The design of a versatile TOF neutron diffractometer providing the complementary use of neutron and X-ray scattering from a biomacromolecular single-crystal with large unit cells

Membrane proteins are major players in important cell processes and, therefore, are key targets for research on human health and drug development. The crystals of these membrane proteins typically have large unit cells with repeat of a few hundred angstroms. The average intensity of a Bragg peak decreases as the number of peaks increases with large unit cells. It is proposed to develop a dedicated best-in-class high-throughput and high-resolution time-of-flight biomacromolecular single-crystal neutron diffractometer at Japan Spallation Neutron Source (JSNS). A new diffractometer is being designed to collect a full hemisphere of Bragg data with a resolution of 1.5–2 Å on a crystal over a lattice constant of 250 Å. This diffractometer will have a spherical array of over 40 detectors, all pointing inward to enclose a basketball-sized chamber where the pulsed neutron beam will collide with the crystal sample. The neutron detectors will be inserted through openings in two aluminum hemispheres, which can be pulled apart to access the interior; the hemispheres themselves will be on sturdy support structures, ensuring open accessibility to the sample area and wide coverage of the solid angle to measure a large number of reflections derived from a biomacromolecular single-crystal with large unit cells. The sample chamber implemented in the spectrometer of this diffractometer could be operated under vacuum or helium gas to provide a clean environment for the neutron detector. The neutron diffractometer will be combined with an X-ray diffractometer for consecutive data collection with two different quantum beams at a measuring station