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Ultra-cold neutron (UCN) is attractive for a search of the neutron electric dipole moment (nEDM). It is crucial to store UCNs with high density in a bottle for nEDM measurement apparatus. To increase the density, time focusing technique can be useful, where slow neutrons are accelerated and fast neutrons are decelerated by using magnetic potential. This device is called “rebuncher.” The rebuncher consists of a gradient magnet, RF coil, and neutron guide. The magnet generates a field gradient of 3.5 T/m (from 1 T to 0.2 T within 24 cm) in the longitudinal direction. By using anisotropic inter-poles, the magnet is compact and keeps the gradient uniform. The fabricated magnet showed good performance as designed. [ABSTRACT FROM PUBLISHER]

As was found in our previous study, the presence of the thermal peak in neutron spectra measured by the 3He ionization chamber makes it difficult to use its complete response function in an unfolding process. In order to significantly reduce the thermal peak counting rate, an active method of rejecting low energy neutrons (<180 eV) based on their time-of-flight has been developed and tested. The method required a modification of the proton accelerator beam line to produce short pulses of protons. The ratio of the number of detection events above thermal peak to the number of events scored in the thermal peak has been improved by a factor of 5. [ABSTRACT FROM AUTHOR]