Upgrade of the ultracold neutron source at the pulsed reactor TRIGA Mainz J. Kahlenberg, D. Ries, K. U. Ross, C. Siemensen, M. Beck, C. Geppert, W. Heil, N. Hild, J. Karch, S. Karpuk et al. (6 more) Eur. Phys. J. A, 53 11 (2017) 226 Published online: 28 November 2017 DOI: 10.1140/epja/i2017-12428-9