Abstract
Although a substantial amount of information is available relating to the propagation of sound in liquefied gases, little or nothing has been done on the design and calibration of transducers at these low temperatures. This paper presents design considerations and measured characteristics of quartz, lithium sulfate, and barium titanate transducers for use at temperatures in the vicinity of −200°C. Measurements were made in liquid nitrogen of dielectric constant, piezoelectric coupling coefficient, and frequency constant in the neighborhood of 400 kc/sec. Completed transducers were calibrated for both receiving and transmitting responses by reciprocity techniques. Complex impedance and beam patterns were also obtained. With proper design, units withstand the thermal shock of sudden immersion LN2 without failure. Noise voltages caused by boiling of the LN2 represent a problem in impedance measurements at resonance. [Work carried out under contract from Bogue Electric Manufacturing Company, Paterson, New Jersey.]
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