On the resolution and intensity of a time-of-flight neutron reflectometer

Abstract

In a neutron reflection experiment, the reflectivity is determined as a function of wave-vector transfer q = 4 π θ / λ , with θ the glancing angle and λ the neutron wavelength. At a continuous neutron source, it may be advantageous to use the time-of-flight technique to determine λ . Then, a chopper system is used to pulse the beam. We will discuss all contributions to both q resolution and intensity. Special attention is paid to the comparison of using a single- and double-disc chopper system. Examples of the performance of both systems are given. The double-disc chopper produces a burst time proportional to λ . By matching the different contributions to the resolution, the resulting intensity can be optimised.