Investigation of Vanadium foils for in situ UCN detection for the UCN$\tau$ lifetime experiment

We will report on preliminary work aimed at developing a new technique for counting trapped ultra-cold neutrons (UCN) for a precision lifetime experiment, UCN$\tau$. We propose to mechanically insert a $^{51}$V foil to capture neutrons in the trap and then count the $^{52}$V decays. The negative potential of $^{51}$V; relatively short half life of $^{52}$V (3.74 minutes); and large imaginary potential makes $^{51}$V ideal for an activation/counting technique. Preliminary measurements show that high counting efficiency and low backgrounds can be obtained by counting $\gamma-\beta$ coincidences.