- Five-fold fully dc-coupled constant fraction discriminator
- Dynamic range 500 : 1
- Count rate up to ≥ 50 MHz, limited by dead time
- Three Modes: CFT, CFR constant fraction discriminator with slow risetime reject,
and LET leading edge trigger
- Pulse pair resolution less than 10 ns, or as limited by dead time
- Threshold stability better than ± 0.02% / oC (± 200 ppm / oC)
- Threshold linearity ± 25 % integral
- Temperature range 0 oC to + 50 oC
The 2155 Pent CFT is a five-fold fully dc-coupled constant fraction discriminator with a dynamic range of up to 500:1. Selected fraction and three operating modes provide optimum time resolution for many detector types and applications.
The unit accepts negative polarity pulses to the 50Ω terminated dc-coupled inputs. On customer request the module can be modified to accept positive input signals. The constant fraction composite signal is formed by the sum of a direct, attenuated (fraction f) signal path and a delayed, unattenuated path. The delay time is selectable according to the propagation delay of a (external) 50Ω BNC cable. Careful selection of fraction and delay cable provides full compensation of timing distortions due to both amplitude and risetime variations in the input signal. Output signals are generated whenever the input signal exceeds the selected threshold set by a front panel potentiometer (T).
Four simultaneous, independent output signals are provided. The two positive NIM voltage
outputs (at the rear panel) are adjustable (internal trim potentiometer) in width from 5 ns to 200 ns. The two independent negative NIM current outputs are derived as fixed width pulses.
The wide dynamic range of the Pent CFT permits its use in many timing applications without the need of fast pulse amplifiers.