# Consistent description of UCN transport properties

## TL;DR

This paper provides a consistent model for UCN guide reflection properties by combining experimental measurements of helium pressure effects with simulations, establishing a reliable diffuse reflection probability.

## Contribution

It introduces a unified description of UCN guide diffuse reflection mechanisms across different guide lengths, supported by experimental data and simulations.

## Key findings

- Diffuse reflection probability is approximately 3%
- Guide transmission depends on helium pressure
- Simulations accurately reproduce experimental results

## Abstract

We have investigated the diffuse reflection probabilities of Replica guides for ultra-cold neutrons (UCN) using the so-called helium method. For the first time we could establish a consistent description of the diffuse reflection mechanism for different lengths of the guide system. The transmission of the guides is measured depending on the helium pressure inside of the guides. A series of simulations was done to reproduce the experimental data. These simulations showed that a diffuse reflection probability of $d = (3.0 \pm 0.5) \cdot 10^{-2}$ sufficiently describes the experimental data.