arXiv subjects

Jens Gundlach

Publications and source records attributed to Jens Gundlach.

5 recordsLinked to original sources

arXiv2026

A Tale of Two Calibrators: Comparing Newtonian and Photon Calibration in Advanced LIGO after the Third Observing Run

Precise calibration of LIGO's strain readout plays a vital role in our ability to extract information from gravitational-wave detections. We present a comparative analysis of two independent direct-force calibration methods: the Newtonian Calibrator (NCal) and Photon Calibrator (PCal) systems. Currently, LIGO relies solely on the PCal system as its absolute calibration reference. To facilitate comparison, a series of direct-force injections were performed using the NCal and PCal systems at the LIGO Hanford observatory just after the completion of the third observing run. We compute the ratio of the measured to expected strain amplitudes for every injection. For each injection frequency across a 30 Hz band, the ratios of NCal and PCal differ by $\sim$0.5-1%, demonstrating a small systematic difference between the two systems. This offset highlights the importance of maintaining multiple independent calibration references to validate LIGO's calibration.

gr-qc↗

arXiv2021

Initial Results from the LIGO Newtonian Calibrator

The precise calibration of the strain readout of the LIGO gravitational wave observatories is paramount to the accurate interpretation of gravitational wave events. This calibration is traditionally done by imparting a known force on the test masses of the observatory via radiation pressure. Here we describe the implementation of an alternative calibration scheme: the Newtonian Calibrator. This system uses a rotor consisting of both quadrupole and hexapole mass distributions to apply a time-varying gravitational force on one of the observatory's test masses. The force produced by this rotor can be predicted to $<1\%$ relative uncertainty and is well-resolved in the readout of the observatory. This system currently acts as a cross-check of the existing absolute calibration system.

gr-qc↗

arXiv2020

Towards windproofing LIGO: Reducing the effect of wind-driven floor tilt by using rotation sensors in active seismic isolation

Modern gravitational-wave observatories require robust low-frequency active seismic isolation in order to keep the interferometer at its ideal operating conditions. Seismometers are used to measure both the motion of the ground and isolated platform. These devices are susceptible to contamination from ground tilt at frequencies below 0.1 Hz, particularly arising from wind-pressure acting on building walls. Consequently, during LIGO's first observing run both observatories suffered significant downtime when wind-speeds were above 7 m/s. We describe the use of ground rotation sensors at the LIGO Hanford Observatory to correct nearby ground seismometers to produce tilt-free ground translation signals. The use of these signals for sensor correction control improved low-frequency seismic isolation and allowed the observatory to operate under wind speeds as high as $15-20$ m/s.

physics.ins-det↗

arXiv2009

Opportunities for Probing Fundamental Gravity with Solar System Experiments

The recent discovery of "dark energy" has challenged Einstein's general theory of relativity as a complete model for our macroscopic universe. From a theoretical view, the challenge is even stronger: general relativity clearly does not extend to the very small, where quantum mechanics holds sway. Fundamental physics models thus require some major revisions. We must explore deeper to both constrain and inspire this needed new physics. In the realm of the solar-system, we can effectively probe for small deviations from the predictions of general relativity: Technology now offers a wide range of opportunities to pursue experiments with accuracies orders of magnitude better than yet achieved. We describe both the relevant theoretical backgrounds and the opportunities for far more accurate solar system experiments.

gr-qc↗

arXiv2008

Temporal Extent of Surface Potentials between Closely Spaced Metals

Variations in the electrostatic surface potential between the proof mass and electrode housing in the space-based gravitational wave mission LISA is one of the largest contributors of noise at frequencies below a few mHz. Torsion balances provide an ideal testbed for investigating these effects in conditions emulative of LISA. Our apparatus consists of a Au coated Cu plate brought near a Au coated Si plate pendulum suspended from a thin W wire. We have measured a white noise level of $30, \uVhz$ above approximately 0.1, mHz, rising at lower frequencies, for the surface potential variations between these two closely spaced metals.

gr-qc↗