Measurement of permittivity through ponderomotive force determination

A numerical simulation of an apparatus developed to measure permittivity in dielectrics is presented. The dependence on permittivity of the ponderomotive forces acting on a dielectric sample in a nonuniform electric field is obtained. A computer analysis (three-dimensional) of the field, for both cylindrical and flat geometries, is performed to calculate the forces accurately. Calculations are carried out by the finite-element approach which proves to be useful and powerful. An experimental apparatus is then described to measure the permittivity of solid dielectric samples, using the calibration curve relating ponderomotive force to permittivity, obtained by the above numerical simulation. Experimental results are reported together with a discussion on the accuracy and sensitivity of the measurements.