"Gabl", an Absolute Free-Fall Laser Gravimeter

Abstract

A high-precision laser gravimeter for measuring the absolute value of gravitational acceleration by the free-fall method has been built in the Siberian Branch of the USSR Academy of Sciences (Novosibirsk). The use of a free-fall interferometer illuminated by a He-Ne laser stabilized by an iodine absorption cell ('"I2) together with high-speed electronic counters and a rubidium frequency standard, plus constructive measures aimed at reducing the action of non-gravitational forces, provide an accuracy of measurements better than lo-' m.s-2. In practice, the relative measurement error in g, as determined from convergence of the results of repeated measurements, is below 4 parts in l o 9 (4 xThe gravimeter is used for geophysical experiments and in the investigation of non-tidal variations of the Earth's gravitational field. m.s-').

Experimental assessment of the speed of light perturbation in free-fall absolute gravimeters

“…Any other constant shift would not change our result. (8) where 0 is a constant irrelevant for the analysis of the trajectory. From equation (8) it can be deduced that the interference fringes occur every time the function ( ) changes by 2 ⁄ , where = 2 .…”

“…Notice that those do not affect the contribution from the gradient at the order of interest. For gravimetry, one needs the connection between the time variations of the intensity and the value of the local gravitational acceleration g. This follows simply from taking the second derivative of the variable inside the cosine in (8).…”

“…To illustrate the measuring principle of a free-fall absolute gravimeter through the time dependence of the intensity, equation (8), we show an expected interference pattern in Figure 2. From (8) and (13) one deduces that if there were no speed-of-light perturbation, the interference fringes would occur each time the mirror moves by a distance 2 ⁄ . Hence the shrinking of the spacing between the fringes for accelerated trajectories.…”

A miniature frequency-stabilized VCSEL system emitting at 795nm based on LTCC modules

“…Moreover, they are also used in commercial applications such as precision machining tools, laser vibrometers [4] and gravimeters [5]. In such applications, on the one hand, there is the need of reducing the power consumption and the dimensions of the laser source, in order to facilitate the fabrication of portable devices; on the other hand, the demand for highly-stable laser sources is rapidly increasing, with the ever more widespread diffusion of applications based on, e.g.…”

Supersolid-Based Gravimeter in a Ring Cavity

“…In addition, it also allows to test more fundamental aspects of physics such as local Lorentz invariance [5], the isotropy of post-Newtonian gravity [6], and quantum gravity [7]. The current generation of gravimeters include: microelectromechanical gravimeters [4], free-fall gravimeters [8][9][10][11][12], spring-based gravimeters [13,14], superconducting gravimeters [15], optomechanical gravimeters [16,17], and atom interferometers [18][19][20][21][22][23].In the above list, the atom interferometry deserves a special position because of the possibility of harnessing quantum features of many-body systems [24]. In principle, by using entangled resources, it is possible to increase the precision of measurement over the shot-noise limit [25].…”