Observation of far-ultraviolet signatures of the $^3$He($n,tp$) reaction

In previous work [1] on the production of Lyman $\alpha$ radiation in the the $^3$He($n,tp$) reaction in a cell of $^3 $He gas at atmospheric pressure, we found that $\approx 50$ Lyman $\alpha$ photons were produced per absorbed neutron. These photons are produced by excited states of T and H created by charge-exchange and excitation collisions of $t$ and $p$ with the background gas [2]. This provides a method of neutron detection with intrinsic discrimination against gamma rays. We are now conducting studies of far-ultraviolet emission in $^3$He mixtures with other gases, e.g. $^4$He, N$_2$, Ne, Ar, Kr, and Xe. The heavier noble gases amplify by factors of over 100 the signals seen in pure $^3$He. The results suggest the possibility of an efficient optical neutron detector with improved economy of use of $^3$He.\\[4pt] [1] A. K. Thompson, {\it et al.}, {\it J. Res. Nat. Inst. Standards Tech.} {\bf 113}, 69 (2008)\newline [2] J. W. Cooper, {\it et al.}, {\it J. Res. Nat. Inst. Standards Tech.} {\bf 114}, 185 (2009)