Resonant photoacoustic cell for low temperature measurements

This paper describes a resonant photoacoustic cell for low temperature measurements. It has the shape of the Helmholtz resonator, with the microphone separated from the sample by a resonant tube. In this way the microphone is kept at room temperature while the sample temperature is lowered. When the sample is placed in a liquid nitrogen tank it is possible to change its temperature from 77 K to 300 K, with the aid of a furnace, which surrounds the sample holder. Two optical fibres lead the laser light to both sides of the sample, making possible the determination of the thermal diffusivity in all temperature intervals, by using the photoacoustic phase-lag method. (C) 1999 Elsevier Science Ltd. All rights reserved.