Development of a New Reflection High-Energy Positron Diffractometer at NEPOMUC.

We report the development of a new positron diffractometer that will be coupled to the high-intensity positron source NEPOMUC located at the research neutron source FRM II. An optional transmission-type remoderator stage utilizing a Ni (100) foil will be installed to further enhance the brightness of the positron beam. The acceleration and focus onto the remoderator foil are realized by an electrostatic lens system. At the sample position we aim to obtain an almost parallel, slightly converging beam with a diameter of less than 1mm. Simulations were run to optimize the focus onto the remoderator foil and the electrostatic acceleration up to energies of 25 keV after remoderation. [ABSTRACT FROM AUTHOR]