A Fast-Slow Coincidence System Employing a Multichannel Time Display

A versatile, solid-state Fast-Slow Coincidence system is described which is used with large NaI(Tl) scintillators and XP1040 photomultipliers. A multichannel time display is provided which consists of a time-to-amplitude converter of the "start-stop" type and a standard 100-channel kicksorter. The calibration of the time analyzer can be varied from 1 nsec to 0.1 nsec per channel. In addition to showing the time spread, the display indicates the coincidence resolving time (2To) which is variable from 1 to 100 nsec by means of front panel helipots. The electronic time jitter of the system, as measured with a fast pulser is less than 0.2 nsec. A resolving time of 8 nsec gives 95% coincidence efficiency for coincidences between the annihilation radiation photo-22 peaks from Na22