An improved trigger-generation scheme for Cerenkov imaging cameras [Paper No.: I5]

An improved trigger-generation scheme for TeV gamma-ray imaging telescopes is proposed. Based on a memory-based majority coincidence circuit, this scheme involves deriving 3-pixel nearest-neighbor coincidences as against the conventional approach of generating prompt coincidence from any 2 pixel of the imaging-camera. As such the new method discriminates against shot-noise-generated triggers, and perhaps, to some extent against background cosmic-ray events also, without compromising on the telescope response to events of γ-ray origin. The net effect is that a Whipple-like imaging system can be operated with a comparatively higher sensitivity than what is possible at present. In addition, a suitably scaled-up value of the chance-trigger rate can be independently derived, thereby making it possible to use this parameter reliably for keeping a log of the 'health' of the experimental system. (author). 9 refs., 5 figs