Jun 28, 2021

As part of the luminosity increase of the Large Hadron Collider (LHC), the first phase of the ATLAS experiment upgrade is coming to an end, before a restart planned for early 2022. To meet the requirements of physics in a highly radiative environment with a high particle flux, the two internal wheels of the muon spectrometer will be replaced by new devices: the New Small Wheels (NSW).
After several years of R&D and production, IRFU has just sent the last of the 32 detection modules that will be integrated into the NSW at CERN. This corresponds to the assembly of about 400 m2 of gas detectors based on Micromegas technology: a record!

Apr 15, 2021

The muon spectrometer of the ATLAS experiment has been an important contribution of IRFU since the design, and IRFU is still in charge of the alignment today. The spectrometer plays a key role in the reconstruction of high-energy muons, the detection of which is crucial for the search of phenomena beyond the Standard Model. The spectrometer consists of about 1200 muon chambers that form a gigantic edifice 44 m long and 24 m in diameter. Despite these imposing proportions, the relative positions of the chambers must be known with an accuracy of the order of 50 μm in order to achieve the optimum performance of the spectrometer. To this end, a network of optical lines is used to continuously monitor the positions of the chambers relative to each other, as well as their deformations. An elaborate procedure for reconstructing the 56,000 parameters determining the alignment (for the central part) has been developed by a team at IRFU in order to obtain the precision required for the reconstruction of high-energy muons. This method, adopted by the ATLAS collaboration, is presented for the first time in an ATLAS note.

Mar 10, 2021
The ATLAS detector equipped with a new charged particle tracking device for the HL-LHC.

The high luminosity phase of the LHC (HL-LHC) should enable the collection of a dataset unprecedented in the history of particle physics. In order to record these data, the Atlas detector will undergo a major upgrade. IRFU, via the Paris-Cluster in synergy with two other laboratories in Ile de France, is committed to the construction of a part of the internal tracker. The year 2021 is brilliantly starting for the Paris-Cluster, which has just passed an important milestone in this endeavour: the first phase of the assembly and testing processes developed by our teams has been validated by the Atlas collaboration.

Jan 19, 2021

The search for double beta decay without neutrino emission (0νββ) is one of the major challenges of contemporary physics, because its observation would make a clear statement about the nature of the neutrino itself and potentially on the origin of the matter/antimatter asymmetry of our universe. The CUPID collaboration, in which several researchers from IRFU and IN2P3 are involved, is actively researching this process using scintillating bolometers as detectors. In June 2020, the CUPID-Mo demonstrator experiment, which is located at the Modane underground laboratory, demonstrated the excellent potential of this detection method with only 2.264 kg of 100Mo and one year of data collection. In the coming years, the objective of the CUPID collaboration is to design one of the most sensitive experiments ever built by increasing the total mass of 100Mo to 250 kg. Three articles have just been published on the technological and methodological choices needed for this change of scale, while maintaining the required performances of the final experiment.

Sep 23, 2021

An experiment performed at GANIL with the new detection device ACTAR TPC (ACTive TARget Time Projection Chamber) allowed for the development of a new technique for the direct reconstruction of the 3D trajectories of the protons emitted by the isomeric state of 54mNi nucleus and simultaneously visualize their decay time (the 4th dimension). This observation is an unprecedented test of theoretical models since it probes some extremely weak components of the wave functions describing the structure of this nucleus. This technique is already foreseen to be used for the measurement of other similar decays. The result of this experiment was recently published in Nature Communications1.

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]. The study of these nucleon pairs in radioactive nuclei is the goal of the ANR project COCOTIER led by IRFU.

Understanding how the nuclear interaction emerges from the basic constituents of matter is one of the challenges of contemporary physics. The nuclear interaction between nucleons (proton or neutron) is seen as a manifestation of the strong force between quarks, which is mediated by the exchange of gluons and holds the nucleon together. In spite of the longstanding efforts, a unified nuclear interaction that allows predicting the properties of all nuclei does not exist yet.

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. It was installed on site in 2015 and saw the beam for the first time in the fall of 2018. In some experiments, these beams will have interacted upstream on the COCOTIER liquid hydrogen target. The latter, funded in part by the Agence Nationale de la Recherche, has just been used for the first time in an experiment in March 2021. These two pieces of equipment are key elements for measuring the properties of nuclei at the limit of nuclear stability and allow current nuclear models to evolve towards more predictive ones.

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. The results have been published in European Journal of Physics A [3].

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.

In Greek mythology, Sirius, Orion's faithful four-legged companion, an outstanding hunter, was transformed into a constellation and placed at his side. This famous canid also gave its name to the brightest star in the night sky. IRFU physicists have just honoured him in their own way, this time in the world of detectors.

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 22, 2021
DAp-AIM scientist helps uncover largest group of rogue planets yet with a panoramic camera built by CEA

Rogue planets are elusive cosmic objects that have masses comparable to the largest planets in our Solar System but do not orbit a star, instead roaming freely on their own. Not many were known until now, but a team of astronomers, using data from facilities across the world, have just discovered at least 70 new rogue planets in our galaxy just a few hundred light-years away in the Scorpion sky region. This is the largest group of rogue planets ever discovered, an important step towards understanding the origins and features of these mysterious galactic nomads.

Dec 15, 2021
New research shows that the spiral structure of the Milky Way is more clumpy then previously thought

The Milky Way is a spiral galaxy. If we could travel out of it we would probably observe a flat disk with spiral arms connected to its central core. Stuck inside the Milky Way, with no bird's eye view and limited precise distance measurement to interstellar clouds, the exact shape of the Galaxy spiral pattern is difficult to assess and remains not well known. 

For decades the astronomers have used several methods to infer the Milky Way large scale structure, and observations have led us to believe that it is likely to be a Grand Design spiral with long, thin and well defined arms like Messier 81. But a recent study of a team including a member of the IRFU Astrophysics Departement is challenging this vision.

These new results are showing that a section of one of the most well know spiral structure of the Milky Way, the Perseus arm, is not as regular and organised as it was thought. Based on the cross-analysis of several observational databases, this study provides precise measurements of the distance to 81 interstellar clouds in a specific section of the putative Perseus arm. By locating interstellar matter in three dimension, the authors reveal a much more perturbed and scattered structure, indicating that the continuous Perseus arm structure previously infered from observations might have been the result of a projection effect, an illusion predicted by W. Burton in 1971. 

 

Dec 01, 2021
Ultralight and super fast

In the world of extrasolar planets, "GJ 367 b" is a featherweight. With half the mass of Earth, the newly discovered planet is one of the lightest of the nearly 5,000 exoplanets known today. It takes about eight hours for the extrasolar planet to orbit its host star. With a diameter of just over 9,000 kilometers, GJ 367 b is slightly larger than Mars but smaller than Earth. This planetary system is located just under 31 light years from our planet and is therefore ideal for further studies of its properties. His discovery demonstrates that it is possible to accurately determine the characteristics of the smallest and lighter exoplanets. Such studies provide new clues to better understand how planets form and evolve.

An international group of 78 researchers from 49 institutions including the Department of Astrophysics (DAp) at CEA / Irfu published this study in the scientific journal Science based on initial observations from the NASA / MIT Transiting Exoplanet Survey Satellite (TESS).

"With an orbital period of only one third of a terrestrial day, the year on GJ 367 b is therefore much shorter than the day on Earth, while the star spins on itself in 48 days, which makes around 1.7 times slower than our Sun ”says Rafael A. García, CEA researcher who is part of the team.

The DAp focused its effort in the characterization of the host-star with TESS as well as using WASP data which allowed us to determine with high precision the rotation period of the star (48 days).  

Oct 12, 2021

Planets that are strongly irradiated by their host stars develop extended atmospheres that can be probed during transits. These atmospheres undergo photoevaporation which can lead to significant changes in the mass and composition of the planets if it continues for several gigayears. These planets are therefore valuable for understanding planetary evolution. The study of the photoevaporation of exoplanets could inform us on the evolution of the atmospheres of the planets of our Solar System whose first atmospheres would have been shaped by this phenomenon. Exoplanets allow us to study this process as it occurs. An international collaboration has studied the HAT-P-32 system (composed of the star of the same name and an exoplanet named HAT-P-32b) by studying two absorption lines: hydrogen and helium. This allowed them to identify remarkable differences between the two lines during the transit, to the surprise of scientists who also thought that hot Jupiters were rather stable to photoevaporation. Although this statement on the long-term stability of hot Jupiters’ atmospheres remains generally true, HAT-P-32b is an exception to this rule and shows that our understanding of planetary evolution remains incomplete!

Sep 21, 2021

After three years of reflection and development, the "Astro-Colibri" application has just been launched. This digital interface, created by researchers at Irfu/DPhP, aims to make information on transient and multi-messenger phenomena easily accessible in real time. The need to react quickly to the most violent explosions in the universe and the large amount of information provided by the global network of observatories requires new approaches and new tools. Through "Astro-Colibri", several observatories now have the capacity to coordinate in monitoring and identifying the sources of physical phenomena in the transient sky.

The platform, which exists in the form of a smartphone application (IOS and Android) and a website, allows alerts to be put into their observational context by cross-referencing them with already known data. This saves researchers a considerable amount of time. In addition, the application anticipates the best possible observation periods for a given observatory. This free interface is also a fun and practical tool for astrophysics enthusiasts who will be able to easily move around this functional application.

Sep 14, 2021

On June 1, 2021, the open source software solution Gammapy was selected by the CTA (Cherenkov telescope array) observatory as a high-level analysis tool (Science Tools) for the reduction and modeling of the data collected by its future network of telescopes being deployed in Chile and the Canary Islands. Gammapy benefited from the participation of some 70 scientists from all over the world with a strong involvement of German and French laboratories, including the Department of Astrophysics at Irfu (Irfu / DAp). Through contributions on analysis methods and data visualization as well as a place on the steering committee, the DAp was able to contribute to this success.

 

Jul 23, 2021

Space-based experiments such as the Fermi satellite's Large Area (LAT), which detects gamma rays above 100 MeV, reveal a population of sources with no astrophysical counterpart at other wavelengths. Some of these have the characteristics required to be "dark matter subhalo" candidates predicted by cosmological simulations to populate the Milky Way halo. The range of dark matter candidates with masses below a few hundred GeV are already excluded by Fermi observations. To test the higher masses, higher energy range observations are needed and the H.E.S.S. ground-based Cherenkov telescope array is the ideal instrument. Thus, a team of physicists from Irfu and laboratories in Heildelberg and Tübingen conducted a thorough selection of some of the most promising objects to be observed by H.E.S.S. to elucidate their possible identification as 'dark matter subhaloes' at TeV. The H.E.S.S. results exclude this interpretation for dark matter particles in the TeV range.  This work was published in the Astrophysical Journal in July 2021 (arxiv link).

Jun 09, 2021

An international team led by several researchers from LFEMI/DAp/CEA has just published a study shedding light on the formation mechanisms of interstellar grains in galaxies. This is one of the key results of the European DustPedia collaboration, which brings together some thirty people from six laboratories: the DAp at CEA-Saclay, the IAS at Orsay, the University of Ghent, the University of Cardiff, the Observatory of Florence and the Observatory of Athens.

Jun 04, 2021

On 29 August 2019, scientists from the H.E.S.S. collaboration recorded one of the brightest cosmic explosions ever observed in the Universe. This gamma-ray burst emitted the most energetic photons ever detected in this type of event. Under the direction of Irfu researchers, the observations continued for several days. The analysis of the data collected calls into question the origin of the rays produced during the explosion. These results has been published  by the international team, which includes researchers from CEA and CNRS, in the journal Science on 4 June 2021.

H.E.S.S., located in Namibia, is a system of five imaging atmospheric Cherenkov telescopes that has been studying cosmic rays since 2003. In 2016, the cameras of the first four telescopes were completely refurbished using state-of-the-art electronics and in particular the NECTAr readout chip designed by the the DEDIP/Irfu laboratory.


The analysis of this exceptional gamma-ray burst was led by a physicist from the DPHP/Irfu astroparticle group.

Jun 01, 2021

Valeria Pettorino was awarded with the 2020 MCAA (Marie Curie Alumni Award) for her outstanding career (CEA/IRFU, Saclay) for her work in the Euclid collaboration and her involvement in the scientific community through various activities such as mentoring, event organisation, communication and more recently science diplomacy. This award is presented by the MCAA association, which is an international network of all researchers who have received a Marie Curie Fellowship.

See : Valeria Pettorino talks about dark energy: from theory to data

May 28, 2021
The MXT camera for the SVOM mission has just been assembled and delivered by the CEA

An X-ray camera, intended to equip the Sino-French SVOM satellite, has just been assembled and delivered by scientists and technicians from the Institute for Research on the Fundamental Laws of the Universe (CEA/Irfu). This high-tech prototype will capture high-energy photons (X-rays) emitted during the explosion of massive stars or the fusion of dense stars. The camera, particularly compact and innovative, integrates in a very limited volume, a complete detection chain, an active thermal control and a filter wheel. It will be placed at the focus of a telescope 1.15 m long to form the MXT (Microchannel X-ray Telescope). With a field of view of 1 square degree, for only 35 kg of mass, the MXT telescope, equipped with an original "faceted" optics inspired by lobster eyes, will make it possible to locate the position of the most powerful cosmic explosions in the Universe with a precision better than 2 arcmin. After various tests, including a calibration campaign in Germany, the assembly will be shipped to China in November 2021 to be integrated into the SVOM satellite, which is scheduled for launch at the end of 2022.

See : Timelapse of the MXT camera assembling in cleanroom

May 27, 2021
Numerical simulations trace the origin of stellar black hole mergers

Since the interferometers of the LIGO-Virgo collaboration detected gravitational waves from the merging of two black holes, black hole binaries have been among the celestial objects that most interrogate scientists. A team of astronomers, including researchers from the Astrophysics Department / AIM Laboratory of CEA Paris-Saclay and the APC laboratory (University of Paris), have determined, using more than 60,000 digital simulations of stellar evolution, the characteristics of the progenitors at the origin of mergers of black hole binaries of mass less than 10 solar masses. According to this study, a phase in the evolution of the binary system known as the common envelope phase plays an essential role in the process eventually leading, or not, to the merger of the two black holes. This work is presented in an article to appear in the journal Astronomy & Astrophysics.

May 17, 2021
After a particularly successful first campaign of tests and measurements, the Dark Energy Spectroscopic Instrument (DESI) has just successfully started its 5-year observing program.

After a particularly successful first campaign of tests and measurements, the Dark Energy Spectroscopic Instrument (DESI) has just successfully started its 5-year observing program. The international collaboration, under the lead of Berkeley Lab, has the ambitious goal to carry out the largest survey of galaxies and quasars. It will be used to draw the most accurate 3D map of the Universe and to elucidate the mystery of "dark energy".
A large, five-year survey to map the Universe and unravel the mysteries of "dark energy" officially began on May 15, 2021 at the Kitt Peak National Observatory near Tucson, Arizona. To carry out its mission, the Dark Energy Spectroscopic Instrument (DESI) will capture and study light from tens of millions of galaxies and other distant objects in the Universe.

Apr 28, 2021

An international collaboration led by a team from the Astrophysics Department/AIM Laboratory of IRFU has predicted and characterised the expected signature of internal magnetic fields in stars through their seismology - called asteroseismology. This study demonstrates that thanks to the very precise data from the Kepler (NASA), TESS (NASA) and soon PLATO (ESA) satellites, we are potentially able to detect magnetic fields in the cores of red giant stars (which are the descendants of low-mass stars such as our Sun and intermediate masses below ~8 solar masses). The results are published in two papers in the journal Astronomy & Astrophysics.

Apr 22, 2021

An international team including researchers from the Astrophysics Department (DAp) of CEA/Irfu, working in particular at the laboratory for the Dynamics of Stars, (Exo) planets and their Environment  (LDE3), has been able to demonstrate that stars rotate faster than expected as they get older. Using asteroseismological techniques - the study of stars through the characterization of their oscillation modes by seismic methods - researchers were able to analyze for the first time a complete sample of 91 stars brooding ages 1 to 13 billion years. These data confirm that the oldest stars slow down their rotation less effectively. This discovery sheds new light on the evolution of star rotation and should make it possible to more accurately calculate the age of stars. These results are published in the journal Nature Astronomy on April 22, 2021.

Feb 28, 2021
An European prize for ground-breaking contributions in stellar astrophysics

The 2021 MERAC Prize for the Best Early Career Researcher in Theoretical Astrophysics is awarded to Dr Antoine Strugarek (CEA Saclay, France) for ground- breaking contributions in stellar astrophysics, including dynamo theory, predictions of solar flares and pioneering work on star-exoplanet interactions. The prize from the MERAC foundation (Mobilization for European Research in Astrophysics and Cosmology) is awarded each year by the European Society of Astronomy (ESA).

Feb 10, 2021

Imaging planets that could potentially sustain life around nearby stars has become a possibility thanks to advances reported by an international team of astronomers in the journal Nature Communications. Using a newly developed system for mid-infrared exoplanet imaging in combination with a very long observation time, they achieved the capability of directly imaging planets about three times the size of Earth within the habitable zones of nearby stars. This experiment, called NEAR (Near Earths in the AlphaCen Region), was performed using VISIR, a mid-infrared instrument built by the Astrophysical Department of CEA-IRFU. The VISIR camera has been adapted to  a 8m large telescope VLT UT4 (Yepun) in Chile, with a specific star-light blocking device and a a built-in adaptive optics sytems to correct for the atmospheric turbulence. A potential Neptune-to Saturn-sized planet orbiting Alpha Centauri may have been pinpointed but still requires further confirmation.

See the video : Breakthrough Watch/NEAR

Feb 03, 2021
A major contribution in International Leadership in Physics

The American Institute of Physics announced the astrophysicist Catherine Cesarsky as the recipient of the 2020 John Torrence Tate Prize for her major international role in leading major astronomical observatories and other prestigious organizations such as the International Astronomical Union. Named after the celebrated American physicist John Torrence Tate (1889-1950), the Tate medal was established in 1959 and is awarded every two years to non-U.S. citizens for their leadership, research contributions, and service to the international physics community.

Catherine Cesarsky, High Commissioner for Atomic Energy from 2009 to 2012 and today High Scientific Advisor to the General Administrator, headed the Department of Astrophysics at CEA from 1985 to 1993, then the direction of all CEA basic research in physics and chemistry from 1994 to 1999. She served as the director general of the European Southern Observatory (ESO) from 1999 to 2007 where she notably supervised the end of construction and the commissioning of the Very Large Telescope (VLT). She chaired the International Astronomical Union (IAU) from 2006 to 2009 and has just been appointed on February 3, 2021 to head the Council of the Square Kilometer Array Observatory, the world's largest radio telescope under construction in Australia and South Africa.

Catherine Cesarsky will be presented with the Tate medal during a plenary session of the European Astronomical Society Annual Meeting, to be held in virtual form in Leiden (Netherlands), in June 2021.

Jan 13, 2021

Nearly 200 researchers were involved in collecting, processing and assembling images of half the sky to prepare for the start of observations by DESI, the Dark Energy Spectroscopic Instrument, which aims to solve the mystery of dark energy.

In order for DESI to begin its 5-year mission (2021-2026) to produce the largest 3D sky map ever made, researchers first needed a gigantic 2D map of the Universe. Based on 200,000 images from 1405 nights of observations on three telescopes and several years of satellite data, this 2D map is the largest ever produced, based on the area of sky covered, the depth of the imagery and the more than one billion images of galaxies it contains.

Jan 11, 2021

he "cosmic noon", when the universe was 4 to 5 billion years old, marked a very active period of star formation for most galaxies. Paradoxically, about a third of the most massive galaxies at that time were dead and no longer forming stars. To date, the shut down of star formation in galaxies is often attributed to gas outflows caused by the feedback of supermassive black holes, but their impact on the galaxies of the young Universe has not yet been definitively established.

Thanks to the ALMA interferometer, a team of astrophysicists in which the Astrophysics Department / AIM Laboratory of CEA Paris-Saclay is strongly involved, has detected an exceptional gas ejection in a massive galaxy at cosmic noon, called ID2299. According to their analyses the scenario of this announced death cannot come from black holes, but from the fusion of two galaxies which is at the origin of the galaxy. What if with this new scenario, we revisit the autopsy reports of dead galaxies... The quantitative observations of this study raise questions. The results have just been published in the journal Nature Astronomy:  https://www.nature.com/articles/s41550-020-01268-x .

Jun 28, 2021

As part of the luminosity increase of the Large Hadron Collider (LHC), the first phase of the ATLAS experiment upgrade is coming to an end, before a restart planned for early 2022. To meet the requirements of physics in a highly radiative environment with a high particle flux, the two internal wheels of the muon spectrometer will be replaced by new devices: the New Small Wheels (NSW).
After several years of R&D and production, IRFU has just sent the last of the 32 detection modules that will be integrated into the NSW at CERN. This corresponds to the assembly of about 400 m2 of gas detectors based on Micromegas technology: a record!

Jun 01, 2021
The ICAR cryomechanisms that will equip the METIS instrument on the world's largest telescope, the ELT, by 2029 have just passed the final design review by an ESO expert committee.

Resulting from a product lineage initiated in 1997 for the developments linked to the VISIR project (VLT Imager and Spectrometer for mid Indra Red), the CEA's cryomechanisms named ICAR (Indexed Cryogenic Actuator for Rotation) will equip the METIS instrument on the largest telescope in the world: the Extremely Large Telescope (ELT) by 2029. For this fifth generation of mechanisms (2004 VISIR, 2010 MIRI, 2012 CAMISTIC, 2017 EUCLID), the IRFU teams had to review the architecture of these mechanisms in order to significantly reduce their manufacturing costs, without degrading their performance (positioning repeatability of 15 µrad peak to peak). The ICAR cryomechanisms have just passed the final design review by a committee of experts from ESO (European Southern Observatory). With this success, the project can now enter the procurement phase for the qualification and series models.

See: video of the design and assembly stages of the prototype over the period 2018-2021

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.

In Greek mythology, Sirius, Orion's faithful four-legged companion, an outstanding hunter, was transformed into a constellation and placed at his side. This famous canid also gave its name to the brightest star in the night sky. IRFU physicists have just honoured him in their own way, this time in the world of detectors.

Apr 15, 2021

The muon spectrometer of the ATLAS experiment has been an important contribution of IRFU since the design, and IRFU is still in charge of the alignment today. The spectrometer plays a key role in the reconstruction of high-energy muons, the detection of which is crucial for the search of phenomena beyond the Standard Model. The spectrometer consists of about 1200 muon chambers that form a gigantic edifice 44 m long and 24 m in diameter. Despite these imposing proportions, the relative positions of the chambers must be known with an accuracy of the order of 50 μm in order to achieve the optimum performance of the spectrometer. To this end, a network of optical lines is used to continuously monitor the positions of the chambers relative to each other, as well as their deformations. An elaborate procedure for reconstructing the 56,000 parameters determining the alignment (for the central part) has been developed by a team at IRFU in order to obtain the precision required for the reconstruction of high-energy muons. This method, adopted by the ATLAS collaboration, is presented for the first time in an ATLAS note.

Mar 10, 2021
The ATLAS detector equipped with a new charged particle tracking device for the HL-LHC.

The high luminosity phase of the LHC (HL-LHC) should enable the collection of a dataset unprecedented in the history of particle physics. In order to record these data, the Atlas detector will undergo a major upgrade. IRFU, via the Paris-Cluster in synergy with two other laboratories in Ile de France, is committed to the construction of a part of the internal tracker. The year 2021 is brilliantly starting for the Paris-Cluster, which has just passed an important milestone in this endeavour: the first phase of the assembly and testing processes developed by our teams has been validated by the Atlas collaboration.

Nov 30, 2021

The CEA teams in collaboration with those of ESS worked for many months on the conditioning of the RFQ delivered to ESS in 2019. On 28 July 2021, the conditioning was successfully completed with 110% of the nominal operating power and the beam passed through the RFQ for the first time on 26 November.
The conditioning of the RFQ marks the end of a multi-year process at CEA for this central component of the future ESS linear accelerator in Sweden.

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. It was installed on site in 2015 and saw the beam for the first time in the fall of 2018. In some experiments, these beams will have interacted upstream on the COCOTIER liquid hydrogen target. The latter, funded in part by the Agence Nationale de la Recherche, has just been used for the first time in an experiment in March 2021. These two pieces of equipment are key elements for measuring the properties of nuclei at the limit of nuclear stability and allow current nuclear models to evolve towards more predictive ones.

Mar 26, 2021

The large aperture (90 mm) quadrupole superconducting electromagnet for the CERN HL-LHC project, manufactured and tested at 4.2 K by the IRFU teams, reached its nominal gradient of 120 T/m (defined for 1.9 K) the 5th of March, 2021. These very good results validate the design and manufacturing process proposed by the IRFU engineers and were the subject of a technology transfer to the industrial companies working on the European project QuaCo (QUAdrupoleCOrector). This magnet was produced as part of the LHC upgrade in luminosity project called HiLumi-LHC. These NbTi magnets are part of the insertion magnets. They may be placed upstream and downstream of detectors such as ATLAS and CMS at the center of which the 2 beams cross to make the collisions. They should ensure the compression of the beams before collisions and thus contribute to increasing the integrated luminosity of the HL-LHC (i.e. the total number of collisions), up to ten times greater than the initial nominal value of the LHC.

Jun 28, 2021

As part of the luminosity increase of the Large Hadron Collider (LHC), the first phase of the ATLAS experiment upgrade is coming to an end, before a restart planned for early 2022. To meet the requirements of physics in a highly radiative environment with a high particle flux, the two internal wheels of the muon spectrometer will be replaced by new devices: the New Small Wheels (NSW).
After several years of R&D and production, IRFU has just sent the last of the 32 detection modules that will be integrated into the NSW at CERN. This corresponds to the assembly of about 400 m2 of gas detectors based on Micromegas technology: a record!

 

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