Design of a wavelength frame multiplication system using acceptance diagrams

TL;DR

This paper presents a method for designing a wavelength frame multiplication system using acceptance diagrams to optimize neutron instrument performance at the European Spallation Source.

Contribution

It introduces a novel application of acceptance diagrams for designing WFM systems, improving understanding and addressing design challenges for neutron instruments.

Findings

Acceptance diagrams effectively aid in WFM system design.

The proposed design enhances wavelength range and resolution.

Potential for improved instrument performance at ESS.

Abstract

The concept of Wavelength Frame Multiplication (WFM) was developed to extend the usable wavelength range on long pulse neutron sources for instruments using pulse shaping choppers. For some instruments, it is combined with a pulse shaping double chopper, which defines a constant wavelength resolution, and a set of frame overlap choppers that prevent spurious neutrons from reaching the detector thus avoiding systematic errors in the calculation of wavelength from time of flight. Due to its complexity, the design of such a system is challenging and there are several criteria that need to be accounted for. In this work, the design of the WFM chopper system for the potential future liquids reflectometer at the European Spallation Source (ESS) is presented, which makes use of acceptance diagrams. They prove to be a powerful tool for understanding the work principle of the system and recognizing potential problems. The authors assume that the presented study can be useful for design or upgrade of further instruments, in particular the ones planned for the ESS.