We describe the current design of the European gravitational sensor (GS) for the LISA Technology Package (LTP) that, on board the mission SMART-2, aims to demonstrate geodetic motion within one order of magnitude of the anticipated LISA performance. We report also the development of a noise model used in assessing the performance and determining the feasibility of achieving the overall noise goals for the GS. This analysis includes environmental effects that will be present in the sensor. Finally, we discuss open questions regarding the GS for LTP and LISA, ground testing, and verification issues.
Quantum measurements using single-photon detectors are opening interesting new perspectives in diverse fields such as remote sensing, quantum cryptography and quantum computing. A particularly demanding class of applications relies on the simultaneous detection of correlated single photons. In the visible and near infrared wavelength ranges suitable single-photon detectors do exist. However, low detector quantum efficiency or excessive noise has hampered their mid-infrared (MIR) counterpart. Fast and highly efficient single-photon detectors are thus highly sought after for MIR applications. Here we pave the way to quantum measurements in the MIR by the demonstration of a room temperature coincidence measurement with non-degenerate twin photons at about 3.1 μm. The experiment is based on the spectral translation of MIR radiation into the visible region, by means of efficient up-converter modules. The up-converted pairs are then detected with low-noise silicon avalanche photodiodes without the need for cryogenic cooling.
The first run of the ultracryogenic resonant bar detector AURIGA is in progress. Diagnostics on the cryogenics, the data acquisition system and on the noise characteristics have been performed, with results in accord with the design. The bar reached 140 mK. In tests down to 2 K the detector noise was very close to `Brownian'.
We report on progress in the development of free-falling
moving test-masses for LISA and for the related
technology demonstration mission. We present simple
formulae to evaluate the performance of the device as a
function of the various design parameters, and we compare
them with preliminary experimental results from a test
prototype we are developing. Quantitative agreement is
found. Finally, we present a control law, along with a
performance simulation, for low-frequency electrostatic
suspension of the test-mass with minimal perturbation of
the motion within the measuring frequency band.
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