An example of a uniformly accelerated particle detector with non-Unruh   response
  We propose a scalar background in Minkowski spacetime imparting constant proper acceleration to a classical particle. In contrast to the case of a constant electric field the proposed scalar potential does not create particle-antiparticle pairs. Therefore an elementary particle accelerated by such field is a more appropriate candidate for an "Unruh-detector" than a particle moving in a constant electric field. We show that the proposed detector does not reveal the universal thermal response of the Unruh type. 
A.M. Fedotov, N.B. Narozhny, V.D. Mur, V.A. Belinski