Ultracold neutron spectra produced by an upgraded supermirror turbine

Ultracold neutrons (UCN) with the velocity below about 10 m/s are produced with the mechanical UCN generator of a supermirror turbine from incident VCN supplied by a liquid deuterium cold source. The upgrading of the turbine is carried out by replacing the original blades of three flat supermirrors by those of five supermirrors arranged in a similar polygonal shape but much narrower channel width, in order to fit in with the distorted VCN spectrum with a much enhanced intensity from the liquid deuterium container. The careful correction for the centrifugal effect on neutrons during the passage in the blades is also performed in the arrangement of the feed guide angle. The time-of-flight measurements of the UCN output indicate about three times higher intensity obtained with the upgraded blades comparing to the original ones. A velocity diagram analysis explaining the measured velocity spectrum is also given. (author)