Neutron diffractometer covering protein crystals with large unit cell at J-PARC

Kurihara, Kazuo; Tomoyori, Katsuaki; Tamada, Taro; Kuroki, Ryota

Many proteins, especially membrane proteins and protein complexes, have larger molecular weight and then unit cells of their crystals have larger volume. Therefore, our group had designed the diffractometer which can cover such crystals with large unit cell volume (target lattice length: 250 ) at J-PARC. In order to separate spots closer to each other in spatial as well as time dimension in diffraction images, our proposed diffractometer adopts longer camera distance (L2 = 800 mm) and selects decoupled hydrogen moderator as neutron source which has shorter pulse width. Under the conditions that L1 is 33.5 m, beam divergence 0.4 deg and crystal edge size 2 mm, this diffractometer is estimated to be able to resolves spots diffracted from crystals with a lattice length of 220 in each axis at d-space of 2.0 . In order to cover large neutron detecting area due to long camera distance, novel large-area detector (larger than 300 mm 300 mm) with a spatial resolution of better than 2.5 mm is under development. The final gain factor of this diffractometer is estimated to be about 20 or larger as compared with BIX-3/4 diffractometers operated in the research reactor JRR-3 at JAEA.