[en] A method for plasma electron density measurements is described. The method uses the competition effect between rotational levels of the rotation-vibration band of CO₂ at 10.6 μm. The investigated plasma, placed in the resonator cavity, changes the laser frequency and the resulting power changes of the competing lines are detected by a differential piezoelectric detector. The operating frequency is stabilized to the equal intensity point by the use of antenna effect stabilization. Measurement of the electron density in the helium plasma is made. (author)

[en] Measurements of electric field changes near the laser tube can be a source of new information of phenomena in the laser plasma. The authors studied a phenomenon called 'antenna effect' which can be used for laser stabilization. The experimental set-up is presented. A bar of metallic foil wound around the water-jacket of CO₂ laser plasma tube was used as a probe ('antenna'). The antenna effect technique provides a convenient method for observing the laser signiture. The antenna effect was used successfully for detectorless stabilization of a laser frequency and in plasma diagnostic set-up. (author)

[en] Possibilities and limits of the routine preparation lines and procedures for D and ¹⁸O isotope analyses of water samples are thoroughly discussed for the specific case when the mass of the sample is limited to single milligrams. It is demonstrated that the classical CO₂-equilibration technique also provides reliable results for masses of water as low as 10 mg. It appears that error in δ¹⁸O for low-mass water samples is influenced mainly by actual accuracy to which this mass is determined. For equilibration of CO₂ with low-mass water samples an interesting relationship was observed: the equilibration time increased continuously with decreasing mass of water. Some suggestions are put forward in order to explain this intriguing effect. (author)

No abstract available

[en] Isotope effects accompanying evaporation of water samples stored in leaky containers were investigated in some detail. It was confirmed that isotope enrichment of the remaining water is in agreement with predictions of the existing isotope models of evaporation processes. The best agreement of model predictions with the experimental data was obtained when maximum values of kinetic enrichment parameter ε_k were adopted (28.5per mille and 25.1per mille for ¹⁸O and D, respectively). This indicates that in this particular case a fully developed laminar sublayer persisted close to the evaporating surface, controlling fractionation of the heavy isotopes. The isotope enrichment rates observed in the experiments (0.35per mille and 1.0per mille change of ¹⁸O and D content, respectively per 1% change of the mass of evaporating water sample) can be applied for eventual correction of isotope results, for a wide range of storage conditions. The experiments carried out in this study allowed more precise assessment of the role of different parameters in the modification of D and ¹⁸O isotope composition of the evaporating water bodies. (author)

[en] A new method of absolute angle measurement based on analysis of interference fringe patterns is proposed. This approach is a bridge between interferometry, offering high accuracy, and other methods that are using position sensors or amplitude effects, which can give information about absolute value of angle. Utilisation of quadrature signals makes it possible to achieve better stability, with comparison to some other methods, thanks to reduced influence of thermal expandability. Usage of special signal processing algorithms facilitates wide measurement range and high resolution. Simulations and experiments show the possibility of achieving the range of 1 deg with arc-sec accuracy. Using commercially available optical and electronic components makes it possible to create lightweight, battery operated device that could be applied in CNC machine alignment process. (paper)

[en] A method of improving intermodal frequency stability of two-mode helium-neon laser has been developed. The approach is based on using in the stabilization circuit a signal processor for real-time analysis of data from an LF amplitude and an HF frequency detector. We propose to use the signal from the LF detector in the initial phase of the stabilization process and the signal from the HF detector afterwards. Experiments proved that with the suggested design it is possible to obtain frequency stability of the intermodal frequency better than 100 Hz or 2*10-10 for 1000s averaging. In the paper we also show the influence the intermodal frequency stability on the absolute stability of the laser frequency. (paper)