Development of drabkin energy filters for J-PARC project

Yamazaki, Dai  ; Soyama, Kazuhiko  ; Ebisawa, Toru*; Tamura, Itaru  ; Tasaki, Seiji*

Drabkin energy filters extract neutrons of required wavelength using spatial neutron spin resonance. If they are applied to pulsed neutrons, they could sharpen pulse width and cut tail neutrons without reducing band-width or peak-intensity. Shaping of J-PARC coupled-moderator pulse by a Drabkin energy filter was simulated. In the simulation, discrete field gradient to Bx is introduced and total field B is varied in accordance with the dominant wavelength at each moment at the filter position. The results suggest that about 90 % or more of tail neutrons from coupled moderator are cut and a fliter with fields of 200 periods could reduce pulse width up to that of decoupled moderator. Effects of fluctuations of width of each half period were studied and it was found that fluctuation within 1 % are tolerable for a flipper with field of 100 or 200 periods.