ISIS entered the international stage for engineering stress measurement in the mid-1990s, with the advent of the ENGIN diffractometer. The success of this instrument led to growing demand for a custom-built diffractometer optimised specifically for engineering measurements, resulting in the development of ENGIN-X; so-called because it was designed to provide an order of magnitude improvement in performance over ENGIN. ENGIN-X finally superseded ENGIN in June 2003, and has in fact surpassed expectations.
Neutron diffractometers are generally built as ‘all-purpose’ instruments, and their designs are compromises which balance the competing requirements to measure the intensities, positions and widths of diffraction peaks simultaneously. In the case of an optimally designed engineering strain scanner such compromises are not necessary, since the overriding requirement of the instrument is the accurate measurement of a lattice parameter, at a known location within the material under study.
An instrument optimized for stress measurement
Designed under these criteria, ENGIN-X is a 50m flight path instrument, sitting outside the main ISIS hall. It sits on a curved 'supermirror' neutron guide, with a large detector complement centered at 90º 2q. It incorporates accurate and large capacity positioning equipment, and a range of sample environment equipment for engineering studies of materials. ENGIN-X also incorporate considerable improvements in user interface software to simplify the experimental procedure for novice users.
The construction of the instrument was funded by the EPSRC, under grant GR/M51963. The project was a joint collaboration between The Open University, Manchester University, Imperial College, Salford University and ISIS.