LOW-T-C AND HIGH-T-C SUPERCONDUCTING DETECTORS FOR HIGH-PRESSURE

An experimental procedure has been accomplished to detect high pressur es by a specific method, which is based on the dependence of the super conducting critical temperature T-c on the external pressure P. For th e realization of such kind of measurements a beryllium-bronze multipli cator has been built to create, control and maintain high pressures an d different kinds of superconducting sensors have been placed inside i t to perceive the pressure and its increase or decrease. The construct ion and sizes of the high-pressure bomb are suitable to fulfil these r equirements. Using oil-pentane mixtures as working media, the arrangem ent of the multiplicator provides long time stationary pressure condit ions for the experiments. From the point of view of sensitivity, In an d Sn seem to be the best materials, the critical temperature of which changes by about 1 K in the pressure interval of 1-18 000 bar. The qua litative relation between T-c and P can be expressed by -dT(c) similar to PTc, but due to nonlinear character of the function T-c = f(P) its actual shape can be determined individually for different ranges of p ressure on the basis of measurements. As far as the pressure dependenc e of the critical temperature of high-T-c superconductors is concerned , the coefficient dT(0)/dP has average values of 0.64 K kbar(-1), 0.04 K kbar(-1) and 0.1 K kbar(-1) for La-Ba-Cu-O, Y-Ba-Cu-O and Hg-Ba-Ca- Cu-O compounds, respectively, giving a good starting condition to fabr icate pressure-detectors from them. (C) 1997 Academic Press Limited.