Evidence of scattering of bulk elementary excitations in isotopically pure liquid helium-II at low temperatures

摘要

This short report is concerned with experimental investigations of bulk elementary excitations (BEEs) in the isotopically pure liquid helium-II at low temperatures below 100 mK. The evidence of BEEs' scattering is introduced in this work. Two identical Au-heaters were used to generate BEEs. The first pulsed heater generates BEE beams to record them. The second heater serves to generate BEE beams in order to scatter the first beams, operating delay time between pulses of the heaters. Experimental signals were recorded by several bolometers situated both above and below the liquid surface: scattered BEEs are travelling in the liquid from the pulsed heater to the bolometer; scattered BEEs, reaching the liquid surface, evaporate 4He-atoms detected by two bolometers positioned in a vacuum; scattered signals are reflected from the liquid surface back to the liquid and are detected by the other bolometer situated in the liquid. It is manifested that the experimental results showed a dramatic decrease in peaks of recorded signals. Also, signal losses for different heater powers were calculated.