A clean, bright, and versatile source of neutron decay products

TL;DR

The paper introduces PERC, a new neutron beam station that provides a clean, well-defined source of neutron decay products with significantly improved precision and reduced background, enabling advanced neutron decay experiments.

Contribution

It presents the design and advantages of PERC, a versatile neutron decay source with enhanced phase space density and minimal background interference.

Findings

Achieves several orders of magnitude increase in phase space density.

Reduces spectral and angular distribution distortions by over tenfold.

Provides a well-separated, distortion-free neutron decay product beam.

Abstract

We present a case study on a new type of cold neutron beam station for the investigation of angular correlations in the beta-decay of free neutrons. With this beam station, called PERC, the 'active decay volume' lies inside the neutron guide, and the charged neutron decay products are magnetically guided towards the end of the neutron guide. Hence, the guide delivers at its exit a beam of decay electrons and protons, under well-defined and precisely variable conditions, which can be well separated from the cold neutron beam. In this way a general-purpose source of neutron decay products is obtained which can be used for various different experiments in neutron decay correlation spectroscopy. A gain in phase space density of several orders of magnitude can be achieved with PERC, as compared to existing neutron decay spectrometers. Neutron beam related background is separately measurable in PERC, and magnetic mirror effects on the charged neutron decay products and edge effects in the active neutron beam volume are both strongly suppressed. Therefore the spectra and angular distributions of the emerging decay particles will be distortion-free on the level of 10^-4, more than 10 times better than achieved today.