The scientific activity covers a wide range of topics: maintenance and dissemination of the national length standard, measurement of laser radiation frequency, standards and measurement methods for dimensional metrology (gauge blocks, angles, diameters and roundness), nanometrology and co-ordinate measuring machines, metrology for space missions.

A reference cavity has been designed within the framework of RUFO (Riferimenti Ultrastabili di Frequenze Ottiche), financed by Regione Piemonte. The spacer is made of ULE, and the design is such as to withstand stresses at launch (30 g).
The nanobalance developed by INRIM was transferred to Alcatel-Alespazio.
On November 2006 the frequency of an INRIM He-Ne/¹²⁷I₂ laser at 633 nm was measured using the frequency comb of the BIPM. The result differs by only 2 kHz from the value recommended by the CIPM.
Originally devised for a gravity survey mission, a technique to accurately measure the relative attitude and distance of two or more spacecraft has been developed and supported by experimental tests. In particular, a set of three optical collimators will allow an attitude control within 0.01" on a full scale working range of 3º.
Femto-second laser-based frequency combs realize the definition of the metre through method b) in the mise en pratique, that is by means of the absolute frequency measurement of radiation. The system is based on a femto-second laser pumped by a diode pumped solid state (DPSS) laser, and a combination of optical and electronic devices. We have started to construct a compact system that will be completed by the end of 2007.

A new method for compensating optical non-linearity in sub-wavelength displacement measurements by means of heterodyne interferometry has been further tested. The method is based on fast phase-shifting for zeroing the phase difference of the heterodyne beat signals at each sub-wavelength displacement to be measured. Use is made of a transverse electro-optic modulator for phase shifting the path of the measuring beam of the heterodyne interferometer. The results show a significant reduction of non-linearity in the full sub-wavelength range.

Phase shifting interferometer with reduced nonlinearity errors.

A scanning device, based on elastic hinges driven by bimorph PZT plates for a sample-moving type SPM microscope, has been rebuilt by adding a tripod system for the z-stage and position sensors for all the xyz displacements. The device has been designed (cooperation with APE Research srl) to operate with samples to be imaged either in transmission or reflection mode by means of SNOM heads.
The morphological and structural properties of MgB₂ thin film and of structures (bridges) fabricated on these films have been characterized using the metrological AFM. In cooperation with the Analytical Chemistry Department of the Università di Torino the SPM characterization of TiO₂ thin films has been continued, to investigate the correlation between structural and photocatalytic properties.

The new CMM installed at the end of 2005 has been put into operation: in addition to ordinary calibrations, a hollow spherical resonator and a silicon X-ray interferometer were measured for the precise determination of the Boltzmann and the Avogadro constants, in cooperation with the INRIM research groups in charge of these projects.

Measurement of the spherical resonator with the CMM.

The measurement capability of the nano-angle generation and measurement facility has been extended from 50 to 250 µrad. The facility, having sub-nanoradian resolution, has made it possible to calibrate a high sensitivity autocollimator developed at NIST and used in the experiment GAMS4 at Institut Laue-Langevin (ILL, Grenoble). Collaboration with the ILL has started in order to use the "angle amplifier" developed at INRIM in the new GAMS5 experiment for the calibration of the gamma ray spectrometer.
A non-contact sensor based on a quasi-confocal optical setup has been made and tested. This sensor will be used for roundness measurements to overcome the problem of wear caused by the probe sliding on the rotating sample. Preliminary results show an agreement between the new and old instrument within the uncertainty of the last one.

Comparison between the mechanical probe reading (magenta) and the optical probe (blue). In yellow the difference between the two, multiplied by a factor 10. The vertical scale is in micrometers.

With the aim of carrying out an experiment for the accurate measurement of the Casimir force, a sensitive micro-autocollimator has been constructed. The instrument has a full scale range > 1º and a resolution better than 0.01"/vHz, when working with a mirror as small as 0.15 mm ². With this instrument, a better parallelism of the two interacting surfaces can be achieved.

The micro-autocollimator under test.

The four-year European project EVIGeM (European Virtual Institute of Geometric Measurement) ended in 2006. According to the project workplan, two legal entities, EVIGeM e.V. and EVIGeM GmbH, were established in Germany to keep alive and further develop the consortium formed in the project. The INRIM is now a member of the EVIGeM e.V. Association. A three-year PhD effort, dealing with a novel and cost-effective technique for compensating the geometrical errors of CMMs ended in 2006.
The ISO/TS 23165:2006 GPS - Guide to the expression of CMM test uncertainty was published after five years preparatory work led by INRIM, which originally raised the problem and then got the consensus on the urgency of this project.
The CMM Club Italia Association - chaired by INRIM - was in full operation. Apart from two seminars (InTeRSeC 12 and 13) - the latter being the first ever in the South of Italy -, it organised the 21^st plenary meeting of the ISO/TC213 in Turin, 2009-09-05/14. It was the first ISO/TC213 meeting ever in Italy, involving 87 people from 16 countries, with 13 different meetings. The Association membership remained steady at 70.
The key comparison EUROMET.L-K2 on long gauge blocks was finalised with the publication of the Final and of the Executive Reports. This key comparison followed up in Europe the world-wide comparison CCL-K2, closed in 2003; INRIM served as linking ring between the two. As in the CCL-K2, the results were positive for INRIM, so that the Executive Report recommends confirming the registered CMC on this basis.
Other activities: coordination of the intercomparison EUROMET.L-K4 on diameter standards and of the EUROMET project 866 on the interferometric calibration of microdisplacement actuators; participation in the intercomparisons on step gauge (EUROMET.L-K5), 100 mm linescale (EUROMET.L-K7) and 2D gratings (NANO5).

Within the "Casimir project", a force sensor based on the use of two coupled quartz tuning forks has been developed. The sensor has a noise limited resolution of 5 pN/vHz and could find application in other research fields like scanning force microscopes.
A new instrument to measure the shape and size of particulate in air is under construction. The instrument is based on the analysis of the angular distribution of laser light scattered by the particles; it should provide faster and more accurate information with respect to the classic analysis based on sampling filters and microscope measurements. The activity is financed by Regione Piemonte and APAT.
A new prototype of the image spectrometer has been built. It has larger mirrors (50 mm diameter) and longer displacement (25 µm). The algorithms for the interpretation of the interferogram have been refined leading to more accurate results. The instrument and the method are patent pending.