超流動⁴He中の流れ場可視化にむけた中性子³He吸収反応による⁴He励起分子集団生成の実証

抄録

For visualization of flows in superfluid ⁴He, an excited helium molecule (excimer) ⁴He₂^* is an ideally suitable flow tracer, because it has a molecular size with a minimum influence to flow, and follows only normal-component flow around 1K but only vortices below 0.5 K. However, to visualize flow fields in 3D, small clouds (clusters) of ⁴He₂^* are required, whose generation method has not been established. To generate such clusters, we proposed the use of neutron-³He absorption reaction. In the proof-of-principle experiments, we have confirmed the ⁴He₂^* generation, while the detail of clusters still remains undetermined. The concept, methods, progress, and present status are shown.