We present a 27-days long common view measurement of an absolute cold atom gravimeter (CAG) and a relative iGrav superconducting gravimeter, which we use to calibrate the iGrav scale factor. This allowed us to push the CAG long-term stability down to the level of 0.5~nm.s$^{-2}$. We investigate the impact of the duration of the measurement on the uncertainty in the determination of the correlation factor and show that it is limited to about 3\textperthousand~by the coloured noise of our cold atom gravimeter. A 3-days long measurement session with an additional FG5X absolute gravimeter allows us to directly compare the calibration results obtained with two different absolute meters. Based on our analysis, we expect that with an improvement of its long term stability, the CAG will allow to calibrate the iGrav scale factor to better than the per mille level (1$σ$ level of confidence) after only one-day of concurrent measurements for maximum tidal amplitudes.
Relativity, Doppler shifts, and retarded times in deriving the correction for the finite speed of light: a comment on 'Second-order Doppler-shift corrections in free-fall absolute gravimeters'
在文章（Rothleitner and Francis 2011 Metrologia 48 187-195）中，从狭义相对论的观点分析了绝对重力仪中由于有限光速引起的校正。相对论的概念最终导致两个经典的方法来解决这个问题：拍频的分析，并引入延迟时间。在第一种方法中，必须假设一个额外的时间延迟，因为从加速反射器反弹的光束的频率在反射点处不同于在干涉点处。延迟时间形式主义等效于单个多普勒频移，但导致与拍频方法相同的校正，即使后者明确地组合了两个多普勒频移。在我们的评论中，我们讨论了这些问题和其他问题，我们发现与建议的治疗的纠正。
In recent years, levitated particles of optical traps in vacuum have shown enormous potential in precision sensor development and searching for new physics. The accuracy of the calibration relating the detected signal to absolute displacement of the trapped particle is a critical factor for absolute measurement performance. In this paper, we suggest and experimentally demonstrate a novel calibration method for optical tweezers based on free-falling particles in vacuum, where the gravitational acceleration is introduced as an absolute reference. Our work provides a calibration protocol with gre…
A time transfer link consisting of PTP White Rabbit (PTP-WR) devices can transfer time with sub-nanosecond accuracy. Originally White Rabbit devices were calibrated as a set of two devices. Progress in calibration makes individual absolute calibrated PTP-WR devices possible. This enables exchange of PTP-WR devices without the need for expensive in-situ end-to-end calibrations. Electrical absolute calibration is the basis of absolute calibration. It calibrates the time relationship between the internal timestamp and the external electrical time reference plane. In this paper we examine the elec…
Absolute gravimeters (AG) are used in geodesy, geophysics, and physics for a wide spectrum of applications. Stable gravimetric measurements over timescales from several days to decades are required to provide relevant insight into geophysical processes. Users of AGs participate in comparisons with a metrological reference in order to monitor the temporal stability of the instruments and determine the bias to that reference. However, since no measurement standard of higher-order accuracy currently exists, users of AGs participate in key comparisons led by the CIPM. These comparisons provide the…
We have developed a solid state probe for an absolute irradiance calibration of the Thomson scattering system on the Large Plasma Device (LAPD), based on Raman scattering off silica. Measurements performed with a triple-grating spectrometer have investigated the intensities of a pulsed laser beam Raman scattered off crystalline and amorphous silica over a range of temperatures of relevance to the LAPD (299 - 498 K). The data were compared with Rayleigh and Raman scattering intensities in gaseous nitrogen. The measurements show that Raman scattering off quartz allows rapid and accurate alignmen…
Quantum cascade laser (QCL) frequency combs have revolutionized mid-infrared (MIR) spectroscopy by their high brightness and fast temporal resolution, and are a promising technology for fully-integrated and cost-effective sensors. As for other integrated comb sources such as micro-combs and interband cascade laser, QCLs have a comb spacing of several GHz, which is adequate for measurements of wide absorbing structures, typically found in liquid or solid samples. However, high-resolution gas-phase spectra require spectral interleaving and frequency calibration. We developed a frequency calibrat…
