The temperature dependence of ultra-cold neutron confinement times

UCN anomaly and the possibility for further decreasing neutron losses in traps

“…More recent results of experiments on UCN storage in Be traps [9] at room temperature and at 90 K confirmed the previous data [4][5][6] (the authors do not give values of loss coefficient Z, but they may be obtained from their curves of storage time as a function of UCN energy).…”

“…For example, the UCN storage experiments with very cold ð$ 10 KÞ beryllium UCN traps led [4][5][6] to the observation of surprisingly large UCN losses, exceeding by two orders of magnitude the predicted ones from transmission cross-sections of cold neutrons and from calculations based on the known excitation spectrum of Be. At room temperature the wall losses in Be traps exceed the calculated ones by an order of magnitude.…”

Loss and spinflip probabilities for ultracold neutrons interacting with diamondlike carbon and beryllium surfaces

“…In Ref. [18] consistency of the temperature dependence within the Debye model is claimed, using hydrogen contamination levels observed directly in other experiments. This interpretation was criticized in Ref.…”

“…Although the early experiments by, for example, Refs. [13][14][15] revealed no temperature dependence, later experiments observed a clear dependence for Be [16][17][18][19], Cu [3], and Fomblin oils [5]. Based on these results, the energy-independent loss parameter per wall collision, η, can be separated into a temperatureindependent part, η 0 , related to the absorption cross section σ a and a temperature-dependent part, η T , related to the inelastic cross section σ ie .…”

“…For σ ie more or less sophisticated approaches, for example in the context of the one-phonon-exchange Debye model and using the incoherent approximation, have been employed (see, e.g., Refs. [1][2][3]17,18]). In this approximation the inelastic cross section σ ie can be related to the coherent and incoherent cross sections, σ coh and σ inc , respectively.…”