6915 Single Channel Constant-Fraction Timing Discriminator



The Model 6915 is a high performance, single channel constant-fraction timing discriminator. Its small rugged packaging makes it ideal for mounting nearby the detector often in remote locations.

Typical time walk plus input slewing of ±75pSec is achieved for inputs from threshold to 100 times threshold. The threshold is adjustable from -25mV to -1Volt, and its setting is easily monitored from a front panel test point that provides a DC voltage equal to the actual threshold setting.

A shaping delay cable is required to form the constant fraction pulse. The shaping delay circuit is made complete by connecting the appropriate cable length between two delay connectors, allowing the user to optimize time resolution by easily matching the characteristics of the detector. A monitor output is also provided to observe the constant-fraction shaped pulse to verify that the delay cable is correct.

A fast veto input has been included to perform an anti-coincidence function. This is helpful for rejection of unwanted events early in the system. Unlike a simple gating function, it provides a way of inhibiting the discriminator without adversely affecting the timing characteristics for the current event being processed.

The outputs of the 6915 are non-updating and adjustable in width from 5nSec to 250nSec providing four individually driven, current switched outputs. They are configured as two normal NIM outputs, one complemented NIM output and one positive TTL output. They have typical risetimes and falltimes of 1.2nSec helping to preserve the excellent timing characteristics. The output transition times and pulse shapes are unaffected by the loading of the outputs in any combination.

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