QFS 2016 Book of Abstracts

Abstracts

P2.31 Investigation of electric response in standing wave of first and second sound Tymofiy Chagovets Institute of Physics of the Czech Academy of Sciences We report an experimental investigation of the electric response of superfluid helium that arises in an acoustic resonator in the presence of a first sound standing wave. Previous experiments showed a strong correlation between the resonance frequency of the electric response and the frequency of the second sound resonance. In recent experiments we observed the appearance of an potential difference on electrostatic probe whose resonance frequency is corresponded to the frequency of the first sound resonance in the experimental range of temperature (1.75 - 2.15K). It was found that the amplitude of the electric potential, ΔU, in resonance is proportional to the amplitude of the pressure oscillations in the first sound wave. Possible reasons of the electric response onset induced by first and sound will be discussed. P2.32 Solid helium study using elasticity-sensitive torsional oscillator under DC rotation Tsuiki tomoya(1,4), Takahashi daisuke(2,4), Murakawa satoshi(3,4), Kono kimitoshi(4), Shirahama keiya(1,4) 1) Keio University, Department of Physics, Yokohama 223-8522 2) Ashikaga Institute of Technology, Department of General Education, Ashikaga 326-8558 3) University of Tokyo, Cryogenic Research Center, Bunkyo-ku 113-0032 4) RIKEN, Low Temperature Phys. Lab., Wako-shi 351-0198 Recent elastic measurement of solid 4 He under DC rotation shows the insensitiveness of its elasticity to DC angular velocity, while the same rotation condition makes the characteristic period change in solid-packed torsional oscillator (TO) experiments. This contradiction must be due to the difference of the AC velocity; TO method is done within 10-100 times larger AC velocity than the elasticity measurements. To study the solid property under DC rotation in large AC velocity, we employ a “floating core” TO (Reppy, JLTP2012) that is sensitive to the elasticity of solid. This should reveal whether the “fast” elastic response affects to the change in period of TO under rotation or not.

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