The ATLAS collaboration announced at the Moriond conference the observation of simultaneous production of four top quarks. This is one of the rarest and heaviest processes ever observed at the Large Hadron Collider (LHC). This measurement, coordinated by IRFU, allows to test the Standard Model of particle physics in its most complex predictions.
Reactor antineutrino anomalies are a decade-long puzzle in neutrino physics. They are manifested by deviations of the order of a few percent between measurements and predictions. These deviations have been observed in the number of antineutrinos measured by more than a dozen experiments at nuclear reactors, and in the shape of the kinetic energy distributions by the seven most recent ones. They could have been the way to a new physics beyond the standard model, but the recent experiments, including the STEREO experiment carried by IRFU, have closed this door.
In a work just published in Physical Review Letter [1], a team of physicists from IRFU and the Laboratoire National Henri Becquerel of DRT have shown that these anomalies could come from biases in the measurements of fission electrons used as a reference for the prediction. They have developed a beta strength function model to reduce the biases in the calculation of the energy spectra of electrons from fission of fissile reactor nuclei. The two "anomalies" on the antineutrino flux and the "bump" at 5 MeV in the antineutrino energy spectrum are now reproduced by their model. This allows to propose an explanation to solve an enigma of more than 10 years.
The final results of the Stereo experiment have just been published in the journal Nature. A record of precision is established for the spectrum of neutrinos emitted by the fission of 235U, measured between 9 and 11m distance from the ILL reactor core in Grenoble. The hypothesis of a sterile neutrino to explain the reactor neutrino anomaly is rejected. The quality of these direct neutrino measurements now surpasses that of the underlying nuclear data describing the beta decays of fission products. Stereo provides the community with a fission neutrino spectrum corrected for all detection effects, which will serve as a reference for future reactor experiments and points out residual biases in the nuclear databases.
The Stereo experiment has just completed a beautiful scientific adventure that began in 2011 with the revelation by the IRFU group of the "reactor antineutrino anomaly". Physicists were left with a significant deficit of 6% between the flux of neutrinos measured at the reactors and the predicted flux. The history of science has taught us enough about the potential richness of new phenomena that can hide behind an anomaly. What was going on here was the possible existence of a new type of neutrino that would open up a new area of physics beyond the standard model. Without any direct interaction with matter, this neutrino, described as "sterile", could however mix with "standard" neutrinos and thus leave an imprint of its existence through ... a deficit of count rate in our detectors.
Reactor antineutrino anomalies are a decade-long puzzle in neutrino physics. They are manifested by deviations of the order of a few percent between measurements and predictions. These deviations have been observed in the number of antineutrinos measured by more than a dozen experiments at nuclear reactors, and in the shape of the kinetic energy distributions by the seven most recent ones. They could have been the way to a new physics beyond the standard model, but the recent experiments, including the STEREO experiment carried by IRFU, have closed this door.
In a work just published in Physical Review Letter [1], a team of physicists from IRFU and the Laboratoire National Henri Becquerel of DRT have shown that these anomalies could come from biases in the measurements of fission electrons used as a reference for the prediction. They have developed a beta strength function model to reduce the biases in the calculation of the energy spectra of electrons from fission of fissile reactor nuclei. The two "anomalies" on the antineutrino flux and the "bump" at 5 MeV in the antineutrino energy spectrum are now reproduced by their model. This allows to propose an explanation to solve an enigma of more than 10 years.
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.
The final results of the Stereo experiment have just been published in the journal Nature. A record of precision is established for the spectrum of neutrinos emitted by the fission of 235U, measured between 9 and 11m distance from the ILL reactor core in Grenoble. The hypothesis of a sterile neutrino to explain the reactor neutrino anomaly is rejected. The quality of these direct neutrino measurements now surpasses that of the underlying nuclear data describing the beta decays of fission products. Stereo provides the community with a fission neutrino spectrum corrected for all detection effects, which will serve as a reference for future reactor experiments and points out residual biases in the nuclear databases.
The Stereo experiment has just completed a beautiful scientific adventure that began in 2011 with the revelation by the IRFU group of the "reactor antineutrino anomaly". Physicists were left with a significant deficit of 6% between the flux of neutrinos measured at the reactors and the predicted flux. The history of science has taught us enough about the potential richness of new phenomena that can hide behind an anomaly. What was going on here was the possible existence of a new type of neutrino that would open up a new area of physics beyond the standard model. Without any direct interaction with matter, this neutrino, described as "sterile", could however mix with "standard" neutrinos and thus leave an imprint of its existence through ... a deficit of count rate in our detectors.
Using the James Webb Space Telescope, a group of astronomers led by MPIA, in collaboration with a team from the Astrophysics Department of CEA Paris-Saclay, searched for an atmosphere on the rocky exoplanet TRAPPIST-1 c. Although the planet is almost identical to Venus in terms of size and mass, its atmosphere turned out to be very different. By analyzing the heat emitted by the planet, they concluded that it may have only a tenuous atmosphere containing a minimum of carbon dioxide. However, this is also consistent with a barren rocky planet devoid of any significant atmosphere. This work gives us a better understanding of how the atmospheres of rocky planets orbiting low-mass stars can withstand strong stellar winds and intense UV radiation.
The results are presented in the journal Nature:
Discovered in 2009, exoplanet GJ1214b orbits a small star just 40 light-years away. With a mass around six times that of Earth and an atmosphere made up of hydrogen and helium, it is considered a "mini-Neptune".
A team from NASA, in collaboration with researchers from CEA Paris-Saclay, pointed the JWST at the planet using the MIRI instrument, built by CEA Paris-Saclay, for some 40 hours. This unprecedented observation made it possible to obtain, for the first time, the phase curve of an exoplanet with MIRI, i.e. complete tracking of the planet's rotation around its star.
By following the evolution of the exoplanet-star system's emission, the research team was able to determine the planet's temperature to within 9°: 280°C on the dayside and 164°C on the night side. Comparing the observations with atmospheric models, the researchers deduce that: 1. the small temperature difference between the two sides, despite the planet's synchronous rotation, means that there is a good exchange of energy between the sides, due to a dense atmosphere. 2. The relatively low temperature on the dayside, given the planet's proximity to its star, indicates that a layer of aerosols in the exoplanet’s upper atmosphere reflects much of the stellar radiation. The type of aerosol with such a property has yet to be determined. 3. The atmosphere contains many elements heavier than hydrogen and helium, probably abundant water.
The results are published in the prestigious journal Nature
The European Research Council has just announced the names of the winners of the Advanced Grant. This 2023 edition rewards in particular two researchers from the CEA's fundamental research department for their work in the fields of astrophysics and neuroscience. Anaëlle Maury is the leader of the PEBBLES project. This project consists of developing an innovative methodology to characterise the properties of dust around very young stars in the process of forming their proto-planetary disks. Dust is one of the key elements in the physical processes regulating the formation of stars and their planetary systems, but recent observations are overturning the models used until now to describe its evolution from submicron grains to pebbles. Observing and modelling the properties of dust grains during the earliest phases of disk formation promises to provide important insights into the conditions leading to the formation of solar systems such as our own. Through PEBBLES, the teams will use new dust models that are better suited to denser astrophysical environments and will use them in comparison with observations from space missions and ground-based observatories from the infrared to the millimetre range.
An international team of researchers has used NASA's James Webb Space Telescope to measure the temperature of the rocky exoplanet TRAPPIST-1 b. This is the world's first detection of thermal emission from a rocky exoplanet as small and “cool” as the rocky planets in our own solar system. TRAPPIST-1 b receives about twice the amount of energy as Venus receives from the Sun and four times more than Earth. The result indicates that the dayside of the planet has a temperature of about 227°C (500 K) and suggests that it has no significant atmosphere. The study, co-authored by three researchers from the Dap, has just been published in the journal Nature, on Monday 27 March.
Magnetars are neutron stars known for their wide variety of electromagnetic emissions coming from the dissipation of their extreme magnetic fields, which are the strongest known in the Universe and can reach 1015 Gauss, or 10 billion times that of the strongest magnet created by humans.
How could these magnetic fields have been formed? This is one of the open questions that a Franco-German team led by the supernovae team of the Department of Astrophysics (DAp) of CEA Paris-Saclay, has recently tried to answer by proposing a numerical modeling of a new scenario of formation of magnetars in a study published in the scientific journal "Astronomy and Astrophysics".
This scenario suggests that the matter falling on the neutron star a few seconds after its formation can trigger a dynamo effect called Tayler-Spruit which would amplify its magnetic field, and this independently of its initial rotation speed. The simulations of this scenario reproduces the measured intensity of magnetar magnetic fields. Therefore, this study represents another step towards the understanding these atypical objects.
CEA has delivered to CNES the flight version of the ECLAIRs instrument software for the SVOM satellite. This concludes a major instrumental development phase conducted by CEA over a period of 6 years to produce what is maybe one of the most complex software packages ever carried on a French scientific space instrument. The latest version of the software equips the ECLAIRs onboard computer, which departed to China in early 2023. It will be used during the satellite integration tests in Shanghai in preparation for the launch planned for early 2024. This software will analyse in real time the data from the instrument in flight, in order to detect gamma-ray bursts and localise them to better than 12 arcmin on the sky, to reorient automatically the satellite for follow-up observations, and to alert the scientific community.
Large ground-based telescopes with mirrors over 8 m in diameter1 use azimuthal mounts to point the stars. When tracking a star, the Earth's rotation causes the observed field on the astrophysics detector to rotate, creating "spun" images. To correct this effect, the instruments mounted on these telescopes use a "field derotator", a mechanism whose main function is to rotate a set of mirrors at very low speed and with very high precision. For the METIS instrument, CEA-Irfu has developed one of the world's very first2 derotators operating at -210°C. Entirely designed, developed and tested by the Irfu Systems Engineering Department, the METIS derotator drive achieves performance beyond the expected specifications. Currently in the testing phase, its qualification will be completed by the end of 2023 at ESO in Garching, Germany.
While the use of field derotation mechanisms is relatively common in ground-based astrophysics instruments, most scientific communities choose to place this mechanism upstream of the cryogenic instrument, so that it operates at ambient temperature. Doing this way, the required levels of accuracy (of the order of a few thousandths of a degree) are achieved using 'standard' components such as motorised stages, optical encoders, ball bearings and lubricated gearboxes.
To reduce the instrumental background noise, the METIS instrument of the future ELT will be entirely cooled down to temperatures around -210°C, so the field derotation mechanism will also have to operate at these temperatures in vacuum.
The commissioning of the 11.7 T Iseult MRI in 2021 crowned almost 20 years of AOC research and development. In an article published in the journal Magnetic Resonance Materials in Physics, Biology and Medicine, Nicolas Boulant and Lionel Quettier, Iseult project leaders for the CEA's Joliot and Irfu Institutes, review the details of this commissioning.
CEA has delivered to CNES the flight version of the ECLAIRs instrument software for the SVOM satellite. This concludes a major instrumental development phase conducted by CEA over a period of 6 years to produce what is maybe one of the most complex software packages ever carried on a French scientific space instrument. The latest version of the software equips the ECLAIRs onboard computer, which departed to China in early 2023. It will be used during the satellite integration tests in Shanghai in preparation for the launch planned for early 2024. This software will analyse in real time the data from the instrument in flight, in order to detect gamma-ray bursts and localise them to better than 12 arcmin on the sky, to reorient automatically the satellite for follow-up observations, and to alert the scientific community.
Low-temperature superconducting materials are widely used in high-field magnets, but their behaviour is closely related to the strains they undergo. Consequently, studies on the impact of stress on mechanical structures are essential. The SUPRAMITEX project is participating in this research effort by using the AMITEX-FFTP parallel code developed as part of the SIMU/MATIX project to carry out non-linear mechanical simulations on heterogeneous microstructures. This work has shown the interest of the AMITEX code to simulate the mechanical behaviour of these components, at different scales, for elastic and elasto-plastic behaviours at simulation scales that were previously unattainable.
The commissioning of the 11.7 T Iseult MRI in 2021 crowned almost 20 years of AOC research and development. In an article published in the journal Magnetic Resonance Materials in Physics, Biology and Medicine, Nicolas Boulant and Lionel Quettier, Iseult project leaders for the CEA's Joliot and Irfu Institutes, review the details of this commissioning.
The recent update of the European Strategy for Particle Physics recommended a feasibility study for the future generation of collider. In this context, the Laboratory Directors Group, of which IRFU is a member, has been mandated by the CERN Council to oversee the development of an accelerator R&D roadmap. One of the objectives of this roadmap is the development of technologies for the manufacture of high-field superconducting magnets, essential for future colliders: this is the HFM (High Field Magnets) project.
The MADMAX project, which was launched in November 2016, is led by the Max Planck Institut für Physik in collaboration with several European institutes. The goal of the project is the discovery of axions with a mass of about 100 µeV, potential candidates for dark matter. To detect these axions, it is necessary to develop a specific detector consisting of an electromagnetic signal amplifier and a magnet proportional to the size of the amplifier and delivering a strong magnetic field. In order to validate the innovations in the fabrication of the magnet conductor, its cooling concept and the quench detection, a demonstrator has been designed, fabricated, integrated and tested between March 2020 and August 2021. It is named MACQU for MADMAX Coil for Quench Understanding. The entire design, from the conductor to the support structure, including the MACQU magnet, its thermal shield and the busbars, was carried out at the CEA. The demonstrator, manufactured by the industrial Bilfinger Noell GmbH, arrived in March 2021 and was successfully tested between May 18 and August 27, 2021. The analysis of the data now completed provides the desired answers and opens up unexpected new avenues of work. The feasibility of the cable concept, its cooling as well as the quench detection for the MADMAX magnet was demonstrated during these tests.
The commissioning of the 11.7 T Iseult MRI in 2021 crowned almost 20 years of AOC research and development. In an article published in the journal Magnetic Resonance Materials in Physics, Biology and Medicine, Nicolas Boulant and Lionel Quettier, Iseult project leaders for the CEA's Joliot and Irfu Institutes, review the details of this commissioning.
Low-temperature superconducting materials are widely used in high-field magnets, but their behaviour is closely related to the strains they undergo. Consequently, studies on the impact of stress on mechanical structures are essential. The SUPRAMITEX project is participating in this research effort by using the AMITEX-FFTP parallel code developed as part of the SIMU/MATIX project to carry out non-linear mechanical simulations on heterogeneous microstructures. This work has shown the interest of the AMITEX code to simulate the mechanical behaviour of these components, at different scales, for elastic and elasto-plastic behaviours at simulation scales that were previously unattainable.
The recent update of the European Strategy for Particle Physics recommended a feasibility study for the future generation of collider. In this context, the Laboratory Directors Group, of which IRFU is a member, has been mandated by the CERN Council to oversee the development of an accelerator R&D roadmap. One of the objectives of this roadmap is the development of technologies for the manufacture of high-field superconducting magnets, essential for future colliders: this is the HFM (High Field Magnets) project.
The MADMAX project, which was launched in November 2016, is led by the Max Planck Institut für Physik in collaboration with several European institutes. The goal of the project is the discovery of axions with a mass of about 100 µeV, potential candidates for dark matter. To detect these axions, it is necessary to develop a specific detector consisting of an electromagnetic signal amplifier and a magnet proportional to the size of the amplifier and delivering a strong magnetic field. In order to validate the innovations in the fabrication of the magnet conductor, its cooling concept and the quench detection, a demonstrator has been designed, fabricated, integrated and tested between March 2020 and August 2021. It is named MACQU for MADMAX Coil for Quench Understanding. The entire design, from the conductor to the support structure, including the MACQU magnet, its thermal shield and the busbars, was carried out at the CEA. The demonstrator, manufactured by the industrial Bilfinger Noell GmbH, arrived in March 2021 and was successfully tested between May 18 and August 27, 2021. The analysis of the data now completed provides the desired answers and opens up unexpected new avenues of work. The feasibility of the cable concept, its cooling as well as the quench detection for the MADMAX magnet was demonstrated during these tests.
On 23 June 2023, GANIL (Grand Accélérateur National d'Ions Lourds), one of the world's leading laboratories for research using ion beams, obtained building permission for the future DESIR experimental room, part-funded by an Equipex. The permit authorises the launch of construction work, starting with deep earthworks in July 2023, with the aim of taking delivery of the building in spring 2025. The first experiments are expected by 2027, providing the nuclear physics, fundamental interaction physics and nuclear astrophysics communities with a unique and internationally competitive research platform.
The MADMAX project, which was launched in November 2016, is led by the Max Planck Institut für Physik in collaboration with several European institutes. The goal of the project is the discovery of axions with a mass of about 100 µeV, potential candidates for dark matter. To detect these axions, it is necessary to develop a specific detector consisting of an electromagnetic signal amplifier and a magnet proportional to the size of the amplifier and delivering a strong magnetic field. In order to validate the innovations in the fabrication of the magnet conductor, its cooling concept and the quench detection, a demonstrator has been designed, fabricated, integrated and tested between March 2020 and August 2021. It is named MACQU for MADMAX Coil for Quench Understanding. The entire design, from the conductor to the support structure, including the MACQU magnet, its thermal shield and the busbars, was carried out at the CEA. The demonstrator, manufactured by the industrial Bilfinger Noell GmbH, arrived in March 2021 and was successfully tested between May 18 and August 27, 2021. The analysis of the data now completed provides the desired answers and opens up unexpected new avenues of work. The feasibility of the cable concept, its cooling as well as the quench detection for the MADMAX magnet was demonstrated during these tests.
