Method and apparatus for time of flight medium energy particle scattering

Abstract

A method and apparatus for determining material properties such as composition and structure of the surfaces of bulk materials and thin film sample members using time-of-flight medium energy particle scattering is provided. The method and apparatus are based upon scattering particles from a sample material or ejecting particles from the sample material. The particles may include both uncharged particles and charged particles. Particles are scattered into a chamber from a sample surface using known methods. The particles pass through the first of two grids which grid is held at ground potential and which limits the electrostatic field. The particles then pass through a very thin carbon foil which is held at a potential of -3kV. On passing through the carbon foil the particles emit secondary electrons. An electric field is created between the carbon foil and the second grid, which accelerates the secondary electrons. The electrons strike a first microchannel plate detector and this generates a start pulse. The scattered particle continues in the chamber to a second microchannel plate detector. When the particle strikes the detecetor a stop pulse is generated. The interval between the start pulse and the stop pulse is used in generating an energy spectrum which is a signature of the composition of the sample material. A very fast timing resolution is provided at low cost using relatively small sized equipment in combination with readily available accelerator equipment.