Present status on DNA ToF backscattering spectrometer in MLF, J-PARC

Matsuura, Masato*; Kawakita, Yukinobu  ; Yamada, Takeshi*; Tominaga, Taiki*; Tamatsukuri, Hiromu   ; Nakagawa, Hiroshi   ; Ouchi, Keiichi*

DNA is a time-of-flight backscattering spectrometer installed at the Materials and Life Science Experimental Facility (MLF) in Japan Proton Accelerator Research Complex (J-PARC), Tokai, Japan. Its purpose is revealing pico to nano second dynamics in a wide field of sciences and industrial applications including soft matter, bio-molecules, chemical molecules, battery, catalyst, and magnetism. A pulse-shaping chopper equipped at the 7.75 m position from the coupled moderator makes this instrument relatively short in the neutron guide length (42 m from the moderator to the sample position). Its maximum rotation speed of 300 Hz provides us fine energy resolutions up to 1.4 micro second for a sample with dimension of 1 cm wide and 1cm tall. Changing phases of the slit opening of the chopper enables us to select energy bands and even to scan a wide energy transfer range with the highest resolution. Two types of analyzer mirrors of Si111 and Si311 cover large momentum transfer ranges of 0.08 to 1.98 and 1.79 to 3.39 , respectively. Frequently used measurement modes are a high-flux mode without rotating the chopper and a high-resolution mode with 225 Hz. Those provides 12 and 3.6 micro eV energy resolutions for a large sample of 1.4 cm wide and 4 cm tall. The back-coat by neutron absorber such as Gd and GdO for Si analyzer mirrors serves us in realizing extremely high signal-to-noise ratio of , which allows us to obtain QENS spectra from a tiny amount of sample or a dilute protein solution. Various conditions of sample environment are available; cryo-furnaces (4 K to 700 K), a 2K cryostat, a top-loading sample stick for applying electric field, a humidity control system, a cryostat with a samples changer for three samples, an inner atmosphere controller for cryo-furnaces and so on. A high temperature furnace up to 1000K, 3.5 Tesla cryo-magnet and a sample changer for 20 samples are under commissioning.