Implementation of a continuous SQUID

As demonstrated in , the SQUID is characterized by excellent intrinsic energy resolution. On the other hand, it is a natural magnetic flux sensor whose performance deteriorates at low frequencies due to technological defects in the manufacture of Josephson junctions. In this section, we will look at its use in quasi-static magnetic measurements, examining the following three aspects:

• coupling the SQUID to the external environment ;

• reduction of the effects of excess noise (1/f) at low frequencies ;

• coupling the SQUID to the solid-state amplifier system.