Temperature dependence of the probability of "small heating" and total losses of ucns on the surface of fomblin oils of different molecular mass

TL;DR

This study investigates how temperature and molecular mass of Fomblin oils affect ultracold neutron losses and heating probabilities, identifying optimal conditions for neutron lifetime experiments.

Contribution

It provides the first detailed analysis of temperature and molecular mass effects on UCN losses on Fomblin oils, guiding material choice for neutron experiments.

Findings

Small heating probability decreases with molecular mass and temperature.

Total loss probability slightly decreases with temperature, minimal at Mw=3300 amu.

Fomblin Y with Mw=3300 amu offers optimal surface properties for UCN experiments.

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 masses Mw=2800, 3300, 6500 amu in the temperature range of 100-300 K. The probability of small heating sharply decreases with increasing Mw and decreasing temperature. The probability of total loss weakly decreases with decreasing temperature and takes the minimum value at Mw=3300 amu. 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.