A superfluid liquid helium target for low-momentum electron scattering experiments at the S-DALINAC

A New Neutron Lifetime Experiment with Cold Neutron Beam Decay in Superfluid Helium-4

The puzzle remains in the large discrepancy between neutron lifetime measured by the two distinct experimental approaches -- counts of beta decays in a neutron beam and storage of ultracold neutrons in a potential trap, namely, the beam method versus the bottle method. In this paper, we propose a new experiment to measure the neutron lifetime in a cold neutron beam with a sensitivity goal of 0.1% or sub-1 second. The neutron beta decays will be counted in a superfluid helium-4 scintillation detector at 0.5 K, and the neutron flux will be simultaneously monitored by the helium-3 captures in the…

Experimental study of ultracold neutron production in pressurized superfluid helium

We have investigated experimentally the pressure dependence of the production of ultracold neutrons (UCN) in superfluid helium in the range from saturated vapor pressure to 20bar. A neutron velocity selector allowed the separation of underlying single-phonon and multiphonon pro- cesses by varying the incident cold neutron (CN) wavelength in the range from 3.5 to 10Å. The predicted pressure dependence of UCN production derived from inelastic neutron scattering data was confirmed for the single-phonon excitation. For multiphonon based UCN production we found no significant dependence on pressure…

Ultracold neutron accumulation in a superfluid-helium converter with magnetic multipole reflector

We analyze accumulation of ultracold neutrons (UCN) in a superfluid-helium converter vessel surrounded by a magnetic multipole reflector. We solved the spin-dependent rate equation, employing formulas valid for adiabatic spin transport of trapped UCN in mechanical equilibrium. Results for saturation UCN densities are obtained in dependence of order and strength of the multipolar field. The addition of magnetic storage to neutron optical potentials can increase the density and energy of the low field seeking UCN produced and serves to mitigate the effects of wall losses on the source performanc…

Ultracold neutron production and up-scattering in superfluid helium between 1.1 K and 2.4 K

Ultracold neutrons (UCNs) were produced in a 4 liter volume of superfluid helium using the PF1B cold neutron beam facility at the Institut Laue-Langevin and then extracted to a detector at room temperature. With a converter temperature of 1.08 K the number of accumulated UCNs was counted to be $91,\!700 \pm 300$. From this, we derive a volumetric UCN production rate of $(6.9 \pm 1.7)\,\mathrm{cm^{-3}\,s^{-1}}$, which includes a correction for losses in the converter during UCN extraction caused by a short storage time, but not accounting for UCN transport and detection efficiencies. The up-sca…

一种用于超流氦实验的低温腔体装置，具备光纤与电学接入

A cryogenic chamber setup for superfluid helium experiments with optical fiber and electrical access

本文设计并构建了一种可在毫开尔文温度下运行、具备光纤和电学接入的超流氦低温腔体，结合自动化气体处理系统实现亚纳米级薄膜厚度控制，并展示了厚度依赖的光力声子激射，为超流氦基础与应用研究提供通用平台。

壁面粗糙且涂覆超流氦的中子阱中电场增强的数值计算

Numerical Calculation of Electric Field Enhancement in Neutron Traps with Rough Walls Coated with Superfluid Helium

该研究针对超冷中子阱液氦膜保持问题，通过数值计算阱壁粗糙尖端的电场分布，估算其对维持足够厚度氦膜的作用，为超冷中子阱设计提供电场调控依据。