Variable Entry Biased Paracentric Hemispherical Deflector: Experimental results on energy resolution for different entry positions

A new hemispherical deflector analyzer (HDA) which is designed for electron energy analysis in atomic collisions has been constructed and tested. Using the crossed beam technique at the electron spectrometer, test measurements were performed for electron beam (200 eV) - Helium atoms interactions. These first experimental results show that the paracentric entries give almost twice as good resolution as that for the conventional entry. Supporting simulations of the entire lens-FFIDA spectrometer are found in relatively good agreement with experiment.