High Tc SQUID based magnetocardiography system in unshielded environment

Incorporating special active shielding for unshielded SQUID based applications, a magnetocardiography (MCG) system has been designed and implemented. The MCG system consists of two High Tc rf SQUID magnetometers which are placed in an axial gradiometer arrangement. The considered active shield is a two stages of shielding system, each of which has been designed for different frequency and dynamic range characteristics. Using this shielding system, the disturbing magnetic signals of the environment could be attenuated such that the nano-tesla artificial heart signal could be obtained in our unshielded laboratory environment. The system is based on a designed liquid nitrogen dewar with rf-interference aluminum shield and appropriate structure for short liftoff. The system incorporates a two channel rf SQUID electronic readout and also the required PID circuit controller for active shielding system. In this work, different parts of the MCG system is explained and the effectiveness of the active shield system and the obtained results of the implemented SQUID based MCG system is presented.