Gravitational wave sensors based on superconducting transducers

Abstract

Following the initial success of LIGO, new advances in gravitational wave (GW) detector systems are planned to reach fruition during the next decades. These systems are interferometric and large. Here we suggest different, more compact detectors of GW radiation with competitive sensitivity. These nonresonant detectors are not interferometric. They use superconducting Cooper pairs in a magnetic field to transform mechanical motion induced by GW into detectable magnetic flux. The detectors can be oriented relative to the source of GW, so as to maximize the signal output and help determine the direction of nontransient sources. In this design an incident GW rotates infinitesimally a system of massive barbells and superconducting frames attached to them. This last rotation relative to a strong magnetic field generates a signal of superconducting currents. The suggested arrangement of superconducting signal sources facilitates rejection of noise due to stray electromagnetic fields. In addition to signal analysis, we provide estimates of mechanical noise of the detector, taking into account temperature and elastic properties of the loops and barbells. We analyze at which parameters of the system a competitive strain sensitivity could be achieved. We have tested the basic idea of the detector in the laboratory and reached the theoretical Johnson-Nyquist noise limit with multiturn coils of normal metal. Realization of full-blown superconducting detectors can serve as viable alternatives to interferometric devices.