Sputtered YBCO film bolometers

Abstract Studies of disordered sputtered films of YBCO, show a multiphase transition to the super-conducting state that can extend from the temperature of liquid helium to that of liquid oxygen. We have tested the use of such thin films as bolometers in the temperature range 4K to 15K as detectors for thermally generated acoustic waves in 4 He gas. In the experimental geometry, the response time of the device is typically 2μs. Temperatures determined from the acoustic velocities are compared to those from resistance thermometry. We have examined the stability of the films under thermal cycling and find some aging effects.