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The vertiginous descent of equipment into the depths of the accelerator tunnels is always a captivating event. The stars of the show over the last few weeks have been the two gleaming cold boxes that have arrived in the new service tunnels of the High-Luminosity LHC (HiLumi LHC), close to the ATLAS and CMS experiments. These two enormous pieces of equipment, manufactured in Germany by the company Linde, are a key component of the future accelerator’s two new refrigerators.
The two refrigerators, which will cool the new magnet systems installed on either side of the ATLAS and CMS experiments to -271.3 °C (1.9 kelvins), are complex systems made up of a number of impressive pieces of equipment. The compressors and cold boxes, which were installed on the surface last December, will pre-cool the helium to -268.6 °C (4.5 kelvins). The last few degrees needed to reach -271.3 °C, less than 2 degrees above absolute zero, will be gained by lowering the pressure of the helium circulating in the magnet cryostats and using four cold compressors connected in series and integrated into one of the cold boxes that have just been delivered.
In parallel, the cryogenic lines that will transport the helium are being installed underground. The teams have already completed the first phase of the installation work.
Two big cold boxes have been lowered in the new High-Luminosity LHC (HiLumi) underground galleries. They are part of the new refrigeration system for the major upgrade of the LHC. (Video: CERN)roryalex Wed, 02/25/2026 - 15:40 Byline Corinne Pralavorio Publication Date Fri, 02/27/2026 - 15:31
With more than 6000 scientists, engineers, technicians, administrators and students, CMS is one of the world’s largest scientific collaborations. From 1 January 2026 to 31 August 2028, Anadi Canepa has the important role of representing the Collaboration as its Spokesperson. Joining her as deputies are Hafeez Hoorani, who continues in his present role until 31 August 2026, and the newly appointed Florencia Canelli, who will remain in office until 31 August 2028.
Previous Spokesperson Gautier Hamel de Monchenault left the role early, at the end of 2025 instead of in August 2026, to become CERN’s Director for Research and Computing. The Collaboration thanks him for his work on its behalf and wishes him all the best going forward.
Anadi Canepa is a senior scientist at Fermi National Accelerator Laboratory (Fermilab). She began her research with the CDF experiment at the Tevatron, focusing on searches for new phenomena and the Higgs boson and contributing to upgrades of the silicon tracker and trigger system (PhD, Purdue University, 2006). In 2015, she became a scientist at Fermilab and joined the CMS Collaboration. She was appointed CMS Deputy Spokesperson during Gautier Hamel de Monchenault’s term of office (2024–2025).
Hafeez Hoorani received his PhD in Experimental High-Energy Physics from the DPNC, University of Geneva, in 1996. He was part of the L3 experiment at LEP, where he was responsible for the level 1 charge particle trigger. He joined CMS in 1995 and, since then, has contributed to its muon system in various capacities.
Florencia Canelli is Professor of Physics at the University of Zurich. She began her research at the D0 experiment at the Tevatron (PhD, University of Rochester, 2003), where she measured the properties of the top quark. Since joining the University of Zurich and CMS in 2012, she has held several leadership roles within the Collaboration.
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Read more on the CMS website.
anschaef Wed, 02/25/2026 - 11:43 Byline CMS collaboration Publication Date Wed, 02/25/2026 - 11:38Many activities are currently progressing across the accelerator chain as the complex moves steadily towards full operation. In the injectors, beam commissioning is advancing well, with the highlights being the start of the physics programme at ELENA on 20 February and the ongoing scrubbing run in the SPS.
The SPS has just completed its first week of beam commissioning. Physics delivery beams have been set up in the SPS ring and low-intensity beams have been prepared for both fast and slow extraction to serve the downstream machines and experimental facilities. The machine has now entered the intensity ramp-up phase during the so-called scrubbing run. This is a crucial commissioning step, required whenever the beam pipe has been opened to air for interventions or routine maintenance, during which surfaces inevitably become contaminated through atmospheric exposure. Although mitigation measures are implemented during these interventions, subsequent surface conditioning with beam is almost always necessary.
As beams circulate in the machine, they induce electromagnetic fields in the surrounding vacuum chambers and equipment. This can lead to local heating and outgassing. In addition, secondary electron emission from insufficiently conditioned surfaces may generate local concentrations of electrons. These electrons are accelerated by the passing beam and bounce off the chamber walls, releasing further electrons in a process known as multipacting. The resulting electron clouds can further degrade the vacuum. If the pressure rises excessively, sensitive equipment may be at risk. For this reason, the beam is injected and stored in a carefully controlled manner, ensuring that the vacuum remains at acceptable levels, below interlock thresholds, while efficiently conditioning the surfaces. Typically, about one week of scrubbing is required before the maximum beam intensities can be reached. For LHC Injectors Upgrade (LIU)-type beams, which will ultimately serve the High-Luminosity LHC (HL-LHC), this corresponds to 288 bunches at 2.3×10¹¹ protons per bunch.
Meanwhile, in the LHC, the final steps before beam injection are under way. First beam had initially been scheduled for 21 February. However, on 11 February a vacuum leak was detected on an edge-welded bellow of a tertiary collimator at Point 2. This type of vacuum bellow is known to represent a structural weak point under certain operating conditions and a dedicated task force was launched in 2025 to study mitigation strategies in view of HL-LHC operation. The leak could not be repaired in situ and the collimator had to be replaced.
The duration of such an intervention is largely dictated by the bake-out of the affected vacuum sector to restore ultra-high vacuum conditions. The vacuum sector concerned is one of the largest in the LHC, making the operation particularly delicate and time-consuming. Given that the intervention was unavoidable and that the second tertiary collimator in the same sector (one horizontal and one vertical) had accumulated a similar number of operational cycles – and therefore presented a comparable risk profile – it was decided to replace both units during the same stop.
A view of the two tertiary collimators being exchanged at Point 2. (Image: CERN)The intervention was carried out in a precise and efficient manner, with close coordination between the many groups involved, including vacuum, collimation, transport, beam instrumentation and cryogenics. The activities are expected to be completed on 26 February, after which the machine will be handed back for the final preparations. Hardware commissioning and machine checkout will be finalised in parallel. As a consequence, first beam injection into the LHC is now scheduled for 27 February, approximately six days later than originally planned.
Once beam is circulating, an intensive nine-day commissioning period will begin. During this phase, the accelerator will be progressively set up for physics operation. This includes orbit correction, optics measurements, collimator alignment, verification of machine protection systems and numerous other checks required to ensure safe and reliable operation at high energy. Only after this comprehensive commissioning phase will the LHC be ready to deliver stable beams for physics and the gradual intensity ramp-up begin.
With Run 3 entering its final stretch and Long Shutdown 3 (LS3) on the horizon, every commissioning step is both a preparation for the present and an investment in the future. The coming days will be decisive as beam returns to the LHC and commissioning moves into its most intense phase.
anschaef Wed, 02/25/2026 - 11:27 Byline Matteo Solfaroli, Deputy Leader of the Operations Group (BE-OP) Publication Date Wed, 02/25/2026 - 11:24Arts at CERN is delighted to announce that Geneva-based French-Congolese artist Monika Emmanuelle Kazi has been selected for the second edition of Resonance. This annual residency programme was launched in November 2024 by CERN, the Republic and Canton of Geneva and the City of Geneva, with the support of the CERN & Society Foundation. Designed for Geneva-based artists, Resonance offers a unique opportunity for artistic experimentation through close exchange with CERN’s scientific community and research environment.
Monika Emmanuelle Kazi holds a master’s degree in Visual Arts from HEAD – Genève. Her interdisciplinary practice engages with haptics and machine learning, resulting in organic installations that combine video, performance and writing. Drawing on objects, family archives and research materials, her installations form systems of visual and everyday references that she calls “iso-objects” – a term inspired by the International Organization for Standardization (ISO). Situated between documentary and fiction, Kazi’s work weaves personal memory into broader global narratives.
For the Resonance residency, Kazi will develop Crystalline Memories, a project exploring perceptions of the future through the lenses of futurology, prospective studies, divinatory practices, cosmogonies and cosmology. Her artwork will draw on research conducted at CERN, particularly the CLOUD and CAST experiments. Through immersion in CERN’s ecosystem, Kazi aims to connect scientific research with reflections on diasporic memory and its erosive forces. Inspired by archetypal myths and cosmogonies, Crystalline Memories will poetically examine the construction of knowledge, the imagination of the future and the fragile memories through which we attempt to navigate both.
“With over 83 applications received, spanning a wide variety of practices, Resonance is establishing itself as an attractive programme that fosters research and experimental practices while connecting the Republic and Canton of Geneva and the City of Geneva’s cultural scene with CERN’s vibrant scientific context and social fabric. Arts at CERN has been delighted by the growing interest in the programme and looks forward to welcoming Monika Emmanuelle Kazi for the second edition of Resonance,” says Giulia Bini, Head of Arts at CERN.
“The City of Geneva was delighted by the breadth and quality of the applications received for the second Resonance residency. The creativity and diversity of the projects are testament to the relevance of this programme, which offers artists a rare opportunity for in-depth dialogue with CERN’s scientific community and provides the members of the jury with a space for exciting discussions about distinctly exploratory projects. This fruitful encounter between artistic imagination and fundamental research affirms the richness of such a partnership, which helps to broaden the diversity of voices and perspectives within our cultural ecosystem,” explains Sophie Sallin, Cultural Advisor for the City of Geneva.
“The Canton of Geneva is committed to promoting a rich culture that is open to other fields of knowledge. We are delighted to be involved in the Resonance artistic residency programme, which builds bridges between artistic creation and scientific research. This initiative also underlines the commitment of a world-renowned scientific organisation to its host city and illustrates the special ties that unite Geneva and CERN through shared cultural enrichment,” says Thierry Apothéloz, President of the State Council of the Republic and Canton of Geneva.
The jury was composed of Giulia Bini, Curator and Head of Arts at CERN; Séverine Fromaigeat, Director of the Barbier-Mueller Museum; Chiara Mariotti, particle physicist at the CMS experiment at CERN; Sophie Sallin, Cultural Adviser for the City of Geneva; and Jérôme Soudan, Cultural Adviser for the Republic and Canton of Geneva.
Following its second edition, the Resonance residency programme will launch a new special edition for 2026.
rodrigug Mon, 02/23/2026 - 15:30 Publication Date Tue, 02/24/2026 - 15:30
In mid-November, CERN was subjected to another phishing attack that tried to lure people to open a malicious link and provide their CERN credentials on a fake CERN Single Sign-On page. While many of us detected and reported the scam, unfortunately up to 11.2% fell for the bait and potentially exposed their password. But, luckily for them, this was just an exercise…
So what did these phishing emails look like? Like any other “standard” package of spam and scam emails that the CERN mail filters block on a daily basis, they looked innocent enough. Simple. Maybe credible. Or not, as they could all also be recognised as dodgy, weird, suspicious or just not for us. They all came from a non-CERN domain, as can be seen in the “From” field of the email: “cofeesuppli3r.you”, “365mailserv.bk”, “kern.bz”, etc. Their message text resembled the “standard” spam. In fact, standard spam mails were used as inspiration for the exercise. And the embedded links did not actually point to the CERN SSO (“auth.cern.ch”) but to external URLs like www[.]hrsupportint[.]com or www[.]doctorican[.]de. Find below six screenshots of the “malicious” emails:
Would you have fallen for and clicked on any of them? Interestingly, of those who did, the “CERN password expires today” from “Pauline Cuvitrina” got the most clicks (50%), followed by the “important update on contracts” (31%) from the “Secretary service” and “DHL” (14%) from “Saniu Walliv”, while just a few people were convinced to have “earned a free coffee” or had an “MS365 Emails problem”(1). Below you can see the distribution per subject and the click rates per department.
The average click rate was about 6%, with variations up to 11.2%(2), but still all in the same ballpark given the statistical error. Actually, one can create any click rate as the rate depends largely on the sophistication of the message text: in another exercise, the CERN Computer Security Office succeeded in getting a click rate of more than 80% from about 120 IT specialists attending an IT conference who were invited by a fake email to “Download your voucher for a free beer in the hotel lobby here”.
While our spam filters and the recently concluded roll-out of two-factor authentication should already provide sufficient protection and usually detect and block such emails, defence-in-depth is better. “Security” is like Swiss Emmental cheese: you need several layers to cover all holes. Hence, next time, before you are tempted to click, please remember: STOP – THINK – DON’T CLICK when you see such an email (or, for that matter, an SMS, WhatsApp message, QR code or plain URL), in order to help protect the Organization. Thanks a lot!
(1) The EP Department with its many users was spared this time as rumours and warnings about the phishing campaign had already made the rounds via the usual communication channels and would have rendered the exercise less useful. (2) The “Dark Lord” email seemed too obvious and was not sent at all in the end. ________ Do you want to learn more about computer security incidents and issues at CERN? Follow our Monthly Report. For further information, questions or help, check our website or contact us at Computer.Security@cern.ch. anschaef Mon, 02/23/2026 - 14:04 Byline Computer Security Office Publication Date Wed, 02/25/2026 - 08:58
In the first few microseconds after the Big Bang, the Universe was in an extremely hot and dense state of matter known as quark–gluon plasma (QGP), which can be reproduced with high-energy collisions between heavy ions such as lead nuclei. In a paper published today in Nature Communications, the ALICE Collaboration reports observing a remarkable common pattern in proton–proton, proton–lead and lead–lead collisions at the Large Hadron Collider (LHC), shedding new light on possible QGP formation and evolution in small collision systems.
Physicists initially believed that colliding small systems, such as protons, could not generate the extreme temperatures and pressures needed to form QGP. But in recent years, signatures of QGP have been observed in proton–proton and proton–lead collisions at the LHC, indicating that the size of the collision system may not be a limiting factor in QGP creation.
A key signature of QGP formation is anisotropic flow, where the particles produced in a collision are not emitted evenly but in preferred directions. For particles moving at intermediate speeds (or momenta), this anisotropic flow depends on the number of quarks they contain: particles that are made up of three quarks (baryons) exhibit stronger flow than those that are composed of two quarks (mesons). The leading explanation for this difference is something called quark coalescence – the process through which the quarks in the QGP combine into larger particles. And as baryons contain one more quark than mesons, they inherit more flow.
In its new study, the ALICE Collaboration measured the anisotropic flow of multiple meson and baryon species produced in proton–proton and proton–lead collisions, by carefully isolating the particles that were genuinely flowing together. The analysis showed that, like in heavy-ion collisions, the anisotropic flow was much stronger for baryons than for mesons at intermediate momenta.
(Right) A proton–proton collision at the LHC in which many particles were created and tracked by the ALICE detector. (Left) Illustration of the anisotropic flow of mesons and baryons that ALICE has studied using data from such collisions, with the large arrows representing the preferred directions. (Image: ALICE/CERN)“This is the first time we have observed, for a large interval in momentum and for multiple species, this flow pattern in a subset of proton collisions in which an unusually large number of particles are produced,” says David Dobrigkeit Chinellato, Physics Coordinator of the ALICE experiment. “Our results support the hypothesis that an expanding system of quarks is present even when the size of the collision system is small.”
The ALICE researchers went on to compare the new flow measurements to predictions from simulations that assume QGP formation and its evolution. They found that models that incorporate the anisotropic flow of quarks and their subsequent coalescence into mesons and baryons successfully explain the observed flow pattern, whereas models that exclude either process fail to capture it. However, even the successful models are not exactly right. There are still discrepancies between the models and data that are largely linked to uncertainties in the modelling of the proton’s substructure and the initial geometry of the collisions.
“We expect that, with the oxygen collisions that were recorded in 2025, which bridge the gap between proton collisions and lead collisions, we will gain new insights into the nature and evolution of the QGP across different collision systems,” said Kai Schweda, ALICE Spokesperson.
roryalex Fri, 02/20/2026 - 16:43 Byline ALICE collaboration Publication Date Fri, 03/20/2026 - 11:40The CMS Collaboration has shown, for the first time, that machine learning can be used to fully reconstruct particle collisions at the LHC. This new approach can reconstruct collisions more quickly and precisely than traditional methods, helping physicists better understand LHC data.
Each proton–proton collision at the LHC sprays out a complex pattern of particles that must be carefully reconstructed to allow physicists to study what really happened. For more than a decade, CMS has used a particle-flow (PF) algorithm, which combines information from the experiment’s different detectors, to identify each particle produced in a collision. Although this method works remarkably well, it relies on a long chain of hand-crafted rules designed by physicists.
The new CMS machine-learning-based particle-flow (MLPF) algorithm approaches the task fundamentally differently, replacing much of the rigid hand-crafted logic with a single model trained directly on simulated collisions. Instead of being told how to reconstruct particles, the algorithm learns how particles look in the detectors, like how humans learn to recognise faces without memorising explicit rules.
When benchmarked using data mimicking that from the current LHC run, the performance of the new machine-learning algorithm matched that of the traditional algorithm and, in some cases, even exceeded it. For example, when tested on simulated events in which top quarks were created, the algorithm improved the precision with which sprays of particles – known as jets – were reconstructed by 10–20% in key particle momentum ranges.
The new algorithm also allows a collision to be fully reconstructed far more quickly than before, because it can run efficiently on modern electronic chips known as graphics processing units (GPUs). Traditional algorithms typically need to run on central processing units (CPUs), which are often slower than GPUs for such tasks.
“New uses of machine learning could make data reconstruction more accurate and directly benefit CMS measurements, from precision tests of the Standard Model to searches for new particles,” says Joosep Pata, lead developer of the new MLPF algorithm. “Ultimately, our goal is to get the most information out of the experimental data as efficiently as possible.”
While the new algorithm was tested under current LHC data conditions, it is predicted to be even more useful for data from the High-Luminosity LHC. Due to start running in 2030, the LHC upgrade will deliver approximately five times more particle collisions, posing a significant challenge to the LHC experiments. By teaching detectors to learn directly from data, physicists are not just improving performance, they are redefining what is possible in experimental particle physics.
Find out more about the algorithm on the CMS website and more about machine learning in particle physics through this CERN colloquium.
ehatters Thu, 02/12/2026 - 11:58 Byline CMS collaboration Publication Date Wed, 02/18/2026 - 12:35
This Valentine’s Day, CERN shines a light on its HEARTS testing facility, loved by those who recently tested their components for the harsh conditions of space.
Late last year, the Large Hadron Collider ended a record-breaking year by colliding lead ions. The HEARTS@CERN facility took advantage of this period to test radiation effects with lead ions. Over the course of two weeks in November and December 2025, 16 companies and research institutes spent more than 200 irradiation hours at CERN testing electronic components and devices for use in space and for high-energy physics applications.
The HEARTS (High-Energy Accelerators for Radiation Testing and Shielding) project, funded by the European Union, is establishing two new European radiation testing facilities for space applications, one at CERN and the other at the GSI Helmholtz Centre for Heavy Ion Research in Germany. Unique in Europe, these two facilities offer very-high-energy heavy-ion electronics testing, so that teams can see how their electronics hold up against particularly strong and penetrative radiation that they could be exposed to in space.
Among the components tested were solid-state drive (SSD) memory storage devices for a Belgian start-up focusing on computers for satellites, as well as printed circuit board (PCB) components for an Italian company building a satellite to investigate the Apophis asteroid during its close approach to Earth in 2029.
The recent tests were the second industrial user pilot campaign at CERN, following the 2024 run that welcomed ten companies and research institutes. Six of the sixteen users participating in the 2025 run paid for access, while the rest either received beamtime hours through their association with the project or applied through the RADNEXT project, which offers transnational access to radiation facilities in Europe.
The HEARTS@CERN facility will host another user run in the summer of 2026 before a short break in 2027 as CERN’s accelerator complex shuts down for maintenance. Calls for industry and scientific users for the 2026 campaign will be announced on the project website.
anschaef Wed, 02/11/2026 - 13:27 Byline Thomas Brent Kate Kahle Publication Date Thu, 02/12/2026 - 10:25The 2026 Chamonix Workshop took place last week and brought together the accelerator and experimental communities to review the recent operational performance of the accelerator complex and discuss challenges ahead. The programme included a look back at the 2025 operation as well as an overview of this year’s final stretch of Run 3 and of the post-LS3 (Long Shutdown 3) operation. With LS3 approaching, discussions centred on the upcoming HL-LHC upgrades, as well as consolidation activities in the North Area and ISOLDE, and on the construction of the HiECN3 facility. The workshop concluded with an outlook on CERN’s longer-term future, including progress on the Future Circular Collider (FCC) project and the implications of the European Strategy for Particle Physics.
As for the current status of the accelerator complex, the transition into the 2026 run – the last year of Run 3 – is particularly rapid. Responsibility was transferred from the year-end technical stop (YETS) coordination team to the Operations Group (BE-OP) to perform the Departmental Safety Officer (DSO) tests, followed by equipment and control checks, machine checkout and, finally, beam commissioning.
The commissioning of Linac4 and the PS Booster (PSB) has progressed smoothly and according to plan. Owing to the very short YETS, little or no work was carried out on the equipment, which allowed the reuse of the 2025 machine settings. This approach proved successful and is a strong indication of the maturity and stability of the systems.
Thanks to the extensive preparation by the equipment groups and an efficient hardware commissioning phase, the PS hardware commissioning was completed in only four days. As a consequence, the PS received its first beam on 24 January, three days ahead of schedule. Most of the PS beams were recommissioned rapidly, allowing the first beam to be delivered to the first physics users of 2026: n_TOF on 2 February and the East Area on 4 February.
The H- beam has returned to ELENA on schedule, marking another important milestone in the restart of the low-energy antiproton programme. In the Antiproton Decelerator (AD), the DSO tests in the target area and the ring have just been completed. The first proton beam on the AD target is planned for 13 February, with the start of physics scheduled for 27 February.
In the SPS, DSO tests are under way to validate the machine and its safety systems, while the hardware tests across the accelerator are nearing completion. Provided that these final tests conclude as planned, the start of beam commissioning is expected for 13 February.
The LHC key passes from the Accelerator Coordination and Engineering Group in the Engineering Department (EN-ACE), on the left, to the Operations Group in the Beams Department (BE-OP), after completion of the DSO tests – always a symbolic moment at the end of a YETS. (Image: CERN)Meanwhile, on the LHC side, DSO tests were successfully carried out on 6 February, marking the shift of responsibility from the YETS coordination team to the operators for the last machine of the complex. Over the coming two weeks, more than 1600 superconducting circuits will be progressively tested up to their nominal currents, corresponding to operation at 6.8 TeV.
Once this extensive powering campaign is completed, only the machine checkout phase will remain between the end of the YETS and the arrival of beam. During machine checkout, all accelerator systems are tested together to verify the overall readiness of the technical infrastructure, before beam injection and circulation can begin (planned for 21 March).
With the injector chain performing strongly and the LHC restart advancing according to plan, the accelerator complex is steadily waking up from the YETS and moving towards the start of the 2026 physics programme. The coming weeks will be decisive as commissioning activities continue across the complex.
anschaef Wed, 02/11/2026 - 11:07 Byline Matteo Solfaroli, Deputy Leader of the Operations Group (BE-OP) Publication Date Thu, 02/12/2026 - 08:03
Every year, on 11 February, CERN celebrates the International Day of Women and Girls in Science. In an effort to amplify diverse voices in STEM, six women scientists from CERN open up about their careers and the lessons they hope to pass on to the next generation.
Francesca is an Italian biomedical engineer pursuing her PhD at CERN, working in the robotics team of the Beams Department. She’s currently working on the MARCHESE project, in affiliation with Campus Bio-Medico University of Rome, focusing on contactless monitoring of physiological parameters. Despite choosing a scientific career and often volunteering in scientific outreach initiatives, Francesca continues to nurture her passion for the humanities and arts. “I firmly believe that collaboration and inclusion are the right paths to improve the world together. I’m driven by a strong curiosity about everything around me.”
Berare is a Turkish experimental physicist who worked with the ATLAS experiment during her MSc and PhD on searches for physics beyond the Standard Model. During her PhD, she became a Support Scientist for the Beamline for Schools (BL4S) competition, which marked the beginning of her journey combining research with science communication. She now works for both BL4S and ELISA, the mini proton accelerator at CERN’s Science Gateway. She fondly remembers the moment when the BL4S 2022 winners arrived at the experimental zone: “I felt incredibly lucky to share my passion with young, curious and really passionate people. We spent two weeks of beam time together watching their ideas turn into reality. All the intricate details of running an experiment, we accomplished them as a team.”
Mia is a Canadian research fellow in the Accelerator Systems Department, working on beam developments for fundamental physics with radioactive molecules. Mia pursued a bachelor’s degree in mechanical engineering before moving to Vancouver for a master’s degree in engineering physics. Her interest in radioactive ion beam production brought her to CERN, where she studied actinide beams for three years as a PhD student in the Marie Curie European Training network “LISA” (Laser Ionisation and Spectroscopy of Actinides) at ISOLDE – a facility at CERN where scientists study the properties of atomic nuclei, with further applications in fundamental studies, astrophysics, and material and life sciences.
Laura is a German mechanical engineer at CERN working on research and development to produce cavities for future accelerators. She studied mechanical and aerospace engineering at the Technical University of Munich. She joined CERN four years ago as a technical student for her master’s thesis and continued as a fellow working on collimators. Laura says that “as a child, I took part in girls’ day initiatives, which sparked my fascination for astrophysics and engineering. Later, it felt natural for me to give something back by organising workshops for young students to make STEM seem less intimidating and more accessible.” She particularly enjoys being close to the CERN Main Workshop and understanding how design ideas become real components.
Paraskevi is a Greek physicist working at CERN’s HiRadMat (High-Radiation to Materials) facility, designed to deliver high-intensity beams to an irradiation area where material samples, as well as accelerator component assemblies, can be tested. She studied physics at NKUA, specialising in nuclear and particle physics, and is now pursuing her PhD at HiRadMat in collaboration with the University of Liverpool, studying novel materials for high-intensity beam diagnostics. “Continuous learning is one of my biggest motivators, and I am looking forward to exploring the limits of our knowledge on beam-material interactions,” says Paraskevi.
Silvia is a Spanish physicist and deputy project manager for the Muon Drift Tube of the CMS detector, a general-purpose detector at the Large Hadron Collider (LHC). She started her career at CERN more than 20 years ago as a technical student, working on prototypes of the first dipoles for the LHC. “My first motivation came in high school, from my teacher,” says Silvia about what made her pursue a career in STEM. “My favourite part about my job is learning. You can learn something new every day.”
In parallel to this initiative, like every year since 2017, from 2 to 6 February 66 women scientists and engineers visited schools in Geneva, Switzerland, and in the Haute-Savoie and Ain regions of France to meet with students. Organised in collaboration with CERN, the University of Geneva, EPFL, LAPP and LAPTh, this event allowed more than 4200 students between 6 and 17 years old to meet a woman scientist, discuss their profession and career path, ask questions and participate in classroom activities.
anschaef Tue, 02/10/2026 - 12:48 Byline Bianca Moisa Publication Date Wed, 02/11/2026 - 08:46The past two years have brought a lot of new computer-security deployments at CERN. Spurred on by the 2023 cybersecurity audit, a lot has already been achieved and 2026 should see the successful implementation of all remaining work packages. We already discussed mandatory requirements for IT service managers and upcoming changes to password policies and improvements to two-factor authentication in the last two issues of the Bulletin. Finally, let’s focus on networking in this one.
2026 will also bring improved and more granular network filtering to the Technical Network (TN) and, later, between the Campus and data centre networks, introducing a pair of redundant firewalls for each. Today’s filtering between the Campus network, the Meyrin and Prévessin data centres and the TN is based on tuples of IP addresses and, in some rare cases, network service (“port numbers”). This “TRUSTED/EXPOSED” mechanism dates back to before 2006, when no filtering between those network domains was deployed at all. Today, that filtering is deemed too coarse as it either broadly “trusts” particular enumerated devices on the Campus or in the data centres and makes those visible to the whole TN, or exposes certain enumerated devices from the TN to all the other networks. With the upcoming TN firewall, such cross-traffic from the TN to the data centres and the Campus network will be identified and controlled in a more fine-grained manner: Which IT services need to be visible to the TN? Using which network ports? In which direction (incoming or outgoing)? Using which transport protocol (TCP? UDP?)? And who are its clients on the TN? The same holds true for devices connected to the TN: Where do they need to expose their data to and how? With the TN firewall hardware deployed before Long Shutdown 3 (LS3), the major task will be to answer those questions and migrate from the current “TRUSTED/EXPOSED” mechanism to the more fine-grained firewall protection rules during LS3. And once we are done with that, an identical firewall will be deployed between the Campus network and the data centres.
In parallel, and linked to more “domestic” matters, all IT services hosted in the Meyrin or Prévessin data centres will consider deploying Openstack’s “Security Groups” once this feature is available. “Security Groups” will allow the service to separate their internal back-end servers from the user-facing front-ends and to better protect those from any other data centre services. At the time of writing, all virtual machines in the “m4” family are eligible, with other types expected to join in 2026–2027. And remember, in the Prévessin data centre this functionality is already in place and ready to be put to good use. Similarly, certain control systems, like those for building automation, will be subjected to better network protection (VLANs) as we have done for the CCTV cameras and general access control systems and printers in 2025.
More generally, 2026 should usher in an encrypted Wi-Fi network using industry-standard WPA protection. While this does not provide end-to-end encryption of your traffic, it secures your traffic from network snooping and protects the CERN network from connections by unauthorised devices. WPA roll-out is planned for early 2026, with a long transition from the old network (“CERN” SSID) to the new one (“CERN-Campus”) such that no device is left behind.
So, thanks a lot helping secure CERN if you are involved with the TN and Campus firewalls or “Security Groups”. The TN admins and Computer Security Office, respectively, will surely reach out to you. And for the upcoming WPA3 Wi-Fi deployment: Just. Try. It. Out. It’s an easy step towards obtaining the best privacy for your communication while further protecting the Organization.
_________
Do you want to learn more about computer security incidents and issues at CERN? Follow our Monthly Report. For further information, questions or help, check our website or contact us at Computer.Security@cern.ch.
anschaef Tue, 02/10/2026 - 12:29 Byline Computer Security Office Publication Date Tue, 02/10/2026 - 12:28In beehives on the CERN site, a buzzing team of bees collaborates to build hexagon after hexagon of honeycomb – a shape that allows the most honey for a given amount of beeswax to be stored. Working nearby, a team of similarly committed scientists has recently pieced together some more high-tech hexagons to form the first prototype “cassette” for the new CMS endcap calorimeters.
These cassettes are the wedge-shaped building blocks of the CMS High-Granularity Calorimeters (HGCALs) which, when complete, will be the largest silicon-based detectors ever built. The two endcaps will be placed on either side of CMS to replace the experiment’s existing endcaps ready for the High-Luminosity LHC (HL-LHC), which is due to start operating in 2030.
As HGCAL physicist Dimitra Tsionou from National Taiwan University explains, the new calorimeter represents a significant advancement in detection technology. “HGCAL is effectively a 5D calorimeter: it performs 3D spatial reconstruction, energy reconstruction, and has very high timing resolution”.
This technology will allow HGCAL to handle the dramatic increase in the number of particles that the HL-LHC will deliver. As well as helping physicists to observe more rare processes, the higher luminosity provided by the HL-LHC will result in 4 to 5 times more simultaneous particle collisions than occur with the existing LHC. 40 million times each second, 140–200 collisions are expected to occur simultaneously, far more than the existing CMS endcaps are capable of measuring.
In addition, the endcaps will need to withstand the higher levels of radiation to which they will be subjected due to the increased number of collisions. HGCAL will not only handle these much harsher conditions but will also match the energy resolution, improve the particle identification and enhance the triggering performance of the existing endcaps.
HGCAL physicist Dimitra Tsionou placing a hexagonal module on a large copper cooling plate, using a vacuum support tool to avoid physical damage. Each module consists of a hexagonal silicon sensor sandwiched between a high-density copper-tungsten alloy baseplate and a printed circuit board. These modules come from six different module assembly centres: IHEP in Beijing, NTU in Taipei, TIFR in Mumbai, UCSB in Santa Barbara, CMU in Pittsburgh and TTU in Texas. (Image: CERN)When particles collide, other particles are produced, many of which will enter the endcaps to be detected by HGCAL. Although the collisions will be simultaneous, they will occur up to 10 cm away from each other, so the particles they produce will reach the endcaps about ten trillionths of a second apart. HGCAL will measure the timing of each particle – the difference between when it arrives in the detector and the moment of the collision – with the exceptional corresponding level of precision.
For the calorimeter to trace the paths of these particles back to the collision they came from, HGCAL needs to have a high density of sensors, the ‘high granularity’ from which its name derives. Each cassette is covered with sensors that will record the energy, position and timing of the particles passing through the 47 layers of the detector.
CERN will construct the 26 layers closest to the collision point, which will form the electromagnetic section and detect electrons and photons. In parallel, Fermilab will construct the 21 layers furthest from the collision point to form the hadronic section that will measure particles like protons and neutrons. A full endcap will have a total active sensor area of about 500 square metres – almost the size of two tennis courts – and will contain more than 3 million detector channels.
The first 26 layers of each endcap will form the electromagnetic section, made entirely from silicon modules assembled into double-sided cassettes. 6 cassettes are required to form two layers of a complete circle, and all 156 cassettes needed for the full section will be assembled and tested at CERN. These cassettes will then be covered with a steel-clad lead “absorber”, which will produce showers of secondary particles when hit by particles originating in the initial collisions. (Video: Karol Rapacz, CMS)“It’s very ambitious”, explained HGCAL physicist and logistics manager Ludivine Ceard from National Taiwan University. “It's the first time that a detector using this technology will be built on this scale and have to operate in such tough conditions.”
When Fermilab has constructed and tested the hadronic cassettes, they will be shipped to CERN and inserted into steel structures, the first of which was produced in Pakistan and is currently being re-assembled at CERN. An electromagnetic section will then be joined to a hadronic section to form a full HGCAL endcap.
Once both HGCAL sections are complete, the electromagnetic section will be placed on top of the hadronic section to form a full calorimeter. (Video: Karol Rapacz, CMS)“There’s so many challenging aspects”, emphasised Ceard, but she added that these challenges are definitely worth it as far as the team is concerned. “HGCAL is really special, the first of its kind”.
(Video: CMS, CERN)ehatters Thu, 01/29/2026 - 11:15 Byline Emma Hattersley Publication Date Thu, 01/29/2026 - 10:48
With accelerator operations for 2025 having ended on 8 December and the Linac4 source restarting already on 5 January, this year’s transition felt particularly short. While there was formally a year-end technical stop (YETS), accelerator activity resumed almost immediately, leaving little sense of a real pause. Nevertheless, many teams made effective use of the short stop, carrying out essential maintenance and selected improvement activities, as outlined in the previous report.
As every year, the CERN accelerator complex is restarting in a carefully sequenced manner, from the Linac4 source through the accelerator complex all the way up to the LHC, together with the attached experimental facilities. Once responsibility is handed over from shutdown coordination to the operations teams, each accelerator follows its established restart sequence: DSO (Departmental Safety Officer) tests to verify the integrity of the safety systems, equipment and control checks, machine checkout, and finally beam commissioning to prepare the beams required for the downstream machines and users.
As can be seen in figure 1, Linac4 and the PS Booster have already completed their standalone beam commissioning successfully and have handed over the baton to the PS. The East Area and the SPS are following closely behind. According to the current schedule, the 2026 physics programme will begin on 5 February with n_TOF, followed by the East Area on 11 February.
Figure 1: Restart sequence of the LHC injector chain. Red bars correspond to hardware commissioning periods, whereas yellow marks beam commissioning periods. The blue background indicates the start of the operational period, with the first physics user coming online. (Image: CERN)
For the LHC (see figure 2), DSO tests are scheduled for the end of next week, followed by around two weeks of hardware recommissioning and machine checkout. This year, the restart falls during the February holiday period, rather than the “notorious” Easter timeframe of previous years, illustrating the squeezed schedule.
Operations in 2026 will bring the Run 3 period to its conclusion, ahead of the upcoming Long Shutdown 3 (LS3). While LS2 focused primarily on the LHC Injector Upgrade (LIU) programme, LS3 will be dedicated to the High-Luminosity LHC (HL-LHC) upgrade, alongside several major projects such as the North Area consolidation, ISOLDE improvements and preparations for AWAKE Run 2c.
Although the official Run 3 target for the LHC of 500 fb⁻¹ of integrated luminosity was already reached by the end of last year, the LHC physics programme continues until 29 June 2026, with ongoing efforts to maximise physics output until the very end of the run. The injector chain will continue delivering proton and ion beams until the injectors’ own shutdowns for LS3, which will start on 31 August 2026.
Next week, the annual Chamonix workshop will take place from Monday to Thursday. Discussions will focus on the end of Run 3, preparations for LS3, the staged restart of Run 4 and a broader outlook on CERN’s future projects.
Challenging months lie ahead as Run 3 draws to a close and preparations for the next phase intensify – stay tuned!
anschaef Wed, 01/28/2026 - 12:38 Byline Bettina Mikulec, Leader of the Operations Group (BE-OP) Publication Date Thu, 01/29/2026 - 09:33On 19 January, CERN welcomed Gitanas Nausėda, President of the Republic of Lithuania. The President was received at Point 5 of the LHC (CMS experiment), in Cessy (France), by the Representative of the French Republic, Joël Bourgeot, as well as CERN’s Director-General, Mark Thomson, the Director for Accelerators and Technology, Oliver Brüning, the Director for Research and Computing, Gautier Hamel de Monchenault, the Director for Stakeholder Relations, Ursula Bassler, the Director for Finance and Human Resources, Jan-Paul Brouwer, the Director for Site Operations, Mar Capeáns, the Chief Information Officer, Enrica Porcari, and the Adviser for Relations with Associate Member States, Christoph Schäfer.
Following a general introduction to CERN’s activities, Lithuania’s President visited the CMS experimental cavern as well as the LHC tunnel. After the visit, the delegation travelled to CERN Science Gateway, where President Nausėda met members of the Lithuanian community working at CERN.
In the afternoon, a CERN–Lithuania Science and Innovation event took place, where CERN and several Lithuanian companies signed a Research and Development Agreement related to the Future Circular Collider Feasibility Study.
Vahagn Khachaturyan, President of the Republic of Armenia (centre), in the ATLAS experimental cavern with ATLAS Collaboration Spokesperson Stéphane Willocq (left) and CERN Director-General Mark Thomson (right). (Image: CERN)Later that day, CERN also welcomed Vahagn Khachaturyan, President of the Republic of Armenia. The President and his delegation were received at Point 1 of the LHC (ATLAS experiment) by CERN’s Director-General, Mark Thomson, the Director for Research and Computing, Gautier Hamel de Monchenault, the Director for Stakeholder Relations, Ursula Bassler, the Adviser for Relations with Non-Member States, Salvatore Mele, and the Adviser for Relations with Associate Member States, Christoph Schäfer.
Following a general presentation of CERN’s activities, Armenia’s President visited the ATLAS control room and experimental cavern. He was also introduced to members of the Armenian community at CERN and met Armenian teachers participating in the Armenian Teacher Programme at CERN.
anschaef Wed, 01/28/2026 - 11:30 Byline Anaïs Schaeffer Publication Date Wed, 01/28/2026 - 11:26The past two years have brought a lot of new computer-security deployments at CERN. Spurred on by the 2023 cybersecurity audit, a lot has already been achieved and 2026 should see the successful implementation of all remaining work packages. We already discussed mandatory requirements for IT service managers in a past issue of the Bulletin. This time we present upcoming changes to passwords and improvements to two-factor authentication, while the focus will be on networking in a future article.
Very early 2026 should bring an evolution of CERN’s password policy. The audit deemed that eight characters, even if a combination of lower-case and capital letters, symbols and numbers, are too few. Following best practice, like that of the NIST 800-63b standard, the CERN Computing Rules require a minimum length of 15 characters, making passwords “passphrases”. That is a lot to memorise. But it is also a lot more secure and harder to crack. And since the need for letter/number/symbol complexity has been dropped, any kind of sentence – the passphrase − would do. Gone are the days of “B055man69”, “Joshua”, “SamFox99” or “a^2+b**2=sqr(c)”. “Last Christmas”, “Strangers in the night” or “Boom Boom Pow” are the new way to go.
At the same time, and still linked to “accounts”, the Computer Security Office will conclude a penetration test conducted by an external company against CERN’s Active Directory (AD) – the holy grail of all computer knowledge at CERN and the usual and obvious target for any ransomware attack. With the AD lost, CERN’s IT systems would be considered to be fully, deeply and entirely compromised. With tremendous cost. Thus, it is imperative to review the current AD’s settings, poke for any possible weaknesses, identify potential vulnerabilities and get them subsequently and swiftly fixed before they can be exploited.
The first quarter of 2026 should also see the termination of the roll-out of two-factor authentication (2FA) to the Organization. While 2FA was deployed to the CERN Single Sign-On in 2023 and 2024, it was activated on the CERN Windows Terminal Services and LXPLUS interactive Linux service for remote desktop (RDP) and SSH access only last September. While this process went generally smoothly, the non-persistence of RDP and SSH connections, i.e. the loss of the RDP/SSH session once the Wi-Fi connection is lost or the laptop is put in sleep mode, is still an issue requiring further improvement. But for that we need your feedback. On our side, however, the game changer should arrive before Easter 2026 with the establishment of a new VPN service. Terminated in 2007 because CERN’s brilliant internet connectivity then also channelled all private/home traffic through CERN, posing a risk to the end users’ privacy and CERN’s reputation, CERN’s VPN service will be resurrected with better functionality* and, this time, a split tunnel configuration so that only traffic towards CERN can get through.
Stay tuned for these changes, hopefully to your benefit and making your (remote) life easier. And check out the next article on sprinting to the networking finish line.
*Linux, MacOS and Windows clients are supported, as is the “WireGuard UDP” protocol. Android and iOS users should also be able to connect, but due to the cacophony of possible clients, they cannot be supported centrally.
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Do you want to learn more about computer security incidents and issues at CERN? Follow our Monthly Report. For further information, questions or help, check our website or contact us at Computer.Security@cern.ch.
anschaef Tue, 01/27/2026 - 12:29 Byline Computer Security Office Publication Date Tue, 01/27/2026 - 12:24Uncertainty is inherent to the scientific process. The measurements that scientists make are only as good as the tools they use to make them. Taking uncertainty into account is part of everyday life for all scientists at CERN, but it is especially important when measuring the dimensions of accelerator and detector components. However, in the world of metrology, the science of measurement, not all laboratories agree on how uncertain they should be.
This is why, over the past few months, eleven laboratories from across Europe have come to CERN to make extremely precise measurements of the same sample object, a silicon carbide girder. By comparing their results, they will be able to come to an agreement on how to determine the uncertainty in their measurements. Many factors influence measurement uncertainty, including the measurement method used, the skills of the operators and the environment in which the measurement is taken.
Precision measurements are extremely important for accelerator laboratories, and CERN is no exception. The Large Hadron Collider (LHC) uses magnets to accelerate beams of protons and direct them onto a collision course. Extreme precision is needed to make this possible given that the components must be aligned with a tolerance of 150 microns over 200 metres. That is a margin of error equivalent to the thickness of a single sheet of paper. The concept of alignment precision is often interpreted inconsistently, and this can lead to unrealistic tolerances that can potentially have a significant negative impact on accelerator performance.
With the High-Luminosity LHC (HL-LHC) and potentially the FCC on the horizon, there are increasing demands for even higher precision. Many other accelerator laboratories are experiencing similar increases in precision requirements.
“We are all looking to become more and more precise and accurate and we are all hitting our limits,” said Patrick Bestmann, a surveying engineer at CERN. “The main issue is that, if somebody asks you how precisely you can do something, a multitude of answers are all correct, depending on the definition.”
For this reason, engineers at a number of European laboratories have organised what is officially called an interlaboratory comparison (ILC), a process recognised by the International Organization for Standardization to help laboratories to ensure measurement consistency and identify potential errors or biases. For this particular ILC, the laboratories all measured a silicon carbide girder, which was built as a prototype for CERN’s proposed Compact Linear Collider.
Now that all the laboratories have completed their measurements of the girder, they will submit them along with their uncertainties. The data will then be compared statistically to identify any outliers.
“It’s not about assigning blame or criticism, but about awareness. If someone regularly overestimates their uncertainty, they need to know, and the same is true if they underestimate it”, said Bestmann.
The laboratories hope to publish the results and present their findings in 2026 in a peer-reviewed paper. Going forward, all the participating laboratories can be sure that, when it comes to uncertainties, they will all be aligned, just like their accelerators.
roryalex Mon, 01/26/2026 - 15:16 Byline Rory Harris Publication Date Mon, 01/26/2026 - 15:15
What if the world’s largest particle accelerator could also heat homes? CERN’s Large Hadron Collider (LHC) is doing just that, thanks to a new heat exchange system. Since mid-January, heat recovered from the LHC has been supplying a heating network for a new residential and commercial area in the nearby French town of Ferney-Voltaire. This network, inaugurated on 12 December, is expected to supply the equivalent of several thousand homes. By avoiding traditional energy sources, such as gas, the network prevents the emission of thousands of tonnes of CO2.
The 27-km LHC has eight surface points and Point 8 is located close to Ferney-Voltaire. The installations at Point 8, particularly the cryogenics, need to be cooled with water. As water circulates through the equipment, the equipment cools and the water heats up. “Typically, hot water would then pass through a cooling tower, releasing heat into the atmosphere so that the cooled water could be reinjected into the equipment,” explains CERN’s energy coordinator, Nicolas Bellegarde. “In the new set-up, hot water initially passes through two 5-MW heat exchangers, which transfer thermal energy to the new heating network in Ferney-Voltaire.”
As one of the new network’s heat sources, CERN provides heat whenever possible, as long as it does not impact its activities. At present, Ferney-Voltaire is only using up to 5 MW from CERN but, with two heat exchangers in the system, this could theoretically be doubled, especially when CERN’s accelerators are fully operational. In summer 2026, CERN will stop the LHC for several years of maintenance and upgrades, known as Long Shutdown 3 (LS3), to prepare for the upcoming High-Luminosity LHC. Some Point 8 installations will continue to be cooled, enabling CERN to supply between 1 and 5 MW to the network during LS3, with the exception of a total of five months spread over this multi-year period.
One of the two 5-MW heat exchangers at LHC Point 8 (Image: CERN)Driven by a commitment to environmentally responsible research, CERN has implemented many initiatives to help reduce the impact of its activities on the environment. Energy recovery is a key part of CERN’s energy management strategy, in line with ISO 50001 requirements, alongside keeping energy consumption to a minimum and improving energy efficiency. Other projects include CERN’s Prévessin Data Centre, inaugurated in 2024, which is equipped with a heat-recovery system set to warm most site buildings from winter 2026/2027, and the future recovery of heat from LHC Point 1 cooling towers to supply buildings on CERN’s Meyrin site. Together, these initiatives will save 25–30 GWh per year as of 2027, marking significant progress in CERN’s responsible energy management.
katebrad Mon, 01/26/2026 - 09:48 Byline Kate Kahle Anna Cook Publication Date Wed, 01/28/2026 - 15:23Millions of asteroids orbit the Sun, most of them unnoticed. Far more rarely, larger objects cause serious damage on the ground, as was seen in the Tunguska explosion in 1908 and in the Chelyabinsk airburst more than a century later. Impacts with global consequences are extremely unlikely, but their potential severity means that they remain a scientifically relevant risk.
If an asteroid were to be discovered on a collision course with Earth and the warning time were short, the options available would be limited. Among the most controversial last-resort strategies is nuclear deflection, an approach that not only raises political and ethical questions but is also subject to a scientific unknown: how does asteroid material respond to an extreme and sudden deposition of energy?
This question is difficult to answer because it cannot be tested at full scale. Asteroids vary widely in composition and internal structure, and direct observations offer only partial clues. Laboratory experiments, meanwhile, struggle to reproduce the relevant pressures and timescales. This is where accelerator facilities can provide a rare experimental bridge between theory and reality.
In the latest issue of the CERN Courier, scientists report on experiments carried out at CERN’s HiRadMat facility, where high-energy proton beams from the Super Proton Synchrotron were used to probe meteorite material under conditions relevant to planetary-defence scenarios. The work addresses the fundamental challenge of obtaining reliable material-response data in a domain where models often outpace measurements.
The experiments reveal behaviours that current assumptions may not fully capture, raising important questions about fragmentation, strength and energy coupling under extreme loading . The results highlight how much remains uncertain and why reducing that uncertainty matters for informed decision -making.
These accelerator-based studies complement a growing body of evidence from space missions, which has shown that asteroids range from loosely bound aggregates to more cohesive bodies. Future rare events, including the close flyby of near-Earth asteroid Apophis in 2029, will provide opportunities to observe how large objects respond to natural stresses. Together, laboratory experiments and space-based measurements are beginning to fill critical gaps in our understanding.
Learn more about this intriguing study in the January/February edition of the CERN Courier.
Insa Meinke Wed, 01/21/2026 - 12:16 Byline Caroline Clavien Publication Date Wed, 01/21/2026 - 16:15What is the fate of the Universe? Why is there more matter than antimatter? What lurks beyond the Standard Model?
Each of these questions requires further study of the Higgs boson. Each is explored in the latest edition of the CERN Courier, the international magazine for particle physicists. Physicists have been studying the Higgs boson intensively since its discovery in 2012, but many questions remain unanswered. The High-Luminosity LHC, which will succeed the LHC in 2030, will provide a dataset of 380 million Higgs bosons, a sample more than ten times larger than any studied to date. LHC physicists Valentina Cairo and Steven Lowette explore what physicists expect to learn from this exceptional dataset. Leading accelerator physicists Gianluigi Arduini, Philip Burrows and Jacqueline Keintzel then report on the findings of a working group that was mandated to compare seven proposals for large-scale colliders to follow the High-Luminosity LHC.
Credit: Photographic reproduction by Guillaume Piolle of Wassily Kandinsky’s Yellow-Red-Blue, Public DomainThe Higgs boson is thought to have first given mass to elementary particles in a Universe-wide reconfiguration of fundamental forces that rippled throughout the cosmos a fraction of a second after the Big Bang. This edition of the Courier also explores another such shift, first imagined by physicists Roberto Peccei and Helen Quinn, that may have taken place even earlier. If correct, the fruit of this theory would be a new elementary particle known as the axion. CERN theorist Clara Murgui explains how this theory has the potential to solve two deep puzzles in fundamental science. Representatives of the MADMAX and ALPHA experiments describe two innovative new ways that will be used to search for the axion in the next ten years.
Also in the January/February edition: the community says farewell to Chen-Ning Yang; news from a busy two months in neutrino physics; the first indirect evidence for primordial monsters; and much more.
cmenard Fri, 01/16/2026 - 14:46 Publication Date Fri, 01/16/2026 - 14:39
The accelerator complex delivered its last beams of 2025 on 8 December before beginning the year-end technical stop (YETS). During a technical stop, the responsibility for accelerator coordination is passed to the Engineering department’s Accelerator Coordination and Engineering group (EN-ACE) to oversee the many interventions planned in the accelerator complex.
LHC core drilling machine in the underground area, with the operating team. (Image: CERN)This YETS has been particularly intense, being both shorter than usual, to maximise the limited time for physics in 2026, and very busy, to make essential preparations for Long Shutdown 3 (LS3), which begins in late June (for the LHC) and late August (for the rest of the complex). At times, more than 500 people per day have been accessing the underground complex.
A large number of activities have been taking place across the accelerator sites in preparation for LS3, ranging from 3D site scans to cabling campaigns to civil engineering works. In this last category, works have been progressing in the HL-LHC galleries, with the performance of some important tests that are necessary to successfully connect the superconducting magnet currents and crab cavities waveguides. A 6-metre-deep test core drilling is currently taking place, which is invaluable as 28 similar cores will be required during LS3 (14 each at Points 1 (ATLAS experiment) and 5 (CMS experiment)), making this test critical for refining procedures and minimising risks to the shutdown schedule. Lessons are being learned as the test drilling encountered some unexpected voids and fissures in the substructure. This allowed some of the water used to lubricate the drilling to escape into the LHC tunnel below – an unpleasant surprise for the technical teams concerned. Fortunately, the consequences are minor, with no equipment damaged, and the techniques for drilling and sealing are being updated to allow current and future works to continue safely and efficiently.
The experimental areas have also been very busy.
AWAKE already started its long shutdown in June 2025 and immediately began the complex choreography of dismantling and de-cabling old equipment in preparation for installation of the next upgrade. This has included the construction of new facilities on the surface of SPS Point 4 to handle the old CERN Neutrinos to Gran Sasso (CNGS) equipment, which now enters the dismantling phase.
The ISOLDE complex started its long shutdown on 8 December. A major activity there is the ISOLDE dump replacement to allow the safe reception of the post-LS3 beam from the Proton Synchrotron Booster (PSB), following the increase from 1.4 GeV to 2 GeV beam energy. The shutdown programme also includes extensive consolidation of the electrical circuits of the PSB-to-ISOLDE transfer line (named the “BTY” line). This began spectacularly with the removal of the first magnets by the Handling and Engineering team (EN-HE), as shown in the images below. In parallel, consolidation and upgrade activities will target several Radioactive Ion Beam delivery systems, in addition to HIE-ISOLDE radiofrequency cryomodule refurbishment work to recover the nominal secondary beam acceleration performance.
Removal of the vertical bend from the PS Booster BTY transfer line (left) and removal of a spectrometer as part of the AWAKE dismantling choreography (right). (Image: CERN)And the North Area complex has been preparing the way for the long shutdown with a large number of activities during this YETS. Some examples of the many activities are: adding new fire compartment doors to improve the safety of the complex; adding new electrical transformers and fibre-optic connections to improve the infrastructure’s robustness; and archiving many high-resolution pictures of the facility in the Panoramas database to allow remote visits by both CERN staff preparing interventions and visitors curious about the facility.
As you read this, the process of handing the accelerators back to the operations teams has already begun, starting with Linac4 and the PS Booster. The Linac4 source is already pulsing, in preparation for what we hope will be a productive although necessarily short year of protons in the CERN accelerator chain in 2026 before LS3 commences.
The Linac4 operations status page showing the source pulsing with 40mA of H- ions on Friday, 9 January – ready for the 2026 run. (Image: CERN)For further reading, the detailed schedule of the YETS25-26 can be found here.
David Nisbet, Group leader of the Accelerator Coordination and Engineering group (EN-ACE)
anschaef Thu, 01/15/2026 - 11:59 Publication Date Fri, 01/16/2026 - 11:52
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