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.
Highlights
In 1962, Gertsenshtein and Pustovoit suggested using a photonic interferometer for gravitational wave (GW) detection [1]
We suggest here that more compact and still higher sensitivity instruments can be realized with the help of the unique features of superconductivity and superconducting electronics
Taking into account that in our case the mass of barbells is mainly localized in spheres rather than distributed evenly as in TOBA, we find that the spectral density of thermo-elastomechanical angular fluctuations is [15,53]
Summary
In 1962, Gertsenshtein and Pustovoit suggested using a photonic interferometer for gravitational wave (GW) detection [1]. It took more than half-century to successfully realize this idea in the LIGO instruments by a large international team of researchers [2,3] opening a new era in astrophysics. To further facilitate progress in this direction, higher sensitivity instruments are required. Various systems more advanced than LIGO are projected (see Table I). They are interferometric and require long optical arm lengths and/or cryogenic cooling. Unlike Weber’s cylinders [12,13,14] or LIGO mirrors [15], utilize not the longitudinal motion caused by the GW, which at a distance L
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