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RESEARCH PRODUCT

Thermal Excitation of Fourth Sound in Liquid Helium II

H. WiechertR. Schmidt

subject

PhysicsWave propagationLiquid heliumDiaphragm (acoustics)chemistry.chemical_elementSignallaw.inventionchemistrylawSecond soundThermalAtomic physicsHeliumExcitation

description

In narrow channels filled with helium II two wave modes propagate, fourth sound1–3 and the fifth wave mode.4–6 According to new results of theoretical studies,7–8 it has been predicted that it should be possible to excite both wave modes mechanically by vibrating the diaphragm of a condenser microphone as well as thermally by periodically heating the surface of a solid body (e.g., a resistance layer). Shapiro and Rudnick3 have produced and detected fourth-sound signals mechanically. In the present contribution it will be experimentally verified that it is also possible to excite fourth sound thermally. Since the theory7,8 gives the result that fourth sound can be generated thermally only if the fifth-wave mode is taken into account, the detection of a thermally excited fourth-sound signal is also a first, indirect proof for the existence of the fifth-wave mode.

https://doi.org/10.1007/978-1-4684-7864-8_105