A high-temperature prototype instrument for downhole acoustic sensing

This paper presents the design for an acoustic instrument which can operate at frequencies of 10–40 kHz and temperatures up to 250°C. It first introduces a high-temperature circuit using Sandia´s Sprytron switching tube and an over-voltage gap. Next, the high-temperature performance of a 2-V Permendur magnetostrictive transducer (for the transmitter), and a piezoelectric material (for the receiver) is described. The problems encountered and the corresponding solutions are revealed. The design of an acoustic isolator and the mechanical housing of this instrument are presented.