T.Kh.Salikhov, O.Sh.Odilov
Tajik national university, Tajikistan, Dushanbe

Optoacoustic method determination of the kinetical coefficients of supefluid helium

The theory of generation of optoacoustic (OA) waves of the first and second sounds in superfluid helium for a case when the illumination lasers beam is sufficiently thin and weakly absorption by liquid. Two cases have been considered: 1) the variation of the amplitude of the illumination beam according the harmonious law; 2) the illumination beam is an impulse. Is shown that in both cases in system are generated optoacoustic waves of the first and second sounds, each of which consist of two components: pressure fluctuations propagated with velocity 1 u (usually) and 2 u (a slowly first sound); temperature fluctuations propagated with velocity 1 u (usually) and 2u (a fast second sound). From the analysis of the obtaining expressions and numerical calculations follows that phase’s ОА signals of a “slow" first sound and usually second sound are high sensitive parameters to kinetic coefficients and, therefore, measurements of these values allow to determination these coefficients.
Full paper pdf