A fast neutron time-of-flight and scattering angle measuring system with online flight time correction

The authors describe a microprocessor-controlled VMEbus system for neutron scattering experiments at the new Berlin Experimental Reactor BER II. The system measures the distribution of neutron times-of-flight (TOF) by spatially distributed detectors (400 single detectors or a multidetector array with 4096 elements) and generates a 2D histogram with 4 K time channels and 4 K detector position channels in a 32 MB memory. An online TOF correction compensates different lengths of neutron flight paths, in order to obtain undistorted spectra if, e.g., a planar detector array is used. The system is designed for very fast processing of the events detected, to allow high neutron counting rates of up to 200000 neutrons/s on the average and up to 2*10/sup 6/ neutrons/s as peak rate. To provide a maximum of flexibility for the user, the operation of the system is based on precalculated tables and parameters which allow a wide variety of system configurations to satisfy very different requirements of the experiments.<>