MWPC Neutron Detector Signal Readout Based On Delay Line

Neutron scattering is an important method of exploring the microstructure of materials. In recent years, with the construction of neutron sources and neutron spectrometers and diffractometers in China, there is an increasing need of readout electronics of neutron detectors. Because of its high detection efficiency, good discrimination of n/y and positon resolution,3He gas multi-wire proportional chamber (MWPC) is widely used on the neutron scattering facilities at home and abroad. The neutron scattering research reactor in China Academy of Engineering Physics is the first neutron scattering application platform in China, on which several neutron spectrometers are equipped with 3He gas MWPC detectors. A design of readout electronics system based on these MWPC detectors is developed in this thesis.By converting the positon information to time differences, delay-line readout technique has the advantage of easy to manufacture and cost effective with only four readout channel needed compared with individual readout methods which need a large number of channels.On the basis of fully study of the critical techniques of readout out electronics and various readout systems, the readout system mainly consists of three parts:time measurement, data process, data transport. Using constant fraction discrimination combined with high accuracy time digital converter TDC-GPX to measure the time differences and field programmable gate arrays to process and control the system, acquired data can be transferred to computer in real time employing a Gigabit Ethernet module based on SOC. Test results show that time resolution of the readout system is 81ps, and the RMS of time measurement is better than 50ps, with differential non-linearity and integral non-linearity better than 0.5LSB and 1LSB respectively. Count rate of 1.3MHz can be achieved under a 250ns delay line. Real neutron experiment demonstrates good two-dimensional image ability of the readout system. Using a modular design based on the NIM standard, the readout system is robust and cost effective, can be updated on line, and can be used on other applications related with time measurement and readout.