OPTIMIZATION OF GERMANIUM MONOCHROMATORS FOR NEUTRON DIFFRACTOMETERS

A computer program TISTA has been employed to study the behavior of re actor-neutrons at the sample position of a neutron spectrometer diffra cted from Ge(lll), (220), and (311) monochromators. Our aim is to desi gn a double axis neutron spectrometer and to determine the behavior of beam intensity and resolution at the sample position. The study will be helpful to design experiments with the existing triple axis neutron spectrometer at TRIGA Mark II research reactor, Dhaka, Bangladesh. Th e optimum values of crystal and instrument parameters have been determ ined through these calculations. The flux density of neutrons and the resolutions of a spectrometer at the sample position have been calcula ted as functions of beam collimation, zero-Bragg-angle deviation, crys tal curvature, distance between sample and monochromator, crystal asym metry, thickness, mosaic spread, crystal length, etc. The present resu lts are compared with those of copper and silicon monochromators.