Pyrolytic carbon: applications of its diamagnetism in metrology

Abstract

This paper presents some current or potential applications in metrology based on the diamagnetism of pyrolytic carbon (PyC). The magnetic repulsion force acting between a piece of PyC subjected to a magnetic flux can be used as magnetic spring either to control the position of the sensitive sensor element or to detect changes of a physical quantity to be measured. The first part of this paper provides examples briefly described of devices based on the diamagnetism of PyC for measuring mechanical quantities. There are two main configurations for magnetic levitation: one, used for measuring acceleration or inclination for instance, is based on the levitation of a PyC tile above a magnet or set of magnets; In the other, used to measure forces caused for example by contact or buoyancy, it is the permanent magnet that is levitated at a stable height above a fixed PyC tile. The second part describes current work at the Laboratoire Commun de Métrologie (LCM-LNE/CNAM) on the development of new laser power sensors using either diamagnetic force changes by photothermal excitation of electrons or diamagnetic torsion spring.