Design of high resolution HTS-SQUID magnetometers for biomagnetic imaging

To image the magnetic fields produced by action, injury and development cur rents in isolated living tissue or small animal preparations one requires a field sensitivity of a few hundred fT/root Hz together with a sub-millimet er spatial resolution. The design constraints of HTS bicrystal SQUID magnet ometers with sub-millimeter resolution are analyzed in order to maximize fi eld sensitivity. The desired combination of sensitivity and spatial resolut ion can be achieved by a multiloop magnetometer of 600 mu m in diameter. Ou r calculations predict a magnetic field sensitivity of 120 fTHz(-1/2) for s ensors with more than five loops. Decreasing the sensor size to 300 pm resu lts in a field sensitivity of 320 fTHz(-1/2) requiring four loops.