Cherenkov detectors designed to date which use optical imaging techniques exploit the fact that cherenkov photons form rings in the focal plane of the device. In a ring imaging cherenkov counter, for example, a high-granularity photon detector is placed in the focal plane of the lens or mirror system to measure the cherenkov ring diameter, which provides information about particle velocity ( and thereby its identity, if the momentum is known), and the ring location, which is determined by the particle's direction [1]. The very high pixel count of these devices can be reduced dramatically in some cases if an axicon (a rotationally symmetric prism) is used to convert the

Now I put the text in a table of width 95%, aligned right. conical cherenkov wavefronts to flat wavefronts, thus reducing the cherenkov rings in the focal plane to dots [2]. The price paid is that the ring diameter is no longer available for particle identification. In differential cherenkov counters [3] operated in beamlines, a mask is placed in the focal plane to select a particular cherenkov ring diameter. The passed photons can then be detected by one or several phototubes. Excellent particle identification can be achieved, but no position measurement is available. Under certain circumstances, it is possible to extract both the particle identity and position by placing a low-granularity photon detector not in the focal plane, but further away from the imaging lens or mirror. In