Effects seen in fast-timing with a surface barrier time-of-flight telescope

It has been found that the timing resolution between two surface barrier detectors is degraded when they are separated to make a time-of-flight telescope. The degradation consists of a broadening of the peak with an asymmetric tail developing on the 'early' time side of the peak. Measurement has shown that these effects vary progressively with the radial distance from the centre of the back detector. Ions which arrive closer to the edge of the detector produce a time peak which is shifted to earlier time than those which arrive in the centre. A further measurement has shown that only small changes in the pulse shape occur for these different events. The suggestion is made that the observed effect is predominantly due to different delays in the pulses which have to propagate different distances across the detector. The propagation velocity in this case was measured to be 20% that of light. An approximate treatment for the detector in terms of a simple delay line is capable of giving a reasonable description of the observed effects. (Auth.)