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Journal Articles

First observation of $$^{28}$$O

Kondo, Yosuke*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; Baba, Hidetada*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.

Nature, 620(7976), p.965 - 970, 2023/08

 Times Cited Count:5 Percentile:92.64(Multidisciplinary Sciences)

no abstracts in English

Journal Articles

Intruder configurations in $$^{29}$$Ne at the transition into the island of inversion; Detailed structure study of $$^{28}$$Ne

Wang, H.*; Yasuda, Masahiro*; Kondo, Yosuke*; Nakamura, Takashi*; Tostevin, J. A.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Poves, A.*; Shimizu, Noritaka*; Yoshida, Kazuki; et al.

Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08

 Times Cited Count:2 Percentile:68.16(Astronomy & Astrophysics)

Detailed $$gamma$$-ray spectroscopy of the exotic neon isotope $$^{28}$$Ne has been performed using the one-neutron removal reaction from $$^{29}$$Ne. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for $$^{28}$$Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

Journal Articles

The Application of radiochronometry during the 4th collaborative materials exercise of the nuclear forensics international technical working group (ITWG)

Kristo, M. J.*; Williams, R.*; Gaffney, A. M.*; Kayzar-Boggs, T. M.*; Schorzman, K. C.*; Lagerkvist, P.*; Vesterlund, A.*; Rameb$"a$ck, H.*; Nelwamondo, A. N.*; Kotze, D.*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 315(2), p.425 - 434, 2018/02

 Times Cited Count:14 Percentile:81.7(Chemistry, Analytical)

In a recent international exercise, 10 international nuclear forensics laboratories successfully performed radiochronometry on three low enriched uranium oxide samples, providing 12 analytical results using three different parent-daughter pairs serving as independent chronometers. The vast majority of the results were consistent with one another and consistent with the known processing history of the materials. In general, for these particular samples, mass spectrometry gave more accurate and more precise analytical results than decay counting measurements. In addition, the concordance of the $$^{235}$$U-$$^{231}$$Pa and $$^{234}$$U-$$^{230}$$Th chronometers confirmed the validity of the age dating assumptions, increasing confidence in the resulting conclusions.

Journal Articles

Deuterium depth profiling in graphite tiles not exposed to hydrogen discharges before air ventilation of JT-60U

Hayashi, Takao; Sugiyama, Kazuyoshi*; Mayer, M.*; Krieger, K.*; Masaki, Kei; Tanabe, Tetsuo*; Sato, Masayasu

Journal of Nuclear Materials, 390-391, p.667 - 670, 2009/05

 Times Cited Count:1 Percentile:10.22(Materials Science, Multidisciplinary)

Absolute concentrations and the depth profiles of D in plasma-facing graphite tiles used in JT-60U were determined by means of the D($$^{3}$$He, p)$$^{4}$$He resonant nuclear reaction. The analyzed samples were not exposed to H discharges before air ventilation. The maximum depth of analysis is about 1.4 $$times$$ 10$$^{24}$$ carbon (C) atoms/m$$^{2}$$, corresponding to a linear depth of 16 $$mu$$m for the density of 1.7 $$times$$ 10$$^{3}$$ kg/m$$^{3}$$. The highest D concentration was found at the inboard mid-plane of first wall area. The maximum D concentration is D/C=0.13, and the concentration decrease with the depth. The D retention within 16 $$mu$$m is 1.9 $$times$$ 10$$^{22}$$ D atoms/m$$^{2}$$. The D retentions in this paper were about 2$$sim$$9 times larger than previous samples, which were located on the same area and exposed to the hydrogen discharges. This indicates the H plasma discharges were effective to remove the D (and T) from graphite tiles in the first wall area.

Journal Articles

Deuterium depth profiling in JT-60U tiles using the D($$^{3}$$He, p)$$^{4}$$He resonant nuclear reaction

Hayashi, Takao; Sugiyama, Kazuyoshi*; Krieger, K.*; Mayer, M.*; Alimov, V. Kh.*; Tanabe, Tetsuo*; Masaki, Kei; Miya, Naoyuki

Journal of Nuclear Materials, 363-365, p.904 - 909, 2007/06

 Times Cited Count:11 Percentile:61.1(Materials Science, Multidisciplinary)

The absolute concentrations and the depth profiles of deuterium in plasma-facing graphite tiles used in JT-60U were determined by means of the D($$^{3}$$He, p)$$^{4}$$He resonant nuclear reaction. The highest deuterium concentration was found at a plasma-facing surface near the outer pumping slot on the outer dome wing tile, where redeposited layers with thicknesses in the micron or submicron range were observed, indicating deuterium codepostion with carbon. In addition, a high flux of high energy deuterium originating from NBI is expected on the outer dome wing as well as on the dome top tile, and could have some contribution to this area of highest deuterium retention. The deuterium content integrated up to about 16 $$mu$$m was $$approx$$2.5$$times$$10$$^{22}$$ D/m$$^{2}$$. The depth profile has a broad peak in the atomic ratio of D/C$$approx$$0.05 at a depth of about 2.5 $$mu$$m. This is mainly because D retained in the top surface was replaced by H due to isotope exchange during H discharges, which were carried out to remove tritium from the plasma-facing wall before air ventilation. In erosion dominated areas such as the outer divertor tiles, the amount of deuterium was one order of magnitude lower than that on the outer dome wing tile. In the first wall area, the highest amount of deuterium with a content of $$approx$$1.0$$times$$10$$^{22}$$ D/m$$^{2}$$ was found in the upper region, nearest to the plasma. Again implantation of high energy deuterium due to NBI could have some contribution to the high deuterium retention.

Journal Articles

Ion beam analysis of H and D retention in the near surface layers of JT-60U plasma facing wall tiles

Sugiyama, Kazuyoshi*; Hayashi, Takao; Krieger, K.*; Mayer, M.*; Masaki, Kei; Miya, Naoyuki; Tanabe, Tetsuo*

Journal of Nuclear Materials, 363-365, p.949 - 954, 2007/06

 Times Cited Count:10 Percentile:58.16(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Measurement of the neutron capture cross section of the $$s$$-only isotope $$^{204}$$Pb from 1 eV to 440 keV

Domingo-Pardo, C.*; Abbondanno, U.*; Aerts, G.*; $'A$lvarez, H.*; Alvarez-Velarde, F.*; Andriamonje, S.*; Andrzejewski, J.*; Assimakopoulos, P.*; Audouin, L.*; Badurek, G.*; et al.

Physical Review C, 75(1), p.015806_1 - 015806_9, 2007/01

 Times Cited Count:34 Percentile:86.95(Physics, Nuclear)

The neutron capture cross section of $$^{204}$$Pb has been measured at the CERN n_TOF installation with high resolution in the energy range from 1 eV to 440 keV. In the interval between 100 keV and 440 keV we report the average cross section. The background in the entire energy range was reliably determined from the measurement of a $$^{208}$$Pb sample. We obtain a Maxwellian average capture cross section for $$^{204}$$Pb at $$kT$$ = 30 keV of 79(3) mb, in agreement with previous experiments. However our cross section at $$kT$$ = 5 keV is about 35 % larger than the values reported so far. The implications of the new cross section for the $$s$$-process abundance contributions in the Pb/Bi region are discussed.

Journal Articles

Resonance capture cross section of $$^{207}$$Pb

Domingo-Pardo, C.*; Abbondanno, U.*; Aerts, G.*; $'A$lvarez, H.*; Alvarez-Velarde, F.*; Andriamonje, S.*; Andrzejewski, J.*; Assimakopoulos, P.*; Audouin, L.*; Badurek, G.*; et al.

Physical Review C, 74(5), p.055802_1 - 055802_6, 2006/11

 Times Cited Count:27 Percentile:81.32(Physics, Nuclear)

The radiative neutron capture cross section of $$^{207}$$Pb has been measured at the CERN n_TOF facility using the pulse height weighting technique in the resoleved region. The measurement has been performed with an optimized setup of two $$C_{6}D_{6}$$ scintillation detectors, which allowed us to reduce scattered neutron backgrounds down to a negligible level. Resonance parameters have been determined for 16 resonances by means of an R-matrix analysis in the neutron energy range from 3 keV to 320 keV. Good agreement with previous measurements was found at low neutron energies, whereas substantial discrepancies appear beyond 45 keV. With the present results, we obtain an s-process contribution of 77$$pm$$8 % to the solar abundance of $$^{207}$$Pb.

Journal Articles

New measurement of neutron capture resonances in $$^{209}$$Bi

Domingo-Pardo, C.*; Abbondanno, U.*; Aerts, G.*; $'A$lvarez, H.*; Alvarez-Velarde, F.*; Andriamonje, S.*; Andrzejewski, J.*; Assimakopoulos, P.*; Audouin, L.*; Badurek, G.*; et al.

Physical Review C, 74(2), p.025807_1 - 025807_10, 2006/08

 Times Cited Count:47 Percentile:90.41(Physics, Nuclear)

The neutron capture cross section of $$^{209}$$Bi has been measured at the CERN n_TOF facility by employing the pulse-height-weighting technique. Improvements over previous measurements are mainly because of an optimized detection system, which led to a practically negligible neutron sensitivity. Because $$^{209}$$Bi is the last stable isotope in the reaction path of the stellar s-process, the Maxwellian averaged capture cross section is important for the recycling of the reaction flow by alpha decays. In the relevant stellar range of thermal energies between $$kT$$ = 5 and 8 keV our new capture rate is about 16% higher than the presently accepted value used for nucleosynthesis calculations. The present cross section measurement is also of relevance for the design of accelerator driven systems based on a liquid metal Pb/Bi spallation target.

Journal Articles

Neutron capture cross section of $$^{232}$$Th measured at the n_TOF facility at CERN in the unresolved resonance region up to 1 MeV

Aerts, G.*; Abbondanno, U.*; $'A$lvarez, H.*; Alvarez-Velarde, F.*; Andriamonje, S.*; Andrzejewski, J.*; Assimakopoulos, P.*; Audouin, L.*; Badurek, G.*; Baumann, P.*; et al.

Physical Review C, 73(5), p.054610_1 - 054610_10, 2006/05

We have measured the neutron capture reaction yield of $$^{232}$$Th at the neutron tim-of-flight facility n_TOF at CERN in the energy range from 1 eV to 1 MeV. The average capture cross section has been extracted in the energy range from 4 keV up to 1 MeV with an overall accuracy better than 4 %. An independent IAEA evaluation shows good agreement with the data.

Journal Articles

Neutron capture cross section of $$^{232}$$Th measured at the n_TOF facility at CERN in the unresolved resonance region up to 1 MeV

Aerts, G.*; Abbondanno, U.*; $'A$lvarez, H.*; Alvarez-Velarde, F.*; Andriamonje, S.*; Andrzejewski, J.*; Assimakopoulos, P.*; Audouin, L.*; Badurek, G.*; Baumann, P.*; et al.

Physical Review C, 73(5), p.054610_1 - 054610_10, 2006/05

 Times Cited Count:45 Percentile:89.88(Physics, Nuclear)

We have measured the neutron capture reaction yield of $$^{232}$$Th at the neutron time-of-flight facility n_TOF at CERN in the energy range from 1 eV to 1 MeV. The average capture cross section has been extracted in the energy range from 4 keV up to 1 MeV with an overall accuracy better than 4%. An independent IAEA evaluation shows good agreement with the data.

Journal Articles

Measurement of the resonance capture cross section of $$^{204,206}$$Pb and termination of the $$s$$-process

Domingo-Pardo, C.*; O'Brien, S.*; Abbondanno, U.*; Aerts, G.*; $'A$lvarez, H.*; Alvarez-Velarde, F.*; Andriamonje, S.*; Andrzejewski, J.*; Assimakopoulos, P.*; Audouin, L.*; et al.

AIP Conference Proceedings 819, p.288 - 292, 2006/03

The neutron capture cross sections of $$^{204}$$Pb and $$^{206}$$Pb have been measured at the CERN n_TOF installation using the time of flight method with the pulse height weighting technique. In a preliminary analysis of $$^{204}$$Pb we have determined by first time the capture cross sections for two strong $$s$$-wave resonances below 2.5 keV. In $$^{206}$$Pb we have determined capture cross sections for a large number of resonances, which were not reported in the two previous capture measurements. We discuss preliminary implications of the new cross sections in the stellar nucleosynthesis of the Pb isotopes.

Journal Articles

Measurement of $$^{139}$$La($$n$$,$$gamma$$) cross section

Terlizzi, R.*; Abbondanno, U.*; Aerts, G.*; $'A$lvarez, H.*; Alvarez-Velarde, F.*; Andriamonje, S.*; Andrzejewski, J.*; Assimakopoulos, P.*; Audouin, L.*; Badurek, G.*; et al.

AIP Conference Proceedings 819, p.283 - 287, 2006/03

We measured the neutron capture cross section of $$^{139}$$La relative to $$^{197}$$Au in the energy range of 0.6 eV to 9 keV at n_TOF, the neutron time-of-flight facility at CERN. The data were fitted using R-matrix formalism to extract resonance parameters which were used to calculate average level spacings. The data were used to determine Maxwellian-averaged neutron capture cross sections which, in turn, were used to calculate the $$^{139}$$La abundance synthesized in a steller model of the main component of the $$s$$ process.

Journal Articles

Neutron cross section measurements at n-TOF for ADS related studies

Mastinu, P. F.*; Abbondanno, U.*; Aerts, G.*; $'A$lvarez, H.*; Alvarez-Velarde, F.*; Andriamonje, S.*; Andrzejewski, J.*; Assimakopoulos, P.*; Audouin, L.*; Badurek, G.*; et al.

Journal of Physics; Conference Series, 41, p.352 - 360, 2006/00

A neutron Time-of-Flight facility (n_TOF) is operative at CERN since 2001. The innovative features of the neutron beam, in particular the high instantaneous flux, the wide energy range, the high resolution and the low background, makes this facility unique for measurements of neutron induced reactions relevant to the field of Emerging Nuclear Technologies, as well as to Nuclear Astrophysics and fundamental Nuclear Physics. The scientific motivations that have led to the construction of this new facility are here presented.

Journal Articles

Measurements at n_TOF of the neutron capture cross section of minor actinides relevant to the nuclear waste transmutation

Cano-Ott, D.*; Abbondanno, U.*; Aerts, G.*; $'A$lvarez, H.*; $'A$lvarez-Velarde, F.*; Andriamonje, S.*; Andrzejewski, J.*; Assimakopoulos, P.*; Audouin, L.*; Badurek, G.*; et al.

AIP Conference Proceedings 769, p.1442 - 1445, 2005/05

Accurate and reliable neutron cross section data for actinides are necessary for the proper design, safety reguartion and precise performance assessment of transmutaion devices. In particular, the neutron capture cross sections of $$^{237}$$Np, $$^{240}$$Pu and $$^{243}$$Am play a key role in the design and optimization of a strategy for the Nuclear Waste Transmutation. The listed cross sections have been measured in 2004 at n_TOF with a high accuracy due to a combination of features unique in the world.

Journal Articles

High-resolution study of $$^{237}$$Np fission cross section from 5 eV to 1 MeV

Furman, W.*; Cennini, P.*; Ketlerov, V.*; Goverdovski, A.*; Konovalov, V.*; Abbondanno, U.*; Aerts, G.*; $'A$lvarez, H.*; Alvarez-Velarde, F.*; Andriamonje, S.*; et al.

AIP Conference Proceedings 769, p.1039 - 1042, 2005/05

A series of measurements of $$^{237}$$Np fission cross section have been performed at the CERN spallation neutron source facility n_TOF. A fast ionization chamber was used as a fission fragment detector. Total experimental uncertainties are determined to be at the level of 3%. Analysis of experimental data in the neutron energy from 5 eV to 1 MeV showed a systematic deviation from the evaluated data (ENDF/B-VI). This discrepancy amounts to up to the factor of 3 for resolved resonances in the neutron energy range of 5 eV - 2 keV, and is in good agreement with some previous experiments. A similar disagreement at the level of 6-7% was found for higher energies around the threshold. This energy range is essential for the transmutation of neptunium in ADS or fast reactors. It is concluded that an updated evaluation of nuclear data for $$^{237}$$Np is required.

Oral presentation

Elementary excitations in an S=1/2 antiferromagnetic chain KCuGaF$$_{6}$$

Tanaka, Hidekazu*; Kurita, Nubuyuki*; Umegaki, Izumi*; Ono, Toshio*; Laver, M.*; Niedermayer, Ch.*; R$"u$egg, Ch.*; Kawamura, Seiko; Nakajima, Kenji; Kakurai, Kazuhisa

no journal, , 

Oral presentation

Joint validation of the in-situ uranium age dating method

Okubo, Ayako; Mayer, K.*

no journal, , 

Under the collaboration between EC-JRC and JAEA, the in-situ age dating method was subject to joint validation, and six different uranium materialswere used for this purpose. The age dating result by in-situ isotope method was consistent with known production dates of the respective samples. The uncertainty evaluation according to GUM for the in-situ isotope method indicates that the measured $$^{234}$$Th/$$^{230}$$Th ratio provides the highest contribution. The accuracy of in-situ isotope method can be improved by higher precision in $$^{234}$$Th/$$^{230}$$Th measurement.

18 (Records 1-18 displayed on this page)
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