An apparatus for the continuous measurement of thickness during the electropolishing of superconducting cavities

An apparatus allowing continuous acquisition of thickness measurements during electropolishing of superconducting cavities is described. The instrument is based on the ultrasound thickness measurement technique and allows the connection of up to six probes. The apparatus has been employed to monitor the surface treatment of PIP-II low beta single cell prototypes developed and manufactured by LASA-INFN and specifically to measure surface removal at different points of interest on the cavity surface. The apparatus facilitated the development and optimization of electropolishing parameters for incorporation into the cavity manufacturing process.

Simplified approach to the Jones calculus in retracing optical circuits

The application of the Jones calculus to optical circuits in which counterpropagating light beams are present is discussed, with particular attention to the conventions associated with the Jones calculus for the description of the polarization state of an optical beam and to the reference system adopted. The reference system adopted here differs from that used by Jones, but it exploits a simpler formalism when used to describe complex optical systems where multiple reflections take place. The differences between these two reference systems are pointed out with particular attention to the behavior of nonreciprocal optical devices and reflectors. An application of the results to a simple optical circuit is presented.

Polarization noise suppression in retracing optical fiber circuits

A novel scheme is proposed in which the presence of a Faraday rotator in a retracing fiber-optic circuit allows the complete, passive, and universal compensation of any birefringence (reciprocal) change occurring in the fiber. The action of the scheme was experimentally tested by inducing thermal and mechanical perturbations on a fiber coil. The results confirm the theoretical expectations and compensating for unwanted birefringence effects.