Generation of
He
clusters via neutron-
He absorption reaction toward visualization of full velocity field in quantum turbulence
Matsushita, Taku*; Sonnenschein, V.*; Guo, W.*; Hayashida, Hirotoshi*; Hiroi, Kosuke
; Hirota, Katsuya*; Iguchi, Tetsuo*; Ito, Daisuke*; Kitaguchi, Masaaki*; Kiyanagi, Yoshiaki*; Kokuryu, Shoma*; Kubo, Wataru*; Saito, Yasushi*; Shimizu, Hirohiko*; Shinohara, Takenao
; Suzuki, So*; Tomita, Hideki*; Tsuji, Yoshiyuki*; Wada, Nobuo*
For flow visualization study of quantum turbulence in superfluid
He,
He
excimers are unique tracers which follow only normal-fluid component flow above 1 K. To generate detectable small
He
clouds (clusters) required for full-space velocity field measurements, we have adopted a new method based on neutron absorption reaction of
He impurities in
He and conducted proof-of-principle experiments. Generation of the
He
excimers was detected by laser-induced fluorescence using photomultiplier tubes. The fluorescence was observed to increase proportionally to the neutron flux, suggesting that a sufficient amount of
He
excimers were generated by neutrons. We also estimated the number of
He
excimers possibly generated by
-rays and found that the relevant contribution was less than 40%. Thus, the majority of the
He
excimers was confirmed to be generated via n-
He absorption reactions.