Cechovs Kosmos

Accurate calibration of test mass displacement in the LIGO interferometers

“…For better visibility, the error bars for the photon calibrator and frequency modulation data are ±3σ estimates of statistical uncertainties only, with σ a representative standard error for the averaged measurements. Estimates of systematic uncertainties for each calibration method [31,20,21] have intentionally been omitted so that the overall systematic uncertainty can be evaluated by comparing the results of the three methods with statistical precision indicated by the error bars, or the scatter in the data for the free-swinging Michelson results. For each ETM, the dashed horizontal lines indicate the simple mean value for the free-swinging Michelson method and the weighted mean values for the photon calibrator and frequency modulation methods.…”

“…Overall systematic uncertainty, estimated from the observed spread in the data and from propagating errors through the many steps of the technique, is approximately 10%. [31] The primary identified sources of systematic uncertainty for the photon calibrator method are rotation due to beam centering offsets and absolute power calibration. With reasonable centering tolerances and the demonstrated power calibration accuracy, the estimated total systematic uncertainty can be reduced to the order of 1%.…”

“…This, together with the independent measurement of detector displacement sensitivity afforded by the photon calibrator, gives us confidence that the LIGO detector calibration is within the stated uncertainty estimates. [31] As we have described above, calibration of the displacement actuators of an interferometric GW detector can be a tedious and complicated enterprise. Future GW detectors will have even more sophisticated actuation and readout chains.…”