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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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