Abstract
A new electrostatic energy analyser is presented. It uses two sets of spherical grids. The first one is a retarding field arrangement in which the particles are decelerated down to energies close to zero. The transmission properties of the retarding field are presented. The particles enter the second part, an inverted spherical accelerating set which sharply focuses the low energy particles into the entrance aperture of a multiplier, whereas the high energy part misses the aperture. By cutting out the fast part, only a narrow energy band reaches the detector and a high signal-to-noise ratio results.