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Marty P.T.,University of Bern | Morel J.,Federal Office of Metrology METAS | Feurer T.,University of Bern
Optics Express | Year: 2010

We present an all-fiber frequency-stabilized ring laser system with an integrated reference gas cell consisting of a hollow core fiber filled with acetylene. Through nonlinear absorption spectroscopy the laser frequency is stabilized to a specific absorption line of acetylene. Three different stabilization schemes are investigated and the minimum Allan deviation obtained after 100 s is 4.4 .10-11. © 2010 Optical Society of America.

Marty P.T.,University of Bern | Morel J.,Federal Office of Metrology METAS | Feurer T.,University of Bern
Journal of Lightwave Technology | Year: 2010

We demonstrate a multi-purpose all-fiber design for gas-filled cavities based on hollow core photonic crystal fibers and on a specially designed fiber connector system. The connector system allows to evacuate and to fill the fiber core with a gaseous medium and keeping it pressure-tight. It also allows connecting the hollow core fiber to standard fibers. We demonstrate the flexibility and functionality by realizing three different all-fiber spectroscopic devices. Firstly, a single pass gas cell for linear absorption spectroscopy, secondly, a double pass gas cell and, thirdly, an all-fiber FabryPerot cavity for nonlinear saturation spectroscopy. © 2010 IEEE.

Thomas Marty P.,University of Bern | Morel J.,Federal Office of Metrology METAS | Feurer T.,University of Bern
Optics Letters | Year: 2011

We investigate the dynamics of an erbium-doped fiber ring laser that is equipped with an intracavity hollow core photonic crystal fiber gas cell. The cell is filled with acetylene as a saturable absorber. We observe cw operation at low pressures, Q switching at intermediate pressure levels, and mode locking at high pressures applied. Moreover, we show that the transition from the cw to the pulsed mode may be exploited for sensitive gas detection. © 2011 Optical Society of America.

Feller U.,Federal Office of Metrology METAS
Accreditation and Quality Assurance | Year: 2011

The International System of Units (SI) follows a concept that goes back to Maxwell. At that time, a logic sound foundation of mathematics was not yet available. This has lead to concepts and terms that are contradictory and in conflict with today's standard mathematical concepts. The inconsistencies that have evolved in metrology due to the lack of appropriate notions are pointed out. This is most important, as the metrology is a field that is internationally well organized under the umbrella of the Meter Convention, an international treaty for acting on all matters relating to units of measurement. Committees and working groups under the Meter Convention have a leading role in the elaboration of important metrological guides, among others the International Vocabulary of Metrology. Therefore, it is highly desirable that their publications use well-founded concepts and terminology. It is consensus that it is desirable to find a system of units on invariant properties of nature and not on human artifacts, e.g., the prototype of the kilogram. However, the current proposals to improve that are in conflict with standard scientific concepts. It is shown in the paper how these inconsistencies can be avoided. The argumentation is based on the interpretation of numbers developed by mathematicians like Cantor, Dedekind, Peano, and others that have led the logic foundation of mathematics with set and number theory. This foundation excludes dogmas that have been forwarded in the last century under the umbrella of the Meter Convention. © 2011 The Author(s).

Fuchs P.,Federal Office of Metrology METAS | Marti K.,Federal Office of Metrology METAS | Russi S.,Federal Office of Metrology METAS
Metrologia | Year: 2012

In order to study the practical means of a dissemination of the redefined kilogram, the mass laboratory of METAS has built a new and unique instrument, which combines high precision mass measurement and element-specific surface chemical analysis by x-ray photoelectron spectroscopy (XPS) under identical conditions. It is especially designed for the analysis of large samples such as real 1kg standards and artefacts of up to 100mm in diameter. In this paper, we first provide a detailed description of the apparatus. In a second step we demonstrate its performance by applying various processes, such as the transfer from ambient to vacuum, cleaning by low-pressure hydrogen plasma, transfer from vacuum to ambient and recontamination in air with time. Real 1kg PtIr standards and surface artefacts have been monitored at individual steps gravimetrically, and in vacuum additionally by XPS. Values for the gain and loss of mass due to the application of different processes are provided. A model for the short-term recontamination after cleaning is presented, showing the initial growth of contaminants is self-limited. © 2012 BIPM & IOP Publishing Ltd.

Marti K.,Federal Office of Metrology METAS | Fuchs P.,Federal Office of Metrology METAS | Russi S.,Federal Office of Metrology METAS
Metrologia | Year: 2012

The new cleaning techniques of low-pressure hydrogen plasma and UV/ozone were directly compared with the established nettoyage-lavage procedure using x-ray photoelectron spectroscopy (XPS) on PtIr and Au-alloy samples. The different cleaning techniques have been validated with respect to the achieved cleanliness, the remaining contaminants and the speed of action. The new techniques were found to be more efficient for the removal of hydrocarbons, delivered reproducible results and the final surface chemical state was achieved repeatedly. For hydrogen plasma we found the speed of action is four times faster than for the UV/ozone cleaning and results in slightly smaller amounts of remaining hydrocarbons. Hydrogen plasma also removed oxygen compounds whereas UV/ozone led to oxidized surfaces. Further cyclic measurements with hydrogen plasma and UV/ozone revealed a fast reduction of oxides upon plasma treatment and a re-oxidation when subsequently treated with UV/ozone. © 2012 BIPM & IOP Publishing Ltd.

Zeier M.,Federal Office of Metrology METAS | Hoffmann J.,Federal Office of Metrology METAS | Wollensack M.,Federal Office of Metrology METAS
Metrologia | Year: 2012

Metas.UncLib is a software library that facilitates the linear propagation of uncertainties through a measurement model. It is able to handle complex-valued and multivariate quantities and supports higher mathematics. It is therefore able to deal with advanced metrological problems that require, e.g., matrix manipulations. The software is optimized for short computation times and low memory use. © 2012 BIPM & IOP Publishing Ltd.

Fuchs P.,Federal Office of Metrology METAS | Marti K.,Federal Office of Metrology METAS | Russi S.,Federal Office of Metrology METAS
Metrologia | Year: 2012

The recontamination and long-term stability of materials suitable for mass standards was studied with x-ray photoemission spectroscopy after low-pressure plasma cleaning using hydrogen and oxygen. The cleaned samples were stored in air or argon at ambient pressure and under UHV conditions and the surface chemical state was monitored continuously. We found the recontamination exhibits initially self-limited growth. In the long term over three years, we found no indication for further accumulation of contaminants. From the uncertainties of our observations we provide an upper limit for the long-term contamination which is the lowest of all the results published up to now. The stability of PtIr and Au upon different cleaning processes and storage conditions is described in detail. © 2012 BIPM & IOP Publishing Ltd.

Hof C.,Federal Office of Metrology METAS | Zwahlen G.,Federal Office of Metrology METAS
Measurement Science and Technology | Year: 2012

A periodic calibration of artificial mastoids is important for reliable audiometric diagnostics based on bone conduction. The calibration procedures recommended by the IEC standard were reviewed in view of the adoption of a new type of impedance head for routine measurements. Thereby it was found that the currently admitted model is based on inadequate simplifications leading to a counter-intuitive frequency dependence of the lumped circuit parameters and to systematic differences in calibration results as obtained by different transducers. The acceleration sensitivity of impedance heads is experimentally shown to depend on both frequency and load. This behavior can be easily explained by a simple lumped circuit model and the above-mentioned drawbacks overcome if taken properly into account. © 2012 IOP Publishing Ltd.

Overney F.,Federal Office of Metrology METAS | Jeanneret B.,Federal Office of Metrology METAS
Metrologia | Year: 2010

In this paper, the realization of an inductance scale from 1 μH to 10H for frequencies ranging between 50Hz and 20 kHz is presented. The scale is realized directly from a series of resistance standards using a fully automated synchronous sampling system. A careful systematic characterization of the system shows that the lowest uncertainties, around 12 μH H -1, are obtained for inductances in the range from 10 mH to 100 mH at frequencies in the kilohertz range. This new measurement system, which was evaluated during an international comparison, provides a primary realization of the henry, traceable to the quantum Hall effect. An additional key feature of this system is its versatility. In addition to resistance-inductance (R-L) comparison, any kind of impedance can be compared: R-R, R-C, L-L or C-C, giving this sampling system a great potential for use in many laboratories around the world. © 2010 BIPM & IOP Publishing Ltd.

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