Temperature dependence of the probability of “small heating” and total losses of UCNs on the surface of Fomblin oils of different molecular mass

Abstract

We measured the temperature dependence of the probability of small heating and total losses of UCNs on the PFPE Fomblin Y surface with various molecular mass ̅ (2800, 3300, 6500 аmu) in the temperature range of 100-300 К. The probability of small heating sharply decreases with increasing ̅ and decreasing temperature. The probability of total loss weakly decreases with decreasing temperature and takes the minimum value at ̅ = 3300 аmu. As this oil provides a homogeneous surface with minimal probabilities of small heating and total losses of UCNs, it is the preferred candidate for experiments on measuring the neutron lifetime.

Production of ultracold neutrons in a decelerating trap

“…High UCN densities are critical in studies of the dynamics of nano-objects on the surface [10,35], and might become important in a number of neutron scattering methods similar to those that use cold and thermal neutrons, including spin-echo spectrometers, reflectometers, small-angle scattering diffractometers, time-of-flight spectrometers, and others. These methods, however, have yet to be adapted to the velocities of very cold neutrons (VCNs), and even more so to the UCN velocities.…”