First results of the CUORICINO experiment

Preliminary results on double beta decay (DBD) of 130 Te, obtained in the first run of the CUORICINO experiment are presented. The set-up consists of an array of 62 crystals of TeO 2 operating as bolometers in a deep underground dilution unit at a temperature of about 10 mK. Due to a total mass of about 41 kg, CUORICINO represents by far the most massive running cryogenic mass to search for rare events. The achieved lower limit on the neutrinoless DBD is 5.5⋅10 23 years, that corresponds to a limit on the Majorana effective mass between 0.37 and 1.9 eV. Performances of the detectors together with the sensitivity estimation are discussed

Study of environmental conditions effects on the mechanical-acoustic properties of microphones

International audienceMore and more applications, such as noise control in hostile environments, acoustic thermometry, gas metrology or optimization of thermoacoustic engines, require performing acoustic measurements with microphones in ?extreme? atmospheric conditions or even non atmospheric ones. Being able to predict and characterize the sensitivity and frequency response of microphones in these conditions of use is then of fundamental purpose. However, regarding the variety of potential applications, it is not realistic to perform microphones calibrations for all environmental conditions of possible interest. The main global properties of microphones should then be predicted by a reliable modelling procedure that enables to take into account the effects of environmental conditions on its mechanical-acoustic properties. Basically, the sensitivity and frequency response of a microphone are determined almost by its geometrical structure and dimensions, and by the mechanical properties of its membrane, which are both related to the temperature of the cartridge. On the other hand, the acoustic behaviour of a microphone strongly depends on the physical properties of the gas in the cartridge, which are function of the nature, static pressure and temperature of the gas and can easily be calculated. For the sake of the present work, an analytical model available in the literature is used to describe the behaviour of a 1/4?? microphone. This global modelling is associated to a mechanical study for predicting the temperature effects on the properties of the constituting materials. A comparison is presented with experimental results obtained for the resonance properties of the membrane in vacuum and for the frequency response under helium atmosphere of a 1/4?? microphone in order to check the validity of the theoretical approach suggested here

Measurement of the Boltzmann Constant k B Using a Quasi-Spherical Acoustic Resonator

International audienceThere is currently great interest in the international metrological community for new accurate determinations of the Boltzmann constant k B , with the prospect of a new definition of the unit of thermodynamic temperature, the kelvin. In fact, k B relates the unit of energy (the joule) to the unit of the thermodynamic temperature (the kelvin). One of the most accurate ways to access the value of the Boltzmann constant is from measurements of the velocity of the sound in a noble gas. In the method described here, the experimental determination has been performed in a closed quasi-spherical cavity. To improve the accuracy, all the parameters in the experiment (purity of the gas, static pressure, temperature, exact shape of the cavity monitored by EM microwaves , etc.) have to be carefully controlled. Correction terms have been computed using carefully validated theoretical models, and applied to the acoustic and microwave signals. We report on two sets of isothermal acoustic measurements yielding the value k B = 1.380 647 74(171) × 10 −23 J · K −1 with a relative standard uncertainty of 1.24 parts in 10 6. This value lies 1.9 parts in 10 6 below the 2006 CODATA value (Mohr et al., Rev. Mod. Phys. 80, 633 (2008)), but, according to the uncertainties, remains consistent with it

Direct comparison of ITS-90 and PLTS-2000 from 0.65 K to 1 K at LNE-CNAM

International audienceIn the temperature range between 0.65 K and 1 K, the international temperature scale of 1990 (ITS-90) is based on 3 He vapour-pressure thermometers and overlaps with the provisional low temperature scale of 2000 (PLTS-2000) defined by the melting pressure of 3 He. An indirect comparison at PTB revealed differences between the two scales of up to 1.5 mK at 0.65 K (Engert et al 2007 Metrologia 44 40-52). Stimulated by the PTB results, we have performed a direct comparison T 90-T 2000 from 0.65 K to 1 K at LNE-CNAM. To test repeatability, the experiment was conducted twice: in 2019 and 2020. We find differences T 90-T 2000 of 0.28 mK at 1 K, increasing to 1.58 mK at 0.65 K. The direct comparison, eliminates the uncertainty component due to the transfer resistance thermometer and its calibration. Except for a point near 1 K, the new results are in accordance with those obtained at PTB (differences of less than 0.22 mK), which makes it possible to improve the accuracy of the equation specified in ITS-90. Keywords: international temperature scale of 1990 (ITS-90), provisional low temperature scale of 2000 (PLTS-2000), vapour pressure of 3 He, melting curve of 3 He, low temperature thermometr

New measurement of the Boltzmann constant k by acoustic thermometry of helium-4 gas

International audienc