Fast processes studied with neutrons (msec time resolution)

In this project we will develop tools to analyse event mode neutron data in a collaboration between Uppsala University, ISIS and the ESS.

Time-resolved neutron scattering experiments with sub-msec resolution will be enabled at ESS starting from day one.Our approach is based on the collection of neutron event mode data combined with meta data from the sample environment. The data are merged by using universal time stamps.

The histogramming is done in the post-processing, which allows any user-defined time interval as well as data mining and mitigates the risk of loss of data due to the failure of equipment.

For reproducable excitations, data over many cycles may be added to improve statistics and avoid dead times - times at which the sample is not illuminated by neutrons.

The tools developed in this project will be implemented for all neutron scattering techniques and become part of the standard ISIS and ESS data reduction and visualisation routines.

During the ramp-up of the ESS our tools will be particularly valuable for beam diagnostics.As performance tests, we will address long-standing scientific challenges in viscoelasticity, and relate the non-linearities in the stress-strain relation of certain polymer systems to the structure or possible inhomogeneities on microscopic length scales.

Gaining this understanding is extremely important to understand why some polymers defy the description with a constitutive equation, which is required to predict, e.g. macroscopic flow.