We calculated allowed 13-decay Gamow-Teller matrix elements of A = 15, 17, 39, 41 mirror nuclei i... more We calculated allowed 13-decay Gamow-Teller matrix elements of A = 15, 17, 39, 41 mirror nuclei in the relativistic scalarvector shell model. The relativistic corrections are shown to present the features of the mechanism needed to account for their incompletc non-relativistic description (missing quenching).
Update of the BIPM comparison BIPM.RI(II)-K1.Ho-166m activity measurements to include the IRA and... more Update of the BIPM comparison BIPM.RI(II)-K1.Ho-166m activity measurements to include the IRA and the NPL and a re-evaluation of the degrees of equivalence for the APMP.RI(II)-K2.Ho-166m comparison
This report summarises the results for the new BIPM.RI(II)-K1.Ge-68 comparison. Six metrology ins... more This report summarises the results for the new BIPM.RI(II)-K1.Ge-68 comparison. Six metrology institutes have participated, enabling the first value of the key comparison reference value(KCRV) to be determined. The KCRV was calculated using the power-moderated weighted mean and the results. A link has been made to the CCRI(II)-K2.Ge-68 comparison held in 2015 through the NIST, NIM,IRA-METAS and the LNE-LNHB who participated in both comparisons. One NMI used the K2 comparison to update their degree of equivalence. The degrees of equivalence between each equivalent activity measured in the International Reference System (SIR) and the KCRV have been calculated and the results are given in the form of a table for the remaining five NMIs in the BIPM.RI(II)-K1.Ge-68 comparison and the 12 other participants in the CCRI(II)-K2.Ge-68 comparison. A graphical presentation is also given. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which app...
The hypothesis that proximity to the Sun causes variation of decay constants at permille level ha... more The hypothesis that proximity to the Sun causes variation of decay constants at permille level has been tested and disproved. Repeated activity measurements of mono-radionuclide sources were performed over periods from 200 days up to four decades at 14 laboratories across the globe. Residuals from the exponential nuclear decay curves were inspected for annual oscillations. Systematic deviations from a purely exponential decay curve differ from one data set to another and are attributable to instabilities in the instrumentation and measurement conditions. The most stable activity measurements of alpha, beta-minus, electron capture, and beta-plus decaying
The half-lives of 44 Sc and 44m Sc were measured by following their decay rate using several meas... more The half-lives of 44 Sc and 44m Sc were measured by following their decay rate using several measurement systems: two ionization chambers and three γ-spectrometry detectors with digital and/or analogue electronics. For 44 Sc, the result was the combination of seven half-life values giving a result of 4.042(7) h, which agrees with the last reported value of 4.042(3) h and confirms the near to 2% deviation from the recommended half-life of 3.97(4) h. Scandium-44 is present as an impurity in the production of 44 Sc by cyclotron proton irradiation. Its half-life was determined by measurements performed a few days after End of Bomardment (EoB), so that the 44 Sc decayed down to a negligible level. Seven measurements were combined to obtain an average of 58.7(3) h, which is in agreement with the recommended value of 58.6(1) h.
ABSTRACT The suggestion made recently by H. Abele et al. that relativistic effects in the interac... more ABSTRACT The suggestion made recently by H. Abele et al. that relativistic effects in the interaction of alpha particles with various nuclei at intermediate energies may remove the existing discrepancy between the theoretical predictions and the experimental data for the reaction cross section is investigated. We use a relativistic model based on the Kemmer-Duffin-Petiau equation and find that relativistic effects do not lead to a reduction in the reaction cross section within the present approach. Alternative explanations are discussed.
The half-life of 137 Cs was measured with an ionization chamber by following the decay of 5 sourc... more The half-life of 137 Cs was measured with an ionization chamber by following the decay of 5 sources over a 30 years period between 1983 and 2013. The ratio between the ionization chamber current for the cesium sources and 226 Ra source was used for the half-life calculation. The value found for the 137 Cs half-life is 10,955.2 ± 10.7 days, where the uncertainty evaluation combines type A and B for one standard deviation. Amersham-Büchler & Co and the Bureau International des Poids et Mesures (BIPM). Its activity was 7.9 MBq in 1982.
In view of current interest in relativistic spin-one systems and the recent work on the Dirac Osc... more In view of current interest in relativistic spin-one systems and the recent work on the Dirac Oscillator, we introduce the Duffin-Kemmer-Petiau (DKP) equation obtained by using an external potential linear in r. Since, in the non-relativistic limit, the spin 1 representation leads to a harmonic oscillator with a spin-orbit coupling of the Thomas form, we call the equation the DKP oscillator. This oscillator is a relativistic generalisation of the quantum harmonic oscillator for scalar and vector bosons. We show that it conserves total angular momentum and that it is exactly solvable. We calculate and discuss the eigenspectrum of the DKP oscillator in the spin 1 representation.
The activity of radiopharmaceuticals in nuclear medicine is measured before patient injection wit... more The activity of radiopharmaceuticals in nuclear medicine is measured before patient injection with radionuclide calibrators. In Switzerland, the general requirements for quality controls are defined in a federal ordinance and a directive of the Federal Office of Metrology (METAS) which require each instrument to be verified. A set of three gamma sources (Co-57, Cs-137 and Co-60) is used to verify the response of radionuclide calibrators in the gamma energy range of their use. A beta source, a mixture of 90 Sr and 90 Y in secular equilibrium, is used as well. Manufacturers are responsible for the calibration factors. The main goal of the study was to monitor the validity of the calibration factors by using two sources: a 90 Sr/ 90 Y source and a 18 F source. The three types of commercial radionuclide calibrators tested do not have a calibration factor for the mixture but only for 90 Y. Activity measurements of a 90 Sr/ 90 Y source with the 90 Y calibration factor are performed in order to correct for the extracontribution of 90 Sr. The value of the correction factor was found to be 1.113 whereas Monte Carlo simulations of the radionuclide calibrators estimate the correction factor to be 1.117. Measurements with 18 F sources in a specific geometry are also performed. Since this radionuclide is widely used in Swiss hospitals equipped with PET and PET-CT, the metrology of the 18 F is very important. The 18 F response normalized to the 137 Cs response shows that the difference with a reference value does not exceed 3% for the three types of radionuclide calibrators.
We consider O+ = O-weak-axial transitions in A = 16 nuclei using the Dirac equation with real Lor... more We consider O+ = O-weak-axial transitions in A = 16 nuclei using the Dirac equation with real Lorentz scalar and time-like vector potentials as the relevant nucleon wave equation. We first examine the 16N(O-) + 160(0+) first-forbidden P-decay using the theory of &hopper and show that the relativistic dynamics strongly enhances the anomalously reduced non-relativistic P-decay rate bringing it closer to the experimental rate. The sensitivity of the P-decay rate to the nuclear model parameters is discussed. We then study the inverse process, the 160(0+) + 16N(O-) muon-capture, using a new formalism and show that the p-capture rate may be reproduced simultaneously with the P-decay rate. An analysis of the sensitivity of the p-capture rate to the induced pionic term and to nuclear model parameters is also made. Overall, although the relativistic effects are appreciable and produce new qualitative features which improve on the standard non-relativistic approach, no conclusive empirical evidence supporting the necessity of adopting the relativistic framework can be inferred. * This term is used to mean that ref. *9) uses the standard non-relativistic expressions for the rates in which the nucleon m is replaced by m*(m + U,).
Nuclear Instruments and Methods in Physics Research, Dec 1, 2006
This paper describes the system of the Swiss national metrological institute (IRA-METAS) for the ... more This paper describes the system of the Swiss national metrological institute (IRA-METAS) for the absolute standardisation of radon gas. This method relies on condensing radon under vacuum conditions within a specified cold area using a cryogenerator, and detecting its alpha particles with an ion-implanted silicon detector, through a very accurately defined solid angle. The accuracy of this defined solid angle standardisation technique was corroborated by another primary measurement method involving 4pg NaI(Tl) integral counting and Monte Carlo efficiency calculations. The 222 Rn standard submitted by IRA-METAS to the Syste`me International de Re´fe´rence (SIR) at the Bureau International des Poids et Mesures (BIPM) has also been found to be consistent with an analogous standard submitted by the German national metrological institute (PTB). IRA-METAS is able to deliver radon standards, with activities ranging from a few kBq to 350 kBq, in NIST-Type ampoules, and glass or steel containers usable for calibrating radon-measuring instruments.
Nuclear Instruments and Methods in Physics Research, Oct 1, 2019
In the framework of the EMPIR project MetroBeta, the development and optimization of a double foc... more In the framework of the EMPIR project MetroBeta, the development and optimization of a double focalizing magnetic spectrometer have been realized in order to measure the beta spectra shape. The acquisition is designed to perform, after focalization by the magnetic field, an energy selection using a window on the deposited energy in the Si detector. The energy calibration is performed using conversion electrons from 109 Cd, 137 Cs, 133 Ba and 207 Bi and the measured energy resolution is 1.3% at 1 MeV. The efficiency is measured experimentally using a 204 Tl source and is used to reconstruct the spectrum shape for beta emitters with end-point energy up to 750 keV. Two beta emitters with allowed transitions, 134 Cs and 60 Co, are used to validate the measurement and the reconstruction method. Finally the measurement of the beta shape of 36 Cl, a non-unique 2nd forbidden transition is presented.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
In this study, the gamma and X-ray emission intensities of 161 Tb were determined using a high-pu... more In this study, the gamma and X-ray emission intensities of 161 Tb were determined using a high-purity germanium spectrometer. The samples used were previously standardised by coincidence counting and Triple to Double Coincidence Ratio (TDCR) methods. A total of 28 gamma-rays and 4 X-rays were measured and compared with previous measurements performed more than 30 years ago. Most of the lines are in agreement, while large discrepancies are observed for 5 lines. The uncertainties have been dramatically decreased with respect to previous measurements giving a better knowledge of the 161 Tb day.
Since the 1990s, regular comparisons of gamma-ray spectrometry in Switzerland were organized to i... more Since the 1990s, regular comparisons of gamma-ray spectrometry in Switzerland were organized to improve laboratory abilities to measure the radioactivity in the environment and food stuffs at typical routine levels. The activity concentration of the test samples and the evaluation of the associated uncertainties remained each year the main required test result. Over the years, the comparisons used certified reference solutions as well as environmental samples. The aim of this study is to research the effect of the comparisons on measurement quality. An analysis of the seven last interlaboratory comparisons revealed that the Swiss measurement capability is up to date. In addition, the results showed that the participants now have an improved evaluation of the uncertainties associated with their measurement.
This paper is concerned with the application of a relativistic shell model to the study of nuclea... more This paper is concerned with the application of a relativistic shell model to the study of nuclear single-particle states. This relativistic model is applied to medium and heavy nuclei and shown to reproduce satisfactorily the single-particle energies and the rms radii. Energy-independent potentials give a reasonable account of the experimental binding energies, but the empirical analysis of the energy dependence of the potentials reveals a Fermi-surface anomaly. The parameters of the model are also analysed and found to vary systematically with both energy and mass number. The relativistic model is then reformulated in terms of folded-model potentials. The single-particle spectrum and charge rms radius of 4°Ca are reasonably reproduced, with an energy-and density-independent nucleon-nucleon force, and their sensitivity to the model parameters is studied.
Background: 161 Tb draws an increasing interest in nuclear medicine for therapeutic applications.... more Background: 161 Tb draws an increasing interest in nuclear medicine for therapeutic applications. More than 99% of the emitted gamma and X-rays of 161 Tb have an energy below 100 keV. Consequently, precise activity measurement of 161 Tb becomes inaccurate with radionuclide dose calibrators when using inappropriate containers or calibration factors to account for the attenuation of this low energy radiation. To evaluate the ionization chamber response, the sample activity must be well known. This can be performed using standards traceable to the Système International de Référence, which is briefly described as well as the method to standardize the radionuclides. Methods: In this study, the response of an ionization chamber using different container types and volumes was assessed using 161 Tb. The containers were filled with a standardized activity solution of 161 Tb and measured with a dedicated ionization chamber, providing an accurate response. The results were compared with standardized solutions of high-energy gamma-emitting radionuclides such as 137 Cs, 60 Co, 133 Ba and 57 Co. Results: For the glass vial type with an irregular glass thickness, the 161 Tb measurements gave a deviation of 4.5% between two vials of the same type. The other glass vial types have a much more regular thickness and no discrepancy was observed in the response of the ionization chamber for these type of vials. Measurements with a plastic Eppendorf tube showed stable response, with greater sensitivity than the glass vials. Conclusion: Ionization chamber measurements for low-energy gamma emitters (< 100 keV), show deviation depending on the container type used. Therefore, a careful selection of the container type must be done for activity assessment of 161 Tb using radionuclide dose calibrators. In conclusion, it was highlighted that appropriate calibration factors must be used for each container geometry when measuring 161 Tb and, more generally, for low-energy gamma emitters.
We calculated allowed 13-decay Gamow-Teller matrix elements of A = 15, 17, 39, 41 mirror nuclei i... more We calculated allowed 13-decay Gamow-Teller matrix elements of A = 15, 17, 39, 41 mirror nuclei in the relativistic scalarvector shell model. The relativistic corrections are shown to present the features of the mechanism needed to account for their incompletc non-relativistic description (missing quenching).
Update of the BIPM comparison BIPM.RI(II)-K1.Ho-166m activity measurements to include the IRA and... more Update of the BIPM comparison BIPM.RI(II)-K1.Ho-166m activity measurements to include the IRA and the NPL and a re-evaluation of the degrees of equivalence for the APMP.RI(II)-K2.Ho-166m comparison
This report summarises the results for the new BIPM.RI(II)-K1.Ge-68 comparison. Six metrology ins... more This report summarises the results for the new BIPM.RI(II)-K1.Ge-68 comparison. Six metrology institutes have participated, enabling the first value of the key comparison reference value(KCRV) to be determined. The KCRV was calculated using the power-moderated weighted mean and the results. A link has been made to the CCRI(II)-K2.Ge-68 comparison held in 2015 through the NIST, NIM,IRA-METAS and the LNE-LNHB who participated in both comparisons. One NMI used the K2 comparison to update their degree of equivalence. The degrees of equivalence between each equivalent activity measured in the International Reference System (SIR) and the KCRV have been calculated and the results are given in the form of a table for the remaining five NMIs in the BIPM.RI(II)-K1.Ge-68 comparison and the 12 other participants in the CCRI(II)-K2.Ge-68 comparison. A graphical presentation is also given. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which app...
The hypothesis that proximity to the Sun causes variation of decay constants at permille level ha... more The hypothesis that proximity to the Sun causes variation of decay constants at permille level has been tested and disproved. Repeated activity measurements of mono-radionuclide sources were performed over periods from 200 days up to four decades at 14 laboratories across the globe. Residuals from the exponential nuclear decay curves were inspected for annual oscillations. Systematic deviations from a purely exponential decay curve differ from one data set to another and are attributable to instabilities in the instrumentation and measurement conditions. The most stable activity measurements of alpha, beta-minus, electron capture, and beta-plus decaying
The half-lives of 44 Sc and 44m Sc were measured by following their decay rate using several meas... more The half-lives of 44 Sc and 44m Sc were measured by following their decay rate using several measurement systems: two ionization chambers and three γ-spectrometry detectors with digital and/or analogue electronics. For 44 Sc, the result was the combination of seven half-life values giving a result of 4.042(7) h, which agrees with the last reported value of 4.042(3) h and confirms the near to 2% deviation from the recommended half-life of 3.97(4) h. Scandium-44 is present as an impurity in the production of 44 Sc by cyclotron proton irradiation. Its half-life was determined by measurements performed a few days after End of Bomardment (EoB), so that the 44 Sc decayed down to a negligible level. Seven measurements were combined to obtain an average of 58.7(3) h, which is in agreement with the recommended value of 58.6(1) h.
ABSTRACT The suggestion made recently by H. Abele et al. that relativistic effects in the interac... more ABSTRACT The suggestion made recently by H. Abele et al. that relativistic effects in the interaction of alpha particles with various nuclei at intermediate energies may remove the existing discrepancy between the theoretical predictions and the experimental data for the reaction cross section is investigated. We use a relativistic model based on the Kemmer-Duffin-Petiau equation and find that relativistic effects do not lead to a reduction in the reaction cross section within the present approach. Alternative explanations are discussed.
The half-life of 137 Cs was measured with an ionization chamber by following the decay of 5 sourc... more The half-life of 137 Cs was measured with an ionization chamber by following the decay of 5 sources over a 30 years period between 1983 and 2013. The ratio between the ionization chamber current for the cesium sources and 226 Ra source was used for the half-life calculation. The value found for the 137 Cs half-life is 10,955.2 ± 10.7 days, where the uncertainty evaluation combines type A and B for one standard deviation. Amersham-Büchler & Co and the Bureau International des Poids et Mesures (BIPM). Its activity was 7.9 MBq in 1982.
In view of current interest in relativistic spin-one systems and the recent work on the Dirac Osc... more In view of current interest in relativistic spin-one systems and the recent work on the Dirac Oscillator, we introduce the Duffin-Kemmer-Petiau (DKP) equation obtained by using an external potential linear in r. Since, in the non-relativistic limit, the spin 1 representation leads to a harmonic oscillator with a spin-orbit coupling of the Thomas form, we call the equation the DKP oscillator. This oscillator is a relativistic generalisation of the quantum harmonic oscillator for scalar and vector bosons. We show that it conserves total angular momentum and that it is exactly solvable. We calculate and discuss the eigenspectrum of the DKP oscillator in the spin 1 representation.
The activity of radiopharmaceuticals in nuclear medicine is measured before patient injection wit... more The activity of radiopharmaceuticals in nuclear medicine is measured before patient injection with radionuclide calibrators. In Switzerland, the general requirements for quality controls are defined in a federal ordinance and a directive of the Federal Office of Metrology (METAS) which require each instrument to be verified. A set of three gamma sources (Co-57, Cs-137 and Co-60) is used to verify the response of radionuclide calibrators in the gamma energy range of their use. A beta source, a mixture of 90 Sr and 90 Y in secular equilibrium, is used as well. Manufacturers are responsible for the calibration factors. The main goal of the study was to monitor the validity of the calibration factors by using two sources: a 90 Sr/ 90 Y source and a 18 F source. The three types of commercial radionuclide calibrators tested do not have a calibration factor for the mixture but only for 90 Y. Activity measurements of a 90 Sr/ 90 Y source with the 90 Y calibration factor are performed in order to correct for the extracontribution of 90 Sr. The value of the correction factor was found to be 1.113 whereas Monte Carlo simulations of the radionuclide calibrators estimate the correction factor to be 1.117. Measurements with 18 F sources in a specific geometry are also performed. Since this radionuclide is widely used in Swiss hospitals equipped with PET and PET-CT, the metrology of the 18 F is very important. The 18 F response normalized to the 137 Cs response shows that the difference with a reference value does not exceed 3% for the three types of radionuclide calibrators.
We consider O+ = O-weak-axial transitions in A = 16 nuclei using the Dirac equation with real Lor... more We consider O+ = O-weak-axial transitions in A = 16 nuclei using the Dirac equation with real Lorentz scalar and time-like vector potentials as the relevant nucleon wave equation. We first examine the 16N(O-) + 160(0+) first-forbidden P-decay using the theory of &hopper and show that the relativistic dynamics strongly enhances the anomalously reduced non-relativistic P-decay rate bringing it closer to the experimental rate. The sensitivity of the P-decay rate to the nuclear model parameters is discussed. We then study the inverse process, the 160(0+) + 16N(O-) muon-capture, using a new formalism and show that the p-capture rate may be reproduced simultaneously with the P-decay rate. An analysis of the sensitivity of the p-capture rate to the induced pionic term and to nuclear model parameters is also made. Overall, although the relativistic effects are appreciable and produce new qualitative features which improve on the standard non-relativistic approach, no conclusive empirical evidence supporting the necessity of adopting the relativistic framework can be inferred. * This term is used to mean that ref. *9) uses the standard non-relativistic expressions for the rates in which the nucleon m is replaced by m*(m + U,).
Nuclear Instruments and Methods in Physics Research, Dec 1, 2006
This paper describes the system of the Swiss national metrological institute (IRA-METAS) for the ... more This paper describes the system of the Swiss national metrological institute (IRA-METAS) for the absolute standardisation of radon gas. This method relies on condensing radon under vacuum conditions within a specified cold area using a cryogenerator, and detecting its alpha particles with an ion-implanted silicon detector, through a very accurately defined solid angle. The accuracy of this defined solid angle standardisation technique was corroborated by another primary measurement method involving 4pg NaI(Tl) integral counting and Monte Carlo efficiency calculations. The 222 Rn standard submitted by IRA-METAS to the Syste`me International de Re´fe´rence (SIR) at the Bureau International des Poids et Mesures (BIPM) has also been found to be consistent with an analogous standard submitted by the German national metrological institute (PTB). IRA-METAS is able to deliver radon standards, with activities ranging from a few kBq to 350 kBq, in NIST-Type ampoules, and glass or steel containers usable for calibrating radon-measuring instruments.
Nuclear Instruments and Methods in Physics Research, Oct 1, 2019
In the framework of the EMPIR project MetroBeta, the development and optimization of a double foc... more In the framework of the EMPIR project MetroBeta, the development and optimization of a double focalizing magnetic spectrometer have been realized in order to measure the beta spectra shape. The acquisition is designed to perform, after focalization by the magnetic field, an energy selection using a window on the deposited energy in the Si detector. The energy calibration is performed using conversion electrons from 109 Cd, 137 Cs, 133 Ba and 207 Bi and the measured energy resolution is 1.3% at 1 MeV. The efficiency is measured experimentally using a 204 Tl source and is used to reconstruct the spectrum shape for beta emitters with end-point energy up to 750 keV. Two beta emitters with allowed transitions, 134 Cs and 60 Co, are used to validate the measurement and the reconstruction method. Finally the measurement of the beta shape of 36 Cl, a non-unique 2nd forbidden transition is presented.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
In this study, the gamma and X-ray emission intensities of 161 Tb were determined using a high-pu... more In this study, the gamma and X-ray emission intensities of 161 Tb were determined using a high-purity germanium spectrometer. The samples used were previously standardised by coincidence counting and Triple to Double Coincidence Ratio (TDCR) methods. A total of 28 gamma-rays and 4 X-rays were measured and compared with previous measurements performed more than 30 years ago. Most of the lines are in agreement, while large discrepancies are observed for 5 lines. The uncertainties have been dramatically decreased with respect to previous measurements giving a better knowledge of the 161 Tb day.
Since the 1990s, regular comparisons of gamma-ray spectrometry in Switzerland were organized to i... more Since the 1990s, regular comparisons of gamma-ray spectrometry in Switzerland were organized to improve laboratory abilities to measure the radioactivity in the environment and food stuffs at typical routine levels. The activity concentration of the test samples and the evaluation of the associated uncertainties remained each year the main required test result. Over the years, the comparisons used certified reference solutions as well as environmental samples. The aim of this study is to research the effect of the comparisons on measurement quality. An analysis of the seven last interlaboratory comparisons revealed that the Swiss measurement capability is up to date. In addition, the results showed that the participants now have an improved evaluation of the uncertainties associated with their measurement.
This paper is concerned with the application of a relativistic shell model to the study of nuclea... more This paper is concerned with the application of a relativistic shell model to the study of nuclear single-particle states. This relativistic model is applied to medium and heavy nuclei and shown to reproduce satisfactorily the single-particle energies and the rms radii. Energy-independent potentials give a reasonable account of the experimental binding energies, but the empirical analysis of the energy dependence of the potentials reveals a Fermi-surface anomaly. The parameters of the model are also analysed and found to vary systematically with both energy and mass number. The relativistic model is then reformulated in terms of folded-model potentials. The single-particle spectrum and charge rms radius of 4°Ca are reasonably reproduced, with an energy-and density-independent nucleon-nucleon force, and their sensitivity to the model parameters is studied.
Background: 161 Tb draws an increasing interest in nuclear medicine for therapeutic applications.... more Background: 161 Tb draws an increasing interest in nuclear medicine for therapeutic applications. More than 99% of the emitted gamma and X-rays of 161 Tb have an energy below 100 keV. Consequently, precise activity measurement of 161 Tb becomes inaccurate with radionuclide dose calibrators when using inappropriate containers or calibration factors to account for the attenuation of this low energy radiation. To evaluate the ionization chamber response, the sample activity must be well known. This can be performed using standards traceable to the Système International de Référence, which is briefly described as well as the method to standardize the radionuclides. Methods: In this study, the response of an ionization chamber using different container types and volumes was assessed using 161 Tb. The containers were filled with a standardized activity solution of 161 Tb and measured with a dedicated ionization chamber, providing an accurate response. The results were compared with standardized solutions of high-energy gamma-emitting radionuclides such as 137 Cs, 60 Co, 133 Ba and 57 Co. Results: For the glass vial type with an irregular glass thickness, the 161 Tb measurements gave a deviation of 4.5% between two vials of the same type. The other glass vial types have a much more regular thickness and no discrepancy was observed in the response of the ionization chamber for these type of vials. Measurements with a plastic Eppendorf tube showed stable response, with greater sensitivity than the glass vials. Conclusion: Ionization chamber measurements for low-energy gamma emitters (< 100 keV), show deviation depending on the container type used. Therefore, a careful selection of the container type must be done for activity assessment of 161 Tb using radionuclide dose calibrators. In conclusion, it was highlighted that appropriate calibration factors must be used for each container geometry when measuring 161 Tb and, more generally, for low-energy gamma emitters.
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