rf break-junction SQUID’s at 77 K

Break-junction rf superconducting quantum interference devices (SQUID’s) have been developed using bulk YBa2Cu3O7 ceramic samples which have been fabricated in the laboratory. The SQUID’s have been produced in both single, and two-hole topologies and their noise characteristics have been measured at 77 K. The equivalent flux noise of the two-hole SQUID at a frequency of 200 Hz was found to be 6.8×10−4 flux quantum/(Hz)1/2.