QFS2016 Book of Abstracts

Abstracts

P2.7 The electrical activity of He II with relative motion of normal and superfluid components Adamenko Igor, Nemchenko Egor V. N. Karazin Kharkiv National University The theory is proposed that explains the experiments [1–3] where an electric potential difference in the relative motion of the superfluid and normal components of superfluid helium (He II) was observed. The theory is based on the fact that in the presence of relative motion quantized vortex rings (QVR), contained in the normal component, have an anisotropic distribution function. This anisotropy and electrical properties of QVR leads to dipole moment density emergence in He II, which creates an electrical potential difference. References [1] A. S. Rybalko, Fiz. Nizk. Temp. 30, 1321 (2004) [2] A.S. Rybalko, S.P. Rybets, Fiz. Nizk. Temp. 31, 820 (2005) [3] T.V. Chagovets, Fiz. Nizk. Temp. 42, 230 (2016) P2.8 Measurement of drag of bubbles in liquid helium at high Reynolds numbers Vadakkumbatt Vaisakh(1), Ghosh Ambarish(1,2). 1) Indian Institute of science, Department of physics, Bangalore, India, 560012. 2) Indian Institute of Science, Centre for Nano Science and Engineering, Bangalore, India, 560012. Multielectron bubbles are micron sized cavities inside liquid helium with electrons localized on the inner surface. Recent experiments on MEBs using a Paul trap showed that they can be trapped for few hundred milliseconds and the properties could be measured in non-destructive manner. Using a new and improved technique, we were able to study MEBs of sizes up to 100 microns. Since MEBs are charged bubbles, their motion can be controlled by electric fields compared to the gas bubbles in other liquids which is governed by gravity. This salient feature of MEBs allowed us to measure the drag of MEBs as a function of Reynolds number by analysing the trajectories. Due to the low viscosity and surface tension of helium compared to other liquids, the measurements could be performed at Morton Numbers that have never been explored. We also show that how the shape of a single MEB evolves from spherical to ellipsoidal as their speeds vary.

58