Jan 23, 2023

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.

Jan 12, 2023

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.

Jan 23, 2023

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.

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.

Jan 12, 2023

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.

Mar 10, 2023

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.

Mar 10, 2023

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.

Mar 10, 2023

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.

 

Retour en haut