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We report the instrumentation of a new positron diffractometer that is connected to the high-intensity positron beam at the neutron induced positron source Munich. Crucial elements for the adaption of the positron beam are presented, which include the magnetic field termination, the optional transmission-type remoderator for brightness enhancement, and the electrostatic system for acceleration and beam optics. The positron trajectories of the remoderated and the twofold remoderated beam have been simulated to optimize the system, i.e., to obtain a coherent beam of small diameter. Within a first beamtime, we tuned the system and characterized the direct beam. For the twofold remoderated beam of 10 keV energy, we experimentally observe a beam diameter of d < 1.3 mm, which agrees well with the simulation. [ABSTRACT FROM AUTHOR]

Low-energy positron beams are applied in a number of experiments in solid state physics and materials science as well as in atomic and particle physics. These experiments comprise of surface studies, depth dependent defect spectroscopy, and fundamental research with leptonic systems. The neutron induced positron source in Munich (NEPOMUC) is operated as a user facility providing a positron beam with an intensity of about 109 moderated positrons per second. In this paper, a review of the status of the positron beam facility with its instruments is given and several experiments are exemplarily highlighted. Recent and future developments for further improving the performance of positron beam experiments are discussed. [ABSTRACT FROM AUTHOR]

The neutron-induced positron source Munich (NEPOMUC) provides a monochromatic low-energy positron beam with an intensity of > 1 × 109e+ s-1 and a full width at half maximum (FWHM) diameter of about 10 mm. To create a small beam focus or sharp positron pulses of 100 ps FWHM the beam brightness needs to be enhanced by remoderation. This is achieved by focusing the primary beam magnetically onto a tungsten single crystal W(100) in reflection geometry. Afterwards the beam exhibits an intensity of > 5 × 107e+s-1 and a diameter of < 2 mm FWHM. To further optimize the beam quality of NEPOMUC we redesigned the remoderation unit. The new setup allows a precise positioning of the remoderator crystal within the focus of the magnetic lens. Additionally, a replacement of the crystal within several minutes and without breaking the beamline vacuum is possible that offers the opportunity for systematic tests of different remoderator materials. [ABSTRACT FROM AUTHOR]