부산대학교 도서관

We designed two different sensor SQUIDs for the readout of the resonant mass gravitational wave detector MiniGRAIL. Both designs have integrated input inductors in the order of 1.5 $\mu{\rm H}$ and are planned for operation in the mK temperature range. Cooling fins were added to the shunt resistors. The fabricated SQUIDs show a behavior that differs from standard dc-SQUIDs. We were able to operate a design with a parallel configuration of washers at reasonable sensitivities. The flux noise saturated to a value of 0.84 $\mu\Phi_{0}/\surd{\rm Hz}$ below a temperature of 200 mK. The equivalent noise referred to the current through the input coil is 155 ${\rm fA}/\surd{\rm Hz}$ and the energy resolution yields 62 $\hbar$ .