Trimmed superconductive magnetic pickup coil circuits

In a superconductive magnetic sensor:

• superconductive primary pickup coil circuit means for sensing a component of magnetic field or gradient of a magnetic field in which said primary pickup coil circuit means is disposed by picking up a magnetic flux proportional to the sensed magnetic field or magnetic field gradient component;
• an auxiliary superconductive trim coil circuit means disposed in said magnetic field common to said pickup coil circuit means for picking up a magnetic flux from said common magnetic field;
• sensor means electromagnetically coupled to said primary pickup coil circuit means and to said trim coil circuit means for combining magnetic flux picked up by both said primary pickup coil circuit means and said trim coil circuit means to derive an output proportional to the combined magnetic flux picked up by said primary pickup coil circuit means and by said trim coil circuit means;
• and
• means for varying the coupling of said auxiliary trim coil circuit means to the magnetic field in which it is disposed and while said auxiliary trim coil circuit is in a superconducting state to effect a change in the trim magnetic flux component coupled into said sensor means while said auxiliary trim coil circuit is in a superconducting state.