Modelling of effects of ripple-induced thermal ion losses on JET and JT-60U H-mode plasmas

A disc inclination detecting apparatus comprises a light-emitting element for projecting a light beam on a disc and a light-sensitive element for receiving a reflected light beam reflected by the disc and outputting a corresponding electric signal, in which the light-sensitive element faces the disc and is positioned together with the light-emitting element in a tangential direction of tracks on the disc. The apparatus also comprises a signal processing circuit for detecting, on the basis of the electric signal, a variation of a position of the reflected light beam on the light-sensitive element in a direction perpendicular to the tangential direction. The variation corresponds to an inclination angle of the disc.