Demonstration of Gd-GEM detector design for neutron macromolecular crystallography applications

TL;DR

This paper demonstrates a Gd-GEM detector prototype for neutron macromolecular crystallography, showing it meets key performance criteria such as efficiency, spatial resolution, and PSF, suitable for use at the ESS.

Contribution

The work presents the successful development and testing of a Gd-GEM detector prototype with improved design for neutron diffraction applications, matching performance of existing Helium-3 detectors.

Findings

Gd-GEM detector has a PSF without long tails, suitable for diffraction measurements.

The detector's efficiency ratio aligns with expectations compared to Helium-3 detectors.

Successful tests at neutron sources demonstrate practical applicability.

Abstract

The European Spallation Source (ESS) in Lund, Sweden will become the world's most powerful thermal neutron source. The Macromolecular Diffractometer (NMX) at the ESS requires three 51.2 x 51.2~cm$^{2}$ detectors with reasonable detection efficiency, sub-mm spatial resolution, a narrow point spread function (PSF) and good time resolution. This work presents measurements with the improved version of the NMX detector prototype consisting of a Triple-GEM detector with natural Gd converter and a low material budget readout. The detector was successfully tested at the neutron reactor of the Budapest Neutron Centre (BNC) and at the D16 instrument at the Institut Laue-Langevin (ILL) in Grenoble. The measurements with Cadmium and Gadolinium masks in Budapest demonstrate that the point spread function of the detector lacks long tails that could impede the measurement of diffraction spot intensities. On the D16 instrument at ILL, diffraction spots from Triose phosphate isomerase w/ 2-phosphoglycolate (PGA) inhibitor were measured both in the D16 Helium-3 detector and the Gd-GEM. The comparison between the two detectors show a similar point spread function in both detectors, and the expected efficiency ratio compared to the Helium-3 detector. Both measurements together thus give good indications that the Gd-GEM detector fits the requirements for the NMX instrument at ESS.