Unruh effect for circular motion in a cavity

A quantum detector moves in a circle of radius r, within a concentric circular cavity of radius R, with constant angular velocity Omega . A quantum field, enclosed in that two-dimensional cavity, is in its ground state. The authors compute the probability that the detector will be excited by the vacuum fluctuations of the field. If R>ct>>r the excitation rate tends to a finite limit, independent of R and t.