Constant Fraction Discriminator - Model 2126

Features

• 200 MHz count rate
• 1000:1 dynamic range
• Walk <±30 ps typically for 100:1 range
• Simultaneous positive and negative outputs
• Normal and high rate counting modes
• Changeable fraction and attenuator module

Description

The Model 2126 is a 200 MHz Constant Fraction Discriminator in a single width NIM. It has independent controls for threshold, walk, output pulse width, and operating mode, and provides maximum flexibility for use in any timing application.

The 2126 is fully dc coupled and provides two operating modes for use over a wide range of input count rates. In the standard operating mode, the 2126 operates to 150 MHz with the front panel potentiometer controlling both the output width and the internal dead time. Alternatively, a special high rate operating mode can be selected which provides operation to 200 MHz (typically 250 MHz) with fixed output width and dead time.

The 50 W input of the 2126 accepts negative pulses with amplitudes up to –5 V. Input protection is provided for inputs outside the expected range. An internal jumper can connect a X2 attenuator to each input to extend the input range to –10 V. A plug-in module provides a means of changing the constant fraction (factory set to 40%). In addition to its normal Constant Fraction (CF) timing mode, the 2126 provides a Constant Fraction with Slow Risetime Reject (SR) timing mode. the SR mode rejects the slow rise time signals characteristic of some detectors, thus improving timing performance.

Two independent fast negative timing outputs and two independent positive timing outputs are provided. This provides maximum flexibility for most timing applications. In addition, a front panel LED indicates the presence of input signals.

The 2126 can operate from standard NIM bin ±12 V and ±24 V power supplies. If a ±6 V power supply is available, the 2126 can be configured to use those supplies for most of its power requirements.