New photothermal cell equipped with Peltier elements for phase transition studies

A new universal cell for studies of phase transitions is proposed and its versatility demonstrated with an intact tomato seed as a sample under investigation, The temperature of the sensor head is regulated by computer controlled Peltier elements. The cell allows fully automated recording of temperature (from -35 to 70 degrees C) profiles. A diode laser (830 nm) was used to generate thermal waves in the sample to observe phase transitions, Pyroelectric materials such as a 9-mu m polyvinylidenefluoride foil and a LiTaO3 single crystal were used as detectors. No influence was observed on the noise behavior of the pyroelectric sensors due to the Peltier elements, An important issue was the thermal isolation of the pyroelectric sensor with respect to the environment, i.e., the temperature of the housing had to be stabilized. (C) 1996 American Institute of Physics.