PTB Braunschweig Research Articles

GPS PPP-AR frequency transfer and its application for comparing atomic fountain primary frequency standards between NRC and PTB

We report on the first characterization of the frequency transfer performance of the GPS precise point positioning with carrier-phase integer ambiguity resolution (PPP-AR) implemented by the Natural Resources Canada (NRCan) online service CSRS-PPP. We show that continuous PPP-AR links of multiple days can be formed by carefully fixing the day boundary phase discontinuity. The stability of the links can reach and (Allan deviation) at 1 d and 7 d averaging times, respectively, and mid to low 10−17 at 20 d–30 d. We compared the atomic fountain primary frequency standards (PFS) between NRC in Ottawa, Canada and PTB in Braunschweig, Germany for 135 d via GPS PPP-AR and precise point positioning links. The NRC and PTB PFS agree within a few parts in 1016, which is well below the combined systematic uncertainty. It is expected that with uncertainty at 10−17, the PPP-AR links will become a powerful tool for remote comparisons of atomic optical clocks, essential for the future redefinition of the SI second.

Response to Mono-Energetic Neutrons and Light Output Function for Liquid Organic Scintillators PYR5/DIPN and THIO5/DIPN

Liquid organic scintillators are important devices for measurements of neutron radiation. Currently, large-scale liquid organic scintillators have capabilities of detecting neutrons, but the determination of the neutron energy spectra is a challenge. This work aims to measure the responses of two liquid two-component scintillators to mono-energetic neutron radiation and to determine their light output function, which is necessary for proper neutron energy spectra determination. Both scintillators are composed of the solvent di-iso-propyl-naphthalene (DIPN) mixed isomers. The first scintillator, labeled PYR5/DIPN, contains the luminophore 1-phenyl-3-(2,4,6-trimethyl-phenyl)-2-pyrazoline with a concentration of 5 g/L. The second scintillator labeled THIO5/DIPN contains the luminophore 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene also with a concentration of 5 g/L. The responses to neutron energies of 1.5 MeV, 2.5 MeV, and 19 MeV are measured at PTB in Braunschweig. The responses to neutron energies of 2.45 MeV and 14 MeV were measured at CTU in Prague using DD and DT reactions. The responses to a silicon filtered beam were measured at Research Centre Řež. The measurements were processed using a two-parameter spectrometric system NGA-01 to discriminate neutrons from gamma rays. The obtained responses are dominated by recoil protons from elastic collisions of neutrons with hydrogen atoms. The edge of the response of recoil protons gives information about the light output of neutrons, compared to gamma rays for the same radiation energy. The light output function for protons in the PYR5/DIPN scintillator is L(Ep)=0.6294Ep−1.00(1−exp(−0.4933Ep0.95)). The light output function for protons in the THIO5/DIPN scintillator is L(Ep)=0.6323Ep−1.00(1−exp(−0.4986Ep0.9883)). The light output functions well resemble the standard shape, and they are quite similar to each other. That suggests a weak influence of the luminophore on the light output function. The light output functions are ready to be incorporated to the response matrix for the neutron energy spectra determination.

EURAMET.M.FF-S13 final report

Main textThe purpose of the Supplementary Comparison (S13) for water flow measurement (EURAMET 1473 and EURAMET.M.FF-S13) is to support the Calibration and Measurement Capabilities (CMC) entry of VTT MIKES, the National Metrology Institute of Finland. For this goal, a bilateral comparison between VTT MIKES and PTB Braunschweig was realized. The laboratory "Hydrodynamic Test Field" of department 1.5 "Liquid Flow" acted as the reference facility. The results of the comparison showed good equivalencies and supports the CMC claim of VTT MIKES.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 CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Measurement and simulation of the new liquid organic scintillator response to fast neutrons

Liquid organic scintillators are important devices for measurements of neutron radiation. This work aims to develop and optimize the composition of liquid organic scintillators so it can be used for fast neutron spectrometry. As the neutron radiation is usually accompanied with γ ray radiation, it is important to have quality γ/n discrimination. The new cocktail for house made liquid organic scintillator is prepared and studied with intention of being able to separate gamma and neutron for neutron energies above 0.5 MeV while keeping lower constraints on practical use (e.g., sealing because of oxygen) than commercial liquid scintillators. In preceding work the composition of liquid scintillators was optimized. Two twocomponent scintillators were selected for further studies. Solvent DIPN (Di-iso-propyl-naphthalene Mixed Isomers) is selected for both. First is mixed with luminophore PYR (1-Phenyl-3-(2,4,6-trimethyl-phenyl)-2-pyrazoline) of concentration 5 g/l. Second is mixed with luminophore THIO (2,5-Bis(5-tert-butyl-benzoxazol-2-yl)thiophene) of concentration 5 g/l. In this work the response of scintillator to monoenergetic beam of neutrons was measured for multiple neutron energies at PTB in Braunschweig. The two parameter spectrometric system NGA-01 is used to analyze the energy and discrimination characteristics. 137 Cs and 60 Co are used as radiation sources for calibration with pure γ rays. Then the response of scintillator for same neutron energies was simulated using GEANT4. The dissipated energy in the scintillator in response to monoenergetic neutrons is obtained. Both, measured and simulated responses are compared. Functional dependence for yield of recoiled products is estimated. It is seen that main recoil product hydrogen proton is well observed in both. From the edge of proton response one can assume the yield for given neutron energy. The recoiled carbon ion (from elastic collision) is on the other side difficult to observe in measured results but clearly seen in dissipated energy plots. It suggests that yield of carbon ion is very small relatively to proton yield. These results will serve as basis for response function evaluation of scintillator which is necessary for evaluation of unknown neutron spectra from measurements with scintillator.

Tests of Various Scintillator Detectors in Selected Mono-Energetic Neutron Beams

In this paper we study quality of three types of organic scintillators stilbene, p-terphenyl and EJ-299-33. We used monoenergetic neutron fields with a wide range of neutron energies in PTB Braunschweig. All the tests were carried out with NGA-01 spectrometer. The results of the measurements are evaluated spectra from the spectrometer. We discuss the quality of each scintillator, such as the FWHM of the peaks.

Wavelength calibration of Brewer spectrophotometer using a tunable pulsed laser and implications to the Brewer ozone retrieval

Abstract. In this contribution we present the wavelength calibration of the travelling reference Brewer spectrometer of the Regional Brewer Calibration Center for Europe (RBCC-E) at PTB in Braunschweig, Germany. The wavelength calibration is needed for the calculation of the ozone absorption coefficients used by the Brewer ozone algorithm. In order to validate the standard procedure for determining Brewer's wavelength scale, a calibration has been performed by using a tunable laser source at PTB in the framework of the EMRP project ENV59 ATMOZ “Traceability for the total column ozone”. Here we compare these results to those of the standard procedure for the wavelength calibration of the Brewer instrument. Such a comparison allows validating the standard methodology used for measuring the ozone absorption coefficient with respect to several assumptions. The results of the laser-based calibrations reproduces those obtained by the standard operational methodology and shows that there is an underestimation of 0.8 % of the ozone absorption coefficients due to the use of the parametrized slit functions.

Design and characterization of an SRAM-based neutron detector for particle therapy

A neutron detector based on registration of radiation effects in Static Random Access Memories (SRAMs) has been developed at the University of Bergen for applications in particle therapy. Nine different SRAMs were tested and a 16 Mibit SRAM from Cypress was chosen for the final detector. The SRAMs were irradiated in beam lines at PTB Braunschweig, the Oslo Cyclotron Laboratory, The Svedberg Laboratory, The Institute for Energy Technology (IFE, Kjeller) and the CERN-EU high-energy reference field. The results from the measurements demonstrate the feasibility of using the selected SRAMs for neutron detection. The results indicate low or no sensitivity to thermal neutrons while the cross section for fast neutrons increases with neutron energy before reaching a more stable level at energies of several tenths of MeV.

A practical method to assess the performance of gravimetric flow test rigs by using the timing error

This paper proposes an improved method to assess the performance of a gravimetric flow test rig. It addresses the study of two of the most important measurement systems: the weighing scale and all mass-related corrections, and the time measurement system. By performing a regular diverter test according to ISO 4185:1980 several times and under different conditions, it was possible to determine not only the statistical variances of the diverter system, but also the variances of the meter under test and of the flow test facility separately. The proposed method allows also under special conditions the determination of systematic errors in the mass determination. The method has been successfully applied at the large water flow calibration facilities of PTB in Braunschweig and Berlin and is recommended as a routine to test the performance of gravimetric flow test facilities.

Determination of (n,γ) Cross Sections of 241Am by Cold Neutron Activation

Accurate cross section data of actinides are crucial for criticality calculations of GEN IV reactors and transmutation but also for analytical purposes such as nuclear waste characterization, decommissioning of nuclear installations and safeguard applications. Tabulated data are inconsistent and sometimes associated with large uncertainties. Neutron activation with external cold neutron beams from high flux reactors offers a chance for determination of accurate capture cross sections scalable to the whole 1/E-region even for isotopes with low-lying resonances like 241Am. Preparation of 241Am samples for irradiation at the PGAA station of the FRM II in Garching has been optimized together with PTB in Braunschweig. Two samples were irradiated together with gold flux monitors to extract the thermal neutron capture cross section after appropriate corrections for attenuation of neutrons and photons in the sample. For one sample, the thermal ground state neutron capture cross section was measured as 663.0 ± 28.8 b. The thermal neutron capture cross section was calculated to 725.4 ± 34.4 b. For the other sample, a ground state neutron capture cross section of 649.9 ± 28.2 b was measured and a thermal neutron capture cross section of 711.1 ± 33.9 b was derived.

Evaluation of a personal and environmental dosemeter based on CR-39 track detectors in quasi-monoenergetic neutron fields

In this paper, the evaluation of the dosimetric capability of a detector based on a CR-39 solid-state nuclear track detector coupled to a 1 cm thickness of PMMA radiator was made with the aim of understanding the applicability of this technique to personal and environmental neutron dosimetry. The dosemeter has been exposed to monoenergetic and quasi-monoenergetic neutron beams at PTB in Braunschweig, Germany and at Ithemba Laboratories, in Faure, South Africa, with peak energies ranging from 0.565 to 100 MeV. The results showed a response that is almost independent of the neutron energy in the whole energy range.

Testing a newly developed single-sphere neutron spectrometer in reference monochromatic fields from 147 keV to 14.8 MeV

A new neutron spectrometer, designed to simultaneously respond from the thermal domain up to hundreds of MeV neutrons, was designed and built in the framework of the INFN project NESCOFI@BTF. It has been called SP2 (SPherical SPectrometer) and it consists of 31 thermal neutron detectors embedded in a 25cm diameter polyethylene sphere with an internal 1cm thick lead shell. The new spectrometer shows similar performance as the Bonner sphere spectrometer, but has the notable advantage of requiring only one exposure to determine the whole spectrum. The SP2 response matrix, previously calculated with MCNP, has been experimentally evaluated with monochromatic reference neutron fields from 147keV to 14.8MeV at PTB Braunschweig. As suitable thermal neutron detectors, Dysprosium activation foils were adopted at this stage. The results of the experiment confirmed the correctness of the response matrix within an overall uncertainty of ±3%. The next phase of the NESCOFI@BTF project will be the replacement of passive detectors with active counters, thus leading to a real-time spectrometric monitor that is expected to significantly innovate the neutron control task in neutron-producing facilities, such as the beam-lines for industrial irradiation or condensed matter studies.

Time transfer through optical fibres over a distance of 73 km with an uncertainty below 100 ps

We demonstrate the capability of accurate time transfer using optical fibres over long distances utilizing a dark fibre and hardware which is usually employed in two-way satellite time and frequency transfer (TWSTFT). Our time transfer through optical fibre (TTTOF) system is a variant of the standard TWSTFT by employing an optical fibre in the transmission path instead of free-space transmission of signals between two ground stations through geostationary satellites. As we use a dark fibre there are practically no limitations to the bandwidth of the transmitted signals so that we can use the highest chip rate of the binary phase-shift modulation available from the commercial equipment. This leads to an enhanced precision compared with satellite time transfer where the occupied bandwidth is limited for cost reasons. The TTTOF system has been characterized and calibrated in a common-clock experiment at PTB, and the combined calibration uncertainty is estimated as 74 ps. In a second step the remote part of the system was operated at Leibniz Universität Hannover, Institut für Quantenoptik (IQ) separated by 73 km from PTB in Braunschweig. In parallel, a GPS time transfer link between Braunschweig and Hannover was established, and both links connected a passive hydrogen maser at IQ with the reference time scale UTC(PTB) maintained in PTB. The results obtained with both links agree within the 1-σ uncertainty of the GPS link results, which is estimated as 0.72 ns. The fibre link exhibits a nearly ten-fold improved stability compared with the GPS link, and assessment of its performance has been limited by the properties of the passive maser.

Experimental study for improving the angle dependence of the response of PADC-based personal neutron dosemeters

Abstract The large angle dependence of the H p (10) response in PADC-based personal neutron dosemeters constitutes a serious concern in operational radiation protection dosimetry. For planar dosemeters, the typical H p (10) response falls by half or more when the incidence angle changes from 0° to 60°. To reduce this source of systematic uncertainty, configurations based on multiple detectors at different angles have been developed, but their complex geometries constitute an important obstacle to the implementation in routine services. This works proposes a simplified configuration, based on two orthogonal PADC detectors, which is suitable for the implementation in the routine service of INFN-LNF (Frascati). This system was tested, using a ISO slab standard phantom, in the following reference neutron fields: 241 Am–Be and 252Cf(D2O) available at ENEA-Bologna, and 1.2 MeV, 5 MeV and 14.8 MeV mono-chromatic beams available at PTB Braunschweig. Incidence angles of 0°, ±15°, ±30°, ±45° and ±60° were chosen. The sum of the track density in the PADC parallel to the phantom and that in the detector normal to the phantom face, was regarded as “dosemeter reading”. On this basis the Hp(10) response was calculated for different energies and incidence angles. As expected, the angular response of the two-orthogonal-element dosemeter is highly improved with respect to that of a single planar PADC.

Selected papers about chemiluminescence of flames

Sensors that allow cheap, reliable and non-intrusive monitoring and subsequent active control of combustion processes are necessary for the development of combustors operating under potentially unstable operation conditions (e.g., for very lean or low-temperature combustion). Chemiluminescence in the UV-Vis region fulfills all of these requirements, and it has been shown that it can be used to determine flame parameters such as stoichiometry and heat release quantitatively. However, even though flame emissions have been studied for more than one century, important facts still remain unknown. Especially, reaction pathways leading to chemiluminescent species such as OH∗, CH∗, C∗2 and CO ∗ 2 are still under debate and cannot be modeled with standard codes for flame simulation. In several cases, even the source species of spectral features observed in flames are unknown. To investigate these processes in more detail, the cooperative research project “Chemiluminescence and Heat Release” has been started in 2006 with support of the Deutsche Forschungsgemeinschaft (DFG) under contract PAK 116. Seven individual projects, contributions from nine groups and institutions including the IWR and PCI at Heidelberg University, DLR Stuttgart, IVG of University of Duisburg– Essen, PC1 at Bielefeld University, EKT at TU Darmstadt, PTB Braunschweig, TCP at Karlsruhe Institute of Technology and LTD at TU Munchen. The project has been very

Evaluation and comparison of measurements of unattached and attached radon progeny in the radon chamber of PTB Braunschweig (Germany) with NRPI Praha (Czech Republic)

On the case of a parallel metrological measurement of unattached and attached concentrations of radon progeny, the evaluation by an inversion of the Jacobi-Porstendörfer room model indicates a real overestimation of the concentration of RaA ((218)Po).

A Bonner Sphere Spectrometer with extended response matrix

This paper describes the design, calibration and applications at high-energy accelerators of an extended-range Bonner Sphere neutron Spectrometer (BSS). The BSS was designed by the FLUKA Monte Carlo code, investigating several combinations of materials and diameters of the moderators for the high-energy channels. The system was calibrated at PTB in Braunschweig, Germany, using monoenergetic neutron beams in the energy range 144 keV–19 MeV. It was subsequently tested with Am–Be source neutrons and in the simulated workplace neutron field at CERF (the CERN-EU high-energy reference field facility). Since 2002, it has been employed for neutron spectral measurements around CERN accelerators.

QA programme for radon and its short-lived progeny measuring instruments in NRPI Prague

To subserve the institutional research and tasks coming out from the Czech National Radon Programme, a new QA programme to calibrate all the known types of devices that measure radon and its short-lived progeny was developed at the Department of Radon mobile group of the National Radiation Protection Institute (NRPI) at Prague. The programme also included calibration of instruments measuring a unique quantity of unattached and attached fractions of short- lived radon progeny Generally, NRPI declares estimation of radon concentration during all routine calibration measurements with an overall uncertainty <5% (one sigma) and of equilibrium-equivalent radon concentration with an overall uncertainty <10% (one sigma). The results of the comparative measurements of the unattached and attached fractions of each short-lived radon progeny carried out with a comparing continuous monitor Fritra 4 in the German reference radon chamber at PTB Braunschweig indicated an acceptable level of agreement, up to 10%.

Final report on intercomparison measurements in the field of gas flow and volume, which are realized at two levels: the second level (B*)

COOMET project no 219/SK-a/00 'Performance of comparison measurements of testing standard equipment working in the gas flowrate range: (A) 0.06 m3/h to 10 m3/h; (B) 100 m3/h to 1000 m3/h', ref. no COOMET.M.FF-S1 has been organized by TC 1.4 'Flow measurement' of COOMET, started in March 2006 and finished in October 2008.Type of comparison – supplementary; Pilot laboratory – SMU, Slovak Institute of Metrology.Participating institutes (and countries): SMU, Slovakia; PTB, Germany; LEI, Lithuania; BelGIM, Belarus; FGUP VNIIR, Russia; SE 'Ivano-Frankovskstandartmetrology', Ukraine; NISM, Moldavia.The comparison was realized at two levels.Within the first level (A*), the comparisons of the test rigs were realized for verification of the diaphragm domestic gas meters in the flow range of 0.12 m3/h to 10 m3/h. The compared measurement means were the set of five diaphragm gas meters of type MKM, size G6. Two laboratories (SMU Bratislava, Slovakia and LEI Kaunas, Lithuania) of the seven participating laboratories at this level are participants in projects of comparisons, which are organized within the regional metrological organization EUROMET.The second level (B*) assured a comparison measurement of testing devices for industry gas meters of flow range from 100 m3/h to 1000 m3/h. The comparison meter was an axial turbine gas meter of DAE type, G650 size serial number 0004455/2005. Seven laboratories participated at this level of the project, including the laboratory of Belarus with a limited flow rate range (from 100 m3/h to 400 m3/h). Three laboratories (PTB Braunschweig, Germany; SMU Bratislava, Slovakia and LEI Kaunas, Lithuania) of the seven participating laboratories at this level are participants of comparisons, which are organized within the regional metrological organization EUROMET; out of that group the laboratory PTB Braunschweig, Germany is also participant in a CIPM key comparison.Based on the given results, one can say that the first comparison in this field within the COOMET regional organization achieved good results.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 COOMET, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Final report on intercomparison measurements in the field of gas flow and volume, which are realized at two levels: the first level (A*)

COOMET project no 219/SK-a/00 'Performance of comparison measurements of testing standard equipment working in the gas flowrate range: (A) 0.06 m3/h to 10 m3/h; (B) 100 m3/h to 1000 m3/h', ref. no COOMET.M.FF-S1 has been organized by TC 1.4 'Flow measurement' of COOMET, started in March 2006 and finished in October 2008.Type of comparison – supplementary; Pilot laboratory – SMU, Slovak Institute of Metrology.Participating institutes (and countries): SMU, Slovakia; PTB, Germany; LEI, Lithuania; BelGIM, Belarus; FGUP VNIIR, Russia; SE 'Ivano-Frankovskstandartmetrology', Ukraine; NISM, Moldavia.The comparison was realized at two levels.Within the first level (A*), the comparisons of the test rigs were realized for verification of the diaphragm domestic gas meters in the flow range of 0.12 m3/h to 10 m3/h. The compared measurement means were the set of five diaphragm gas meters of type MKM, size G6. Two laboratories (SMU Bratislava, Slovakia and LEI Kaunas, Lithuania) of the seven participating laboratories at this level are participants in projects of comparisons, which are organized within the regional metrological organization EUROMET.The second level (B*) assured a comparison measurement of testing devices for industry gas meters of flow range from 100 m3/h to 1000 m3/h. the comparison meter was an axial turbine gas meter of DAE type, G650 size serial number 0004455/2005. Seven laboratories participated at this level of the project, including the laboratory of Belarus with a limited flow rate range (from 100 m3/h to 400 m3/h). Three laboratories (PTB Braunschweig, Germany; SMU Bratislava, Slovakia and LEI Kaunas, Lithuania) of the seven participating laboratories at this level are participants of comparisons, which are organized within the regional metrological organization EUROMET; out of that group the laboratory PTB Braunschweig, Germany is also participant in a CIPM key comparison.Based on the given results, one can say that the first comparison in this field within the COOMET regional organization achieved good results.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 COOMET, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Measurement of the fluence response of the GSI neutron ball dosemeter in the energy range from thermal to 19 MeV

At high-energy particle accelerators, area monitoring needs to be performed in a wide range of neutron energies. In principle, neutrons occur from thermal energies up to the energy of the accelerated ions, which is for the present GSI (Gesellschaft für Schwerionenforschung) accelerator facility approximately 1-2 GeV per nucleon. There are no passive dosemeters available, which are designed for the use at high-energy accelerators. At GSI, a neutron dosemeter was developed, which is suitable for the measurement of high-energy neutron radiation by the insertion of a lead layer around Thermoluminescence (TL) detection elements (pairs of TL 600/700) at the centre of the dosemeter. The design of the sphere was derived from the construction of the extended range rem-counters for the measurement of ambient dose equivalent H(10). In this work, the dosemeter fluence response was measured in the quasi-monoenergetic neutron fields of the accelerator facility of the PTB in Braunschweig and in the thermal neutron field of the GKSS research reactor FRG-1 in Geesthacht. For the accelerator measurements, the reactions (7)Li(p,n)(7)Be, (3)H(p,n)(3)He and (2)H(d,n)(3)He were used to produce neutron fields with energy peaks between 144 keV and 19 MeV. The measured fluence responses are 27% too low for thermal energies and show an agreement with approximately 14% for the accelerator produced neutron fields related to the computed fluence responses (MCNP, FLUKA calculations). The measured as well as the computed fluence responses of the dosemeter are compared with the corresponding conversion coefficients.