| 1. |
- Adlarson, Patrik, et al.
(författare)
-
Backward single-pion production in the pd -> He-3 pi(0)reaction with WASA-at-COSY
- 2018
-
Ingår i: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 54:9
-
Tidskriftsartikel (refereegranskat)abstract
- New data on the production of single neutral pions in the pd -> He-3 pi(0) reaction are presented. For fifteen proton beam momenta between p(p) = 1.60GeV/c and p(p) = 1.74 GeV/c, differential cross sections are determined over a large fraction of the backward hemisphere. Since the only previous systematic measurements of single-pion production at these energies were made in collinear kinematics, the present work constitutes a significant extension of the current knowledge on this reaction. Even this far above the production threshold, significant changes are found in the behaviour of the angular distributions over small intervals in beam momentum.
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| 2. |
- Adlarson, Patrik, et al.
(författare)
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Measurement of the (n)over-right-arrowp -> d pi(0) pi(0) reaction with polarized beam in the region of the d(*)(2380) resonance
- 2016
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 52:5, s. 1-7
-
Tidskriftsartikel (refereegranskat)abstract
- We report on a high-statistics measurement of the most basic double-pionic fusion reaction over the energy region of the d (*)(2380) resonance by use of a polarized deuteron beam and observing the double fusion reaction in the quasifree scattering mode. The measurements were performed with the WASA detector setup at COSY. The data reveal substantial analyzing powers and confirm conclusions about the d(*) resonance obtained from unpolarized measurements. We also confirm the previous unpolarized data obtained under complementary kinematic conditions.
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| 3. |
- Al-Adili, Ali, et al.
(författare)
-
Extraction of angular momenta from isomeric yield ratios : Employing TALYS to de-excite primary fission fragments
- 2019
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 55:4
-
Tidskriftsartikel (refereegranskat)abstract
- The generation of angular momentum in fission is difficult to model, in particular at higher excitation energies where data are scarce. Isomeric yield ratios (IYR) play an important role in deducing angular momentum properties of fission fragments (FF), albeit this requires some assumptions and simplifications. To estimate FF angular momentum, fission codes can be used to calculate IYRs and compare them to experimental data. Such measurements have systematically been performed at the IGISOL facility using novel experimental techniques. In conjunction, a new method has been developed to infer the angular momentum of the primary FF using the nuclear reaction code TALYS. In this work, we evaluate this new method by comparing our TALYS calculations with values found in the literature and with results from the GEF fission code, for a few well-studied reactions. The overall results show a consistent performance of TALYS and GEF, as well as of many reported literature values. However, some deviations were found, possibly pinpointing the need to re-examine some of the reported literature values. A sensitivity analysis was also performed, in which the role of excitation energy, neutron emission, discrete level structure and level density models were studied. Finally, the role of multiple chance fission, of relevance for the reactions studied at IGISOL, is discussed. Some literature data for this reaction were also re-analyzed using TALYS, revealing significant differences.
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| 4. |
- Al-Adili, Ali, et al.
(författare)
-
Simulations of the fission-product stopping efficiency in IGISOL
- 2015
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 51:59, s. 1-7
-
Tidskriftsartikel (refereegranskat)abstract
- At the Jyväskylä Ion Guide Isotope Separator On-Line (IGISOL) facility, independent fission yields are measured employing the Penning-trap technique. Fission products are produced, e.g. by impinging protons on a uranium target, and are stopped in a gas-filled chamber. The products are collected by a flow of He gas and guided through a mass separator to a Penning trap, where their masses are identified. This work investigates how fission-product properties, such as mass and energy, affect the ion stopping efficiency in the gas cell. The study was performed using the Geant4 toolkit and the SRIM code. The main results show a nearly mass-independent ion stopping with regard to the wide spread of ion masses and energies, with a proper choice of uranium target thickness. Although small variations were observed, in the order of 5%, the results are within the systematic uncertainties of the simulations. To optimize the stopping efficiency while reducing the systematic errors, different experimental parameters were varied; for instance material thicknesses and He gas pressure. Different parameters influence the mass dependence and could alter the mass dependencies in the ion stopping efficiency.
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| 5. |
- Al Jebali, Ramsey, et al.
(författare)
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A helium gas scintillator active target for photoreaction measurements
- 2015
-
Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 51:10
-
Tidskriftsartikel (refereegranskat)abstract
- A multi-cell He gas scintillator active target, designed for the measurement of photoreaction cross sections, is described. The target has four main chambers, giving an overall thickness of 0.103 g/cm(3) at an operating pressure of 2MPa. Scintillations are read out by photomultiplier tubes and the addition of small amounts of N-2 to the He, to shift the scintillation emission from UV to visible, is discussed. First results of measurements at the MAX IV Laboratory tagged-photon facility show that the target has a timing resolution of around 1 ns and can cope well with a high-flux photon beam. The determination of reaction cross sections from target yields relies on a Monte Carlo simulation, which considers scintillation light transport, photodisintegration processes in He-4, background photon interactions in target windows and interactions of the reaction-product particles in the gas and target container. The predictions of this simulation are compared to the measured target response.
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| 6. |
- Ananthanarayan, B., et al.
(författare)
-
An analytic approach to sunset diagrams in chiral perturbation theory : Theory and practice
- 2016
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 52:12
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the use of several code implementations of the Mellin-Barnes method available in the public domain to derive analytic expressions for the sunset diagrams that arise in the two-loop contribution to the pion mass and decay constant in three-flavoured chiral perturbation theory. We also provide results for all possible two mass configurations of the sunset integral, and derive a new one-dimensional integral representation for the one mass sunset integral with arbitrary external momentum. Thoroughly annotated Mathematica notebooks are provided as ancillary files in the Electronic Supplementary Material to this paper, which may serve as pedagogical supplements to the methods described in this paper.
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| 7. |
- Assie, M., et al.
(författare)
-
The Giant Pairing Vibration in heavy nuclei Present status and future studies
- 2019
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Ingår i: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 55:12
-
Tidskriftsartikel (refereegranskat)abstract
- The Giant Pairing Vibration, a two-nucleon collective mode originating from the second shell above the Fermi surface, has long been predicted and expected to be strongly populated in two-nucleon transfer reactions with cross sections similar to those of the low-lying Pairing Vibration. Recent experiments have provided evidence for this mode in C-14,C- 15 but, despite sensitive studies, it has not been definitively identified in Sn or Pb nuclei where pairing correlations are known to play a crucial role near their ground states. In this paper we review the basic theoretical concepts of this "elusive" state and the status of experimental searches in heavy nuclei. We discuss the hindrance effects due to Q-value mismatch and the use of weakly-bound projectiles as a way to overcome the limitations of the (p,t) reactions. We also discuss the role of the continuum and conclude with some possible future developments.
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| 8. |
- Barucca, G., et al.
(författare)
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Precision resonance energy scans with the PANDA experiment at FAIR : Sensitivity study for width and line shape measurements of the X(3872)
- 2019
-
Ingår i: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 55:3
-
Tidskriftsartikel (refereegranskat)abstract
- This paper summarises a comprehensive Monte Carlo simulation study for precision resonance energy scan measurements. Apart from the proof of principle for natural width and line shape measurements of very narrow resonances with PANDA, the achievable sensitivities are quantified for the concrete example of the charmonium-like X(3872) state discussed to be exotic, and for a larger parameter space of various assumed signal cross-sections, input widths and luminosity combinations. PANDA is the only experiment that will be able to perform precision resonance energy scans of such narrow states with quantum numbers of spin and parities that differ from JPC=1--.
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| 9. |
- Bhagwat, A., et al.
(författare)
-
Cluster emission from superheavy nuclei
- 2018
-
Ingår i: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 54:11
-
Tidskriftsartikel (refereegranskat)abstract
- The process leading to cluster emission from superheavy nuclei in the range 100 122 has been systematically investigated. This topic is of importance because it opens up the possibility of identifying superheavy elements through deposition of clusters in the detection system. In this paper we evaluate the cluster decay half lives by considering the cluster as a particle. The motion of this particle in the field induced by the daughter nucleus is determined by solving the corresponding Schrodinger equation imposing outgoing boundary conditions (Gamow state). The corresponding Wood-Saxon potential is fitted to obtain the energies provided by a mass formula that has been established recently to have a very high degree of precision. The resulting expression for the decay width is exact, i.e. no approximation besides the assumption of a preformed cluster is introduced. It is found that the heavy cluster emission probability in the superheavy region is much smaller than the corresponding a emission probability.
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| 10. |
- Chulkov, L. V., et al.
(författare)
-
Light nuclei in the vicinity of the dripline and beyond
- 2015
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 51:8
-
Forskningsöversikt (refereegranskat)abstract
- After a brief historical overview of the field of physics with radioactive beams, we give an update of the most recent experimental achievements for nuclei at or beyond the nuclear driplines. Long-lived exotic nuclear states are discussed including multi-nucleon radioactivity and exotic isomers. Studies of correlations between decay products in three-body decays and analysis in a Jacobi-coordinate framework are discussed with special emphasis on the difficulty in the interpretations of data obtained in different reactions. We give examples of systematic studies that the vast amount of now existing data allows, such as shell closures, competition between single-particle states in isotopes, isotones and mirror nuclei. The Thomas-Ehrman shift, Garvey-Kelson-type mass relations and IMME analysis of isobaric multiplets with isospin $ T = 3/2$ and 2 are also discussed as well as alternative interpretations in certain cases.
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| 11. |
- Collaboration, The PANDA, et al.
(författare)
-
Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR
- 2016
-
Ingår i: European Physical Journal A. - : Springer Publishing Company. - 1434-6001 .- 1434-601X. ; 52:10
-
Tidskriftsartikel (refereegranskat)abstract
- Simulation results for future measurements of electromagnetic proton form factors at P ¯ ANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision with which the proton form factors can be determined is estimated. The signal channel p¯ p→ e+e- is studied on the basis of two different but consistent procedures. The suppression of the main background channel, i.e.p¯ p→ π+π-, is studied. Furthermore, the background versus signal efficiency, statistical and systematical uncertainties on the extracted proton form factors are evaluated using two different procedures. The results are consistent with those of a previous simulation study using an older, simplified framework. However, a slightly better precision is achieved in the PandaRoot study in a large range of momentum transfer, assuming the nominal beam conditions and detector performance.
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| 12. |
- Doncel, Maria, et al.
(författare)
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Determination of lifetimes of nuclear excited states using the Recoil Distance Doppler Shift Method in combination with magnetic spectrometers
- 2017
-
Ingår i: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 53:10
-
Tidskriftsartikel (refereegranskat)abstract
- The current work presents the determination of lifetimes of nuclear excited states using the Recoil Distance Doppler Shift Method, in combination with spectrometers for ion identification, normalizing the intensity of the peaks by the ions detected in the spectrometer as a valid technique that produces results comparable to the ones obtained by the conventional shifted-to-unsifted peak ratio method. The technique has been validated using data measured with the gamma-ray array AGATA, the PRISMA spectrometer and the Cologne plunger setup. In this paper a test performed with the AGATA-PRISMA setup at LNL and the advantages of this new approach with respect to the conventional Recoil Distance Doppler Shift Method are discussed.
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| 13. |
- Døssing, Thomas, et al.
(författare)
-
Collective enhancements in nuclear level densities
- 2019
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 55:12
-
Tidskriftsartikel (refereegranskat)abstract
- Contributions to the nuclear level density from a deformed core and from surface vibrations are discussed. The influence of symmetries of the nuclear shape is highlighted by quoting and discussing analytic Fermi gas level densities for irregular, deformed and spherical shapes. A thorough evaluation of the rotational enhancement factor to the level density is carried out for 17 well deformed rare-earth nuclei. Counted experimental levels are compared to levels obtained from the combinatorial level-density model, applying the Folded-Yukawa potential with BCS quasiparticle paring. It is found that the phase space of the rotating core contributes fully to the level density at the low energies where reliable information of experimental levels exists. The analysis is inspired by recent thermal Shell Model Monte Carlo results, which are also included in the comparison. The situation at the neutron excitation energy is also discussed, together with the conditions for vibrational enhancement. Experiments aimed at investigating the fade-away of collective enhancements are briefly discussed.
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| 14. |
- Ertoprak, Aysegul, et al.
(författare)
-
M1 and E2 transition rates from core-excited states in semi-magic Ru-94
- 2018
-
Ingår i: European Physical Journal A. - : Springer. - 1434-6001 .- 1434-601X. ; 54:9
-
Tidskriftsartikel (refereegranskat)abstract
- Lifetimes of high-spin states have been measured in the semi-magic (N = 50) nucleus Ru-94. Excited states in Ru-94 were populated in the Ni-58(Ca-40, 4p)Ru-94* fusion-evaporation reaction at the Grand Accelerateur National d'Ions Lourds (GANIL) accelerator complex. DSAM lifetime analysis was performed on the Doppler broadened line shapes in energy spectra obtained from gamma-rays emitted while the residual nuclei were slowing down in a thick 6 mg/cm(2) metallic Ni-58 target. In total eight excited-state lifetimes in the angular momentum range I = (13-20)h have been measured, five of which were determined for the first time. The corresponding B(M1) and B(E2) reduced transition strengths are discussed within the framework of large-scale shell model calculations to study the contribution of different particle-hole configurations, in particular for analyzing contributions from core-excited configurations.
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| 15. |
- Farget, F., et al.
(författare)
-
Transfer-induced fission in inverse kinematics: Impact on experimental and evaluated nuclear data bases
- 2015
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 51:12, s. 1-9
-
Tidskriftsartikel (refereegranskat)abstract
- Inverse kinematics is a new tool to study nuclear fission. Its main advantage is the possibility to measure with an unmatched resolution the atomic number of fission fragments, leading to new observables in the properties of fission-fragment distributions. In addition to the resolution improvement, the study of fission based on nuclear collisions in inverse kinematics beneficiates from a larger view with respect to the neutron-induced fission, as in a single experiment the number of fissioning systems and the excitation energy range are widden. With the use of spectrometers, mass and kinetic-energy distributions may now be investigated as a function of the proton and neutron number sharing. The production of fissioning nuclei in transfer reactions allows studying the isotopic yields of fission fragments as a function of the excitation energy. The higher excitation energy resulting in the fusion reaction leading to the compound nucleus Cf-250 at an excitation energy of 45MeV is also presented. With the use of inverse kinematics, the charge polarisation of fragments at scission is now revealed with high precision, and it is shown that it cannot be neglected, even at higher excitation energies. In addition, the kinematical properties of the fragments inform on the deformation configuration at scission.
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| 16. |
- Fäldt, Göran
(författare)
-
Entanglement in joint Lambda(Lambda)over-bar decay
- 2015
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 51:7
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the joint decay in the reaction . This reaction may provide information on the electromagnetic form factors of the Lambda baryon, in the time-like region. We present a conventional diagram-based calculation where production and decay steps are coherent and summations over final-state proton and anti-proton spins are performed. The resulting cross-section distribution is explicitly covariant as it is expressed in scalar products of the four-momentum vectors of the participating particles. We compare this calculation with that of the folding method which we extend and make explicitly covariant. In the folding method production and decay distributions, not amplitudes, are folded together. Of particular importance is then a correct counting of the number of possible intermediate-hyperon-spin states.
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| 17. |
- Fäldt, Göran
(författare)
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Polarization observables in the e+e- ->(Lambda)over-bar Lambda reaction
- 2016
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 52:5
-
Tidskriftsartikel (refereegranskat)abstract
- Cross-section, vector-polarization, and tensor-polarization distributions are calculated for the reactions e(+)e(-) -> (p) over barp and e(+)e(-) ->(Lambda) over bar Lambda . Each reaction requires six characteristic functions that are bilinear in the, possibly complex, electromagnetic Form factors, denoted G(E)(P-2) and G(M) (P-2), of p and A. For the hyperon reaction also the joint-decay distributions of A and A are calculated. Their knowledge allows a complete determination of the hyperon electromagnetic form factors, without measuring hyperon spins. We explain how this is done in practice. For some tensor-polarization components our results are in conflict with previously repeatedly published distributions.
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| 18. |
- Gaffney, L. P., et al.
(författare)
-
Low-energy Coulomb excitation of 62Fe and 62Mn following in-beam decay of 62Mn
- 2015
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 51:10, s. 1-9
-
Tidskriftsartikel (refereegranskat)abstract
- Sub-barrier Coulomb excitation was performed on a mixed beam of 62Mn and 62Fe, following in-trap β− decay of 62Mn at REX-ISOLDE, CERN. The trapping and charge breeding times were varied in order to alter the composition of the beam, which was measured by means of an ionisation chamber at the zero-angle position of the Miniball array. A new transition was observed at 418 keV, which has been tentatively associated to a (2+,3+)→ 1g.s. + transition. This fixes the relative positions of the β-decaying 4+ and 1+ states in 62Mn for the first time. Population of the 21 + state was observed in 62Fe and the cross-section determined by normalisation to the 109Ag target excitation, confirming the B(E2) value measured in recoil-distance lifetime experiments.
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| 19. |
- Granados, Carlos, et al.
(författare)
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The electromagnetic Sigma-to-Lambda hyperon transition form factors at low energies
- 2017
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 53:6
-
Tidskriftsartikel (refereegranskat)abstract
- Using dispersion theory the low-energy electromagnetic form factors for the transition of a Sigma to a Lambda hyperon are related to the pion vector form factor. The additionally required input, i.e. the two-pion-Sigma-Lambda amplitudes are determined from relativistic next-to-leading-order (NLO) baryon chiral perturbation theory including the baryons from the octet and optionally from the decuplet. Pion rescattering is again taken into account by dispersion theory. It turns out that the inclusion of decuplet baryons is not an option but a necessity to obtain reasonable results. The electric transition form factor remains very small in the whole low-energy region. The magnetic transition form factor depends strongly on one not very well determined low-energy constant of the NLO Lagrangian. One obtains reasonable predictive power if this low-energy constant is determined from a measurement of the magnetic transition radius. Such a measurement can be performed at the future Facility for Antiproton and Ion Research (FAIR).
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| 20. |
- Holmberg, Måns, et al.
(författare)
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The relativistic chiral Lagrangian for decuplet and octet baryons at next-to-leading order
- 2018
-
Ingår i: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 54:6
-
Tidskriftsartikel (refereegranskat)abstract
- A complete and minimal relativistic Lagrangian is constructed at next-to-leading order for SU(3) chiral perturbation theory in the presence of baryon octet and baryon decuplet states. The Lagrangian has 13 terms for the pure decuplet sector, 6 terms for the transition sector from baryon octet to decuplet and (as already known from the literature) 16 terms for the pure octet sector. The minimal field content of 25 of these terms is meson-baryon four-point interactions. 3 terms give rise to the mass splitting for baryon octet and decuplet states, respectively. 2 terms give rise to overall mass shifts. 4 terms provide anomalous magnetic moments and a decuplet-to-octet magnetic transition moment. 1 term leads to an axial vector transition moment. It is shown that meson-baryon three-point coupling constants come in at leading order whereas no additional one appears in the minimal Lagrangian at next-to-leading order. Those low-energy constants that give rise to mass splitting and magnetic moments, respectively, are determined. Predictions are provided for radiative decays of decuplet to octet baryons.
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| 21. |
- Hueyuek, Tayfun, et al.
(författare)
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Conceptual design of the early implementation of the NEutron Detector Array (NEDA) with AGATA
- 2016
-
Ingår i: European Physical Journal A. - : Springer-Verlag New York. - 1434-6001 .- 1434-601X. ; 52:3
-
Tidskriftsartikel (refereegranskat)abstract
- The NEutron Detector Array (NEDA) project aims at the construction of a new high-efficiency compact neutron detector array to be coupled with large gamma-ray arrays such as AGATA. The application of NEDA ranges from its use as selective neutron multiplicity filter for fusion-evaporation reaction to a large solid angle neutron tagging device. In the present work, possible configurations for the NEDA coupled with the Neutron Wall for the early implementation with AGATA has been simulated, using Monte Carlo techniques, in order to evaluate their performance figures. The goal of this early NEDA implementation is to improve, with respect to previous instruments, efficiency and capability to select multiplicity for fusion-evaporation reaction channels in which 1, 2 or 3 neutrons are emitted. Each NEDA detector unit has the shape of a regular hexagonal prism with a volume of about 3.23 l and it is filled with the EJ301 liquid scintillator, that presents good neutron-gamma discrimination properties. The simulations have been performed using a fusion-evaporation event generator that has been validated with a set of experimental data obtained in the Ni-58 + Fe-56 reaction measured with the Neutron Wall detector array.
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| 22. |
- IDS Collaboration, HASH(0x3dac240), et al.
(författare)
-
Beta-delayed proton emission from 20Mg
- 2016
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 52:10, s. 304-
-
Tidskriftsartikel (refereegranskat)abstract
- Beta-delayed proton emission from 20 Mg has been measured at ISOLDE, CERN, with the ISOLDE Decay Station (IDS) setup including both charged-particle and gamma-ray detection capabilities. A total of 27 delayed proton branches were measured including seven so far unobserved. An updated decay scheme, including three new resonances above the proton separation energy in 20 Na and more precise resonance energies, is presented. Beta-decay feeding to two resonances above the Isobaric Analogue State (IAS) in 20 Na is observed. This may allow studies of the 4032.9(2.4)keV resonance in 19 Ne through the beta decay of 20 Mg, which is important for the astrophysically relevant reaction 15O(?,?)19Ne. Beta-delayed protons were used to obtain a more precise value for the half-life of 20 Mg, 91.4(1.0)ms.
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| 23. |
- Jansson, Kaj, 1987-, et al.
(författare)
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Simulated production rates of exotic nuclei from the ion guide for neutron-induced fission at IGISOL
- 2017
-
Ingår i: European Physical Journal A. - : Springer. - 1434-6001 .- 1434-601X. ; 53:12
-
Tidskriftsartikel (refereegranskat)abstract
- An investigation of the stopping efficiency of fission products, in the new ion guide designed for ion production through neutron-induced fission at IGISOL in Jyväskylä, Finland, has been conducted. Our simulations take into account the new neutron converter, enabling measurements of neutron-induced fission yields, and thereby provide estimates of the obtained yields as a function of primary proton beam current. Different geometries, targets, and pressures, as well as models for the effective charge of the stopped ions were tested, and optimisations to the setup for higher yields are suggested. The predicted number of ions stopped in the gas lets us estimate the survival probability of the ions reaching the downstream measurements stations.
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| 24. |
- Jansson, Kaj, 1987-, et al.
(författare)
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The impact of neutron emission on correlated fission data from the 2E-2v method
- 2018
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 54
-
Tidskriftsartikel (refereegranskat)abstract
- The double-energy double-velocity (2E-2v) method allows assessing fission-fragment mass yields prior to and after prompt neutron emission with high resolution. It is, therefore, considered as a complementary technique to assess average prompt neutron multiplicity as a function of fragment properties. We have studied the intrinsic features of the 2E-2v method by means of event-wise generated fission-fragment data and found short-comings in the method itself as well as in some common practices of application. We find that the 2E-2v method leads to large deviations in the correlation between the prompt neutron multiplicity and pre-neutron mass, which deforms and exaggerates the so-called “sawtooth” shape of nubar(A). We have identified the treatment of prompt neutron emission from the fragments as the origin of the problem. The intrinsic nature of this deficiency risks to render 2E-2v experiments less interesting. We suggest a method to correct 2E-2v data that can even be applied on existing measurements.
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| 25. |
- Kalamara, A., et al.
(författare)
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Determination of the Ir-193(n, 2n) reaction cross section and correction methodology for the Ir-191(n, gamma) contamination
- 2019
-
Ingår i: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 55:10
-
Tidskriftsartikel (refereegranskat)abstract
- The cross section of the Ir-193(n, 2n)Ir-192 reaction has been determined by means of the activation technique, relative to the Al-27(n, alpha) and Au-197(n, 2n) reference reactions cross sections, at neutron beam energies ranging from 10 to 21 MeV. The quasi-monoenergetic neutron beams were produced at the 5.5 MV Tandem T11/25 Accelerator Laboratory of NCSR "Demokritos" via the H-2(d, n) and H-3(d, n) reactions. The induced gamma-ray activity of the irradiated target and reference foils was measured with high resolution HPGe detectors. In order to correct for the contribution of the Ir-191(n, gamma)Ir-192 reaction, which is open to low energy parasitic neutrons, a recently developed analysis method was implemented and it is presented in great detail. Furthermore, cross section theoretical calculations were carried out using the EMPIRE and TALYS codes over a wide energy range.
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