Gains from the upgrade of the cold neutron triple-axis spectrometer FLEXX at the BER-II reactor

TL;DR

The paper details the upgrade of the FLEXX cold neutron triple-axis spectrometer, highlighting significant improvements in neutron flux and resolution, enabling advanced measurements with smaller samples.

Contribution

It presents a comprehensive characterization of the upgraded FLEXX spectrometer, including flux, resolution, and performance enhancements over the previous version.

Findings

Tenfold increase in neutron flux.

Narrower incoherent elastic energy widths.

Enhanced capability for small sample measurements.

Abstract

The upgrade of the cold neutron triple-axis spectrometer FLEXX is described. We discuss the characterisation of the gains from the new primary spectrometer, including a larger guide and double focussing monochromator, and present measurements of the energy and momentum resolution and of the neutron flux of the instrument. We found an order of magnitude gain in intensity (at the cost of coarser momentum resolution), and that the incoherent elastic energy widths are measurably narrower than before the upgrade. The much improved count rate should allow the use of smaller single crystals samples and thus enable the upgraded FLEXX spectrometer to continue making leading edge measurements.