A fibre-optic displacement sensor for a cyclotron environment based on a modified triangulation method

Due to the very high magnetic and radio frequency fields and generally hostile environment inside cyclotrons, electronic devices are hindered from functioning. By implementing a modified triangulation method we developed a purely dielectric PC interfaced sensor head, which will be placed inside the cyclotron for electrode-position measurement. This represents a completely new cyclotron diagnostic tool designed to cope with cyclotron alignment problems. In this paper we present the motivations for developing such a sensor, the theoretical analysis, overall sensor design for two-coordinate simultaneous measurement and measurement results. A resolution of 10 μm within a 5 mm range was achieved independently of laser diode power variation, target reflectance variation and induced attenuation in optical fibres.