A new neutron single-crystal diffractometer dedicated for biological macromolecules (BIX-4)

A new neutron single-crystal diffractometer (BIX-4) has been constructed at 1G-B port of JRR-3M in JAERI. Since at 1G-B port another diffractometer for biology, BIX-3, and a high-resolution powder diffractometer (HRPD) coexist, the monochromator house needed to be reconstructed. The main architecture of BIX-4 is based on that of BIX-3. BIX-4 uses an elastically-bent perfect-Si crystal monochromator and neutron imaging plates as BIX-3. In addition, several optimizations of the monochromator and modifications from previous BIX-3 are carried out. The final gain of the neutron intensity at the detector position is estimated to be 2.5 times larger than previous BIX-3. That higher performance increases the opportunities to apply neutron crystallography to biological macromolecules which give only weak reflections and/or small crystals.