Articles you may be interested inA nuclear magnetic resonance spectrometer for operation around 1 MHz with a sub-10 -mK noise temperature, based on a two-stage dc superconducting quantum interference device sensor Sensitivity enhancement of Quantum Design dc superconducting quantum interference devices in two-stage configuration Rev. Sci. Instrum. 72, 3694 (2001); 10.1063/1.1389496 Two-stage superconducting-quantum-interference-device amplifier in a high-Q gravitational wave transducer Radio-frequency amplifier with tenth-kelvin noise temperature based on a microstrip direct current superconducting quantum interference device

We present the performances and the strain sensitivity of the first spherical gravitational wave detector equipped with a capacitive transducer and readout by a low noise two-stage SQUID amplifier and operated at a temperature of 5 K. We characterized the detector performance in terms of thermal and electrical noise in the system output signal. We measured a peak strain sensitivity of 1:5 10 ÿ20 Hz ÿ1=2 at 2942.9 Hz. A strain sensitivity of better than 5 10 ÿ20 Hz ÿ1=2 has been obtained over a bandwidth of 30 Hz. We expect an improvement of more than 1 order of magnitude when the detector will operate at 50 mK. Our results represent the first step towards the development of an ultracryogenic omnidirectional detector sensitive to gravitational radiation in the 3 kHz range.

The MiniGRAIL detector was improved. The sphere was replaced by a slightly larger one, having a diameter of 68 cm (instead of 65 cm), reducing the resonant frequency by about 200 Hz to around 2.9 kHz. The last four masses of the attenuation system were machined to increase their resonant frequency and improve the attenuation around the resonant frequency of the sphere. In the new sphere, six holes were machined on the TIGA positions for easy mounting of the transducers. During the last cryogenic run, two capacitive transducers and a calibrator were mounted on the sphere. The first transducer was coupled to a double-stage SQUID amplifier having a commercial quantum design SQUID as a first stage and a DROS as a second stage. The second transducer was read by a single-stage quantum design SQUID. During the cryogenic run, the sphere was cooled down to 4 K. The two-stage SQUID had a flux noise of about 1.6 µφ 0 Hz −1/2 . The detector was calibrated and the sensitivity curve of MiniGRAIL was determined.PACS numbers: 04.80.Nn, 95.55.Ym The new sphereThe old MiniGRAIL sphere turned out to have an unexpectedly low quality factor of about 1.5 million below 200 mK [1]. This is about a factor of ten lower than the Q-factor measured in small spherical samples of CuAl6% and of the Brazilian Schenberg detector [2] which was cast from the same material, but with an improved casting process. The reason for the reduced quality of the MiniGRAIL sphere could be the casting process or a crack in the sphere

Exploitation of external knowledge through constrained filtering guarantees improved performance. In this paper we show how multiscan processing of such information further enhances the track accuracy. This can be achieved using a Fixed-Lag Smoothing procedure, and a proof of improvement is given in terms of entropy reduction. Such multiscan algorithm, i.e., named KB-Smoother ("Fixed-lag smoothing for Bayes optimal exploitation of external knowledge," F. Papi et al., Proc. 15th Int. Conf. Inf. Fusion, 2012) can be implemented by means of a SIR-PF. In practice, the SIR-PF suffers from depletion problems, which are further amplified by the Smoothing technique. Sequential MCMC methods represent an efficient alternative to the standard SIR-PF approach. Furthermore, by borrowing techniques from genetic algorithms, a fully parallelizable multitarget tracker can be defined. Such approach, i.e., named Interacting Population (IP)-MCMC-PF, was first introduced in "Multitarget tracking with interacting population-based MCMC-PF" (M Bocquel et al., Proc. 15th Int. Conf. Inf. Fusion, 2012). In this paper, we propose and analyze a combination of the KB-Smoother along with the IP-MCMC-PF. As will be shown, the combination of the two methods yields an improved track accuracy while mitigating the loss of particles diversity. Simulation analyses for single and multitarget tracking scenarios confirm the benefits of the proposed approach.

We present measurements on a two-stage SQUID system based on a dc-SQUID as a sensor and a DROS as an amplifier. We measured the intrinsic noise of the dc-SQUID at 4.2 K. A new dc-SQUID has been fabricated. It was specially designed to be used with MiniGRAIL transducers. Cooling fins have been added in order to improve the cooling of the SQUID and the design is optimized to achieve the quantum limit of the sensor SQUID at temperatures above 100 mK. In this paper we also report the effect of the deposition of a Nb film on the quality factor of a small mass Al5056 resonator. Finally, the results of Q-factor measurements on a capacitive transducer for the current MiniGRAIL run are presented.