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Division of Electronics, Detectors and Computing for Physics (DEDIP)

Institute of Research into the Fundamental Laws of the Universe

« The Nuclear Physics Division

Observation of the unstable oxygen-28 nucleus

Feb 08, 2024

Observation of the unstable oxygen-28 nucleus

Exotic, very neutron-rich nuclei: a laboratory for nuclear interactions

For the first time, an experiment has provided key observations on the spectroscopy of the neutron-rich unbound oxygen nuclei (proton number Z = 8), oxygen 28 (N = 20) and its neighboring isotope at N = 19, oxygen 27. They were produced in high-energy reactions and observed by direct detection of their decay products, 24O and three or four neutrons.

Jan 22, 2024

Modeling reactor antineutrino spectra: a major step forward!

A comprehensive revision of the summation method lays new and solid foundations for the calculation of antineutrino spectra emitted by a nuclear reactor. This major advance sheds new light on the origin of the reactor antineutrino anomalies, and will be

Supported by CEA's "digital simulation" cross-disciplinary program, Irfu, the Laboratoire National Henri Becquerel of DRT and the Service d'Étude des Réacteurs et de Mathématiques Appliquées of DES teamed up to carry out a thorough review of calculations of antineutrino spectra from nuclear reactors.

Modeling reactor antineutrino spectra: a major step forward!

Mapping the configuration of neutrons in the nuclear halo

May 30, 2023

Mapping the configuration of neutrons in the nuclear halo

The final piece of a longstanding adventure started in 2014 with an experiment led by Irfu and RIKEN Nishina Center has been set with the publication of a paper containing the comparative study of dineutron correlation in 11Li, 14Be and 17B [1]. This paper published in Phys. Lett. B completes a series of publications on the topic [2,3] issued from the same experiment using the MINOS device designed and built at Irfu. It suggests that such kind of correlations is a universal feature of Borromean halo nuclei.

Apr 13, 2023

Ab initio description of collective excitations in doubly open-shell nuclei

Prediction of nuclear properties based on a realistic description of the strong interaction is the main quest of low-energy nuclear theory. One of the issues lies is the cost of solving Schrödinger’s equation that scales exponentially with the number of nucleons. Consequently, theoretical predictions based on first principles have long been limited to very light nuclei, to nuclei with specific proton and neutron numbers offering simplifications or to their ground states.

Ab initio description of collective excitations in doubly open-shell nuclei

Imaging nuclei with relativistic ion collisions

Nov 07, 2022

Imaging nuclei with relativistic ion collisions

A new window into the deformation of nuclei has been recently opened with the realisation that nuclear collision experiments performed at high-energy colliders, such as the BNL Relativistic Heavy Ion Collider (RHIC) or the CERN Large Hadron Collider (LHC), give access to the shape of the colliding isotopes.

Oct 13, 2022

First measurement of the pygmy resonance using neutron inelastic scattering reaction at GANIL-SPIRAL2 NFS

The pygmy dipole resonance (PDR) is a vibrational mode of the nucleus that occurs in neutron-rich nuclei. It is described as the oscillation of a neutron skin against a core symmetric in number of protons and neutrons (Figure 1). The PDR has been the subject of numerous studies, both experimental and theoretical.

First measurement of the pygmy resonance using neutron inelastic scattering reaction at GANIL-SPIRAL2 NFS

A glimpse of nuclear couple through transparent nuclei

Jun 24, 2021

A glimpse of nuclear couple through transparent nuclei

DPhN physicists have played a decisive role in the first measurement of pairs of nucleons using a new method, that will pave the way to the study of short range interactions in radioactive nuclei.

Nucleons are social particles. Not only do they enjoy living in communities inside nuclei, but they also form couples within these communities. Indeed, one can observe protons and neutrons forming pairs inside nuclei. DPhN physicists have played a decisive role in the first measurement of such pairs of nucleons using a new method, that will pave the way to the study of these close (or short range) interactions in radioactive nuclei. The results have recently been published in Nature Physics [Pat21].

Jun 04, 2021

GLAD and COCOTIER : IRFU cryogenics at GSI

Two state-of-the-art instruments, GLAD and COCOTIER, were designed and built at Irfu in the last few years and are now operational in the R3B experimental room of the GSI heavy ion accelerator (Darmstadt, Germany). Both are intended to be part of the equipment that will be used at FAIR, the new machine under construction at the GSI site. GLAD is a large acceptance spectrometer for the analysis of relativistic radioactive heavy ion beam reactions.

GLAD and COCOTIER : IRFU cryogenics at GSI

SIRIUS, the faithful companion of S3

May 19, 2021

SIRIUS, the faithful companion of S3

IRFU engineers and physicists and their collaborators have just completed the development of a modern Sirius, a key element of the super spectrometer separator (S³) under construction at GANIL.

The ancients understood that heroes, like Orion with Sirius, need their faithful companion. IRFU engineers and physicists and their collaborators are no exception to the rule and have just completed the development of a modern Sirius, a key element of the super spectrometer separator (S3) under construction at GANIL. The tests having been successful and the system has been moved to GANIL for its final installation.

Apr 14, 2021

A distorting nuclear mirror

Two “mirror” nuclei, in which the numbers of neutrons and protons are interchanged, have markedly different shapes—a finding that defies current nuclear theories. This striking result has been obtained by Irfu researchers in collaboration with an international team and has been recently published in Physics Review Letter [1] and highlighted as editor’s suggestion [2].

A distorting nuclear mirror

Investigation in the mendelevium - lawrencium family: true or false twins?

Aug 20, 2020

Investigation in the mendelevium - lawrencium family: true or false twins?

The spectroscopy of a mendelevium isotope, 251Md composed of 101 protons and 150 neutrons, reveals a surprise: when it rotates, it behaves exactly like a lawrencium isotope made of 103 protons and 152 neutrons. The experiment carried out at the University of Jyväskylä in Finland required the most advanced tools to study these rare and ephemeral nuclei: filtering and identification of the nuclei, gamma ray and electron detection.

May 29, 2020

Heavy elements: how state-of-the-art electronics brings answer on longstanding questions

The simple question “Where does the Periodic Table end?” has excited scientific interest for a long time. In this context, understanding the structure of the heaviest nuclei, and through it their stability, is of major importance. A decade ago, there was no promising path to tackle this scientific quest.

Heavy elements: how state-of-the-art electronics brings answer on longstanding questions

Nuclear-physics and quantum-chemistry theoreticians join forces to accurately predict the properties of the atomic nucleus

Jun 07, 2019

Nuclear-physics and quantum-chemistry theoreticians join forces to accurately predict the properties of the atomic nucleus

Predicting properties of, e.g., molecules or atomic nuclei from first principles requires to solve the Schrödinger equation with high accuracy. The computing cost to find exact solutions of the Schrödinger equation scales exponentially with the number of particles constituting the system. Thus, with nuclei composed of tens or hundreds of nucleons, it necessitates accurate approximate methods of lower computing cost.

May 22, 2019

New Cross-Section Measurements Reveal Surprising Importance of Pairing

Pairing is ubiquitous in physics. From superconductivity to quantum shell structure, coupling particles into pairs is one of nature's preferred ways to lower the energy of a system. New results obtained at the Radioactive Isotope Beam Factory (RIBF, Japan) with the MINOS device, which was conceived and constructed at Irfu, show for the first time that pairing also plays an important role in single-proton removal reactions from neutron-rich nuclei.

New Cross-Section Measurements Reveal Surprising Importance of Pairing

The exotic 78Ni joins the closed club of the few doubly-magic nuclei

May 02, 2019

The exotic 78Ni joins the closed club of the few doubly-magic nuclei

An international collaboration led by the institutes of CEA-IRFU and of RIKEN (Japan) demonstrates, for the first time, the exceptional stability of the very-neutron rich nickel-78 nucleus and its doubly-magic character. The experiment at RIKEN was made possible by the unique combination of the MINOS device developed at CEA-Irfu and the very exotic beams produced by the RIBF facility of the Japanese accelerator.These results are published in Nature [Nat19].

Jan 24, 2019

How to describe nuclear properties ab initio at a low computational cost?

Prediction of nuclear properties based on a realistic description of the strong interaction is at the heart of the ab initio endeavor in low-energy nuclear theory. Ab initio calculations have long been limited to light nuclei or to nuclei with specific proton and neutron numbers. Theoreticians from Irfu/DPhN have developed a new ab initio method from which properties of many more nuclei than before can be predicted while drastically decreasing the computational cost.

How to describe nuclear properties ab initio at a low computational cost?

Zirconium-98, a three-faceted nucleus

Nov 20, 2018

Zirconium-98, a three-faceted nucleus

During an experiment carried out at GANIL in Caen (France), an international team, led by researchers from Irfu and the University of Oslo, studied the shape of the Zirconium-98 nucleus. The shape of a nucleus corresponds to the area where its protons and neutrons can be found. Understanding it means mastering the behaviour of each proton/neutron and their arrangement related to the nuclear force. The objective was to determine the shape of the nucleus in different excited states.

Sep 21, 2018

The first triplet of superconducting multipoles of the S3 spectrometer arrived in Ganil

The first triplet of superconducting multipoles of the S3 Super Separator Spectrometer arrived at Ganil on August 29, 2018. S3 is one of the experiment rooms of the Spiral2 facility. The magnet, with a mass of 2.8 tonnes, is 1.8 m long and almost as high. This innovative type of magnet is very compact despite the number of optical functions it can generate (quadrupole, sextupole, octupole and dipole). It is the first of a series of seven to be delivered to the Ganil.

The first triplet of superconducting multipoles of the S3 spectrometer arrived in Ganil

Highlighting shell effects in the quasi-fission process: an essential step for the synthesis of new super-heavy elements!

Feb 02, 2018

Highlighting shell effects in the quasi-fission process: an essential step for the synthesis of new super-heavy elements!

During an experiment carried out at the accelerator of the Australian National University (Canberra, Australia), a French-Australian collaboration (GANIL Caen, IPN Orsay, IRFU/DPhN Saclay, ANU Canberra) first identified the fragments created in quasi-fission reactions with atomic numbers Z up to plutonium (Z=94) and mass A. For this study, near-fission reactions were induced during collisions between 48Ti projectile ions, accelerated to 276 MeV, and target atoms of 238U.

Jun 14, 2017

Competing shapes in the neutron-rich Krypton isotopes

An international team has performed the first spectroscopy of the very neutron-rich isotopes 98,100 Kr. The collaboration, led by scientists from the CEA Irfu and RIKEN (Japan) included several European groups and physicists from IPN-Orsay. This experiment showed that there are two coexisting quantum configurations at low excitation energy in the 98Kr nucleus.

Competing shapes in the neutron-rich Krypton isotopes

Neither a Sphere nor a Pyramid: an Ellipsoid!

Jan 24, 2017

Neither a Sphere nor a Pyramid: an Ellipsoid!

An international team led by IRFU and the Japanese research institute RIKEN was able to study the structure of a neutron-rich zirconium nucleus (110Zr)—a first, calling certain models into question. Produced by an accelerator at RIKEN and measured by the MINOS detector, this heavy nucleus proves to be more deformed than expected.

Aug 04, 2016

Radii and masses of oxygen isotopes: a puzzle for nuclear forces

A comparison between experiment and theory on the ground state observables of the oxygen nuclei

The comparison of ab initio calculations and experimental data was the subject of original work initiated by physicists from the Nuclear Physics Department of the CEA-Saclay: for the first time, this study combines two types of fundamental observables of the nucleus: mass (binding energy of the fundamental state) and size in terms of nuclear radius, in the form of the mean square radius of the density of matter (all nucleons, protons and neutrons), and the proposed comparison is extended to the most neutron-rich isotopes.

Radii and masses of oxygen isotopes: a puzzle for nuclear forces

Exploring the most exotic nuclei with MINOS

Nov 02, 2015

Exploring the most exotic nuclei with MINOS

The "exotic" nuclei pose the challenge of a universal description of the nuclear structure and raise the question of the evolution of the shell structure. An IRFU team has developed the Magic Number Off Stability (MINOS) project to answer these questions.

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