Upgrade of the NEPOMUC Remoderator

M. Dickmanna, W. Eggera, G. Kögela, S. Vohburgerb, C. Hugenschmidtb aInstitut für Angewandte Physik und Messtechnik LRT2 Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, 85577 Neubiberg, Germany bHeinz Maier-Leibnitz Zentrum (MLZ) and Physik Department E21 Technische Universität München, Lichtenbergstraße 1, 5748 Garching, Germany

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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.

DOI:10.12693/APhysPolA.137.149 PACS numbers: 78.70.Bj, 41.75.Fr, 36.10.Dr\\vs*{8pt}