QFS2016 Book of Abstracts

Abstracts

P3.28 Microwaves radiation by roton streams in superfluid helium Khodusov Valery, Naumovets Artem Karazin Kharkov national university, physical and technical department, Ukraine, Kharkov, Ak. Kurchatov ave, 31 The process of two rotons annihilation into two microwave photon is considered in present work. The possibility of such process follows from an analysis of the two roton Raman scattering experiments in the superfluid helium [1]. In the Rybalko’s experiments generation of microwaves in the disk dielectric resonator was observed with a frequency of 180 GHz [2]. It is equal to the energy of the roton gap. Microwave were excited by a heat flows, which were created by the Kapitsa guns. The explanation of this generation is possible through the processes of two bound rotons annihilation. [1] C A Murray 1975 J. Phys. C: Solid State Phys. 8 L90 [2] Rybalko A.S. arxiv.org/pdf/0811.2114 P3.29 Thermal boundary resistance between simple objects and liquid 3 He Harriet van der Vliet(1), Lev Levitin(1), Antonio Corcoles(1,2), Jan Nyeki(1), Andrew Casey(1), John Saunders(1) 1) Physics department, Royal Holloway, University of London, UK 2) at IBM Watson centre, Yorktown Heights, NY, USA The thermal boundary resistance (R) between materials and liquid helium is crucial in the cooling of materials into the microkelvin regime, yet not fully understood. We have designed a set-up to measure R between a simple metallic object (wire or foil) and liquid 3 He. The metal is cooled in a 3 He immersion cell, precooled with a copper nuclear demagnetisation cryostat. The temperature of the metal is determined by a SQUID based current sensing noise thermometer. Measurements on a 25 micron diameter gold wire found a crossover to very weak temperature dependence of R below 3 mK. Follow-up experiments on a 7 micron gold foil will also be reported to search for potential size effects.

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