Czech Metrology Institute Research Articles

Final report on EURAMET.T-K7.1: Bilateral key comparison of water triple point cells

This is the final report of key comparison EURAMET.T-K7.1, a bilateral comparison of water triple point cells between the Czech Metrology Institute, CMI, and the Slovensky Metrologicky Ustav, SMU, of Slovakia. The comparison was requested by CMI, and the measurement protocol was compatible with the one used for key comparison EUROMET.T-K7. The results show a satisfactory degree of equivalence between SMU and CMI, and allow linkage to the parent key comparison EUROMET.T-K7. As a consequence, CMI is able to support CMCs at the temperature of the triple point of water and submit them for publication in the KCDB.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Comparison of the Josephson voltage standards of the CMI and the BIPM (part of the ongoing BIPM key comparison BIPM.EM-K10.b)

A comparison of the 10 V Josephson array voltage standard of the Bureau International des Poids et Mesures (BIPM) was made with that of the Czech Metrology Institute (CMI), Czech Republic, in February 2011. For this exercise, option B of the comparison protocol was applied for the nominal voltage of 10 V. The BIPM provided a reference voltage for measurement by the CMI using its Josephson standard with its own measuring device (option B of the comparison protocol). The final results are in good agreement within the combined relative standard uncertainty of 10.3 parts in 1010 for the nominal voltage of 10 V.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

A Conversation with Czech Metrology Institute

A Conversation with Czech Metrology Institute

International comparisons of high-frequency electrical capacity standards

In 2007‐2008, we performed comparisons between the Russian Federation and the Czech Republic in the region of measurements on electrical capacity at high frequency. The purpose of the comparisons was to provide mutual relationship of results in the calibration of means of capacitance measurement in both countries by confirming the estimates of uncertainties arising in the comparisons. Comparison participants: Siberian State Research Institute of Metrology ( SNIIM) in Russia (pilot institute); and Czech Metrological Institute (CMI) in the Czech Republic. For the comparison, we used a set of transported standards developed in SNIIM of capacity 10, 100, and 1000 pF, working frequencies 1, 10, 20, and 30 MHz. In the region of measurement, the unit of electrical capacity in Russia was the special central standard GET 107-77 [1, 2] on the basis of the units of length and time. The transfer of the dimension of the unit by the secondary and the working standards was provided by the method of comparison and reglamentation of the intergovernal standard [3] and confirmed in the SNIIM by calibration methods. The standard measurement apparatus and the SNIIM standards, including the transported standards, had unified two-conduction connecting devices: unipolar coaxial-cylindrical joiners with the following characteristics: internal diameter of an outside electrode of coaxial 20 mm, an outside diameter of an internal electrode of 13.18 mm, and a wave resistor of a coaxial system of 25 Ω. The standard capacities of 10, 100, and 1000 pF of 16380A [4] in the Czech Republic were calibrated in the BIPM at a frequency of 1 kHz. At the working frequencies, the standards were calibrated from the frequency dependence of the capacitance (frequency course) at the INRIM Metrological Institute of Italy [5, 6]. The calibration in frequency course was performed at frequencies up to 15 MHz and used without loss of accuracy up to a frequency of 20 MHz (for a capacitance of 1000 pF) for 30 MHz (for capacitances of 10 and 100 pF). From the calibrated standards, the dimensions of unity were transmitted by means of standard measuring apparatus, in particular broad-band autobalance meters of impedance. The stan

3D dose distribution measurements in brachytherapy using radiochromic gel dosimeters

The paper informs about the joint research project “Increasing cancer treatment efficacy using 3D brachytherapy” which is a three-year project carried out in cooperation with European national metrology institutes and co-funded by the European Community's Seventh Framework Program for research and technological development. The goal of the project is to improve the measurement and standardization of dose-to-water rate by brachytherapy (BT) sources. The paper gives a summary of the individual parts of the whole project and describes in more detail the task of the Czech Metrology Institute: the determination of spatial distribution of dose-to-water by BT sources using radiochromic gel dosimeters, including a new gel with suppressed diffusion. The response of irradiated gels is evaluated using the optical cone beam computed tomography (CT) technique. The characteristics of the optical CT scanner are discussed with respect to CCD camera performance and light source. The optimized composition of the new gel and its dosimetric properties are highlighted. The results show that the radiochromic gels are convenient for measuring the 3D distribution of dose-to-water and could be an alternative to current methods of dose distribution measurements.

Radon-in-water standard

The radon-in-water standard installed at the Czech Metrology Institute in 1994 is based on a generator producing radium-free radon solution and on a measurement system for generator calibration and stability checking. The generator consists of about 6 L cylindrical vessel with a solid phase 222Rn source with 99.9% air emanation power and an external circuit for solution homogenisation. Standard solutions are prepared by charging water in the vessel with radon for an appropriate period; radon volume activity of the solution may vary from 300 to 2000 Bq/L; its uncertainty is less than 2.5%.

Radionuclide activity measurements in environmental samples of water, soil and grass: CCRI(II)-S4 comparison report

In the frame of the Mutual Recognition Arrangement of the International Committee for Weights and Measures, the Consultative Committee for Ionizing Radiation Section II—Measurement of Radionuclides—proposed to the national metrology institutes of Member States signatories of the Metre Convention, to participate in an interlaboratory comparison exercise on the determination of gamma emitting radionuclides in soil, grass and water. The exercise was piloted by the Reference Materials Group at the IAEA's Laboratories in Seibersdorf (Austria).The exercise is classed as a supplementary comparison, with reference CCRI(II)-S4 and the present report will be referenced in the Bureau International des Poids et Mesures (BIPM) key comparison database (KCDB).Five national metrology institutes took part in the present interlaboratory comparison exercise: the Czech Metrology Institute, the National Centre of Metrology, Bulgaria, National Institute of Standards and Technology, USA, the National Physical Laboratory, UK, and Physikalisch-Technische Bundesanstalt, Germany. In addition, two expert laboratories participated in this comparison: the Japan Chemical Analysis Centre, Japan, and the IAEA Chemistry Unit of the Physics, Chemistry and Instrumentation Laboratory in Seibersdorf, Austria.This comparison was aimed at: supporting calibration and measurement capability (CMC) claims of national metrology institutes for radionuclide measurements in different matrices (grass, soil and water), and assigning the certified reference value of the 372 grass Certified Reference Material.This report presents the sample preparation methodology, participants' results and data comparison approach.Appendix I contains the analytical results sorted according to the analyte with the Mixture Models Median (MM-median) graphs. Appendix II reports tables of results evaluation, including uncertainty budgets sorted by institute. Appendix III contains the documentation used in this comparison. The comparison study materials were prepared and distributed to the participating laboratories in June 2006. The deadline for receiving the results from the participants was set at 15 September 2006. The participating laboratories were requested to analyse the samples employing the methods used in their routine work.The comparison results have demonstrated that in the case of 40K, 54Mn, 60Co, 65Zn, 134Cs, 137Cs and 241Am the participating institutes could produce reliable and comparable analytical results of the highest metrological traceability within ±10% for soil, water and grass samples. However, 109Cd was the most problematic nuclide.It was found that there is a need for corrective action to improve the methodology of correction for matrix effect in the case of this nuclide in a mineral matrix, where a complex interference is present.The analytical uncertainties associated with the results were, in general, appropriate for the analytes and matrices considered in the current comparison.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI Section II, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Comparison of the dimensions of electrical resistance units, supported on the basis of the hall quantum effect, in the All-Russia Research Institute of Metrological Service and the Czech Metrological Institute

VNIIMS (Russia) and CMI (Czech Republic) quantum Hall resistance standards are compared using a VNIIMS portable resistance standard of 1 and 10 kΩ. Conformity is established for the dimensions of units within the limits of relative expanded (k = 2) uncertainty of 10 −7 .

Development of a switched integrator amplifier for high-accuracy optical measurements

In the field of low flux optical measurements, the development and use of large area silicon detectors is becoming more frequent. The current/voltage conversion of their photocurrent presents a set of problems for traditional transimpedance amplifiers. The switched integration principle overcomes these limitations. We describe the development of a fully characterized current-voltage amplifier using the switched integrator technique. Two distinct systems have been developed in parallel at the United Kingdom's National Physical Laboratory (NPL) and Czech Metrology Institute (CMI) laboratories. We present the circuit theory and best practice in the design and construction of switched integrators. In conclusion the results achieved and future developments are discussed.

Energy calibration measurements of MediPix2

Real-time measurement of the composition and spectroscopic characteristics of the radiation field inside the ATLAS detector and cavern will be carried out with MediPix2 devices. In view of this application, a calibration of the low energy threshold was performed by illuminating the devices with low energy photons, using 241Am sources and X-rays. A procedure was thereafter established for the calibration of all MediPix2 devices to be used in ATLAS. Using X-ray tubes with filters at the Czech Metrology Institute, photons of energies between 8 and 250 keV were obtained and the detection efficiency of the MediPix devices to these radiations was determined. An exponential decrease of the photon intensity as a function of detector depth was observed, illuminating the detector with the beam almost parallel to the surface. The properties of the decrease of intensity were used to determine the exact incident angle of the beam.

Gaseous standards preparation with the radionuclide Ar-41 for stack monitors calibration and verification in nuclear facilities

The Czech Metrology Institute performs calibration and verification of noble gases stack monitors in nuclear power plants and nuclear research facilities. Together with Kr-85 and Xe-133, the radionuclide Ar-41 is measured using HPGe detectors and its activity is determined using a gamma-ray peak at 1293 keV. The counting efficiency used in these measurements was calculated by the Monte Carlo method using the MCNP code. Radioactive gas standard is prepared by irradiation of argon in a high-pressure vessel by a Cf-252 neutron generator. The inner shape and thickness of the cylinder walls were determined by radiography. The argon volume under normal conditions is determined from the high-pressure vessel volume and by a precise gas pressure measurement. As a result, the activity concentration of Ar-41 at normal conditions is certified.

Determination of emission probabilities of gamma photons in the decay of 56Co

The emission probabilities of gamma photons in the decay of 56Co were determined at Czech Metrology Institute (CMI) by means of an HPGe detector. This detector was calibrated experimentally and by MCNP-computation in the energy range from 40 to 2754 keV for a point source geometry and source-to-detector distance of 25 cm. Experimental and computed peak and total efficiencies were compared and calibration curves were determined. Full-peak efficiencies were calculated for all 56Co γ-ray energies, and were used to calculate the emission probabilities. A set of point sources was prepared from a 56Co solution. The solution was standardized using the 4π β– γ coincidence method, and an ampoule was sent to international reference system for activity measurement of γ-ray emitting radionuclides (SIR). Each point source was measured with the HPGe detector at a source-to-detector distance of 25 cm. Coincidence emission probabilities of all the gamma photons were calculated and used to determine the summing correction factors.

Final report on CCQM-K9.2: Subsequent key comparison on pH determination of phosphate buffer by Harned cell measurements

CCQM-K9.2 was performed supplementary to the key comparison CCQM-K9 on the pH determination of a phosphate buffer with nominal pH ~ 6.9 (at 25 °C). The sample composition was very similar in both comparisons. Only the source of the starting material used for sample preparation was different. The comparison was restricted to the use of the primary method for pH (Harned cell measurement) as defined in the IUPAC Recommendations [2]. The measurement temperatures were 15 °C, 25 °C, 37 °C.CCQM-K9.2, CCQM-K.9 and the first supplementary comparison CCQM-K9.1 [5] are activities of the Electrochemical Working Group (EAWG) of the CCQM. All three comparisons were coordinated by the PTB, Germany.The Danish Primary Laboratory (DPL) successfully took part in the CCQM-K9. Meanwhile the primary set-up for pH in Denmark moved from DPL affiliated to Radiometer Medical to DFM, Denmark. The subsequent comparison allows assessing the degree of equivalence for the measurement of pH at DFM after the move. Due to the interest of other laboratories in demonstrating their progress in pH measurements on the primary level the CCQM-K9.2 supplementary comparison was extended to other participants than DFM, namely NMIJ, VNIIFTRI, INMETRO and CMI.The reported quantity for CCQM-K9.2 was not the pH of the sample but the acidity function at zero chloride molality (see chapter 12). To calculate the pH value from the acidity function it is necessary to know the ionic strength of the sample buffer solution, which was undisclosed by the coordinator.With the exception of the Czech Metrology Institute, CMI, good agreement in the determined acidity function is found between the participants.The results reported by DFM and by PTB agree within their measurement uncertainty at all measurement temperatures.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Monte Carlo study of reference photon fields in the irradiation halls of the Czech Metrology Institute

The MCNPX code was used to obtain characteristics of collimated photon beams from a 60Co source and a radiotherapy 60Co irradiator “Chisobalt 2 B75” was exploited for calibration and verification of dosimeters in the Czech Metrology Institute, Inspectorate for Ionizing Radiation (CMI-IIR; Czech metrology body). First, for each source, a longitudinal profile of air kerma rate on the beam axis and a transversal profile of air kerma rate at a distance of 1 m from the front of the source's collimator were simulated, and the results were compared with the experimental data obtained with ionization chambers. Measured and calculated data were in good agreement. Second, the number of scattered photons in the fluence spectra along and across the beam axes, and their contribution to air kerma were specified. Third, the individual contributions of photons scattered in collimator, air, floor, walls, mobile platform and other parts of the irradiation halls to the total air kerma rate on the beam axis were calculated for the purposes of future improvement of metrological parameters of photon beams in CMI-IIR.

Final report on the supplementary comparison Euromet.M.P-S2 (bilateral comparison) in the pressure range from 30 Pa to 7000 Pa

A bilateral comparison was carried out in order to test the degree of equivalence between the newly established pressure balances of the Czech Metrological Institute and the Physikalisch-Technische Bundesanstalt (PTB). The comparison was carried out without using a transfer standard, but with a differential capacitance diaphragm gauge as an indicator of the small differential pressure between the two pressure balances when the target pressures were generated in the two systems. The Czech Metrological Institute brought its force balanced piston gauge FPG by the DHI company to the site of the PTB pressure balance, which was a Furness Rosenberg system FRS 5 by the Furness company. In the range under comparison from 30 Pa to 7000 Pa full equivalence was obtained with the En value ranging from 0.01 to 0.47.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by EUROMET, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Absolute Frequency Measurement of the R(12) 26-0 and R

A direct phase coherent determination of the absolute frequency of the a15 component in the R(12) 26-0 and b10 component in the R(106) 28-0 transitions in 127I2 at 543 nm has been made at the International Bureau of Weights and Measures. Lasers from the Czech Metrology Institute (Czech Republic), the National Institute of Metrology (China), the Centro Nacional de Metrologia (Mexico), the Standards, Productivity and Innovation Board (Singapore), the Centre for Metrology and Accreditation (Finland), the Danish Institute of Fundamental Metrology (Denmark), the National Physical Laboratory (U.K.), and the International Bureau of Weights and Measures took part. The mean frequency values found are f(a15)=551579856480.4 kHz, uc=4.8 kHz and f(b10)=551580162397.1 kHz, uc=4.6 kHz for the current group of lasers, where uc is the combined standard uncertainty. This constitutes a 30-fold improvement in accuracy for this radiation, which is recommended for the realization of the definition of the meter. If only lasers equipped with an iodine cell temperature control are considered, the group of lasers shows a dispersion of 7 kHz. This value is indicative of the level of reproducibility that can be expected at present for this type of standard

Comparison on step height measurements in the nano and micrometre range by scanning force microscopes

The ability to make traceable measurements of step height is vital for the worldwide nanotechnology community. In contrast to the former CCL-S2 so-called NANO2 comparison, this Euromet comparison focuses only on measurements made using scanning force microscopes (SFM).The Czech Metrology Institute (CMI), CNR Istituto di Metrologia G Colonnetti (IMGC), Swiss Federal Office of Metrology and Accreditation (METAS) and Physikalisch-Technische Bundesanstalt (PTB – Pilot laboratory) agreed to participate in this comparison using their SFM to measure the step height on three standards with nominal values of 40 nm, 1000 nm and 2000 nm. The reference value for each standard was calculated using the weighted mean of all measurements that fulfilled the En ⩽ 1 criteria.Most of the results were in a good agreement with the reference values except for one instrument which failed to measure the largest step height. This shows first that SFM are able to measure step heights up to 2000 nm with very small uncertainty, and secondly, that each instrument has to be very carefully examined before it can be used on a daily basis to provide calibrations for industry and science.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the EUROMET, according to theprovisions of the CIPM Mutual Recognition Arrangement (MRA).

The new method of traceability of a force-balanced piston gauge used as primary vacuum standard

The force-balanced piston gauge is a primary vacuum standard developed in the 1990s. The general principle of the instrument was first presented in Ooiwa A (Metrologia 30 (1994) 607). Non-rotating piston is connected to an electronic dynamometer and centered by means of transient gas flow in a double tapered gap between piston and cylinder. More details about it can be found in Delajoud, Girard(NCSL International Workshop and Symposium 2002; Vakuum Forschung Praxis 15 (2003) 24) and Tesar, Prazak(Vacuum 67 (2002) 307).Czech Metrology Institute developed its own method of the primary traceability of this instrument through the determination of its effective area. In this paper, there will be described experimental setup of this comparison as well as the experimental results from the traceability calibrations of the effective area in gauge and absolute mode using experimental method of hydrostatic comparison with the classical rotating piston balances and a digital non-rotating piston balance. It will, of course, include the uncertainty budget of this way of traceability and the final uncertainty of the pressure generation of the instrument.

Application of pulse mixing method in software coincidence counting

In recent years the software coincidence counting system, designed for absolute activity measurement, has been developed in the Czech Metrology Institute. In this system a true coincidence count rate is calculated from the records of time and amplitude data of individual pulses and may be determined by two different methods. The first one uses a coincidence resolving time, in a manner similar to a classical coincidence measurement. The second method applies the pulse mixing method formulae, so that it does not use the resolving time and the correction for accidental coincidences. Both methods have been tested on the same data from a 4 πβ (PC)- γ coincidence measurement of 60Co sources. The difference between the results obtained from both calculation methods applied on the data from the same measurement did not exceed 0.015%. The details of both methods and the results of their comparison are presented.

Results from international comparisons at the bipm providing a world-wide reference network of /sup 127/ I/sub 2/ stabilized frequency-doubled nd:yag lasers

Frequency comparisons have been carried out between iodine-stabilized Nd:YAG lasers from the Bureau International des Poids et Mesures, the Bureau National de Metrologie-Institut National de Metrologie, the Czech Metrology Institute, the Centre for Metrology and Accreditation, and the National Metrology Institute of Japan/National Institute of Advanced Industrial Science and Technology. The comparison data of these lasers can now be linked to the results of recent absolute frequency measurements of lasers from different institutes.