scholarly journals Isomer yields in nuclear fission

2021 ◽  
Vol 256 ◽  
pp. 00002
Author(s):  
A. Al-Adili ◽  
Z. Gao ◽  
M. Lantz ◽  
A. Solders ◽  
M. Österlund ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Penning Trap ◽  
Nuclear Fission ◽  
Recent Measurement ◽  
Ion Cyclotron Resonance ◽  
Phase Imaging ◽  
Fission Process ◽  
Open Question ◽  
Spin Distributions ◽  
First Time

The generation of angular momentum in the fission process is still an open question. To shed light on this topic, we started a series of measurements at the IGISOL-JYFLTRAP facility in Finland. Highprecision measurements of isomeric yield ratios (IYR) are performed with a Penning trap, partly with the aim to extract average root-mean-square (rms) quantities of fragment spin distributions. The newly installed Phase-Imaging Ion-Cyclotron Resonance (PI-ICR) technique allows the separation of masses down to tens of keV, which is suffcient to disentangle many isomers. In this paper, we first summarize the previous measurements on the neutron and proton-induced fission of uranium and thorium, e.g. the odd cadmium and indium isotopes (119 ≤ A ≤ 127). The measurements revealed systematic trends as function of mass number, which stimulated further exploration. A recent measurement was performed at IGISIOL and several new IYR data will soon be published, for the first time. Secondly, we employ the TALYS nuclear-reaction code to model one of the newly measured isomer yields. Detailed GEF and TALYS calculations are discussed for the fragment angular momentum distribution in 134I.

scholarly journals Comparing fission-product yields from photon-induced fission of 240Pu and neutron-induced fission of 239Pu as a test of the Bohr hypothesis in nuclear fission

2020 ◽  
Vol 242 ◽  
pp. 01008
Author(s):  
Jack Silano ◽  
Anton Tonchev ◽  
Roger Henderson ◽  
Nicolas Schunck ◽  
Werner Tornow ◽  
...  
Keyword(s):  
Fission Product ◽  
Excitation Energy ◽  
Compound Nucleus ◽  
Nuclear Fission ◽  
Photon Beams ◽  
Fission Process ◽  
Product Yields ◽  
Fission Product Yields ◽  
Induced Fission ◽  
First Time

Fission product yields (FPYs) are a uniquely sensitive probe of the fission process, with well established dependence on the species of nucleus undergoing fission, its excitation energy and spin. Thus FPYs are well suited for testing Bohr’s hypothesis in the context of nuclear fission, which states that the decay of a compound nucleus with a given excitation energy, spin and parity is independent of its formation. Using FPYs, we have performed a new highprecision test of the combined effects of the entrance channel, spin and parity on the fission process from two of the most commonly used particles to induce fission neutrons and photons. The 239 Pu(n,f) reaction at En = 4.6 MeV and the 240 Pu(γ,f) reaction at Eγ = 11.2 MeV were used to produce a 240 Pu∗ compound nucleus with the same excitation energy. The FPYs from these two reactions were measured using quasimonoenergetic neutron beams from the TUNL’s FN tandem Van de Graaff accelerator and quasimonenergetic photon beams from the High Intensity γ-ray Source (HIγS) facility. The FPYs from these two reactions are compared quantitatively for the first time.

scholarly journals Study of radial motion phase advance during motion excitations in a Penning trap and accuracy of JYFLTRAP mass spectrometer

2021 ◽  
Vol 57 (11) ◽  
Author(s):  
D. A. Nesterenko ◽  
T. Eronen ◽  
Z. Ge ◽  
A. Kankainen ◽  
M. Vilen
Keyword(s):  
Mass Spectrometer ◽  
Penning Trap ◽  
Cyclotron Frequency ◽  
Phase Evolution ◽  
Radial Motion ◽  
Cluster Ions ◽  
Ion Cyclotron Resonance ◽  
Phase Imaging ◽  
Mass Measurements ◽  
Accuracy Of Measurements

AbstractPhase-imaging ion-cyclotron-resonance technique has been implemented at the Penning-trap mass spectrometer JYFLTRAP and is routinely employed for mass measurements of stable and short-lived nuclides produced at IGISOL facility. Systematic uncertainties that impose limitations on the accuracy of measurements are discussed. It was found out that the phase evolution of the radial motion of ions in a Penning trap during the application of radio-frequency fields leads to a systematic cyclotron frequency shift when more than one ion species is present in the trap during the cyclotron frequency measurement. An analytic expression was derived to correctly account for the shift. Cross-reference mass measurements with carbon-cluster ions have been performed providing the mass-dependent and residual uncertainties.

scholarly journals Employing TALYS to deduce angular momentum rootmean-square values, Jrms, in fission fragments

2020 ◽  
Vol 239 ◽  
pp. 03019
Author(s):  
A Al-Adili ◽  
A. Solders ◽  
V. Rakopoulos
Keyword(s):  
Angular Momentum ◽  
Nuclear Reaction ◽  
Fission Process ◽  
Fission Fragments ◽  
Angular Momenta ◽  
Isomeric Yield ◽  
Consistent Performance ◽  
Spin Distributions ◽  
Nuclear Applications ◽  
Do So

Fission fragments exhibit large angular momenta J, which constitutes a challenge for fission models to fully explain. Systematic measurements of isomeric yield ratios (IYR) are needed for basic nuclear reaction physics and nuclear applications, especially as a function of mass number and excitation energy. One goal is to improve the current understanding of the angular momentum generation and sharing in the fission process. To do so, one needs to improve the modeling of nuclear de-excitation. In this work, we have used the TALYS nuclear-reaction code to relax excited fission fragments and to extract root-mean-square (rms) values of initial spin distributions, after comparison with experimentally determined IYRs. The method was assessed by a comparative study on 252Cf(sf) and 235U(nth,f). The results show a consistent performance of TALYS, both in comparison to reported literature values and to other fission codes. A few discrepant Jrms values were also found. The discrepant literature values could need a second consideration as they could possibly be caused by outdated models. Our TALYS method will be refined to better comply with contemporary sophisticated models and to reexamine older deduced values in literature.

scholarly journals Radioactive ion beam manipulation at the IGISOL-4 facility

2020 ◽  
Vol 239 ◽  
pp. 17002
Author(s):  
Heikki Penttilä ◽  
Olga Beliuskina ◽  
Laetitia Canete ◽  
Antoine de Roubin ◽  
Tommi Eronen ◽  
...  
Keyword(s):  
Penning Trap ◽  
Ion Beam ◽  
Ion Source ◽  
Low Energy ◽  
Nuclear Spectroscopy ◽  
Ion Cyclotron Resonance ◽  
Phase Imaging ◽  
Laser Ion Source ◽  
Laser Ionization ◽  
Successful Operation

The IGISOL-4 facility in the JYFL Accelerator Laboratory of the University of Jyvaskyla (JYFL-ACCLAB) produces low-energy radioactive ion beams, primarily for nuclear spectroscopy, utilizing an ion guide-based, ISOL-type mass separator. Recently, new ion manipulation techniques have been introduced at the IGISOL-4 including the application of the PI-ICR (Phase-Imaging Ion Cyclotron Resonance) technique at the JYFLTRAP Penning trap, as well as commissioning of a Multi-Reflection Time-Of-Flight (MR-TOF) separator/spectrometer. The successful operation of the MR-TOF also required significant improvement of the Radio-Frequency Quadrupole (RFQ) cooler and buncher device beam pulse time structure. In addition, laser ionization techniques have been developed for particular cases, for example, a hot cavity laser ion source for silver production. A new stable isotope ion source and a beam line has been introduced for tuning and calibration purposes. In addition to the installations at the IGISOL-4 facility, the extension of the vacuum-mode recoil separator MARA (Mass Analysing Recoil Apparatus), MARA-LEB (MARA Low Energy Branch) has been under development. MARA-LEB will utilize the gas-cell technique and laser ionization to convert MeV-scale radioactive beams to low-energy ones.

VIBRATIONAL SPECTROSCOPY OF CO/Cu(211) WITH A CO TERMINATED TIP

1999 ◽  
Vol 13 (20) ◽  
pp. 709-715 ◽  
Author(s):  
FRANCESCA MORESCO ◽  
GERHARD MEYER ◽  
KARL HEINZ RIEDER
Keyword(s):  
Vibrational Spectroscopy ◽  
Scanning Tunneling Microscope ◽  
Scanning Tunneling ◽  
Rotational Mode ◽  
Tunneling Microscope ◽  
Vibrational Excitations ◽  
Translational Mode ◽  
Inelastic Tunneling ◽  
Open Question ◽  
First Time

Vibrational excitations of an isolated CO molecule adsorbed on a Cu(211) surface have been, for the first time, observed with a CO terminated scanning tunneling microscope tip. Both the frustrated translational and rotational modes were observed, and in agreement with the case of a metallic tip. The presence of a CO molecule on the tip, transferred by controlled vertical manipulation, strongly influences the frustrated translational mode of the CO molecule, while it does not affect the frustrated rotational mode. The present work demonstrates that scanning tunneling vibrational spectroscopy is also possible with a molecule at the end of the tip, opening new interesting fields of research and putting some more light on the still open question of inelastic tunneling and its selection rules.

Investigation of the synthesis of the unknown superheavy nuclei 309,312126

2019 ◽  
Vol 28 (07) ◽  
pp. 1950056 ◽  
Author(s):  
T. V. Nhan Hao ◽  
N. N. Duy ◽  
K. Y. Chae ◽  
N. Quang Hung ◽  
N. Nhu Le
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Charge Asymmetry ◽  
Evaporation Residue ◽  
Fission Process ◽  
Dinuclear System ◽  
Mass Asymmetry ◽  
Interacting Systems ◽  
First Time ◽  
Text Element

In this paper, we applied the method developed by Santhosh and Safoora in [Phys. Rev. C  94 (2016) 024623; 95 (2017) 064611] to theoretically investigate the fusion, evaporation-residue (ER) and fission cross-sections of the synthesis of the unknown superheavy [Formula: see text]126 nuclei produced by using the [Formula: see text]Ni + [Formula: see text]Cf and [Formula: see text]Zn + [Formula: see text]Cm combinations. The charge asymmetry, mass asymmetry and fissility of the DiNuclear System (DNS) in the synthesis of the mentioned combinations are also estimated. The calculated results show that the ER cross-sections for the synthesis of the [Formula: see text]126 nuclei are predicted to be much less than 1.0[Formula: see text]fb. In particular, it has been found that there may exist a valley of the ER cross-sections in the synthesis of a superheavy [Formula: see text] element, which produces the [Formula: see text]126 isotope. Subsequently, a model for the mass dependence of the ER cross-section in the synthesis of the [Formula: see text]126 isotopes has been proposed for the first time. On the other hand, the quasi-fission process strongly dominates over the fusion in the two concerned interacting systems. The present results, together with those reported in the previous studies, indicate that the investigated projectile–target combinations are not capable for the synthesis of the [Formula: see text]126 isotopes due to tiny fusion cross-sections (about 2–3[Formula: see text]zb), which go beyond the limitations of available facilities. Further studies are thus recommended to search for alternative interacting systems. In conclusion, this work provides useful information for the synthesis of the gap isotopes [Formula: see text]126, which have not been well studied up to date.

The Creation of Pakistan

2017 ◽  
Author(s):  
Ayesha Jalal
Keyword(s):  
Religious Affiliation ◽  
Self Determination ◽  
Colonial Rule ◽  
Indian Territory ◽  
Identity Based ◽  
Muslim Majority ◽  
British Colonial ◽  
The Moment ◽  
Open Question ◽  
First Time

The All-India Muslim League first voiced the demand for a Muslim homeland based on India’s northwestern and northeastern provinces in March 1940. Seven years later at the moment of British decolonization in the subcontinent, Pakistan emerged on the map of the world, an anomaly in the international community of nations with its two wings separated by a thousand miles of Indian territory. Over a million people died in the violence that accompanied partition while another 14½ million moved both ways across frontiers demarcated along ostensibly religious lines for the first time in India’s six millennia history. Commonly attributed to the age-old religious divide between Hindus, Muslims, and Sikhs, the causes of Pakistan’s creation are better traced to the federal problems created in India under British colonial rule. Despite sharing a common identity based on religious affiliation, Indian Muslims were divided along regional, linguistic, class, sectarian, and ideological lines. More Muslims live in India and Bangladesh than in Pakistan today, highlighting the clear disjunction between religiously informed identities and territorial sovereignty. Mohammad Ali Jinnah, the leader of the All-India Muslim League, tried resolving the problem by claiming in 1940 that Indian Muslims were not a minority but a nation, entitled to the principle of self-determination. He envisaged a “Pakistan” based on undivided Punjab and Bengal. Since this left Muslims in the Hindu-majority provinces out of the reckoning, Jinnah left it an open question whether “Pakistan” and Hindustan would form a confederation covering the whole of India or make treaty arrangements as two separate sovereign states. In the end Jinnah was unable to achieve his larger aims and had to settle for a Pakistan based on the Muslim-majority districts of Punjab and Bengal, something he had rejected out of hand in 1944 and then again in 1946.

scholarly journals Description of the Fission Process: Nuclear Models for Fission Dynamics

2020 ◽  
Vol 242 ◽  
pp. 03005
Author(s):  
M. Verriere ◽  
M.R. Mumpower ◽  
T. Kawano ◽  
N. Schunck
Keyword(s):  
National Security ◽  
Heavy Nucleus ◽  
First Principles ◽  
Energy Generation ◽  
Nuclear Fission ◽  
Theoretical Understanding ◽  
Fission Process ◽  
New Approaches ◽  
Nuclear Models ◽  
The Universe

Nuclear fission is the splitting of a heavy nucleus into two or more fragments, a process that releases a substantial amount of energy. It is ubiquitous in modern applications, critical for national security, energy generation and reactor safeguards. Fission also plays an important role in understanding the astrophysical formation of elements in the universe. Eighty years after the discovery of the fission process, its theoretical understanding from first principles remains a great challenge. In this paper, we present promising new approaches to make more accurate predictions of fission observables.

scholarly journals Exploring the formation by core accretion and the luminosity evolution of directly imaged planets

2019 ◽  
Vol 624 ◽  
pp. A20 ◽  
Author(s):  
Gabriel-Dominique Marleau ◽  
Gavin A. L. Coleman ◽  
Adrien Leleu ◽  
Christoph Mordasini
Keyword(s):  
Mass Star ◽  
Population Synthesis ◽  
Direct Imaging ◽  
Solar Mass ◽  
High Eccentricity ◽  
Body Dynamics ◽  
Low Mass ◽  
Open Question ◽  
Core Accretion ◽  
First Time

Context. A low-mass companion to the two-solar mass star HIP 65426 has recently been detected by SPHERE at around 100 au from its host. Explaining the presence of super-Jovian planets at large separations, as revealed by direct imaging, is currently an open question. Aims. We want to derive statistical constraints on the mass and initial entropy of HIP 65426 b and to explore possible formation pathways of directly imaged objects within the core-accretion paradigm, focusing on HIP 65426 b. Methods. Constraints on the planet’s mass and post-formation entropy are derived from its age and luminosity combined with cooling models. For the first time, the results of population synthesis are also used to inform the results. Then a formation model that includes N-body dynamics with several embryos per disc is used to study possible formation histories and the properties of possible additional companions. Finally, the outcomes of two- and three-planet scattering in the post-disc phase are analysed, taking tides into account for small-pericentre orbits. Results. The mass of HIP 65426 b is found to be mp = 9.9−1.8+1.1 MJ using the hot population and mp = 10.9−2.0+1.4 MJ with the cold-nominal population. We find that core formation at small separations from the star followed by outward scattering and runaway accretion at a few hundred astronomical units succeeds in reproducing the mass and separation of HIP 65426 b. Alternatively, systems having two or more giant planets close enough to be on an unstable orbit at disc dispersal are likely to end up with one planet on a wide HIP 65426 b-like orbit with a relatively high eccentricity (≳ 0.5). Conclusions. If this scattering scenario explains its formation, HIP 65426 b is predicted to have a high eccentricity and to be accompanied by one or several roughly Jovian-mass planets at smaller semi-major axes, which also could have a high eccentricity. This could be tested by further direct-imaging as well as radial-velocity observations.

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