General Time of Flight Technique for High Resolution Diffraction on Continuous and Pulsed Sources

The notorious success of pulsed sources in powder diffraction is much more the result of the use of time of flight TOF method than an advantage of the sources themselves. This is illustrated by the outstanding characteristics of the first modern TOF powder diffractometer at a reactor source, which is under construction at the Hahn Meitner Institut HMI Berlin. This instrument EXED Extreme Environment Diffractometer will provide ultra high resolution comparable to synchrotron radiation instruments, the flexibility of variable resolution to achieve very high intensity at conventional resolutions, and the capability to operate with scattering angle domains strongly restricted by extreme sample environment equipment. With a slight modification the basic TOF chopper system of EXED can also be used to achieve pulse shaping in powder diffraction work on short and long pulse spallation sources in order to get enhanced and variable resolution. The modification required includes additional frame overlap choppers to implement frame multiplication to use the data collection time between source pulses most efficiently. The 6 amp; 61549;s wavelength independent minimum primary pulse length opens up the way to achieve the same resolution as highly successful synchrotron X ray diffractometer