Accession Number : ADA136951

Title :   Absolute Electroacoustic Measurement of Temperature Oscillations in Superfluid Helium by the Reciprocity Method.

Descriptive Note : Master's thesis,


Personal Author(s) : Ogg,B. R. ; Valdivia,J. , Jr

Report Date : DEC 1983

Pagination or Media Count : 161

Abstract : An experiment will be described which has verified for the first time an extension of the reciprocity calibration technique to reversible thermal transducers in superfluid helium. A plane-wave resonator of circular cross-section was capped at both ends by reversible teflon slit-electret diaphragms to generate or detect thermal waves. The resonator also incorporated a heater and a d.c.- biased carbon resistance thermometer to set independent upper and lower limits on the thermal excursions within the resonator. The temperature excursions measured by the reciprocity method fell between the upper and lower limits, which, for lower modes, were separated by only a few percent. For higher modes, the lower limit departed from the upper limit due to the thermal inertia of the resistance thermometer, but the reciprocity result remained only a few percent below the upper bound set by the thermophone over nearly a decade in frequency. The 'slit-electret' transducers had sensitivities in excess of 100 V/K, and temperature oscillations as small as 10 to the 10th power K/square root of HZ were detected.

Descriptors :   *Electroacoustic transducers, *Acoustic measurement, Oscillation, Electroacoustics, Liquid helium, superfluidity, Calibration, Acoustic impedance, Theses, Resonators, Data acquisition, Computer programming

Subject Categories : Electrical and Electronic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE