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Recent publications
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Jang, Y.; Moon, B.; Lee, J.; Watanabe, H.; Nishimura, S. & Phong, V.
[Show all 43 contributors for this article]
(2026).
Yrast-state lifetimes in 94Pd at the transition between the isoscalar and isovector coupling regimes.
Physical Review C.
ISSN 2469-9985.
114(2).
doi:
10.1103/smjm-rplr.
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Half-lives of yrast excited states in 94Pd were measured using isomeric decay spectroscopy. The experiment was performed at Radioactive Isotope Beam Factory, where 94Pd ions were produced via in-flight fragmentation of a 124Xe beam impinging on a 9Be target. These ions were implanted into the GARi active stopper array, and isomeric delayed 𝛾 rays were detected with the IDATEN fast-timing array consisting of 48 LaBr3(Ce) detectors. The half-lives were determined using the generalized centroid difference method, yielding the 𝑇1/2 values of ≤15 ps, 13(11) ps, ≤13 ps, 693(72) ps, and ≤19 ps for the (2+1), (4+1), (6+1), (8+1), and (10+1) states, respectively. Reduced transition probabilities were deduced from the measured half-lives and discussed in the context of shell-model calculations employing the JUN45 effective interaction. The results indicate that 94Pd, with 𝑁=𝑍+2, lies in a transitional regime between the 𝑁=𝑍 isoscalar-pairing domain (92Pd) and the 𝑁=50 isovector-dominated region (96Pd).
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Bell, Lauren Tracy; Siem, Sunniva; Larsen, Ann-Cecilie; Bürger, A.; Markova, Maria & Ingeberg, V. W.
[Show all 12 contributors for this article]
(2026).
Extracting the nuclear level density and γ-ray strength function of 90Zr.
Physical Review C.
ISSN 2469-9985.
114(1).
doi:
10.1103/p9y9-xxjf.
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In this work, we have extracted the nuclear level density (NLD) and 𝛾-ray strength function (𝛾SF) using the Oslo method on particle-𝛾 coincidence data from the 90Zr(𝑝,𝑝′𝛾)90Zr reaction. We have applied the shape method to the same data set, providing a model-independent 𝛾SF and a cross-check on the slope of the Oslo-method NLD and 𝛾SF. Further, we have combined the 𝛾SF from this work with photonuclear data, thus covering the 2.5<𝐸𝛾<18MeV energy range. We see an increase in strength in the region around 𝐸𝛾≈9MeV, consistent with previous (𝛾,𝛾′) and (𝛾,𝑛) data. On the other hand, surprisingly, we do not observe a strong low-energy increase at low transition energies. The resulting NLD and 𝛾SF were used as inputs to the nuclear reaction code talys to estimate the cross sections and astrophysical reaction rates for the 89Zr(𝑛,𝛾)90Zr 89Y(𝑝,𝛾)90Zr reactions. We find good agreement with available experimental cross sections and JINA calculations for the 89Y(𝑝,𝛾) results, but not for the 89Zr(𝑛,𝛾) reaction rate for stellar temperatures above 0.7 GK. Based on our data, we provide a much more narrow uncertainty band for the 89Zr(𝑛,𝛾) cross section and reaction rate.
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Pedersen, Line Gaard; Sahin, Eda; Görgen, Andreas; Garrote, Frank Leonel Bello; Tsunoda, Y. & Otsuka, T.
[Show all 67 contributors for this article]
(2026).
Evolution of the nuclear structure in neutron-rich Cu isotopes: first spectroscopy of odd-odd $$^{74}$$Cu and $$^{76}$$Cu.
European Physical Journal A.
ISSN 1434-6001.
62(6).
doi:
10.1140/epja/s10050-026-01873-w.
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Abstract Excited states in the odd-odd isotopes $$^{74}$$ 74 Cu and $$^{76}$$ 76 Cu were observed for the first time in a spectroscopic study following the $$\beta $$ β decay of $$^{74}$$ 74 Ni and $$^{76}$$ 76 Ni. The experiment was performed at the Radioactive Isotope Beam Factory at RIKEN Nishina Center using the EURICA setup and the BigRIPS separator. Level schemes were constructed based on the analysis of $$\gamma $$ γ - $$\gamma $$ γ coincidences. The time correlations between $$\beta $$ β and $$\gamma $$ γ decay showed no evidence for population of isomeric states in either nucleus. The experimental results are compared to large-scale Monte Carlo shell-model calculations with the A3DA-m interaction. The low-lying states in $$^{74}$$ 74 Cu and $$^{76}$$ 76 Cu are interpreted as spin multiplets arising from the coupling of an odd proton in the $$2p_{3/2}$$ 2 p 3 / 2 or $$1f_{5/2}$$ 1 f 5 / 2 orbital with an odd neutron in the $$1g_{9/2}$$ 1 g 9 / 2 or $$2p_{1/2}$$ 2 p 1 / 2 orbital. The results provide information on the evolution of single-particle orbitals along the chain of neutron-rich Cu isotopes and on the proton-neutron interaction in the vicinity of $$^{78}$$ 78 Ni, which serve as important benchmarks for shell-model calculations. The non-observation of the low-energy isomeric state at 65 keV in $$^{76}$$ 76 Cu, combined with the observed decay pattern from higher-lying states, strongly supports a spin-parity assignment of $$3^{(-)}$$ 3 ( - ) for the ground state and ( $$6^{-}$$ 6 - ) for the isomeric state, resolving a long-standing ambiguity discussed in previous studies.
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Markova, Maria; Larsen, Ann-Cecilie; Neumann-Cosel, P. von; Litvinova, E.; Goriely, S. & Bell, Lauren Tracy
[Show all 17 contributors for this article]
(2026).
Exploring the statistical properties of the neutron-deficient 109In isotope with the Oslo method.
Physical Review C.
ISSN 2469-9985.
113(4).
doi:
10.1103/qrvh-s12k.
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The nuclear level density and the 𝛾-ray strength function of the neutron-deficient 109In isotope were extracted for the first time with data from the 106Cd(𝛼,𝑝𝛾)109In reaction using a combination of the Oslo and the shape methods. Both quantities are consistent with those of neighboring Cd and Sn nuclei but show substantial discrepancies with currently available model predictions. In contrast to earlier observations in the neighboring isotopic chains, 109In does not exhibit any significant enhancement of the dipole strength near the neutron separation energy. To interpret this feature, random-phase time-blocking approximation calculations have been performed for 109In and the neighboring 110,112Sn nuclei. The experimental data were also employed to estimate cross sections and rates of the radiative neutron- and proton-capture reactions, 108In(𝑛,𝛾)109In and 108Cd(𝑝,𝛾)109In, respectively, with the reaction code talys. Our (𝑝,𝛾) cross section is in excellent agreement with direct measurements over a wide range of proton energies, while the (𝑛,𝛾) cross section demonstrates notable deviations from predictions in the jina reaclib library. The new results on the statistical properties of 109In provide valuable constraints that may help address the problem of large model uncertainties compromising the accuracy of astrophysical 𝑝-process simulations.
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Henriksen, Ellen Karoline; Bøe, Maria Vetleseter; Sørborg, Øystein & Larsen, Ann-Cecilie
(2026).
Educational reconstruction of nuclear astrophysics in a design-based research project.
Physical Review Physics Education Research.
22.
doi:
10.1103/ybmb-vknr.
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This paper presents the first iteration of development and classroom testing of Stars and Elements, a web-based learning resource for Norwegian upper secondary physics students, focused on how heavy elements are produced in stars and neutron star mergers. Combining the Model of Educational Reconstruction (MER) with the pedagogical link-making framework and Design-Based Research (DBR), we identified core ideas to be communicated, reviewed the physics curriculum and research on student understanding and motivation, and formulated design hypotheses that guided development of a 90-minute learning resource with animations, videos, interactive tasks, peer discussion, and teacher consolidation. Six classes (N = 120) participated; data comprised students’ written responses to three open tasks, brief evaluations, and classroom observations. Most students could describe central concepts and processes concerning red giant stars and neutron star mergers as sites for heavy element production, notably the slow and rapid neutron capture processes, and many benefited from animations and varied task formats. Some displayed uncertain grasp of concepts such as fusion and beta decay. Nature of science (NoS) aspects concerning how physics knowledge is developed were found to be insufficiently represented. From these findings we propose design principles for research-based learning resources on similar topics, including emphasizing explicit link‑making across scales and prior knowledge, scaffolding for challenging nuclear concepts, multimodal visualisations, and explicit NoS focus. We argue that combining MER, link-making and DBR is a promising approach for developing learning resources that reflect the frontiers of science while having a solid grounding in the classroom.
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Rykkelid, Anne Marit; Skeie, Hilde Solesvik; Tormodsrud, Vera Helene; Siem, Sunniva; Malinen, Eirik & Edin, Nina Frederike Jeppesen
(2026).
Cell survival and DNA damage along the distal edge of the proton Bragg peak.
International Journal of Radiation Biology.
ISSN 0955-3002.
p. 1–10.
doi:
10.1080/09553002.2026.2666062.
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Staniszewska, Magdalena; Hübner, Ralph; Locatelli, Camilla; Howard, Douglas; Forni, Matilde & Man, Francis
[Show all 13 contributors for this article]
(2026).
Ensuring enantiomeric consistency in FAPI radiopharmaceuticals: comparative analysis of (S)- and (S/R)-FAPI-46/-74 confirms pharmacological equivalence.
EJNMMI Radiopharmacy and Chemistry.
11(1).
doi:
10.1186/s41181-026-00432-4.
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Background
Enantiomeric composition may impact binding and potentially performance of a drug product but is not routinely tested and minimum acceptance criteria are not always established. Some batches of the precursors FAPI-46 and FAPI-74 used clinically contain a mixture of (S)- and (R)-enantiomers. This study investigates the in vitro pharmacodynamic characteristics of different enantiomeric compositions of FAP-targeting radioligands FAPI-46 and FAPI-74 and in vivo pharmacokinetics of FAPI-46 in naïve mice.
Results
(S)-, (R)-, and (S/R)-enantiomers of radiolabeled FAPI-46 and FAPI-74 were evaluated for stability in human serum, binding affinity, internalization, retention, and selectivity using HT1080-hFAP cells and HEK293-hCD26 cells. All enantiomeric compositions showed high stability in human serum with minimal serum protein adhesion. (S)- and (S/R)-enantiomers exhibited comparable binding, internalization, and retention characteristics. High selectivity for FAP over CD26/DPP4 was maintained. (R)-enantiomers showed no specific binding to FAP. Additionally, the same enantiomers of 68Ga-labeled FAPI-46 were evaluated by dynamic positron emission tomography (PET) imaging (0–60 min post-injection) and ex vivo organ biodistribution in naïve BALB/c mice (10, 30, and 60 min, or 4 h post-injection) to compare their pharmacokinetic profiles. PET imaging revealed nearly identical time-activity curves for the enantiomers of [68Ga] Ga-FAPI-46, indicating similar whole-body distribution within 1 h post-injection, with rapid renal clearance and minimal muscle uptake. Ex vivo organ biodistribution confirmed comparable pharmacokinetic profiles between enantiomers, with no significant differences in tissue distribution.
Conclusion
These findings provide important validation that current clinical (S/R)-mixtures of FAPI-46/-74 exhibit pharmacokinetic and pharmacodynamic behavior comparable to pure (S)-enantiomers, supporting regulatory confidence and cross-trial reproducibility in the global FAPI-46/-74 imaging landscape.
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Heines, J. S.; Modamio, Victor; Görgen, A.; Korten, W.; Clément, E. & Dudouet, J.
[Show all 29 contributors for this article]
(2026).
Triaxiality of neutron-rich ruthenium nuclei studied by lifetime measurements.
European Physical Journal A.
ISSN 1434-6001.
62(3).
doi:
10.1140/epja/s10050-025-01782-4.
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Abstract The breaking of axial symmetry in nuclei enables otherwise precluded behaviours, making it an interesting phenomenon to study. Experimental fingerprints such as very low-lying $$2_2^+$$ 2 2 + states suggest pronounced triaxial deformation for the neutron-rich ruthenium isotopes. Nevertheless, theoretical calculations differ in the description of the triaxial deformation and its evolution with neutron number, making experimental data crucial to understanding it. We investigated the evolution of the degree of triaxiality and $$\gamma $$ γ rigidity in neutron-rich ruthenium isotopes by measuring lifetimes of excited states in $$^{108-112}$$ 108 - 112 Ru with the recoil distance Doppler-shift method. The experiment was carried out at the Grand Accélérateur National d’Ions Lourds using the Advanced Gamma Tracking Array coupled to the Variable Mode Spectrometer. We obtained B ( E 2) values for 29 transitions in the studied nuclei and compared them with fully microscopic symmetry conserving configuration mixing calculations, and phenomenological generalized triaxial rotor and triaxial particle-rotor models. The models generally reproduce the measured transition strengths, and show an increase in triaxiality with neutron number, reaching near maximum triaxiality in $$^{112}$$ 112 Ru. The results are consistent with a transition from $$\gamma $$ γ soft to $$\gamma $$ γ rigid motion as the neutron number increases.
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Neumann-Cosel, Peter von
(2025).
Angela and the electric dipole response: giant and pygmy, hot and cold, isoscalar and isovector.
European Physical Journal A.
ISSN 1434-6001.
61(8).
doi:
10.1140/epja/s10050-025-01657-8.
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The impact of Angela Bracco’s work on the electric dipole response of nuclei is discussed using three examples of current nuclear structure problems: disentangling different contributions to the decay width of the giant dipole resonance, the equivalence of photoabsorption and emission and the nature of the pygmy dipole resonance.
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Piętka, I. Z.; Wrzosek-Lipska, K.; Garrett, P. E.; Zielińska, M.; Próchniak, L. & Nannini, A.
[Show all 94 contributors for this article]
(2025).
PROBING LOW-ENERGY STATES IN<sup>110</sup>Cd USING COULOMB EXCITATION.
Acta Physica Polonica B, Proceedings Supplement.
ISSN 1899-2358.
18(2).
doi:
10.5506/APhysPolBSupp.18.2-A26.
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A campaign of Coulomb-excitation experiments to study the electromagnetic structure of 110Cd was performed using beams of 14N, 32S, and 60Ni. The use of various reaction partners enables disentangling the contributions of individual electromagnetic matrix elements involved in the excitation process, yielding, among others, a precise determination of the lifetime of the 2+2 state in 110Cd.
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Markova, Maria; Larsen, Ann-Cecilie & Garrote, Frank Leonel Bello
(2025).
PYGMY DIPOLE RESONANCE IN Sn ISOTOPES AND ITS ASTROPHYSICAL IMPACT.
Acta Physica Polonica B, Proceedings Supplement.
ISSN 1899-2358.
18(2).
doi:
10.5506/APhysPolBSupp.18.2-A3.
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The low-lying electric dipole strength in 111−113,116−122,124Sn was extracted with the Oslo method to systematically investigate the pygmy dipole resonance (PDR) and its evolution in Sn isotopes. The nuclear level densities (NLD) and the γ-ray strength functions (GSF) obtained from the Oslo data were used as inputs in the TALYS reaction code to produce radiative neutron-capture cross sections, Maxwellian-averaged cross sections, and rates relevant for the heavy-element nucleosynthesis. Despite a relatively small observed impact of the PDR, the experimentally extracted 121,123Sn(n, γ) 122,124Sn cross sections provide a notable reduction of a currently available theoretical uncertainty for the abundances of Sb isotopes in the i-process simulations.
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Wiedeking, Mathis; Goriely, Stephane; Guttormsen, Magne; Herwig, Falk; Larsen, Ann-Cecilie & Liddick, Sean N.
[Show all 10 contributors for this article]
(2025).
Unlocking i-process nucleosynthesis by bridging stellar and nuclear physics.
Nature Reviews Physics.
7(12),
p. 696–712.
doi:
10.1038/s42254-025-00885-7.
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The origin of chemical elements and their abundances across the cosmos remain one of the central questions in physics. The formation of elements heavier than iron is traditionally attributed to three main mechanisms: the slow and rapid neutron-capture processes (s and r processes) and the p process (mostly driven by photodisintegration reactions). However, certain astronomical observations reveal elemental abundance patterns inconsistent with these processes. These discrepancies prompted the introduction of the intermediate neutron-capture process (i process), which operates at neutron densities between the s and r processes, and which has emerged as a key area of research. Observations of elemental abundances of stars confirm that the i process does indeed take place. Identifying the required astrophysical conditions and contributions of the i process sensitively depend on neutron-capture reaction rates involving unstable atomic nuclei. Important advancements have been achieved through these new astronomical observations and cutting-edge experimental and analytical techniques in nuclear physics, in addition to models of nuclear physics and nucleosynthesis. State-of-the-art facilities and theoretical models are revolutionizing our ability to explore the i process and offer fresh perspectives on the nuclear behaviour under extreme stellar conditions. This Review underscores the synergy between groundbreaking astronomical and nuclear physics research, bridging nuclear physics and observational astrophysics, and advancing our understanding of i-process nucleosynthesis.
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Dembski, Cade; Spyrou, Artemis; Brown, B. Alex; Liddick, Sean N.; Berg, Hannah C. & Bleuel, Darren L.
[Show all 25 contributors for this article]
(2025).
Extreme shape coexistence observed in 70Co.
Communications Physics.
8(1).
doi:
10.1038/s42005-025-01998-2.
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The shape of the atomic nucleus is a property that underpins our understanding of nuclear systems, impacts the limits of nuclear existence, and enables probes of physics beyond the Standard Model. Nuclei can adopt a variety of shapes, including spheres, axially deformed spheroids, and pear shapes. In some regions of the nuclear chart where a spherical nucleus would naively be expected, deformed nuclear states can result from the collective action of constituent protons and neutrons. In a small subset of nuclei both spherical and deformed nuclear states have been experimentally observed, a phenomenon termed shape coexistence. We present spectroscopic evidence for the coexistence of Jπ = 1+ spherical and deformed states in 70Co, separated by less than 275 keV. This close degeneracy of levels with the same Jπ and different shapes demonstrates an extreme example of shape coexistence resulting from the interplay of independent particle motion and collective behavior in highly unstable nuclear systems and identifies the Co isotopes as a transition point between deformed ground states observed in the Cr isotopes and spherical configurations observed in the closed-shell Ni isotopes.
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Markova, Maria; Larsen, Ann-Cecilie & Garrote, Frank Leonel Bello
(2025).
Approaching the pygmy dipole resonance in Sn isotopes with the Oslo method.
The European Physical Journal Conferences.
ISSN 2101-6275.
322(04002).
doi:
10.1051/epjconf/202532204002.
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The γ-ray strength functions (GSF) and nuclear level densities (NLD) below the neutron separation energy were extracted for 111−113,116−122,124Sn from particle-γ coincidence data with the Oslo method in a model consistent way. Combined with results of a recent systematic Coulomb excitation study, the Oslo GSFs were used to extract bulk characteristics of the low-lying electric dipole response, commonly associated with the pygmy dipole resonance (PDR). A resonance-like peak on top of the tail of the isovector giant dipole resonance was observed in all of the isotopes. It is centered at 8 MeV and exhausts ≈2% of the classical Thomas-Reiche-Kuhn (TRK) sum. For the heaviest isotopes, the data suggest also a second peak located at ≈6.5 MeV, which might potentially be the isovector component of the PDR. At variance with microscopic calculations, no clear increase of the total low-lying E1 strength with neutron excess was observed in the experimental data. The results also suggest that association of the full low-lying electric dipole strength with the PDR, especially in its neutron skin interpretation, might be unfounded.
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Markova, Maria; Neumann-Cosel, Peter von & Litvinova, Elena
(2025).
Systematics of the low-energy electric dipole strength in the Sn isotopic chain.
Physics Letters B.
ISSN 0370-2693.
860.
doi:
10.1016/j.physletb.2024.139216.
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We present a systematic study of the mass dependence of the low-energy electric dipole strength (LEDS) in Sn isotopes in the range 𝐴 = 111 − 124 based on data obtained with the Oslo method and with relativistic Coulomb excitation in forward-angle (𝑝, 𝑝′) scattering. The combined data cover an energy range of 2 − 20 MeV which permits, with minimal assumptions, a decomposition of the total strength into the contribution from the lowenergy tail of the isovector giant dipole resonance (IVGDR) and possible resonance-like structures on top of it. In all cases, a resonance peaked at about 8.3 MeV is observed, exhausting an approximately constant fraction of the Thomas-Reiche-Kuhn (TRK) sum rule. For heavier isotopes (𝐴 ≥ 118) a consistent description of the data requires the inclusion of a second resonance centered at 6.5 MeV, representing the isovector response of the pygmy dipole resonance (PDR). Its strength corresponds to a small fraction of the total LEDS only and shows an approximately linear dependence on mass number. The experimental results are compared to microscopic calculations to investigate the importance of an inclusion of quasiparticle vibration coupling (qPVC) for a realistic description of the LEDS. A possible interpretation of the experimentally observed two-bump structure is given.
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Heines, Johannes Sørby; Modamio, Victor; Görgen, Andreas; Korten, Wolfram; Ljungvall, Joa & Pasqualato, G.
[Show all 45 contributors for this article]
(2025).
NEW LIFETIME MEASUREMENTS
IN THE RUTHENIUM CHAIN: INVESTIGATING
THE EVOLUTION OF TRIAXIALITY.
Acta Physica Polonica B, Proceedings Supplement.
ISSN 1899-2358.
18(2).
doi:
10.5506/APhysPolBSupp.18.2-A22.
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We have used the recoil distance Doppler-shift method to measure lifetimes of excited states in 108Ru, 110Ru, and 112Ru. Excited states in these nuclei were populated by fusion–fission reactions between a 238U beam and a 9Be target in an experiment at GANIL. Fission fragments were identified event by event in the VAMOS++ spectrometer, while γ-rays were detected by the Advanced Gamma Tracking Array (AGATA). The lifetimes in the ground state band are consistent with rotational structures and constant B(E2) values indicate that the deformation does not change significantly across the chain of studied ruthenium nuclei. Preliminary results for lifetimes of states in the γ-band indicate a well deformed triaxial shape with a γ parameter close to 30◦ in 110Ru, with a slight change towards oblate deformation in 112Ru.
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Torvund, Gulla Louise Serville; Ernoult, Marc; Courtin, Fanny; Doligez, Xavier; Gjestvang, Dorthea & Siem, Sunniva
[Show all 7 contributors for this article]
(2025).
Multi-MOX: Facilitating plutonium multi-recycling in the French PWR fleet.
Annals of Nuclear Energy.
ISSN 0306-4549.
223.
doi:
10.1016/j.anucene.2025.111641.
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This study examines the Multi-MOX (MMOX) strategy for plutonium multi-recycling in PWRs using the CLASS fuel cycle simulation tool with assembly-level calculations. MMOX facilitates the multi-recycling of used nuclear fuel by mixing reprocessed plutonium from various sources to create viable fresh nuclear fuel. The strategy significantly curtails the growth of the plutonium inventory, but does not stabilize it entirely in the long term. Although lower fuel burnup reduces plutonium build-up, it increases the production of minor actinides. Comparing MMOX with non-recycling and mono-recycling scenarios, we find that it reduces plutonium inventory by 35% and 19%, respectively. Despite a higher level of minor actinide production, MMOX decreases overall transuranic element production. Additionally, MMOX reduces the need for interim spent fuel storage by a factor of ten compared to non-recycling and by two-thirds compared to mono-recycling, while substantially lowering the age of stockpiled used nuclear fuel.
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Li, Kevin Ching Wei; Neveling, R.; Adsley, P.; Fujita, H.; Papka, P. & Smit, F. D.
[Show all 15 contributors for this article]
(2024).
Understanding the total width of the 3−1 state in 12C.
Physical Review C.
ISSN 2469-9985.
109(1).
doi:
10.1103/PhysRevC.109.015806.
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Background: Recent measurements indicate that the previously established upper limit for the 𝛾-decay branch of the 3− 1 resonance in 12C at 𝐸𝑥=9.641(5) MeV may be incorrect. As a result, the 3−1 resonance has been suggested as a significant resonance for mediating the triple-𝛼 reaction at high temperatures above 2 GK. Accurate estimations of the 3−1 contribution to the triple-𝛼 reaction rate require accurate knowledge of not only the radiative width, but also the total width. Purpose: In anticipation of future measurements to more accurately determine the 𝛾-decay branch of the 3−1 resonance, the objective of this work is to accurately determine the total width of the 3−1 resonance. Method: An evaluation was performed on all previous results considered in the current ENSDF average of 46(3) keV for the physical total width (FWHM) of the 3−1 resonance in 12C. A new 𝐑-matrix analysis for the 3−1 resonance was performed with a self-consistent, simultaneous fit of several high-resolution 12C excitation-energy spectra populated with direct reactions. Results: The global analysis performed in this work yields a formal total width of Γ(𝐸𝑟)=46(2) keV and an observed total width of Γobs(𝐸𝑟)=38(2) keV for the 3−1 resonance. Conclusions: Significant unaccounted-for uncertainties and a misstated result were discovered in the previous results employed in the ENSDF for the physical (or observed) total width of the 3−1 resonance. These previously reported widths are fundamentally different quantities, leading to an invalid ENSDF average. An observed total width of Γobs(𝐸𝑟)=38(2) keV is recommended for the 3−1 resonance in 12C. This observed total width should be employed for future evaluations of the observed total radiative width for the 3−1 resonance and its contribution to the high-temperature triple-𝛼 reaction rate.
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Markova, Maria; Larsen, Ann-Cecilie; Tveten, Gry Merete; Neumann-Cosel, Peter von; Eriksen, Tomas Kvalheim & Garrote, Frank Leonel Bello
[Show all 16 contributors for this article]
(2023).
Nuclear level densities and γ -ray strength functions of Sn 111,112,113 isotopes studied with the Oslo method.
Physical Review C.
ISSN 2469-9985.
108(1).
doi:
10.1103/PhysRevC.108.014315.
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The 111,112,113Sn isotopes have been studied with (p,dγ), (p,p′γ), and (d,pγ) reactions to extract the nuclear level densities (NLDs) and γ-ray strength functions (GSFs) of these nuclei below the neutron separation energy by means of the Oslo method. The experimental NLDs for all three nuclei demonstrate a trend compatible with the constant-temperature model below the neutron separation energy while also being in good agreement with the NLDs of neighboring Sn isotopes, obtained previously with the Oslo-type and neutron evaporation experiments. The extracted microcanonical entropies yield ≈1.5 kB entropy of a valence neutron in both 111Sn and 113Sn. Moreover, the deduced microcanonical temperatures indeed suggest a clear constant-temperature behavior above ≈3 MeV in 111,113Sn and above ≈4.5 MeV in 112Sn. We observe signatures for the first broken neutron pairs between 2 and 4 MeV in all three nuclei. The GSFs obtained with the Oslo method are found to be in good agreement below the neutron threshold with the strengths of 112,114Sn extracted in the (p,p′) Coulomb excitation experiments.
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Pasqualato, G; Ansari, S.; Heines, Johannes Sørby; Modamio, Victor; Görgen, Andreas & Beckmann, Kristine Sønstevold
[Show all 52 contributors for this article]
(2023).
Shape evolution in even-mass <sup>98 - 104</sup> Zr isotopes via lifetime measurements using the γγ -coincidence technique.
European Physical Journal A.
ISSN 1434-6001.
59(11).
doi:
10.1140/epja/s10050-023-01172-8.
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The Zirconium (Z = 40) isotopic chain has attracted interest for more than four decades. The abrupt lowering of the energy of the first 2+ state and the increase in
the transition strength B(E2; 2+→ 0+) going from 98Zr to 100Zr has been the first example of “quantum phase transition” in nuclear shapes, which has few equivalents in the nuclear chart. Although a multitude of experiments have been
performed to measure nuclear properties related to nuclear shapes and collectivity in the region, none of the measured lifetimes were obtained using the Recoil Distance Doppler Shift method in the γγ-coincidence mode where a gate on the direct feeding transition of the state of interest allows a strict control of systematical errors. This work reports the results of lifetime measurements for the first yrast excited states in 98−104Zr carried out to extract reduced transition
probabilities. The new lifetime values in γγ-coincidence and γ -single mode are compared with the results of former experiments. Recent predictions of the Interacting Boson Model with Configuration Mixing, the Symmetry Conserving Configuration Mixing model based on theHartree–Fock–Bogoliubov approach and the Monte Carlo Shell Model are presented and compared with the experimental data.
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Lemasson, A.; Dudouet, J.; Rejmund, M.; Ljungvall, J.; Görgen, Andreas & Korten, W.
(2023).
Advancements of γ -ray spectroscopy of isotopically identified fission fragments with AGATA and VAMOS++.
European Physical Journal A.
ISSN 1434-6001.
59.
doi:
10.1140/epja/s10050-023-01053-0.
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View all works in NVA
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Siem, Sunniva
(2026).
Presentation of The Norwegian Nuclear Research Centre (NNRC) and new BSc and MSc program in Nuclear Science.
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Siem, Sunniva & Pellegri, Luna
(2026).
Almost 15 years of fruitful Nuclear Physics collaboration between South Africa and Norway.
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Siem, Sunniva & Stavik-Døvle, Grete
(2026).
Studieprogrammene i nukleære fag: Studentenes kompetanse når de begynner på masteroppgaven.
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Tomkiv, Yevgeniya & Meir, Michaela Georgine
(2026).
15 Years After Fukushima - Advancing Science & Global Collaboration.
doi:
https:/www.linkedin.com/feed/update/urn:li:activity:7440366580175187968.
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It is 15 years since a tsunami and earthquake devastated the coast of the Fukushima prefecture, and led to the accident at the Fukushima Daichi Nuclear Power Plant. A team led by NNRC's Deputy Director Prof. Deborah Oughton is currently visiting the Institute of Environmental Radioactivity at Fukushima University (IER) to attend the 12th Annual Symposium, “Fukushima Voices: 15 years of Nature and Humanity” (https://lnkd.in/egm5JVFz), and to discuss future collaboration in research and education.
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Lind, Ole Christian & Meir, Michaela Georgine
(2026).
Research highlight in NATURE: PNAS study on the sunken submarine Komsomolets.
doi:
https:/www.linkedin.com/feed/update/urn:li:activity:7447250454100606976.
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The study investigates the current status of the Soviet nuclear-powered submarine Komsomolets (K-278), which sank in the Norwegian Sea in 1989. Resting at a depth of 1,680 meters with both a nuclear reactor and two nuclear warheads on board, the wreck is a critical site for understanding long-term nuclear risks in the deep ocean.
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Paulsen, Wanja & Meir, Michaela Georgine
(2026).
Strengthening Norway's Nuclear Expertise: A Joint Initiative by UiO, NMBU and DSA.
doi:
https:/www.linkedin.com/feed/update/urn:li:activity:7449427917899522048.
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On April 9th, the Norwegian Radiation and Nuclear Safety Authority, Direktoratet for strålevern og atomsikkerhet (DSA), hosted in collaboration with Universitetet i Oslo (UiO) (UiO) and NMBU - Norwegian University of Life Sciences a strategic workshop "Sammen om å øke den nasjonale kompetansen i nukleære fag" (Together to strengthen the national competence in nuclear subjects) at Radisson Blu Plaza Hotel focused on master’s student supervision in businesses in the nuclear sector.
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Meir, Michaela Georgine
(2026).
10th anniversary of the Oslo Workshop on Nuclear Level Density and Gamma Strength.
doi:
https:/www.linkedin.com/feed/update/urn:li:activity:7462823722547339264.
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The 10th anniversary of the Oslo Workshop on Nuclear Level Density and Gamma Strength, organized by Norwegian Nuclear Research Centre and University of Oslo took place throughout the week of 18–22 May. The workshop was opened by the Dean of The Faculty of Mathematics and Natural Sciences, Solveig Kristensen, who highlighted developments in our research field, the impact of the Oslo Method, and NNRC's societal mission.
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Meir, Michaela Georgine & Siem, Sunniva
(2026).
UiO and iThemba LABS: Formalizing a Decade of Scientific Collaboration.
doi:
https:/www.linkedin.com/feed/update/urn:li:activity:7467550847309348864.
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The University of Oslo officially renewed the research partnership with iThemba LABS in South Africa. This milestone is the second renewal of a collaboration that first began in 2017. As Deputy Director at iThemba LABS Dr. Rudolph Nchodu, pointed out, this is now one of the largest collaborations we have in terms of the number of people involved. The formal signing by Vice Dean Øystein Prytz and Deputy Director Rudolph Nchodu provides a solid framework for the next five years, giving our joint research and student exchange programs the stability needed.
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Meir, Michaela Georgine & Brynildsen, Elisabeth
(2026).
From nuclear physics to smarter cancer treatment.
doi:
https:/www.linkedin.com/feed/update/urn:li:activity:7467945495009726464.
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Nuclear technology master’s student Elisabeth Brynildsen defended her thesis on turning proton‑irradiated tantalum into new tools for cancer treatment and medical imaging. She investigates how to produce two promising isotopes, 177 Ta and 178Ta, and tests whether they could work for ultra‑precise therapy and SPECT scans. Her results add fresh data that can help develop safer and more effective radioactive drugs in the future.
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Theodossiou, Theodossis & Meir, Michaela Georgine
(2026).
Pioneering study on a small molecule called phenazine methosulfate (PMS).
doi:
https:/www.linkedin.com/feed/update/urn:li:activity:7472287357455650817.
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Members of our Norwegian Nuclear Research Centre community have co‑authored a pioneering study on a small molecule called phenazine methosulfate (PMS). The work conducted on brain cancer cells shows that PMS can briefly “jump‑start” energy production, even when the respirational energy systems are blocked by drugs ...
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Meir, Michaela Georgine & Tokstad, Camilla Almli
(2026).
Advancing Cancer Treatment with Nuclear Physics.
doi:
https:/www.linkedin.com/feed/update/urn:li:activity:7477303373604614144.
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Camilla’s research, conducted at NNRC, Universitetet i Oslo (UiO) | University of Oslo and Berkeley Lab, provides a major boost for the future of targeted radionuclide therapy (TRT). Her work focused on the production of Antimony-119 (119Sb), a "perfect" candidate for cancer treatment because it emits Meitner–Auger electrons. These electrons deposit a high local dose of energy over a very short distance, allowing for the precise destruction of cancer cell DNA while sparing the surrounding healthy tissue.
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Meir, Michaela Georgine & Grieg, Claudia Emilia
(2026).
New Insights into Iodine: From Stellar Physics to Reactor Safety.
doi:
https:/www.linkedin.com/feed/update/urn:li:activity:7477632298516127744.
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In her master's thesis, Claudia Grieg performed the first indirect measurement of the 132I (n,g) 133I astrophysical reaction rate. Working at the Oslo Cyclotron Laboratory, she utilized the Oslo Method to identify a low-energy enhancement (upbend) and a pygmy dipole resonance in the nucleus of 133I. This data is crucial for accurately modeling the i-process, bringing us closer to solving the mystery of the origin of heavy elements in our universe.
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Meir, Michaela Georgine & Görgen, Andreas
(2026).
New Insights into the Shape of Neutron-Rich Nuclei.
doi:
https:/www.linkedin.com/feed/update/urn:li:activity:7491108539730583552.
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Just before summer William finished his master's degree studying the shape and structure of neutron-rich atomic nuclei. The work investigated excited states in the neutron-rich fission fragment ¹¹⁴Pd, measuring lifetimes in the picosecond range. The data were obtained in an experiment at GANIL in France, using the Advanced Gamma Tracking Array AGATA together with the VAMOS++ spectrometer, and analyzed using the recoil distance Doppler shift technique.
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Meir, Michaela Georgine
(2026).
Celebrating new research at NNRC!
doi:
https:/www.linkedin.com/feed/update/urn:li:activity:7503833920371621888.
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After the summer break, we had several research achievements to celebrate at the Norwegian Nuclear Research Centre (NNRC) at the University of Oslo: Three papers have been published, including one in Nature, with another also featured in Phys.org News. Two more papers have been accepted for publication and two additional manuscripts have been submitted to Physical Review C. The published papers cover nuclear structure, properties of exotic nuclei, nuclear astrophysics and nuclear fission - reflecting the broad research activities within our centre.
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Meir, Michaela Georgine; Olafsen-Solberg, Iris & Vatnar:, Samanta
(2026).
One centre, many opportunities — studying nuclear science with NNRC.
doi:
https:/www.linkedin.com/feed/update/urn:li:activity:7506654029847130113.
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After completing their bachelor’s project together this spring, Iris Olafsen-Solberg and Samanta Vatnar have now started the NukTek master’s programme at the Department of Physics, University of Oslo. Their bachelor’s project combined nuclear physics at UiO with radiochemistry at NMBU - Norwegian University of Life Sciences and investigated the production and separation of technetium-95m (Tc-95m) for environmental monitoring.
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Paulsen, Wanja & Meir, Michaela Georgine
(2026).
Upcoming experiment with scientists from the University of Naples Federico II and the Università di Catania in Italy at OCL.
doi:
https:/lnkd.in/p/eTXjq6E9.
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Last week, several scientists from the University of Naples Federico II and the Università di Catania in Italy visited the Norwegian Nuclear Research Centre and the Oslo Cyclotron Laboratory at the Universitetet i Oslo (UiO) | University of Oslo to prepare for an upcoming experiment. Through this collaboration, we will perform an alpha-scattering experiment on a magnesium target to investigate carbon-carbon fusion inside stars. When carbon fuses with carbon inside stars, magnesium becomes a gateway to elements such as neon and sodium. It is therefore very important to have a detailed understanding of the nuclear properties of magnesium. This gives us a better understanding of how the elements we and our Earth consist of were created
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Meir, Michaela Georgine & Hisanawi, Josef Ali Hasan
(2026).
From Maritime to Terrestrial Reactors: Making Better Use of Nuclear Fuel.
doi:
https:/www.linkedin.com/feed/update/urn:li:activity:7510673513075142658/.
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In his thesis, “Neutronic Analysis of a Hybrid Maritime–Terrestrial Fuel Cycle in Fluoride-Salt-Cooled High-Temperature Reactors”, Josef Hisanawi explored an innovative idea for making better use of nuclear fuel: Could fuel, first used in a compact reactor for maritime applications, be transferred to a larger land-based reactor and used further?
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Lee, Hyeji
(2026).
Coulomb Dissociation of 17B.
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The neutron halo is one of the most intriguing features in systems with a large excess of neutrons compared to protons, providing valuable information about weakly bound many-body systems near the neutron drip line. 17B has long been regarded as a two-neutron halo nucleus based on various experimental observations. However, recent studies suggest otherwise due to a dominant d-wave configuration of the valance neutrons and due to the presence of a thick neutron skin.
In this work, we report the first measurement of electric dipole (E1) excitation of 17B. A kinematically complete measurement was performed at RIBF, RIKEN, using the SAMURAI spectrometer. A 17B beam at 270MeV/u was impinged on a Pb target causing Coulomb dissociation (CD), and the breakup fragments 15B and two neutrons were detected in coincidence. From this measurement, the differential CD cross section and the E1 strength distribution were extracted. The observed E1 strength distribution indicates that 17B has a weakly developed halo. These results provide important structural information on 17B and they contribute to setting the criteria required for neutron halo formation.
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Lee, Hyeji
(2026).
Coulomb Dissociation of 17B.
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The neutron halo is one of the most intriguing features in systems with a large excess of neutrons compared to protons, providing valuable information about weakly bound many-body systems near the neutron drip line. 17B has long been regarded as a two-neutron halo nucleus based on various experimental observations. However, recent studies suggest otherwise due to a dominant d-wave configuration of the valance neutrons and due to the presence of a thick neutron skin.
In this work, we report the first measurement of electric dipole (E1) excitation of 17B. A kinematically complete measurement was performed at RIBF, RIKEN, using the SAMURAI spectrometer. A 17B beam at 270MeV/u was impinged on a Pb target causing Coulomb dissociation (CD), and the breakup fragments 15B and two neutrons were detected in coincidence. From this measurement, the differential CD cross section and the E1 strength distribution were extracted. The observed E1 strength distribution indicates that 17B has a weakly developed halo. These results provide important structural information on 17B and they contribute to setting the criteria required for neutron halo formation.
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Siem, Sunniva
(2026).
Innspill fra Norsk Nukleært Forskningssenter.
doi:
https:/www.regjeringen.no/no/aktuelt/innspillsmoter-om-kjernekraft/id3171050/.
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Energidepartementet inviterer til to tematiske innspillsmøter knyttet til NOU 2026:4 Kjernekraft i Norge. Begge møtene gjennomføres på Ingeniørenes Hus i Oslo (Kronprinsens gate 17). Det første innspillsmøtet omhandler kraftpolitiske sider ved kjernekraft (kraftmarked, kraftsystem, teknologi, kostnader og produksjon). Foredrag omhandler høringsinnspill fra Norsk Nukleært Forskningssenter, UiO.
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Siem, Sunniva
(2026).
Beredskap starter før krisen inntreffer. Hvem tar vare på fagmiljøene vi ikke har råd til å miste?
doi:
https:/www.nnrc.uio.no/resultater/film-podcast/2026-08-12_arendalsuke.html.
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Fra UiOs arrangement under Arendalsuka 12. august 2026, som handler om hvordan Norge kan bevare små, spesialiserte fagmiljøer som er kritiske for samfunnets beredskap, blant annet innen nukleære fag og pandemiberedskap. Professor og senterleder Sunniva Siem snakker om hvorfor Norge trenger å opprettholde langsiktig kompetanse og sterke fagmiljøer innen nukleære fag – også før en krise oppstår. Hun deltar også i diskusjonen om hvordan kritiske, spesialiserte forskningsmiljøer kan sikres og videreutvikles over tid.
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Oughton, Deborah Helen; Tomkiv, Yevgeniya & schneider, thierry
(2026).
Ethical Dimensions of Radiological Protection in Armed Conflict Situations.
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The EU Project RRADEW (“Resilience to RADiological Events in Wartime”) has the objective to enhance nuclear emergency preparedness, response, and recovery (EPR&R) in the context of war or armed conflict disasters. As a cross-cutting issue throughout the project, RRADEW addresses ethical challenges of both radiation protection and the strategies for building resilient societies.
While some aspects of radiological protection during armed conflicts are similar to those within other radiological and nuclear emergencies, new ethical challenges arise from the different actors and stakeholders (e.g., military personnel, communities under attack, aggressors), different threats and constraints on available options (. Taking a departure in the ethical values proposed by ICRP (justice, dignity, well-being and prudence), an ethical matrix was applied to explore the ethical landscape of armed conflicts situations. Key factors include challenges between roles and responsibilities of emergency responders, military and workers, and in particular duties towards families and colleagues. In addition to respecting the dignity of individuals, promoting solidarity and empathy at a community level would be of key importance. Likewise, the so-called procedural ethical values (transparency, accountability, sustainability) highlight the difficulties in assessing which principle should take precedence, and can be further aggravated in an armed conflict situation where other considerations (e.g., national security, military intelligence) are added.
Finally, while it was clear that ethical reflection related to, for example, resilience, autonomy and dignity, in the context of armed conflict is of utmost importance, the greatest challenge will remain how to make these ethics work in armed conflict.
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Hartmann, Christian Magnus & Kalantzopoulos, Georgios
(2026).
Presentation of NNRC Research Topic 3: nuclear simulations.
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Torsvoll, Marius; Wirgenes, Maia Oline Grund; Al-Adili, Ali; Haug, Henrik Sørlie; Heines, Johannes Sørby & Siem, Sunniva
[Show all 13 contributors for this article]
(2026).
Very asymmetric fission yields of 233U(nth, f) at LOHENGRIN.
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In this work we report on a fission yield experiment done with the LOHENGRIN recoil mass spectrometer. Understanding the dynamics of nuclear fission requires accurate knowledge of the charge and mass distributions of fission fragments, particularly in rare and poorly studied regions. We present a dedicated investigation of the assymetric fission yields in 233U(nth,f), targeting fragment masses below A = 70, a region previously unexplored for this system. A particular focus is on confirming an expected enhancement of the yields of fragments near mass 70, potentially indicative of a super-asymmetric fission mode influenced by nuclear structure effects, such as the Z = 28 major shell closure. The experiment employed the LOHENGRIN recoil mass spectrometer in combination with a ΔE/E Frischgrid ionization chamber. This allows the identification of the mass of light fission fragments. The far asymmetric mass region will serve for benchmarking theoretical models and improving our understanding of shell effects in fission.
During the presentation, we discussed the necessary correction steps during the analysis, including digital signal processing, scanning ionic charge and kinetic energy distributions, and target burn-up. Moreover, we discuss a comparison of different foil stacks that can be used as passive attenuators in the next beam-time campaign. Preliminary results from this work suggest a yield enhancement in the studied region, implying that the fissioning system U234* may exhibit a similar effect like the heavier systems. We finish by discussing the outlook and preparations for upcoming beam times at ILL.
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Torsvoll, Marius; Wirgenes, Maia Oline Grund; Al-Adili, Ali; Solders, Andreas; Köster, Ulli & Daugas, Jean-Micheal
[Show all 13 contributors for this article]
(2026).
Very asymmetric fission yields in U(n,f) at LOHENGRIN.
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The super assymmetric fission mode and yield enhancement around A = 70 has been observed in actinides as light as U. Modern fission codes modeling the fission process do not predict an enhancement like that found in U233 and heavier actinides. The super asymmetric region has not been measured for U233 and our goal is to explore the yields in the mass region from A = 90 to A = 67.
In summary our goal is to extract the unmeasured fission yields in the super asymmetric region of U233(nth, f) with a special emphasis on investigating the possibility of a yield enhancement at atomic mass number A = 70
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Olsen, William Eivik
(2026).
Machine Learning Methods for Fast Nuclear Reactor Simulations.
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Presentasjon av forskning på maskinlæringsmetoder for reaktorsimuleringer fremført under NFS studentkonferanse 4. september 2026.
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Wirgenes, Maia Oline Grund
(2026).
A time correction scheme performed by using an ionization chamber as a time projection chamber.
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The presentation described the use of the LOHENGRIN recoil mass spectrometer and a 90 degree tilted Frisch-grid ionization chamber to improve the energy resolution of fission fragment measurements. The Reversed Energy Dispersion magnet of the LOHENGRIN focuses fragments with different kinetic energies to nearly the same spatial region at the detectors focal plane, encoding differences in energy primarily in the exit angle. A system of 13 shutters located at the focal plane defines the angular (energy) acceptance. Opening one or several shutters increases the measured fission fragment yields, but also introduce angle‑dependent trajectories in the ionization chamber. By rotating the chamber so that the focal plane is perpendicular to the electrodes, the detector is effectively operated in a time‑projection‑chamber–like mode: variations in entrance angle translate into different electron drift paths and drift times along the field direction. We exploit this drift‑time information to correct for angle‑induced distortions in the collected charge and thereby recover the intrinsic energy resolution of the fission fragments.
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Wirgenes, Maia Oline Grund
(2026).
Comparative Neutronics Analysis of Uranium-based Fuel Matrices on the BANDI-60 SMR for Maritime Applications.
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Nuclear propulsion is a potential solution for decarbonizing the shipping industry by 2050. To be viable,
it must demonstrate economic competitiveness, high safety standards, and responsible spent-fuel manage-
ment. This study investigates fuel utilization and performance optimization in a Small Modular Reactor
(SMR), where the South Korean BANDI-60 functions as a baseline model. A fuel- and enrichment-variation
analysis is conducted through depletion simulations with the open-source Monte Carlo code OpenMC. 13
fuel matrix configurations are examined, evaluating their effects on cycle length, burnup, and radionuclide
inventory evolution. The results show that fuel matrix continuity and the fuel-to-moderator ratio strongly
influence fuel utilization and overall reactor performance. These parameters drive observable differences in
energy production potential and actinide buildup across the models. The study highlights the importance of
fuel microstructure and composition in achieving efficient, sustainable reactor operation for future marine
nuclear propulsion systems.
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Ingeberg, Vetle Wegner; Görgen, Andreas; Inoue, Azusa; Kumar, Neeraj; Larsen, Ann-Cecilie & Li, Kevin Ching Wei
[Show all 9 contributors for this article]
(2026).
OSCAR at ISOLDE.
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For the next run period at ISOLDE, the Nuclear Physics group at the University of Oslo are considering proposing a longer experimental campaign with the Oslo SCintillator ARay (OSCAR). The main aims of such a campaign will be to measure the nuclear level density and -ray strength function of key nuclei relevant for nuclear structure and nuclear astrophysics (e.g. i-process nucleosynthesis). Other cases of interest could be spectroscopy of resonances in light exotic nuclei or rare event searches. In addition, we would also invite other interested groups to propose experiments with the setup while it is present at HIE-ISOLDE.
The OSCAR array is the largest LaBr:Ce detector array in the world (at least in terms of detector volume). It offers exceptional efficiency for high-energy -rays without compromising on either energy or time resolution. It consists of 30 large 3.5x8-inch large volume LaBr3:Ce detectors, an icosahedron frame with six rings covering polar angles from to . Detectors can be mounted in a distance of 16.3 to 22 cm from the target, resulting in solid angle coverage of 57%. This translates to about 15% full energy efficiency at 1332 keV and close to 5% at 10 MeV in the closest configuration.
In this presentation I will present the physics cases and our preliminary plans for such a campaign.
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Görgen, Andreas & Heines, Johannes Sørby
(2026).
Evolution of triaxiality in the mass 𝑨≈𝟏𝟏𝟎 region.
doi:
https:/workshops.ill.fr/event/549/overview.
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Strong triaxiality is rare in the nuclear chart, and such nuclei can serve as useful tests of theoretical predictions. The breaking of axial symmetry also enables phenomena which cannot occur in symmetrically deformed nuclei, making it an interesting phenomenon to study. The neutron rich region around mass 110 presents several cases of strong triaxiality, namely in the ruthenium, molybdenum and palladium chains. Ruthenium especially is considered one of the best examples of strong triaxial deformation near the ground state in the entire nuclear chart.
This contribution presents new results from an experiment performed at GANIL to measure lifetimes of excited states in this region with the recoil distance Doppler-shift method. The studied nuclei were populated in a fusion-fission reaction, and identified event by event in the Variable Mode Spectrometer (VAMOS++). The Advanced Gamma Tracking Array (AGATA) provided high resolution gamma spectra of the decaying fission fragments.
We present new B(E2) values for transitions in 108–112Ru, and compare them with phenomenological triaxial rotor predictions and fully microscopic symmetry conserving configuration mixing calculations. Triaxiality is shown to be increasing from 108Ru to 112Ru, with the latter exhibiting near maximum triaxiality. The results are consistent with a simultaneous transition from γ soft to γ rigid deformation. New results for molybdenum and palladium isotopes will also be presented.
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Görgen, Andreas
(2026).
Recent Physics Results and Future Directions of the OSCAR Detector at the Oslo Cyclotron Laboratory.
doi:
https:/agenda.infn.it/event/46675/overview.
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The physics program at the Oslo Cyclotron Laboratory (OCL) pursues experimental studies of statistical properties of highly excited atomic nuclei using the Oslo Scintillator Array (OSCAR). The thirty large-volume (3.5” × 8”) LaBr3:Ce detectors of OSCAR are coupled to an array of segmented silicon telescope detectors to detect particle-gamma coincidences following light-ion induced nuclear reactions. These measurements produce gamma-ray spectra as a function of excitation energy. Primary gamma-ray spectra are extracted with a subtraction algorithm and decomposed into the nuclear level density and the gamma-ray strength function - a procedure that has become known as the “Oslo method”. The experiments probe resonant structures on the low-energy tail of the giant dipole resonance, including the pygmy dipole resonance, the scissors resonance, and the low-energy enhancement. Systematic studies reveal how these resonances evolve with nuclear deformation and neutron excess. Experimental level densities and gamma-ray strength functions can furthermore be used to constrain neutron-capture cross sections in Hauser-Feshbach calculations. This method provides experimentally constrained capture cross sections also for cases where direct measurements with neutrons are not possible, for example for branch points in the astrophysical s-process. Recent results from studies performed at OCL will be presented, together with prospects for future OSCAR experiments both at OCL and other laboratories.
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Siem, Sunniva
(2025).
Future Fission Experiments at the Oslo Cyclotron Laboratory and a short presentation of NNRC.
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Siem, Sunniva
(2025).
Training and education opportunities in the nuclear sector: NNRC and nuclear science BSc and MSc programmes at UiO.
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Torsvoll, Marius; Al-Adili, Ali; Haug, Henrik Sørlie; Heines, Johannes Sørby; Wirgenes, Maia Oline Grund & Siem, Sunniva
[Show all 10 contributors for this article]
(2025).
Very asymmetric fission yields of 233U(nth, f) at LOHENGRIN.
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Super asymmetric fission represents a rare but informative fission mode, providing sensitive insight into shell effects and scission configurations in the nuclear fission process. In this work, new measurements of neutron induced fission of U233 at thermal neutron energies are presented, with a particular focus on very light fission fragments with mass numbers below A = 80. The experiment was performed at the Institut Laue Langevin using the LOHENGRIN recoil mass spectrometer in combination with a delta E-E Frisch grid ionization chamber. For the first time, fission yields of U233(nth,f)have been measured from A = 90 down to A = 68. The data promise to be important benchmarks for fission model development and are also relevant for applications related to the thorium fuel cycle.
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Görgen, Andreas; Heines, Johannes Sørby & Modamio, Victor
(2025).
Triaxiality of neutron-rich ruthenium nuclei studied by lifetime measurements.
doi:
https:/indico.ibs.re.kr/event/701/.
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Neutron-rich ruthenium nuclei with mass around A≈110 are considered some of the best examples for nuclei with triaxial shape in their ground state. Quantitative information about the deformation in general and the degree of triaxiality in particular was obtained from lifetime measurements of short-lived excited states in 108Ru, 110Ru, and 112Ru. Lifetimes were measured using the recoil distance Doppler shift (RDDS) technique for states in both the ground-state band and the K=2 gamma band for the Ru isotopes under study. Combining the lifetimes with known branching rations, the measurements provide a multitude of new B(E2) transition strengths. The excited states were populated in fusion-fission reactions between a 238U beam at 6.2 A MeV and a 9Be target in an experiment performed at GANIL. The fission fragments were identified in mass, charge, and atomic number in the magnetic spectrometer VAMOS on an event-by-event basis. The velocity of nuclei exiting the target foil was slowed down in a degrader that was mounted in a plunger device at variable distances from the target. The AGATA gamma-ray tracking array was used to measure picosecond lifetimes with the RDDS method. The experiment produced a wide range of neutron-rich fission fragments, for which lifetimes could be measured under identical experimental conditions. An overview of the results will be presented, with emphasis on the chain of Ru isotopes. The comparison of experimental results with the triaxial rotor model and with beyond-mean field calculations provides quantitative information on the evolution of triaxiality in the chain of Ru isotopes.
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Kjelsberg, Ronny; Wahlström, Erik; Görgen, Andreas & Gjerde, Vegard
(2025).
Physics of the future (Panel).
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Panel debate: Physics of the future
What is the role of physics in society?
What kind of students are wanted by industry?
How do we educate such students?
How does AI affect this?
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Bell, Lauren Tracy
(2024).
Nuclear level densities and gamma-ray strength functions for two well deformed even-even samarium isotopes.
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Larsen, Ann-Cecilie
(2024).
Indirect measurements of neutron-capture rates for exotic, neutron-rich nuclei relevant to the intermediate and rapid neutron-capture processes.
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Paulsen, Wanja; Siem, Sunniva; Li, Kevin Ching Wei & Eriksen, Tomas Kvalheim
(2025).
A saga on the γ-decay branching ratio of the Hoyle state at the Oslo Cyclotron Laboratory.
Universitetet i Oslo.
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The triple-α process is a fundamental cornerstone of stellar nucleosynthesis, facilitating the production of 12C, a vital building block for life. Through the triple-α process, three helium nuclei can fuse to ultimately produce a stable 12C nuclide. At medium stellar temperatures between 0.1–2.0 GK, the Hoyle state in 12C mediates the triple-α reaction, making a comprehensive understanding of its properties essential for accurately modeling the stellar production of 12C, as well as the subsequent stellar nucleosynthesis. Numerous measurements of the decay modes of the Hoyle state have been conducted since its discovery, yielding a relatively well-constrained value of for it’s radiative branching ratio, describing the probability of producing 12C through the triple-α process. However, a recent measurement published by Kibédi et al. [Phys. Rev. Lett. 125, 182701 (2020)] reported a highly discrepant value of Γrad/Γ = 6.2(6) × 10−4 for the radiative branching ratio from the Hoyle state. Given the astrophysical significance of the Hoyle state, resolving this conflict is crucial. This study seeks to address this discrepancy through a new measurement of the γ-decay branching ratio of the Hoyle state, together with a comprehensive reanalysis of the data published by Kibédi et al. [Phys. Rev. Lett. 125, 182701 (2020)].
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Emblemsvåg, Jan; Ordonez, Cesar; Tamm, Cristian Garrido; Ortigosa, Javier Santos; Colilles, Yolanda Mugica & Pérez, Alejandria
[Show all 21 contributors for this article]
(2024).
Final Report of the Nuclear Propulsion for Merchant Ships I (NuProShip I) project.
Norges Teknisk og Naturvitenskapelig Universitet.
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This report contains the results of two years of research (2023 and 2024) performed under the context of Nuclear Propulsion for Merchant Ships (NuProShip) I, funded by the Research Council of Norway. The successor project, NuProShip II, is well underway as of January 2025. Starting from the nuclear reactor core and working ourselves outwards to the reactor systems, waste handling, ship systems, ship design, crew and more, we have performed a number or research tasks as presented in this report. Since we started at the nuclear reactor core, based on the idea that we need the right nuclear technology before anything else, the report is dominated by the large amount of work done to select the best possible reactor technologies. We have selected reactors among all the known reactor concepts by yearend 2022, some 80+ of them, as detailed in Chapter 2. First, we applied a set of 11 exclusion criteria that were very clearcut, after which we had about 8 possible reactor concepts left. These 8 reactor concepts were subsequently subjected to another 26 criteria for further selection. The end result is three reactor concepts; 1) molten-salt reactor using TRISO fuel designed by Kairos Power (USA), 2) a helium gas-cooled reactor using TRISO fuels designed by Ultra Safe Nuclear Corporation (USA), and 3) a lead-cooled reactor designed by Blykalla (Sweden). By selecting these reactor concepts and studying their intrinsic properties, we realized that one single reactor technology cannot address the entire shipping industry. In NuProShip II, we will continue working on this. Preliminary results, however, indicate that the MSR will work best with large ships that need steam turbines. The helium gas-cooled reactor will work best with ships that need electric propulsion system. The lead-cooled reactor will work best in situations where the load is more stable situations such as baseload operation. Once these overall findings were clear, the two other work packages – discussed in Chapters 3 and 4 – could start working in earnest. In Chapter 3 we find a lot of insights from a ship design and class society perspective. This is a complex area, and to gain a complete overview of it is difficult, which will go on well into NuProShip II as well. This is evident for the HAZID overview for which many issues are still not solved. However, we have started to get a very good overview of the class requirements and international regulations. Most of the results presented here must nonetheless be viewed as preliminary. The challenge is to go from the high, conceptual level down to a concrete ship, such as the Cadiz Knutsen owned by Knutsen OAS. This ship has served as a mental reminder of what we are working on, and the ship is also used as a practical working case. The same can be said about the work presented in Chapter 4. Researching what skills the crew needs, what qualifications they must have and therefore develop an education and training system is also complex work. The fact is that none of the reactor technologies we have identified have ever been used at sea. The closest is the lead-bismuth cooled reactor used unsuccessfully in the Russian navy. One finding that seems to be very clear is that some remote monitoring/operations of ships must be implemented. Naval ships are today largely self-contained, and for that reason they have a reactor crew that is too large for commercial chips of any sort due to both the availability of crew but ultimately also costs. Therefore, remote monitoring/operations is seen as key enabler. Obviously, all the topics discussed in Chapter 3 are also extended well into NuProShip II. The report does not contain much information about costs. The reason is that it is basically too early for making any trustworthy estimates. However, this will be adressed in NuProShip II.
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