A 10 ns multichannel photon counter

Abstract

A 512 channel photon counter with a resolution time of 10 ns per channel is described. The input of photon count data to the instrument is made via a derandomizer and shift register which are implemented in ECL circuitry. A 512 bit TTL buffer memory stores one cycle of data within the instrument and this information is read out to a small on-line computer at the end of each cycle. The computer, a PDP-12, accumulates and displays the data in a double precision word in memory giving a capacity of 16.8*106 counts per channel. Use of the instrument for the measurement of weak fluorescence with high time resolution is described.