A single-supply, high rate, small size and cheap electronic chain for /sup 3/He neutron counters

The paper describes a complete counting chain (charge preamplifier, shaping amplifier and threshold discriminator) devoted to /sup 3/He neutron detectors. Since it is characterized by single supply operation, high counting rare, small size and low cost, it is well suited for high efficiency neutron well detectors where a large number (10-100) of counting tubes are used. Such detectors are commonly used for verification of Plutonium docks. The preamplifier adopts an innovative circuit with the gate of the input JFET floating and a DC feedback loop that stabilizes the output voltage acting on the input cascode second transistor. Static and dynamic analysis, including the effects of the detector bias network is reported. The shaping amplifier transfer function is a fifth order approximation of the Gaussian response. All the complex pole pairs an realized with a single fourth order Voltage Controlled Voltage Source cell thus minimizing component count. Experimental signals and spectra, obtained with shaping time constants in the 1 /spl mu/s-100 ns range, an reported and discussed.