2-DIMENSIONAL POSITION-SENSITIVE DETECTION FOR MEDIUM-ENERGY ION-SCATTERING

We have designed and built a two-dimensional position sensitive ion de tector for use in combination with a toroidal electrostatic analyser. The detector is part of a medium-energy ion scattering set-up, which w e exploit to determine the atomic structure and composition of surface s and interfaces. The ion position is resolved in the angular and ener gy dispersive directions of the analyser by means of microchannel plat es and a charge-dividing collector. The analyser/detector combination has an acceptance in the angular direction of 20-degrees and in the ba ckscatter energy direction of 2.0% of the central pass energy. The det ection system has an angular resolution of 0.10-degrees and a relative energy resolution of 1.0 X 10(-3) (FWHM). All detection events are pr ocessed individually by a transputer system controlling a VME-bus inte rface and capable of handling a periodic count rate of 65 kHz. A Silic on Graphics workstation serves as a user-interface.