We report the first successful extraction of accumulated ultracold neutrons (UCN) from a converter of superfluid helium, in which they were produced by downscattering neutrons of a cold beam from the Munich research reactor. Windowless UCN extraction is performed in vertical direction through a mechanical cold valve. This prototype of a versatile UCN source is comprised of a novel cryostat designed to keep the source portable and to allow for rapid cooldown. We measured time constants for UCN storage and extraction into a detector at room temperature, with the converter held at various temperatures between 0.7 and 1.3 K. The UCN production rate inferred from the count rate of extracted UCN is close to the theoretical expectation.
Ultracold Neutron Sources: An Essentially Enhanced Optimal Operation Temperature for Ortho-Deuterium-Based Superthermal Converters
Heinz Maier-Leibnitz Zentrum (MLZ), Technical University Munich（海因茨·迈尔-莱布尼茨中心，慕尼黑工业大学）；Technical University Munich, TUM School of Natural Sciences, Physics Department（慕尼黑工业大学，自然科学学院，物理系）
High-Density Ultracold Neutron Source for Low-Energy Particle Physics Experiments
Universität Heidelberg（海德堡大学）；Institut Laue–Langevin（朗之万研究所）；University of Illinois at Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）；Technische Universität München（慕尼黑工业大学）；STFC Rutherford Appleton Laboratory（STFC卢瑟福阿普尔顿实验室）
Performance of the upgraded ultracold neutron source at Los Alamos National Laboratory and its implication for a possible neutron electric dipole moment experiment
