Jan 16, 2023
After several years of development at Saclay, the first part of the Falstaff spectrometer was moved to GANIL in 2021 and then installed on NFS for the study of uranium 235. The experiment that took place in November and December 2022 was the first to use an actinide target on SPIRAL2. It demonstrated the good performance of this device.
Dec 13, 2022
Nucleons (protons or neutrons) are the constituents of the nucleus of atoms. The exploration of their internal structure is traditionally done by determining "form factors". These quantities are accessible through the study of elastic electron-proton scattering and electron-positron annihilation reactions into proton-antiproton (or the time reverse reaction of proton-antiproton annihilation into electron-positron).
Nov 07, 2022
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
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.
Sep 22, 2022
The first measurement of Short-Range Correlations (SRC) in an exotic nucleus took place in May 2022 with the Cocotier instrument at the GSI facility in Darmstadt, Germany. This experiment is a milestone in the program that was started in 2017 with a grant from the French Research Agency that allowed physicists to build a liquid hydrogen target (see previous highlight). The goal of this experiment is to test the hypothesis that nucleon can form compact pair, the so-called SRC pair.
Jun 17, 2022
The DPhN, in collaboration with the Department of Reactor Studies of Cadarache (DES) and the Institute of Particle and Nuclear Physics of Charles University in Prague (Czech Republic), studied the properties of gamma rays emitted by uranium isotopes during neutron capture reactions. Gamma-ray spectra measured at CERN's n_TOF facility were used as a test bed for nuclear reaction models and their ingredients, including the photon strength function that characterises the ability of a nucleus to emit or absorb photons.
Mar 03, 2022
The objective of the realization of efficient compact neutron sources is to make it possible to perform neutron scattering experiments, with practically the same qualities as those carried out with neutron beam lines from research reactors of the Orphée type*. These compact sources are obtained from a protons beam of medium-energy (3-50 MeV) and high current (100 mA) impinging on a light element target as beryllium. This interaction creates a neutron emission.
Jun 24, 2021
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
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.
May 25, 2021
Since 2010 the question of the size of the proton is at the heart of a controversy between atomic physicists and hadronic physicists. Indeed, very precise measurements of atomic physics have concluded that the size of the proton is much smaller than expected, in very strong disagreement with the experiments of elastic scattering. In collaboration with the University of Perugia, a physicist from IRFU has investigated to find the reason for such a difference.
May 19, 2021
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
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].
Dec 15, 2020
In December 2019, the NFS (Neutrons For Science) facility received its first proton beams, delivered by the linear accelerator of the new Spiral2 facility at the GANIL. On the fringes of the progressive commissioning of the accelerator in 2020, short beam periods were used to successfully test several NFS components. The first experiments are planned at the facility in the fall of 2021.
Dec 08, 2020
In 2016, the announcement of the first direct detection of gravitational waves opened a new window of observation to probe our universe in a new way. The LISA (Laser Interferometer Space Antenna) space observatory promoted by ESA (European Space Agency) will allow the direct detection of gravitational waves undetectable by terrestrial interferometers.
Aug 20, 2020
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.
Jul 23, 2020
Meteorites are bombarded throughout their journey by cosmic radiation. This cosmic ray exposure (CRE) is a formidable footprint of their history, provided of course that we know how to decipher it. The interaction of cosmic radiation with the atomic nuclei constituting the meteorite will produce so-called cosmogenic isotopes, very often radioactive.
Jul 21, 2020
The combination of the AGATA multi-detector [right] and the VAMOS spectrometer [left] showed that the balance between the two contributions was more complex than previously envisaged.
Jul 02, 2020
The 2020 edition of the Large Hadron Collider Physics Conference (LHCP) took place from 25 to 30 May 2020. Due to the COVID-19 pandemic, the conference, originally planned to be hosted in Paris, was held entirely online.
Jun 08, 2020
After more than four years of research and development, design and manufacturing work, the MFT (Muon Forward Tracker), a new detector that will equip the ALICE experiment at the LHC, has seen its construction finalized and is currently under commissioning at CERN.
Apr 29, 2020
Nucleons (protons and neutrons), the components of the atomic nucleus, can be polarized. This means that their spins are preferentially aligned along a quantization axis. The spin is a quantum property of a particle and has its classical analogue in a spinning top. The strong interaction that acts among nucleons in the atomic nucleus is sensitive to the polarization.
Mar 10, 2020
INCL (Liège intranuclear cascade) is a simulation code known for its ability to model light particle-nucleus interactions. It is used in very various fields, such as proton therapy, neutron sources, radioactive ion beams or ADS's (Accelerator Driven Systems). In order to extend its capabilities in the field of higher energy reactions, in connection with cosmic rays or with the study of hypernuclei, a team of physicists led by Irfu has recently developed a new version of the code involving strange particles.
Oct 30, 2019
The FIFRELIN code simulates nuclear fission and de-excitation of the nuclei produced therein. STEREO is a compact neutrino detector that looks for a hypothetical sterile neutrino. Two a priori separate topics developed at CEA, the first at DEN, the second at DRF/Irfu, which have however recently met to achieve unprecedented precision on a crucial ingredient in the detection of neutrinos: the de-excitation of a gadolinium nucleus after the capture of a neutron.
Sep 25, 2019
It is possible to trace the shape of a drum from its vibration modes. Similarly, it is possible to measure the 3D structure of the proton and access its elementary components, quarks and gluons, from observables obtained using deeply virtual Compton scattering experiments off the proton.  By studying this scattering process, we can access this geometric information. This research topic is very active and mobilizes a large international theoretical and experimental community.
Aug 07, 2019
The series of Jefferson Laboratory (USA) experiments dedicated to the measurement of electron-proton elastic scattering showed that the extracted information on the proton structure did not agree when extracted from two kinds of experiments. To reconcile these results, it was suggested that, beyond the exchange of one photon, that is the dominant mechanism, the exchange of a second photon could become important.
Jun 07, 2019
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
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.
May 15, 2019
The predictions of nuclear properties based on a realistic description of the strong interaction is at the heart of the ab initio endeavour 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 novel ab initio methods that led to a significantly increase of the number of nuclei that can be accessed.
May 02, 2019
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].  
Mar 21, 2019
The STEREO experiment releases new results based on the detection of about 65000 neutrinos at short distance from the research reactor of the ILL-Grenoble. The improved accuracy is rejecting the hypothesis of a 4th neutrino in a large fraction of the domain predicted from the reactor neutrino anomaly. Profiting from a good control of the detector response, STEREO now also releases its first absolute measurements of the neutrino rate and the spectrum shape.
Jan 24, 2019
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.

 

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