# Exact resolution function for double-disk chopper neutron time-of-flight spectrometers : Application to reflectivity

## TL;DR

This paper derives an exact resolution function for double-disk chopper neutron time-of-flight spectrometers, improving data fitting accuracy in reflectometry by accounting for multiple factors without Gaussian approximations.

## Contribution

It presents a precise calculation method for the resolution function in neutron spectrometers, surpassing traditional Gaussian approximations.

## Key findings

- Exact resolution function improves data fitting accuracy.
- Calculation accounts for wavelength distribution, tilt, collimation, and gravity.
- Numerical implementation matches theoretical derivations.

## Abstract

The exact resolution function in transfer vector for the reflectometer HERM\`ES at Laboratoire L\'eon Brillouin is calculated as an example of neutron time-of-fligh spectrometer with double-disk chopper. Calculation accounts for wavelength distribution of the incident beam, tilt of the chopper axis, collimation and gravity, without approximation of gaussian distributions or independence of these different contributions. Numerical implementation is provided that matches the sections of the paper. We show that data fitting using this exact resolution function allows us to reach much better results than its usual approximation by a gaussian profile.