High-Tc dc SQUID cooled by pulse-tube cooler and corrosion measurements

We developed an YBCO high-Tc dc superconducting quantum interference device (SQUID) system cooled by a pulse-tube cooler. To stabilize and control the operating temperature of SQUID, a temperature controlling method, using dc SQUID itself as the temperature sensor, was developed. With the temperature controller, the temperature fluctuation could be reduced to about 50 mK and the dc SQUID magnetometer could keep locking for over 8 h. Using this dc SQUID magnetometer, we did some corrosion measurements in shielding. The field produced by the corrosion of aluminum plate with one side immersed in corrosion solution could be successfully detected.