The Study Of Digital Data Acquisition System On GTAF

Data of neutron capture cross-section（n，γ）for some nuclei are very important inthe nuclearastrophysics,the nuclear application,the design of the nuclear reactor andthe transmutation of the nuclear spent fuel. There are strong request for theimprovements of the accuracy on the neutron capture cross sections in the field ofinnovative nuclear engineering, so the method and the instrument for measurementneed to be developed.The GTAF（Gamma-ray Total Absorption Facility）,which is a BaF₂scintillationcalorimenter with an ability of absorbing γ rays totally was constructed atCIAE（China Institute of Atomic Energy）. The design of the detector is such that a full4π array would consist of42crystals of two different shapes, each shape coveringthe same solid angle. The4πdetector has nearly100%detection efficiency,for it isirrelevant to the multiplicity of γray. BaF₂crystal is the fastest inorganic scintillatorin the world,so it is beneficial to the neutron energy measurement with time of flight.Otherwise BaF₂crystal has low neutron sensitivity that greatly reduces the detectorbackground, it is good for the measurement of neutron capture cross section.Anode signals of the BaF₂detectors were acquired using the Flash ADC combinedwith the computer system. The circuit can be easily connected and the date can besaved with comprehensive information compared to the traditional method. It isConvenient for offline analysis.The energy spectrum of⁶⁰Co and¹³⁷Cs source, the time spectrum, and the totalenergy spectrum were obtained on GTAF; Differences of the pulse shape were studiedby off-line data analysis. α particles and the γ rays have been identified by the pulseshape discrimination. The Ra background has been eliminated; The digital dataacquisition method applied by the4π BaF₂system has been discussed. The digitaldata acquisition system and the online monitoring system have been successfully built.This work is very important for the GTAF in the future experiments.