{"paper":{"title":"Solid deuterium surface degradation at ultracold neutron sources","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":["hep-ex","nucl-ex"],"primary_cat":"physics.ins-det","authors_text":"A.Anghel, A.Hawari, A.R.Young, A.Saunders, B.Blau, B.Lauss, B.Wehring, C.Cude-Woods, C.L.Morris, C.White, D.Ries, E.Korobkina, E.M.Lutz, G.Bison, G.Medlin, G.Zsigmond, K.Kirch, K.Leung, L.J.Broussard, M.Daum, M.Makela, M.Wohlmuther, N.Hild, P.Huffman, P.Schmidt-Wellenburg, R.W.Pattie, S.M.Clayton, T.L.Bailey, T.M.Ito, V.Talanov","submitted_at":"2018-04-23T11:47:36Z","abstract_excerpt":"Solid deuterium (sD_2) is used as an efficient converter to produce ultracold neutrons (UCN). It is known that the sD_2 must be sufficiently cold, of high purity and mostly in its ortho-state in order to guarantee long lifetimes of UCN in the solid from which they are extracted into vacuum. Also the UCN transparency of the bulk sD_2 material must be high because crystal inhomogeneities limit the mean free path for elastic scattering and reduce the extraction efficiency. Observations at the UCN sources at Paul Scherrer Institute and at Los Alamos National Laboratory consistently show a decrease"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1804.08616","kind":"arxiv","version":2},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}