Signal Processing of Nuclear Pulse for Neutron Flux Meters Used in Nuclear Research Reactors

Pulse shaper is a part of startup amplifier which is the most important element in pulse shaping of a nuclear pulse. Startup amplifier usually has three major stages: a differential preamplifier, pulse shaper, and a discriminator. This system is traditionally implemented on a Printed Circuit Board (PCB) with discrete components which is deemed bulky, noisy, and complicated. In this thesis, MATLAB is used for system level analysis in order to simulate this system and to find out optimum design parameters. Input signal pulses are modeled in M-file. Thermal and flicker noises are taken into account as well. The designed shaper is of Semi-Gaussian type. The optimum time constants and numbers of integrators are determined from the system level analysis. The pulse shaper transfer function is implemented using passive elements. In practice, cascading passive filters together to produce larger-order filters is difficult to implement accurately as the dynamic impedance of each filter order affects its neighboring network. However, to reduce the loading effect we can make the impedance of each following stage 10x the previous stage. Then a proposal pulse shaper is designed in CMOS technology. A Current Multiplier Cell (CMC) is used to implement capacitors which use inverters and op-amp only. The whole circuit is designed in a 0.13µm IBM-CMOS process