Overview of a new biological neutron diffractometer (iBIX) in J-PARC

Since 2004, Ibaraki Prefectural Government in Japan has started to construct a Time-of-Flight (TOF) neutron diffractometer for biological macromolecules for industrial use at J-PARC, near JRR-3 in JAEA. From 2008, Ibaraki University will operate this machine with the support of Ibaraki Prefecture in order for users to do experiments. The diffractometer is designed so that it can measure crystals the maximum cell dimension of which is up to around 160 إ. It is expected to measure more than 100 samples per year if they have 2 mm3 in crystal volume. As a result, the efficiency will be more than 100 times higher than that of the present high performance diffractometer, BIX-4 in JRR-3 reactor in JAEA. To realize this performance, a coupled moderator (intense neutrons, but broad pulse in time resolution) was selected. In addition, two important and key items should be developed: a new detector with high spatial resolution (less than 1 mm) and a special program to de-convolute overlapped Bragg reflections on the raw data. The detector uses ZnS:Ag/6LiF scintillator with wavelength-shift-fiber (WLSF) system. The program has been designed using a complicated kind of profile-fitting method. The current status of these developments as well as the diffractometer constructions is reported.