9 research outputs found
Theoretical Analysis of a Large Momentum Beamsplitter using Bloch Oscillations
In this paper, we present the implementation of Bloch oscillations in an
atomic interferometer to increase the separation of the two interfering paths.
A numerical model, in very good agreement with the experiment, is developed.
The contrast of the interferometer and its sensitivity to phase fluctuations
and to intensity fluctuations are also calculated. We demonstrate that the
sensitivity to phase fluctuations can be significantly reduced by using a
suitable arrangement of Bloch oscillations pulses
Limits to the sensitivity of a low noise compact atomic gravimeter
A detailed analysis of the most relevant sources of phase noise in an atomic
interferometer is carried out, both theoretically and experimentally. Even a
short interrogation time of 100 ms allows our cold atom gravimeter to reach an
excellent short term sensitivity to acceleration of g at 1s.
This result relies on the combination of a low phase noise laser system,
efficient detection scheme and good shielding from vibrations. In particular,
we describe a simple and robust technique of vibration compensation, which is
based on correcting the interferometer signal by using the AC acceleration
signal measured by a low noise seismometer.Comment: 30 pages, 14 figure
Inter-comparison of the g-, f- and p-modes calculated using different oscillation codes for a given stellar model
In order to make astroseismology a powerful tool to explore stellar
interiors, different numerical codes should give the same oscillation
frequencies for the same input physics. This work is devoted to test, compare
and, if needed, optimize the seismic codes used to calculate the
eigenfrequencies to be finally compared with observations. The oscillation
codes of nine research groups in the field have been used in this study. The
same physics has been imposed for all the codes in order to isolate the
non-physical dependence of any possible difference. Two equilibrium models with
different grids, 2172 and 4042 mesh points, have been used, and the latter
model includes an explicit modelling of semiconvection just outside the
convective core. Comparing the results for these two models illustrates the
effect of the number of mesh points and their distribution in particularly
critical parts of the model, such as the steep composition gradient outside the
convective core. A comprehensive study of the frequency differences found for
the different codes is given as well. These differences are mainly due to the
use of different numerical integration schemes. The use of a second-order
integration scheme plus a Richardson extrapolation provides similar results to
a fourth-order integration scheme. The proper numerical description of the
Brunt-Vaisala frequency in the equilibrium model is also critical for some
modes. An unexpected result of this study is the high sensitivity of the
frequency differences to the inconsistent use of values of the gravitational
constant (G) in the oscillation codes, within the range of the experimentally
determined ones, which differ from the value used to compute the equilibrium
model.Comment: 18 pages, 34 figure
Quantum Physics Exploring Gravity in the Outer Solar System: The Sagas Project
We summarise the scientific and technological aspects of the SAGAS (Search
for Anomalous Gravitation using Atomic Sensors) project, submitted to ESA in
June 2007 in response to the Cosmic Vision 2015-2025 call for proposals. The
proposed mission aims at flying highly sensitive atomic sensors (optical clock,
cold atom accelerometer, optical link) on a Solar System escape trajectory in
the 2020 to 2030 time-frame. SAGAS has numerous science objectives in
fundamental physics and Solar System science, for example numerous tests of
general relativity and the exploration of the Kuiper belt. The combination of
highly sensitive atomic sensors and of the laser link well adapted for large
distances will allow measurements with unprecedented accuracy and on scales
never reached before. We present the proposed mission in some detail, with
particular emphasis on the science goals and associated measurements.Comment: 39 pages. Submitted in abridged version to Experimental Astronom