Study on a neutron guides for neutron beam transport in the straight section of C3 cold neutron beam line at JRR-3

Tamura, Itaru  ; Arai, Masaji ; Murayama, Yoji

The neutron guides installed in the curved section of C3 cold neutron beam line have been replaced by the neutron guides with supermirror (m = 3). Since the radius of curvature of the C3 beam line was not changed, we should carry out the design of the neutron guides in the straight section of C3 beam line in order to supply the short wavelength neutron. One of the best solutions to above-mentioned problem is to adopt a tapered guide just before the neutron beam port. Therefore, the tapered guide was designed so that neutron beam with the wavelenght of 2 and with a maximum divergence of 0.45 degree was focused on the monochromator of the neutron beam instrument. Compared with the case of the alignment installed the straight neutron guide with supermirror (m = 3), we obtained that the calculation result of transport efficiency increased by 1.45 times in the case of the alignment installed the tapered neutron guide with supermirror (m = 3) just before beam port.