, using either hydrogen or helium plasmas at atmospheric pressures.The estimated cost to completely desulfurize I metric ton of oil containing 5,2% by weight of sulfur is about $20.00 by the use of this new technology.

A new technology for producing large volume microwave plasmas is introduced, Microwave energy is coupled into the plasma by means of a slow wave structure, and plasma volumes well in excess of 1000 cm3 can readily be achieved with 2.5 kW of microwave power at 2.45 GHz. General operating characteristics and some experimental data are presented.