The activities carried out concern: the study of primary standards of force and torque, high-medium-low pressures and hardness, for the realization and dissemination of the national scales; primary techniques and instruments for dynamic acceleration and absolute gravimetry, both for measurements and calibrations; experimental and theoretical activity for the realization of the kilogram based on the 28Si atom.
The evaluation of the combined uncertainty in the real measurements ambient of Mass Spectrometer Leak Detectors (MSLDs) is an important step in the acceptance test. The MSLDs represent the best choice for sealing tests. The calibration of the device is performed with reference to known helium gas flow-rates, the so-called standard leaks, calibrated against primary gas flow-meters (gas flow-rate range from 2×10-8 mbar L/s to 1×10-3 mbar L/s). The behaviour of the MSLD was studied both alone and in the test configuration. In the first case some metrological characteristics were taken into account (background signal, noise, time constant, correction factor and repeatability); in the second case a more complex geometry is the source of additional uncertainty components (i.e. pressure measurements inside the object and composition of the tracer gas mixture, considerably high in industrial plants). A combined relative expanded uncertainty of 16×10-2 was found for the MSLD alone, growing up to 20×10-2 for the whole apparatus and to 28×10-2 when a gas mixture is used.
Leak detection system for on line test: schematic of the connection of a MSLD to a test chamber (a, b, c calibrated leaks).
In the framework of an industrial contract the design and construction of a series of pressure balances started with the aim of measuring pressure in liquid media up to 120 MPa in industrial environments. The realised pressure balances are compact, easily transportable and equipped with all measuring sensors, for the corrections of the main influence quantities. The main metrological characteristics related to three prototype piston-cylinder units allow to obtain piston fall rates well below 100 µm·s-1 at the maximum pressure of 120 MPa, pressure sensitivities of the order of 20 ppm and a relative expanded uncertainty of pressure measurements varying from 1.5×10-4 to 1×10-4 in the pressure range from 10 MPa to 120 MPa.
120 MPa pressure balance: measuring unit.
The main developments on transportable absolute gravimeter IMGC-02 concerned the optimisation of the software code used to acquire and process the data collected. Different solutions have been experimentally tested to smooth the vibrations coming from the ground floor and, at the same time, a new study is getting started dealing with an inertial system to be used as reference in laser interferometric measurements. The measurement capabilities have been confirmed by the results of the comparison between the IMGC-02 and the absolute gravimeter FG5-216 of the European Center for Geodynamics and Seismology (ECGS), Luxemburg, carried out at the INRIM gravity laboratory. The IMGC-02 also measured the gravity field at the INRIM force laboratory for the calibration of masses for the new dead weight force standard machine. The collaborations with several laboratories (BIPM-Paris, ECGS, INGV-Napoli, OGS-Trieste) have been carried on.
In dynamic accelerations a survey of vibrations in a civil room has been developed at the request of a private company. The measurements have demanded the setting up of a specific program for vibration measurements of buildings, following UNI 9614 standard specifications.
The IMGC-02 at the INRIM force laboratory.
INRIM participated in two CIPM key comparisons with the 1 MN deadweight Force Standard Machine: CCM.F-K2.a up to 100 kN e CCM.F-K3.b for force up 500 kN. A new data acquisition system for the INRIM 500 kN and 100 kN six-component dynamometers has been realized, in order to improve the dynamic properties and the analysis of the overloading effects of the primary force standard machines. The construction of the new 1.2 kN dead weight force standard machine has been carried on. In stress analysis at cryogenic temperatures, the metrological characterization (considering force and displacement) of the 100 kN tensile test machine has been performed.
INRIM six-component 100 kN dynamometer.
The proposed new international definition of the Rockwell C scale has been accepted for use in the realization of the National Scales. The metrological characterization of primary hardness standard machines, indentation measuring systems and measuring systems for diamond indenters have been carried out for several NMIs: INMETRO (Brazil), NCM (Bulgaria), NIM (China), UME (Turkey).
The measuring system for the geometrical verification of hardness indenters.
In relativistic quantum mechanics, frequency and mass are linked by the Planck-Einstein relation mc2= hf. Hence, use is made of this relation and of nuclear spectroscopy to determine nuclear binding energies and masses in terms of frequency and of the h/c2 ratio. This weighing procedure is different from those used in mass metrology: in a neutron capture reaction, the daughter isotope is lighter than the ensemble formed by the mother isotope and the neutron. The mass difference is measured by the frequencies of the γ-ray cascade emitted in the decay of the capture state. The experimental set-up uses the intense neutron source and the γ spectrometry facility of the Institut Laue Langevin; INRIM is taking care of the extension of absolute frequency measurements to γ-rays via calibrated Si crystals, which act as diffracting gratings in a γ-ray spectrometer. If the value of the Compton frequency mc2/h of an atom is provided, the kilogram can be realized by manufacturing an artefact whose number of atomic constituents is known. A link will then be made with the macroscopic scale: crystallization enables the atoms in a 28Si sphere to be counted with 10-8 accuracy and its mass related to the 28Si Compton frequency. In order to gather the needed competences and to share the costs, the technologies necessary for such an atomic realization of the kilogram are being developed by an international consortium; in this framework, INRIM is linking atomic and macroscopic scales by measuring, via combined x-ray and optical interferometry, the atomic spacing of silicon with nine significant digits.
Movable part of the x-ray interferometer for the measurement of the silicon lattice parameter.