A1421

The CAEN Mod.A1421 is a charge-sensitive preamplifier, shaper, and discriminator that provides both analog and logic outputs. It is designed for use with neutron detector tubes in various applications. The preamplifier is optimized for position-sensitive thermal neutron detectors, where high counting rates and good spatial resolution (low noise) are required. It is also suitable for counting applications when used with monitor counters like the R7771B and R7780, such as in the non-destructive analysis of nuclear materials by passive or active neutron methods for containment monitoring and waste control.
The device is equipped with a detector input on an BNC or HN connector and an external HV input on an BNC connector (which powers the internal decoupling circuits). Additionally, it features two rear 3-pin male connectors (ref.: RT3MP REAN) to power the preamplifier, also allowing for daisy-chain operation. It includes two trimmers to adjust the discriminator threshold and the discriminator output width. A digital input is available on a LEMO connector for cascading the summing of the discriminator signals.
The preamplifier can be powered directly by the R7771B or by the A325 DC/DC power supply unit, produced by CAEN. A 1- meter-long power cable (Model A324) is provided with the preamplifier.
Two versions of this preamplifier have been designed: a standard version (Version A), suitable for most applications, and a version for active measurements (Version B), where the sample is activated using a neutron generator. Version A includes a polezero compensation circuit and is suitable for applications requiring Pulse Height Analysis (PHA), where neutron spectroscopy or position sensitivity may be needed alongside neutron counting. In contrast, Version B provides bipolar output pulses that are not pole-zero compensated and includes dedicated optimizations required for active interrogation measurements, ensuring a fast recovery from saturation conditions once the neutron generation burst is complete.

Developed in collaboration with Institut Laue-Langevin in Grenoble.