Czech Metrology Institute Research Articles

A two-layer Timepix3 stack for improved charged particle tracking and radiation field decomposition

Abstract We characterize a novel instrument designed for radiation field decomposition and particle trajectory reconstruction for application in harsh radiation environments. The device consists of two Timepix3 assemblies with 500 µm thick silicon sensors in a face-to-face geometry. These detectors are interleaved with a set of neutron converters: 6LiF for thermal neutrons, polyethylene (PE) for fast neutrons above 1 MeV, and PE with an additional aluminum recoil proton filter for neutrons above ∼4 MeV. Application of the coincidence and anticoincidence technique together with pattern recognition allows improved separation of charged and neutral particles, their discrimination against γ-rays and assessment of the overall directionality of the fast neutron field. The instrument's charged particle tracking and separation capabilities were studied at the Danish Center for Particle Therapy (DCPT), the Proton Synchrotron, and Super Proton Synchrotron with protons (50–240 MeV), pions (1–10 GeV/c and 180 GeV/c). After developing temporal and spatial coincidence assignment methodology, we determine the relative amount of coincident detections as a function of the impact angle, present the device's impact angle resolving power (both in coincidence and anticoicidence channels). The detector response to neutrons was studied at the Czech Metrology Institute (CMI), at n_ToF and the Los Alamos Neutron Science Center (LANSCE), covering the entire spectrum from thermal up to 600 MeV. The measured tracks were assigned to their corresponding neutron energy by application of the time of flight technique. We present the achieved neutron detection efficiency as a function of neutron kinetic energy and demonstrate how the ratio of events found below the different converters can be used to assess the hardness of the neutron spectrum. As an application, we determine the neutron content within a PMMA phantom just behind the Bragg-peak during clinical irradiation condition with protons of 160 MeV.

An Experimental Setup for Power Loss Measurement up to 1 kHz using an Epstein Frame at CMI

Abstract This paper describes an experimental setup used at the Czech Metrology Institute (CMI) to measure the specific power loss of oriented and non-oriented electrical steel sheets up to 1 kHz using an Epstein frame. Special attention is given to a) a description of the hardware that is used, b) a description of the feedback control and measurement software, and c) an analysis of the sources of uncertainty and validation. Calibration expanded uncertainty of (0.5 up to 1.6)% for k = 2 can be achieved with this setup.

Involvement and use of European Metrology Programme for Innovation and Research EMPIR in the Czech Metrology Institute – a positive example of the use of European cooperation

The Czech Metrology Institute (CMI) has been the national metrology institute of the Czech Republic since 1993. The significant development of the CMI's fundamental metrology departments and the gradual growth of the CMI's scientific and research capacities are linked to its successful participation in the European Metrology Research Programme (EMRP) and the European Metrology Programme for Innovation and Research (EMPIR). In total, 28 countries have participated in the EMPIR Programme, with Switzerland, Norway, Serbia, Bosnia and Herzegovina, Turkey and the UK in addition to the EU Member States. The necessary organisational and administrative background for the realisation of the EMPIR Programme was provided by EURAMET e.V., a European Regional Metrology Organisation operated as a non-profit association under German law. The most important benefit of the Programme for the CMI and the Czech Republic is the successful implementation of the research results of individual EMPIR projects. Within the framework of this implementation of the EMPIR results in the CMI, 6 new state measurement standards of the Czech Republic have already been established and another 4 are in the stage of preparation for announcement. Furthermore, 23 new or significantly modified measurement methods have been developed based on the results within the CMI and are now provided as a service by the CMI. Finally, participation in the EMPIR projects has been used to train 42 new CMI scientists in various fields of measurement. If to add to this the use of the results of the former EMRP Programme, it can be concluded that the development of metrology at the CMI over the last 10 years has been strongly conditioned by successful participation in European Metrology Programmes and the ability of the CMI to subsequently apply the results of individual projects to its laboratory practice.

Freeform digital twin approach to develop the HP 300 freeform verification standard

Inspired by previous experience in freeform metrology practice and industrial needs, the Czech Metrology Institute developed the freeform standard Hyperbolic paraboloid 300 of dimensions 300mm×300mm×160mm with a freeform functional area of approximately 64000mm2. The paper presents a mathematical–metrological approach to finding a suitable strategy for calibrating the freeform standard on a coordinate measuring machine with a tactile probing system. The calibration strategy consists in the development of a freeform digital twin of the standard, i.e. a continuous digital representation of a freeform measured value with associated uncertainty. A procedure to estimate the uncertainty of the coordinate freeform measurement is described, too. After calibration, the Hyperbolic paraboloid 300 standard will become a verification gauge suitable for use as a precision reference in advanced freeform metrology similar to common verification gauges widely used in length metrology.

A training centre for intraocular pressure metrology

The eye-tonometers are the important medical devices with measuring function which are necessary for the screenings of the intraocular hypertension (a serious risk factor for the glaucoma). However, it is not an easy task to ensure their correct metrological traceability. There is needed not only a wide range of various equipment but also the relevant know-how. Hence, a training centre for this quantity was established at the Czech Metrology Institute (CMI) within the framework of a smart specialisation concept for the intraocular pressure (IOP) metrology. The paper briefly outlines its history, scope, methodologies and future development plans

Practical X-ray beam spectrometry with cadmium telluride detector in 10–300 kVp range at Czech Metrology Institute. Part II. Unfolding

The paper summarizes computational methods and software tools used at Czech Metrology Institute for unfolding of X-ray photon fluence spectra from detector spectra measured with a cadmium telluride (CdTe) spectrometer directly in the X-ray beam. Fluence spectra were determined using multi-channel unfolding software GRAVEL. Response functions were calculated by Monte Carlo (MC) method using the general-purpose code MCNP® in version 6.2 with EPRDATA14 photon cross-section tables. The detailed MC model of the CdTe spectrometer was developed and it was validated by comparison with full-energy peak detection efficiencies measured with selected radionuclide sources. The adopted methods and tools enable to fulfil requirements of the ISO 4037 standard dealing with the necessity of direct measurement of X-ray beam photon fluence spectra whose parameters do not comply with the ones listed in the standard. The instrumentation part for the X-ray beam spectrometry at CMI is described in a separate paper [1].

Practical X-ray beam spectrometry with cadmium telluride detector in 10–300 kVp range at Czech Metrology Institute. Part I. Instrumentation

The paper describes instrumentation used at Czech Metrology Institute for measurement of photon fluence spectra directly in X-ray beams. Detector with a cadmium telluride (CdTe) sensor was characterized by means of energy resolution and precise energy calibration. The hole trapping effect in CdTe causing full-energy peak deformations in measured spectra was adopted consisting of analytical models of incomplete charge collection and carrier trapping based on Hecht equation. The detector collimator provided by the manufacturer was modified with additional tungsten shielding that effectively absorbs the majority of photons scattered in the collimator body resulting in significant improvement of the consistency of measured and Monte Carlo simulated detector response. The purpose-made alignment platform increased the accuracy of orientation of the collimator axis improving the measurement in high photon fluence rate beams using collimation disks with very small apertures (down to 100 μm in diameter). The adopted instrumentation and methods for X-ray beam spectrometry enabled to fulfil the requirements of the new ISO 4037:2019-ed.2.0 standard for reference metrology laboratories. Software-focused part dealing with Monte Carlo simulations and procedures for photon fluence spectra unfolding is summarized in [1].

Results of the EURAMET.RI(II)-K2.Ho-166 key comparison for the activity of the radionuclide 166Ho per unit mass of aqueous solution

Main textThis is the final report for the EURAMET.RI(II)-K2.Ho-166 key comparison of the activity of the radionuclide 166Ho per unit mass of aqueous solution which was organized in 2017 by Czech Metrology Institute (CMI) within the joint research project "Metrology for clinical implementation of dosimetry in molecular radiotherapy" (MRTDosimetry; 15HLT06) of the European Metrology Programme for Innovation and Research (EMPIR). The key comparison reference value of (2623.6 ± 3.6) kBq·g-1 was determined from the results of three participants at the reference time of 1 December 2017 00:00 UTC. The details of the comparison are presented and analysed in this paper.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Analytical solutions of some model cases of piston-cylinder assemblies

Pressure balances are an important part of the sets of primary pressure standards in many national metrology institutes. The most critical factor determining their accuracy is the effective area of their piston-cylinder assemblies (PCAs). This can be determined (for PCAs with undistorted pressure) by applying a numerical procedure based on a theory by Dadson while knowing a gapprofile (of an axisymmetric PCA approximation). The pressure balances are also a basis for the primary pressure scale of the Czech Metrology Institute. Hence, we wanted to test our programme by computing the effective area from the geometrical data. Therefore, we solved the analytical formulae of Dadson et al (1982) The Pressure Balance—Theory and Practice (London: Her Majesty’s Stationery Office) for several simple geometries with a constant gap width, which are easy to calculate analytically. It is shown that the analytical results always agreed perfectly with the results of our programme. This success confirmed the correctness of our programme. However, it also pointed out a problem of discretization which can be non-negligible, even in the case of relatively simple geometries. We assume that the analytical formulae obtained can be of practical use for any other pressure metrology laboratory requiring an independent way to confirm their own PCA-modelling software.

Determination of a Pu-Be source neutron spectrum at Czech Metrology Institute

Contrary to the radionuclide neutron sources of 252Cf and 241Am-Be type, which are most widely used for the dosimetric instrumentation calibrations, the spectral source strength and spectrum averaged fluence to dose equivalent conversion coefficients of Pu-Be source are not recommended by an international standard. This work describes the determination of those parameters for the Pu-Be source used at Czech Metrology Institute (CMI) by means of a Bonner spectrometer in combination with neutron emission rate measurement in a manganese bath.

Timepix3 detector network for nuclear waste monitoring

In the framework of the MICADO project we proposed an active long-term nuclear waste monitoring system based on Timepix3 technology. Particle detectors based on Timepix3 are capable of particle type discrimination and provide spectrometric information in combination with precise timing information. To maximize the versatility of the setup, the Timepix3 detectors employed are equipped with a range of different sensors. To enable measurement of neutrons, two quadrants of the detectors are covered by neutron converters, allowing detection of thermal neutron by capture in 6Li, as well as detection of fast neutrons through recoil protons generated in a polyethylene converter. Within this project a new housing for the detector unit and the readout was developed, with the network currently comprising of 9 such detectors. A specifically developed in-house software handles simultaneous operation of all devices, cluster analysis and data visualization. Energy calibration was performed using an X-ray tube with several fluorescence foils as well as photons from an 241Am source. The neutron and gamma/X-ray detection efficiency calibration was carried out at the Czech Metrology Institute and the results are presented here. Tests on simultaneous operation of all 9 devices were performed using uraninite and 241Am sources.

The physical chemistry primary traceability at CMI

This article describes the actual achievements in the field of physical chemistry and introduces the methods of traceability used in the Department of Primary Metrology of Physical Chemistry in the fields of electrolytic conductivity, pH and coulometry.The Department of Primary Metrology of Physical Chemistry is located in Brno, the second largest city of the Czech Republic.The basic theory and the construction of the primary measurement standard of electrolytic conductivity is described. The primary conductometric cell consists of three parts. The length parameters of the most important middle part are precisely measured. The original conductometric cell was modified to reduce the volume of the measured liquid. The measurement standard participated in key comparisons with further publishing results in KCDB and in 2018 it was established as the state measurement standard of electrolytic conductivity in the range (0.005‒10) S‧m‒1.In 1999, the construction of the primary pH measurement standard began. The primary measurement standard consisted of five Harned cells without transfer. The challenge was the design of Harned cells. In 2005, a new, simpler design of Harned cells was used. After determining the standard potential of the five reference electrodes, the acidity function of the buffer is determined. The measurement standard participated in key comparisons with further publishing results in KCDB and in 2014 it was established as the state pH measurement standard.The Czech Metrology Institute is also a producer of certified reference materials for pH and electrolytic conductivity. It was accredited by the Czech Institute for Accreditation according to the EN/ISO 17034 standard in 2015.In 2015, the new primary measurement standard for substance quantities was put into operation. Coulometry as a primary method is used to realise and transfer the unit of substance through primary reference materials. In 2019, it successfully participated in the key comparison CCQM-K73.2018. It is planned to establish the primary measurement standard for the quantity of substances as a state measurement standard in the near future.

Water Molecule-Triggered Anisotropic Deformation of Carbon Nitride Nanoribbons Enabling Contactless Respiratory Inspection

The exploitation of the interaction between nanostructured matter and small molecules, such as H2O at interfaces via dynamic hydrogen bonding, is essentially the key for smart, responsive nanodevic...

Characterization of a precision modular sinewave generator

At the Czech Metrology Institute (CMI) we have developed a precision modular sinewave generator for impedance ratio bridges. The generator was developed to improve previously available designs regarding amplitude and phase accuracy, linearity, absolute stability, stability of the ratio between two outputs and harmonic distortion. It generates up to 7 Vrms in a frequency range from 1 mHz up to 20 kHz, extendable to 100 kHz with small changes to the filters. The amplitude resolution is better than 0.01 μV V−1 of full scale with an output voltage stability of 0.05 μV V−1/30 min and a stability for the ratio between two outputs of 0.02 × 10−6 over several hours. The generator can be powered from internal batteries and is controlled via optically isolated connections. The internal clock and voltage references can be replaced by external ones, optically coupled in the case of the clock. In this paper, we discuss experimental results obtained with the generator used as a signal source in digital impedance bridges with relative combined uncertainties from 10–5 down to 10–8. The generators have been used in a bridge to drive a quantum Hall resistor in the AC regime. The use of a generator with an AC quantum voltmeter will also be discussed. The generator is not only applicable in the field of AC impedance metrology but also for on-site comparisons of AC quantum voltage standards or, in general, where there is a need for precision voltage sources.

Equipment for Testing Measuring Devices at a Low-Level Radon Activity Concentration.

The National Institute for Nuclear, Biological, and Chemical Protection, under the European project 16ENV10 MetroRADON (the European metrology program for innovation and research, EMPIR), has developed unique equipment for the testing of measuring devices at low-level radon activity concentrations. The equipment consists particularly of an airtight low-level radon chamber (LLRCH) with an inner volume of 324 liters; a Rn-222 type RF 5 flow-through source with a Ra-226 activity of 4.955 kBq developed by Czech Metrological Institute within the above-mentioned project; and a pressure vessel as a radon-free air source. The mass flow controller of the Bronkhorst EL-Flow type is a part of the apparatus and ensures the requested airflow through the radon source—partialized if necessary—through the chamber. The homogeneity of the atmosphere in the chamber is ensured by means of a continuously regulated fan (airflows in the range of 0.1–3.5 m·s−1 can be established). Another important chamber component is the measuring device of climatic conditions, since temperature, air pressure, and relative humidity must be determined. The construction of the equipment allows the time-stable radon activity concentration to be maintained at a precise level for several days. Radon concentration values can be arbitrarily and continuously set in the range from 100 Bq·m−3 to 300 Bq·m−3.

Supplementary comparison COOMET.M.P-S4 of gas absolute pressure standards up to 7 MPa, and gauge up to 2 MPa

This report describes the results of a successful two-phase interlaboratory comparison between Georgian National Agency for Standards and Metrology (GeoSTM), Czech Metrology Institute (CMI) and Slovak Metrology Institute (SMU) denoted as COOMET.M.P-S4. The ranges of the absolute pressure from 0 MPa to 7 MPa and gauge pressure from 0 MPa to 2 MPa were chosen as the most suitable for a mutual comparison. A digital pressure gauge, DHI RPM4 served as a transfer standard in both phases. Firstly, bilateral interlaboratory comparison (BILC) between two participants, CMI (pilot and reference laboratory) and GeoSTM, started in March 2017 and finished in April 2017. Secondly, interlaboratory comparison (ILC) between three participants, CMI (pilot and reference laboratory), SMU (co-reference laboratory) and GeoSTM, started in October 2018 and finished in February 2019. SMU took part only in the absolute pressure comparison.Main textTo 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 CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Final report on supplementary comparison COOMET.M.M-S4 of multiples and submultiples of the kilogram

This report describes the results of bilateral supplementary comparison COOMET.M.M-S4 (also known as COOMET 722/AZ/17). The comparison measurements between the two participants Czech Metrology Institute (CMI) (pilot laboratory) and Azerbaijan Institute of Metrology (AzMI) were started in December 2016 and finished in February 2017.The transfer standards were OIML Class E2 standard weights with nominal mass values of 5 kg, 500 g, 20 g, 2 g and 100 mg. Agreement between the two participants is good.Main textTo 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 CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Development of the new 10 N·m deadweight torque standard machine in Czech metrology institute

In order to expand the range of the torque standards in Czech metrology institute (CMI) and fulfil requirements from the industry, new deadweight torque standard machine (DWTSM) is being designed and manufactured. This paper describes the development and construction of a new torque standard machine at CMI. It is focused on design, engineering and assembly of the main parts of the machine such as the lever arm, weights, air bearing, counter torque device, weights operating units and pedestal.

Characterization of the new free-air primary standard for medium-energy X-rays at CMI

In 2011 a decision was made by Czech Metrology Institute to build a free-air ionization chamber (FAC) intended to be used as a primary standard of air kerma rate for medium-energy X-rays (photon energy from 40 to 300 keV, including mammography X-ray qualities) in order to replace currently used secondary ionization chamber and to decrease the uncertainty of air kerma reference value. In the period of 2013–2017, the FAC has been designed, manufactured and put into operation. Correction factors were measured or calculated by a Monte Carlo method. FAC performance was preliminary tested using a calibrated secondary chamber. Physical characteristics of the FAC are described and a summary of the correction factors with the uncertainty budget is presented.

An investigation of the base metal thermocouples uncertainty components in ILC comparison

This paper is about unique the interlaboratory large comparison organized under EA-2/14 - Procedure for Regional Calibration ILCs in Support of EA MLA and describe final results of the comparison and several pitfalls when measuring temperature with base metal thermocouple. Interlaboratory comparison (ILC) serves as a tool for comparison of measurement results carried out by accredited or non-accredited calibration laboratories in the relevant field of measurement. ILC represents very effective means to demonstrate technical competence of the participant and also serves as a technical base for accreditation. The subject of this comparison was calibration of several pieces the N-type thermocouples. The pilot laboratory of this ILC was the Department of primary metrology of thermo-technical quantities of the Czech Metrology Institute. The reference values of the test items were provided by the above mentioned organizational unit this company. The evaluation of the measurement results of participating laboratories was performed on the basis of En score (EN ISO/IEC 17043). In this ILC program 47 accredited calibration laboratories from different European countries and also from Bosnia and Hercegovina, Switzerland and Turkey have participated. The results of this comparison demonstrate satisfactory agreement of the majority of the participants measured values with the reference ones within their stated expanded uncertainties. The article also highlights the basic and often neglected components of uncertainty.