This article presents corrosion data and microstructural analysis data of austenitic stainless st... more This article presents corrosion data and microstructural analysis data of austenitic stainless steels AISI 316L and AISI 347H exposed to supercritical water (25 MPa, 550°C) with 2000 ppb of dissolved oxygen. The corrosion tests lasted a total of 1200 h but were interrupted at 600 h to allow measurements to be made. The microstructural data have been collected in the grain interior and at grain boundaries of the bulk of the materials and at the superficial oxide layer developed during the corrosion exposure.
The 5th International Symposium on Supercritical Water-Cooled Reactors (ISSCWR-5), Vancouver, Bri... more The 5th International Symposium on Supercritical Water-Cooled Reactors (ISSCWR-5), Vancouver, British Columbia, Canada, March 13-16, 2011
A new detector setup (NICE-detector) based on an organic plastic scintillator is presented. It wi... more A new detector setup (NICE-detector) based on an organic plastic scintillator is presented. It will be used during experiments measuring neutron-induced reactions with a charged particle in the exit channel. The proposed design was tested at the Goethe University Frankfurt. One of the test cases was the capture cross-section of 209Bi at different astrophysically important energies, including thermal capture cross-section and resonance integral. This research presents the performance of the detector setup, as well as preliminary results for the calculated cross-sections. The preliminary results demonstrate that the newly developed NICE-detector can be used to determine capture cross-sections with sufficient accuracy, and might be adopted in the future as an alternative for charged particle measurements in different nuclear and astrophysical applications.
180m Ta is nature's rarest (quasi) stable isotope and its astrophysical origin is an open questio... more 180m Ta is nature's rarest (quasi) stable isotope and its astrophysical origin is an open question. A possible production site of this isotope is the slow neutron capture process in asymptotic giant branch stars, where it can be produced via neutron capture reactions on unstable 179 Ta. We report a new measurement of the 179 Ta(n, γ) 180 Ta cross section at thermal-neutron energies via the activation technique. Our results for the thermal and resonance-integral cross sections are 952 ± 57 and 2013 ± 148 b, respectively. The thermal cross section is in good agreement with the only previous measurement [Phys. Rev. C 60, 025802 (1999)], while the resonance integral is different by a factor of ≈1.7. While neutron energies in this work are smaller than the energies in a stellar environment, our results may lead to improvements in theoretical predictions of the stellar cross section.
The design and operation of innovative nuclear systems requires a better knowledge of the capture... more The design and operation of innovative nuclear systems requires a better knowledge of the capture and fission cross sections of the Pu isotopes. For the case of capture on 242Pu, a reduction of the uncertainty in the fast region down to 8-12% is required. Moreover, aiming at improving the evaluation of the fast energy range in terms of average parameters, the OECD NEA High Priority Request List (HPRL) requests high-resolution capture measurements with improved accuracy below 2 keV. The current uncertainties also affect the thermal point, where previous experiments deviate from each other by 20%. A fruitful collaboration betwen JGU Mainz and HZ Dresden-Rossendorf within the EC CHANDA project resulted in a 242Pu sample consisting of a stack of seven fission-like targets making a total of 95(4) mg of 242Pu electrodeposited on thin (11.5 μm) aluminum backings. This contribution presents the results of a set of measurements of the 242Pu(n, γ) cross section from thermal to 500 keV combini...
This manuscript summarizes the results of radiative neutron capture cross-section measurements on... more This manuscript summarizes the results of radiative neutron capture cross-section measurements on two stable germanium isotopes, 70 Ge and 73 Ge. Experiments were performed at the n_TOF facility at CERN via the time-of-flight technique, over a wide neutron energy range, for all stable germanium isotopes (70,72,73,74, and 76). Results for 70 Ge [Phys. Rev. C 100, 045804 (2019)] and 73 Ge [Phys. Lett. B 790, 458 (2019)] are already published. In the field of nuclear structure, such measurements allow to study excited levels close to the neutron binding energy and to obtain information on nuclear properties. In stellar nucleosynthesis research, neutron induced reactions on germanium are of importance for nucleosynthesis in the weak component of the slow neutron capture processes. topics: n_TOF, neutron time-of-flight, neutron capture cross-section, MACS
The capture cross section of 209 Bi(n,γ) 210g Bi was measured at different astrophysically energi... more The capture cross section of 209 Bi(n,γ) 210g Bi was measured at different astrophysically energies including thermal capture cross section (25 meV), resonance integral, and the Maxwellian averaged cross section at a thermal energy of kT = 30 keV. The partial capture cross section (σ g) was determined using the activation technique and by measuring the 210 Po activity. The newly developed and tested NICE detector setup was used to measure the α-activity of the 210 Po. Using this setup the thermal and resonance integral cross sections were determined to be 16.2 ± 0.97 mb and 89.81 ± 8.0 mb, respectively. And the Maxwellian average cross section was measured to be 2.01 ± 0.38 mb. I. INTRODUCTION Accurate data of the 209 Bi(n,γ) 210 Bi cross section are necessary to explain the elemental abundances near the s-process termination point. Furthermore, capture cross section values have become an essential matter after considering Pb-Bi as a coolant material in the fast reactors and as a target material in the Accelerator-Driven Systems (ADS). According to the s-process scenario, 209 Bi is the heaviest stable isotope (or long-lived, t 1/2 10 19 Y [1]). Since the unstable nuclei between 209 Bi and the meta-stable Th/U isotopes can not be overcome during s-process conditions, 209 Bi resembles the end point of the sprocess. Figure 1 depicts the s-process near Bi, the neutron capture on 209 Bi leads to the production of 210 Bi in either its ground state 210g Bi or in the long-lived state 209m Bi (E = 271.3 keV). All nuclei produced in their ground state undergo β-decay (t 1/2 = 5.03 days) to feed the α-unstable 210 Po isotope, which terminates the s-process chain and recycles its flow back to 206 Pb by emission of 5.3 MeV α-particles (t 1/2 138 days). 210 Po with a relatively long half-life can capture another neutron and contribute to the production of 207 Pb. On the other hand, the long-lived isomer state (t 1/2 = 3.04 × 10 6 Y) can also capture a neutron and lead to the production of 211 Bi, which undergoes α-decay into 207 Tl. A number of experimental data of 209 Bi(n,γ) 210g Bi capture cross section at different neutron energies were reported in previous studies, including thermal neutrons [2-5], neutrons in the resonance region [6-9], and neutrons with quasi-Maxwellian distribution at kT = 30
73 Ge(n, γ) cross sections were measured at the neutron time-of-flight facility n TOF at CERN up ... more 73 Ge(n, γ) cross sections were measured at the neutron time-of-flight facility n TOF at CERN up to neutron energies of 300 keV, providing for the first time experimental data above 8 keV. Results indicate that the stellar cross section at kT = 30 keV is 1.5 to 1.7 times higher than most theoretical predictions. The new cross sections result in a substantial decrease of 73 Ge produced in stars, which would explain the low isotopic abundance of 73 Ge in the solar system.
Please carefully read the Production queries at the end of the document High-accuracy determinati... more Please carefully read the Production queries at the end of the document High-accuracy determination of the neutron flux in the new experimental area n TOF-EAR2 at CERN
We report on the measurement of the ^{7}Be(n,p)^{7}Li cross section from thermal to approximately... more We report on the measurement of the ^{7}Be(n,p)^{7}Li cross section from thermal to approximately 325 keV neutron energy, performed in the high-flux experimental area (EAR2) of the n_TOF facility at CERN. This reaction plays a key role in the lithium yield of the big bang nucleosynthesis (BBN) for standard cosmology. The only two previous time-of-flight measurements performed on this reaction did not cover the energy window of interest for BBN, and they showed a large discrepancy between each other. The measurement was performed with a Si telescope and a high-purity sample produced by implantation of a ^{7}Be ion beam at the ISOLDE facility at CERN. While a significantly higher cross section is found at low energy, relative to current evaluations, in the region of BBN interest, the present results are consistent with the values inferred from the time-reversal ^{7}Li(p,n)^{7}Be reaction, thus yielding only a relatively minor improvement on the so-called cosmological lithium problem. ...
With the R 3 BLAND setup at GSI we have measured exclusive relative-energy spectra of the Coulomb... more With the R 3 BLAND setup at GSI we have measured exclusive relative-energy spectra of the Coulomb dissociation of 18 C at a projectile energy around 425 AMeV on a lead target, which are needed to determine the radiative neutron-capture cross sections of 17 C into the ground state of 18 C. Those data have been used to constrain theoretical calculations for transitions populating excited states in 18 C. This allowed to derive the astrophysical cross section σ * nγ accounting for the thermal population of 17 C target states in astrophysical scenarios. The experimentally verified capture rate is significantly lower than those of previously obtained Hauser-Feshbach estimations at temperatures T9 ≤ 1 GK. Network simulations with updated neutron-capture rates and hydrodynamics according to the neutrino-driven wind model as well as the neutron-star merger scenario reveal no pronounced influence of neutron capture of 17 C on the production of second-and third-peak elements in contrast to earlier sensitivity studies.
The n TOF neutron time-of-flight facility at CERN is used for high quality nuclear data measureme... more The n TOF neutron time-of-flight facility at CERN is used for high quality nuclear data measurements from thermal energy up to hundreds of MeV. In line with the CERN open data policy, the n TOF Collaboration takes actions to preserve its unique data, facilitate access to them in standardised format, and allow their re-use by a wide community in the fields of nuclear physics, nuclear astrophysics and various nuclear technologies. The present contribution briefly describes the n TOF outcomes, as well as the status of dissemination and preservation of n TOF final data in the international EXFOR library.
New neutron cross section measurements of minor actinides have been performed recently in order t... more New neutron cross section measurements of minor actinides have been performed recently in order to reduce the uncertainties in the evaluated data, which is important for the design of advanced nuclear reactors and, in particular, for determining their performance in the transmutation of nuclear waste. We have measured the 241 Am(n,γ) cross section at the n TOF facility between 0.2 eV and 10 keV with a BaF 2 Total Absorption Calorimeter, and the analysis of the measurement has been recently concluded. Our results are in reasonable agreement below 20 eV with the ones published by C. Lampoudis et al. in 2013, who reported a 22% larger capture cross section up to 110 eV compared to experimental and evaluated data published before. Our results also indicate that the 241 Am(n,γ) cross section is underestimated in the present evaluated libraries between 20 eV and 2 keV by 25%, on average, and up to 35% for certain evaluations and energy ranges.
Neutron-induced reaction cross sections are important for a wide variety of research fields rangi... more Neutron-induced reaction cross sections are important for a wide variety of research fields ranging from the study of nuclear level densities, nucleosynthesis to applications of nuclear technology like design, and criticality and safety assessment of existing and future nuclear reactors, radiation dosimetry, medical applications, nuclear waste transmutation, accelerator-driven systems and fuel cycle investigations. Simulations and calculations of nuclear technology applications largely rely on evaluated nuclear data libraries. The evaluations in these libraries are based both on experimental data and theoretical models. CERN's neutron time-of-flight facility n TOF has produced a considerable amount of experimental data since it has become fully operational with the start of its scientific measurement programme in 2001. While for a long period a single measurement station (EAR1) located at 185 m from the neutron production target was available, the construction of a second beam line at 20 m (EAR2) in 2014 has substantially increased the measurement capabilities of the facility. An outline of the experimental nuclear data activities at n TOF will be presented.
This article presents corrosion data and microstructural analysis data of austenitic stainless st... more This article presents corrosion data and microstructural analysis data of austenitic stainless steels AISI 316L and AISI 347H exposed to supercritical water (25 MPa, 550°C) with 2000 ppb of dissolved oxygen. The corrosion tests lasted a total of 1200 h but were interrupted at 600 h to allow measurements to be made. The microstructural data have been collected in the grain interior and at grain boundaries of the bulk of the materials and at the superficial oxide layer developed during the corrosion exposure.
The 5th International Symposium on Supercritical Water-Cooled Reactors (ISSCWR-5), Vancouver, Bri... more The 5th International Symposium on Supercritical Water-Cooled Reactors (ISSCWR-5), Vancouver, British Columbia, Canada, March 13-16, 2011
A new detector setup (NICE-detector) based on an organic plastic scintillator is presented. It wi... more A new detector setup (NICE-detector) based on an organic plastic scintillator is presented. It will be used during experiments measuring neutron-induced reactions with a charged particle in the exit channel. The proposed design was tested at the Goethe University Frankfurt. One of the test cases was the capture cross-section of 209Bi at different astrophysically important energies, including thermal capture cross-section and resonance integral. This research presents the performance of the detector setup, as well as preliminary results for the calculated cross-sections. The preliminary results demonstrate that the newly developed NICE-detector can be used to determine capture cross-sections with sufficient accuracy, and might be adopted in the future as an alternative for charged particle measurements in different nuclear and astrophysical applications.
180m Ta is nature's rarest (quasi) stable isotope and its astrophysical origin is an open questio... more 180m Ta is nature's rarest (quasi) stable isotope and its astrophysical origin is an open question. A possible production site of this isotope is the slow neutron capture process in asymptotic giant branch stars, where it can be produced via neutron capture reactions on unstable 179 Ta. We report a new measurement of the 179 Ta(n, γ) 180 Ta cross section at thermal-neutron energies via the activation technique. Our results for the thermal and resonance-integral cross sections are 952 ± 57 and 2013 ± 148 b, respectively. The thermal cross section is in good agreement with the only previous measurement [Phys. Rev. C 60, 025802 (1999)], while the resonance integral is different by a factor of ≈1.7. While neutron energies in this work are smaller than the energies in a stellar environment, our results may lead to improvements in theoretical predictions of the stellar cross section.
The design and operation of innovative nuclear systems requires a better knowledge of the capture... more The design and operation of innovative nuclear systems requires a better knowledge of the capture and fission cross sections of the Pu isotopes. For the case of capture on 242Pu, a reduction of the uncertainty in the fast region down to 8-12% is required. Moreover, aiming at improving the evaluation of the fast energy range in terms of average parameters, the OECD NEA High Priority Request List (HPRL) requests high-resolution capture measurements with improved accuracy below 2 keV. The current uncertainties also affect the thermal point, where previous experiments deviate from each other by 20%. A fruitful collaboration betwen JGU Mainz and HZ Dresden-Rossendorf within the EC CHANDA project resulted in a 242Pu sample consisting of a stack of seven fission-like targets making a total of 95(4) mg of 242Pu electrodeposited on thin (11.5 μm) aluminum backings. This contribution presents the results of a set of measurements of the 242Pu(n, γ) cross section from thermal to 500 keV combini...
This manuscript summarizes the results of radiative neutron capture cross-section measurements on... more This manuscript summarizes the results of radiative neutron capture cross-section measurements on two stable germanium isotopes, 70 Ge and 73 Ge. Experiments were performed at the n_TOF facility at CERN via the time-of-flight technique, over a wide neutron energy range, for all stable germanium isotopes (70,72,73,74, and 76). Results for 70 Ge [Phys. Rev. C 100, 045804 (2019)] and 73 Ge [Phys. Lett. B 790, 458 (2019)] are already published. In the field of nuclear structure, such measurements allow to study excited levels close to the neutron binding energy and to obtain information on nuclear properties. In stellar nucleosynthesis research, neutron induced reactions on germanium are of importance for nucleosynthesis in the weak component of the slow neutron capture processes. topics: n_TOF, neutron time-of-flight, neutron capture cross-section, MACS
The capture cross section of 209 Bi(n,γ) 210g Bi was measured at different astrophysically energi... more The capture cross section of 209 Bi(n,γ) 210g Bi was measured at different astrophysically energies including thermal capture cross section (25 meV), resonance integral, and the Maxwellian averaged cross section at a thermal energy of kT = 30 keV. The partial capture cross section (σ g) was determined using the activation technique and by measuring the 210 Po activity. The newly developed and tested NICE detector setup was used to measure the α-activity of the 210 Po. Using this setup the thermal and resonance integral cross sections were determined to be 16.2 ± 0.97 mb and 89.81 ± 8.0 mb, respectively. And the Maxwellian average cross section was measured to be 2.01 ± 0.38 mb. I. INTRODUCTION Accurate data of the 209 Bi(n,γ) 210 Bi cross section are necessary to explain the elemental abundances near the s-process termination point. Furthermore, capture cross section values have become an essential matter after considering Pb-Bi as a coolant material in the fast reactors and as a target material in the Accelerator-Driven Systems (ADS). According to the s-process scenario, 209 Bi is the heaviest stable isotope (or long-lived, t 1/2 10 19 Y [1]). Since the unstable nuclei between 209 Bi and the meta-stable Th/U isotopes can not be overcome during s-process conditions, 209 Bi resembles the end point of the sprocess. Figure 1 depicts the s-process near Bi, the neutron capture on 209 Bi leads to the production of 210 Bi in either its ground state 210g Bi or in the long-lived state 209m Bi (E = 271.3 keV). All nuclei produced in their ground state undergo β-decay (t 1/2 = 5.03 days) to feed the α-unstable 210 Po isotope, which terminates the s-process chain and recycles its flow back to 206 Pb by emission of 5.3 MeV α-particles (t 1/2 138 days). 210 Po with a relatively long half-life can capture another neutron and contribute to the production of 207 Pb. On the other hand, the long-lived isomer state (t 1/2 = 3.04 × 10 6 Y) can also capture a neutron and lead to the production of 211 Bi, which undergoes α-decay into 207 Tl. A number of experimental data of 209 Bi(n,γ) 210g Bi capture cross section at different neutron energies were reported in previous studies, including thermal neutrons [2-5], neutrons in the resonance region [6-9], and neutrons with quasi-Maxwellian distribution at kT = 30
73 Ge(n, γ) cross sections were measured at the neutron time-of-flight facility n TOF at CERN up ... more 73 Ge(n, γ) cross sections were measured at the neutron time-of-flight facility n TOF at CERN up to neutron energies of 300 keV, providing for the first time experimental data above 8 keV. Results indicate that the stellar cross section at kT = 30 keV is 1.5 to 1.7 times higher than most theoretical predictions. The new cross sections result in a substantial decrease of 73 Ge produced in stars, which would explain the low isotopic abundance of 73 Ge in the solar system.
Please carefully read the Production queries at the end of the document High-accuracy determinati... more Please carefully read the Production queries at the end of the document High-accuracy determination of the neutron flux in the new experimental area n TOF-EAR2 at CERN
We report on the measurement of the ^{7}Be(n,p)^{7}Li cross section from thermal to approximately... more We report on the measurement of the ^{7}Be(n,p)^{7}Li cross section from thermal to approximately 325 keV neutron energy, performed in the high-flux experimental area (EAR2) of the n_TOF facility at CERN. This reaction plays a key role in the lithium yield of the big bang nucleosynthesis (BBN) for standard cosmology. The only two previous time-of-flight measurements performed on this reaction did not cover the energy window of interest for BBN, and they showed a large discrepancy between each other. The measurement was performed with a Si telescope and a high-purity sample produced by implantation of a ^{7}Be ion beam at the ISOLDE facility at CERN. While a significantly higher cross section is found at low energy, relative to current evaluations, in the region of BBN interest, the present results are consistent with the values inferred from the time-reversal ^{7}Li(p,n)^{7}Be reaction, thus yielding only a relatively minor improvement on the so-called cosmological lithium problem. ...
With the R 3 BLAND setup at GSI we have measured exclusive relative-energy spectra of the Coulomb... more With the R 3 BLAND setup at GSI we have measured exclusive relative-energy spectra of the Coulomb dissociation of 18 C at a projectile energy around 425 AMeV on a lead target, which are needed to determine the radiative neutron-capture cross sections of 17 C into the ground state of 18 C. Those data have been used to constrain theoretical calculations for transitions populating excited states in 18 C. This allowed to derive the astrophysical cross section σ * nγ accounting for the thermal population of 17 C target states in astrophysical scenarios. The experimentally verified capture rate is significantly lower than those of previously obtained Hauser-Feshbach estimations at temperatures T9 ≤ 1 GK. Network simulations with updated neutron-capture rates and hydrodynamics according to the neutrino-driven wind model as well as the neutron-star merger scenario reveal no pronounced influence of neutron capture of 17 C on the production of second-and third-peak elements in contrast to earlier sensitivity studies.
The n TOF neutron time-of-flight facility at CERN is used for high quality nuclear data measureme... more The n TOF neutron time-of-flight facility at CERN is used for high quality nuclear data measurements from thermal energy up to hundreds of MeV. In line with the CERN open data policy, the n TOF Collaboration takes actions to preserve its unique data, facilitate access to them in standardised format, and allow their re-use by a wide community in the fields of nuclear physics, nuclear astrophysics and various nuclear technologies. The present contribution briefly describes the n TOF outcomes, as well as the status of dissemination and preservation of n TOF final data in the international EXFOR library.
New neutron cross section measurements of minor actinides have been performed recently in order t... more New neutron cross section measurements of minor actinides have been performed recently in order to reduce the uncertainties in the evaluated data, which is important for the design of advanced nuclear reactors and, in particular, for determining their performance in the transmutation of nuclear waste. We have measured the 241 Am(n,γ) cross section at the n TOF facility between 0.2 eV and 10 keV with a BaF 2 Total Absorption Calorimeter, and the analysis of the measurement has been recently concluded. Our results are in reasonable agreement below 20 eV with the ones published by C. Lampoudis et al. in 2013, who reported a 22% larger capture cross section up to 110 eV compared to experimental and evaluated data published before. Our results also indicate that the 241 Am(n,γ) cross section is underestimated in the present evaluated libraries between 20 eV and 2 keV by 25%, on average, and up to 35% for certain evaluations and energy ranges.
Neutron-induced reaction cross sections are important for a wide variety of research fields rangi... more Neutron-induced reaction cross sections are important for a wide variety of research fields ranging from the study of nuclear level densities, nucleosynthesis to applications of nuclear technology like design, and criticality and safety assessment of existing and future nuclear reactors, radiation dosimetry, medical applications, nuclear waste transmutation, accelerator-driven systems and fuel cycle investigations. Simulations and calculations of nuclear technology applications largely rely on evaluated nuclear data libraries. The evaluations in these libraries are based both on experimental data and theoretical models. CERN's neutron time-of-flight facility n TOF has produced a considerable amount of experimental data since it has become fully operational with the start of its scientific measurement programme in 2001. While for a long period a single measurement station (EAR1) located at 185 m from the neutron production target was available, the construction of a second beam line at 20 m (EAR2) in 2014 has substantially increased the measurement capabilities of the facility. An outline of the experimental nuclear data activities at n TOF will be presented.
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