New precise measurement of the Cotton-Mouton effect in helium

The birefringence of helium in the presence of a transverse magnetic field (Cotton-Mouton effect) is studied experimentally. A very sensitive ellipsometer, based on a high finesse Fabry-Perot cavity and coupled to a superconducting magnet, is used to detect this very tiny effect. Birefringence is measured varying the pressure of the sample.