Mobile High-$T_{\rm c}$ SQUID System for MCG Measurement

We developed a mobile high critical temperature (high-T _c) superconducting quantum interference device (SQUID) system for a magnetocardiogram (MCG) measurement. The device is composed of a small cryostat, a high-T _c SQUID magnetometer, and digital flux-locked loop (FLL) electronics. A small commercially obtained vacuum bottle enables the device to be hand-held. Large dynamic range was achieved through the digital FLL processing. We also proved the feasibility of this mobile high-T _c SQUID system using simple construction. MCG measurements while holding a cryostat and also in unshielded conditions were successfully demonstrated.