On the impossibility of measuring a galvano-gravitomagnetic effect with current carrying semiconductors in a space-based experiment
In this paper we investigate the feasibility of a recently proposed space-based experiment aimed to detect the effect of the Earth's gravitomagnetic field in space-borne semiconductors carrying radial electric currents and following identical, in principle, circular equatorial orbits along opposite directions. Identical voltages of gravitomagnetic origin would be induced across the orbiting semiconductors, while equal and opposite gravitoelectric larger voltages would be generated. It turns out that the deviations from the proposed idealized orbital configuration due to the unavoidable orbital injection errors would make impossible the measurement of the gravitomagnetic voltage of interest.
Application of high performance DC SQUIDs in precision measurement technique
In this review the performance of a DC SQUID system with Nb-NbO/sub x/-Pb/In/Au window-type Josephson junctions is described. The SQUIDs and the SQUID control units were developed for universal applications in precision measurement technique. Under optimum conditions a flux noise level of 2/spl times/10/sup -6/ /spl Phi//sub 0///spl radic/Hz was achieved corresponding to an energy resolution of 3/spl times/10/sup -31/ J/Hz. The contribution gives the design of the DC SQUID device and summarizes recent results of its application in precision measurement technique. The applications include a cryogenic current comparator for non-destructive measurement of the beam intensity produced in a particle accelerator, a high-sensitive SQUID voltmeter for investigations of the low-field Hall coefficient of high purity metals, the upgrade of a multichannel RF SQUID neuromagnetometer for biomagnetic research, and a planned high-precision experiment in fundamental physics.<<ETX>>
The rotation of LAGEOS and its long‐term semimajor axis decay: A self‐consistent solution
We develop a self-consistent model for the evolution of the spin axis of LAGEOS and the related long-term semimajor axis perturbations, due to asymmetric emission/reflection of radiation from the satellite's surface. We show that the theory developed by Bertotti and Iess [1991] for the evolution of LAGEOS's rotation under magnetic and gravitational torques, which we have somewhat generalized here, can lead to a successful fit of the observed semimajor axis residuals, provided the correct initial conditions for the direction of the spin axis are chosen. The remaining residuals have an rms dispersion of 0.50 × 10−12 m/s2, comparable to that of previous solutions, based on purely empirical fits of the spin axis direction as a function of time. The spectrum of the residuals indicates that they are probably due to unmodeled radiation forces (e.g., from Earth albedo and/or penumbra passages). Our solution allows us to predict the future evolution of LAGEOS's rotation for about another decade in the future, until the spin rate will become so slow that some basic assumptions of the theory will fail. A similar model can also be used to model/predict the coupled spin-orbit evolution of the LAGEOS II satellite, launched in late 1992, although the available data still cover a span of time too short for reaching significant quantitative conclusions concerning this satellite.