The UCN$tau$ experiment is designed to measure the lifetime $tau_{n}$ of the free neutron by trapping ultracold neutrons (UCN) in a magneto-gravitational trap. An asymmetric bowl-shaped NdFeB magnet Halbach array confines low-field-seeking UCN within
the apparatus, and a set of electromagnetic coils in a toroidal geometry provide a background holding field to eliminate depolarization-induced UCN loss caused by magnetic field nodes. We present a measurement of the storage time $tau_{store}$ of the trap by storing UCN for various times, and counting the survivors. The data are consistent with a single exponential decay, and we find $tau_{store}=860pm19$ s: within $1 sigma$ of current global averages for $tau_{n}$. The storage time with the holding field deactiveated is found to be $tau_{store}=470 pm 160$ s; this decreased storage time is due to the loss of UCN which undergo Majorana spin-flips while being stored. We discuss plans to increase the statistical sensitivity of the measurement and investigate potential systematic effects.
The dynamical structure factor of solid $^{15}$N$_{2}$ in the $alpha$ phase ($T<35$K) is measured at the IN4 time-of-flight spectrometer at the Institut Laue Langevin, and the potential performance of this substance as a UCN converter is assessed. Th
e cross-section to down-scatter neutrons to ultra-cold neutron energies is determined as a function of incident energy, as well as the up-scattering mean free path. The UCN production cross-section is found to be approximately 20% of that of deuterium. However, UCN with energy 181 neV have an up-scattering mean free path of 46 cm at $T=5.9$ K, which is $sim20$ times larger than deuterium. Therefore, a large volume $alpha-^{15}$N$_{2}$ source may produce an improved UCN density if sufficient isotopic purity can be achieved.
