Concentration of neutron velocity for high-density ultra-cold neutrons

Accelerator technique for neutrons is discussed in this article. In the case of pulsed neutrons, the velocity is well-defined as a function of their arrival time. Electromagnetic neutron accelerator/decelerator synchronized with the neutron time-of-flight is capable of selectively changing the neutron velocity and concentrating the velocity distribution. Possible enhancement of the neutron intensity at a specific neutron velocity is calculated by using numerical simulations. This technique, for example, can be applied to efficient conversion of ultra-cold neutrons with superfluid helium. (author)