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The influence of phase errors on the accuracy of the neutron diffraction peak parameters is discussed. It is shown that a constant phase error leads to both a distortion of the shape and a shift of the center of gravity of a reflection peak. A method was developed which takes the phase error into account and corrects for the peak shift.

Three different modes of operation have been realized for the Fourier-RTOF diffractometer FSS at the GKSS Research Center which produce peak shapes that are either a Gaussian or the first or second derivative of it. The triangular shape of the modulation function of the neutron intensity as well as the rectangular shape of the optical pickup signal cause deviations from the ideal shapes of the reflection peaks. Distortions caused by the constraints on the upper limit of the modulation frequency cause specific oscillations, which are superimposed on the diffraction peaks. The characteristic properties of the three modes of operation are discussed.

The quality of a neutron time-of-flight diffractometer can be significantly improved by setting up its detectors in time-focusing geometry. In order to fully exploit the time-focusing method, the nominal resolution of the spectrometer must be thoroughly investigated by analysing the contributions of several different factors. In this paper analytic formulae are given, which describe the different components contributing to the resolution function and the conditions which optimize the resolution are derived. It is shown how the analytic integral equations can be solved numerically. The programs allow iterative computations to optimize a detector system composed of many individual detector elements, considering the specimen size and instrumental resolution. The flow diagram of the programs to calculate numerically the detector system is briefly discussed and the precision of the individual optimal detector position coordinates is given.