We report on the strategy used to optimize the sensitivity of our search for a neutron electric dipole moment at the Paul Scherrer Institute. Measurements were made upon ultracold neutrons stored ...within a single chamber at the heart of our apparatus. A mercury cohabiting magnetometer together with an array of cesium magnetometers were used to monitor the magnetic field, which was controlled and shaped by a series of precision field coils. In addition to details of the setup itself, we describe the chosen path to realize an appropriate balance between achieving the highest statistical sensitivity alongside the necessary control on systematic effects. The resulting irreducible sensitivity is better than 1 × 10
−26
e
cm. This contribution summarizes in a single coherent picture the results of the most recent publications of the collaboration.
The neutron and its hypothetical mirror counterpart, a sterile state degenerate in mass, could spontaneously mix in a process much faster than the neutron β-decay. Two groups have performed a series ...of experiments in search of neutron – mirror-neutron (
n
−
n
′) oscillations. They reported no evidence, thereby setting stringent limits on the oscillation time τ
nn
′
. Later, these data sets have been further analyzed by Berezhiani et al.(2009–2017), and signals, compatible with
n
−
n
′ oscillations in the presence of mirror magnetic fields, have been reported. The Neutron Electric Dipole Moment Collaboration based at the Paul Scherrer Institute performed a new series of experiments to further test these signals. In this paper, we describe and motivate our choice of run configurations with an optimal filling time of 29 s, storage times of 180 s and 380 s, and applied magnetic fields of 10 μT and 20 μT. The choice of these run configurations ensures a reliable overlap in settings with the previous efforts and also improves the sensitivity to test the signals. We also elaborate on the technique of normalizing the neutron counts, making such a counting experiment at the ultra-cold neutron source at the Paul Scherrer Institute possible. Furthermore, the magnetic field characterization to meet the requirements of this
n
−
n
′ oscillation search is demonstrated. Finally, we show that this effort has a statistical sensitivity to
n
−
n
′ oscillations comparable to the current leading constraints for
B
′ = 0.
Ultracold neutrons were stored in a volume, using a magnetic dipole field shutter. Radial confinement was provided by material walls. Low-field seeking neutrons were axially confined above the ...magnetic field. High-field seeking neutrons are trapped inside the magnetic field. They can systematically shift the measured neutron lifetime to lower values in experiments with magnetic confinement.
Abstract We present a framework that supports physics teaching assistants in their teaching duties during exercise classes and that fosters their professional teaching development. The framework ...relies on the concept of Communities of Practice combining pedagogy with strategies and support for social interaction. We are discussing the positive effects of this novel approach on teaching, as well as its challenges.
The UCNA experiment was designed to measure the neutron β-asymmetry parameter A0 using polarized ultracold neutrons (UCN). UCN produced via downscattering in solid deuterium were polarized via ...transport through a 7 T magnetic field, and then directed to a 1 T solenoidal electron spectrometer, where the decay electrons were detected in electron detector packages located on the two ends of the spectrometer. A value for A0 was then extracted from the asymmetry in the numbers of counts in the two detector packages. We summarize all of the results from the UCNA experiment, obtained during run periods in 2007, 2008–2009, 2010, and 2011–2013, which ultimately culminated in a 0.67% precision result for A0.
At the Paul Scherrer Institute (PSI), a very intense source of ultracold neutrons (UCN) is being built. The UCN converter of solid deuterium must be contained in a vessel. Produced UCN leave that ...vessel through its top lid. To decide on the design of the vessel and the top lid, we have measured the transmission of neutrons with velocities between 3 and 20
m/s through different material foils. Contrary to expectations, we found that transmission through aluminium and aluminium alloys is equal or even higher compared to zirconium and reactor-grade zirconium alloys, respectively.
To complete our study of ultracold neutron (UCN) storage-vessel coatings, we have measured the Fermi potential for neutrons on diamondlike carbon coatings produced by laser induced vacuum arc ...deposition. A sample with an sp3 content of 0.45, measured using, for the first time, neutron transmission had a Fermi potential of (249±14)neV. A second sample with an sp3 fraction of 0.67, measured using cold neutron reflectometry, gave (271±13)neV. These values complete the demonstration that there is a viable alternative to Be in UCN physics.
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