Cern News

CERN Science Gateway: interactive exhibitions for everyone

The opening of CERN Science Gateway is imminent and, inside the impressive building, teams are adding the final touches to the labs for schools, auditorium for events and three permanent, hands-on exhibitions.

CERN Science Gateway’s exhibitions are unlike anything CERN has developed before. The Microcosm, which closed its doors last year, showcased CERN behind the scenes and was primarily aimed at visitors with some prior understanding of physics. In contrast, the Science Gateway exhibits, which are as hands-on and interactive as possible, target visitors aged 8 and up, from those with no scientific background to the most experienced of particle physicists – there’s something for everyone.

Spanning the Route de Meyrin in two tubes reminiscent of CERN’s accelerators are two of the three permanent exhibitions: Discover CERN and Our Universe. The walkway from the Science Gateway reception takes you first to Discover CERN, which is divided into Accelerate, to your right, and Collide, to your left. Accelerate houses a real, working particle accelerator, an LHC dipole magnet and a wealth of interactive exhibits to demonstrate the science and engineering concepts behind accelerator development. Collide features slices of a detector, guiding you through colliding and detecting particles, analysing the collisions and all the technological developments needed to make this happen.

Similarly, Our Universe, located in the second tube, is divided into Exploring the Unknown to your right and Back to the Big Bang to your left. Back to the Big Bang takes visitors on a trip back through time to find out where their particles come from. It situates CERN’s research within the timeline of the Universe, featuring interactive exhibits on scientific concepts from dark matter to nucleosynthesis in stars and telling the CERN stories behind them. Exploring the Unknown is a more reflective space, inviting visitors to contemplate some of the big mysteries in physics, through themes such as the void and the invisible. Developing from a dialogue between artists and theorists, it features four artworks specially commissioned for Science Gateway: Round About 4 Dimensions by Julius von Bismarck, data.gram by Ryoji Ikeda, Chroma VII by Yunchul Kim and TAFAA-SINGULARITY by Chloé Delarue. Each artist has previously been an artist in residence at the Arts at CERN programme.

Bird’s eye diagram of the new Science Gateway buildings. The two squares to the left house the reception, the auditorium and the labs. In the larger central tube are the Discover CERN exhibitions, to the right of them are the Our Universe exhibitions, and to the very right is the Quantum World exhibition.

Next to the two tubes is the exhibition Quantum World. Here, visitors can experience the strange laws of quantum physics as if they were themselves a particle. This immersive experience is audio-guided and interactive. In addition, playful hands-on exhibits include quantum tennis, quantum karaoke and a double slit experiment.

The interactive exhibits were all developed in collaboration with CERN scientists and expert exhibition developers. Each activity was tested with the target audiences in mind and many encourage open exploration and collaboration between visitors, with help from the Science Gateway guides.

“The exhibits give all visitors the chance to interact with CERN’s science, technology and even the people,” explains Emma Sanders, head of the Science Gateway exhibition team. “We really enjoyed the CERNois visits last week and often heard members of the CERN community keen to come back soon with members of their family.

“CERN thrives on collaboration,” continues Emma, “and Science Gateway is no exception. I thank all the many members of the CERN community who have been involved in developing the exhibitions, as well as all the guide volunteers, for making this exciting interactive experience possible.”

Want to explore the exhibitions further? It’s not too late to become a CERN Science Gateway guide. Interactions with real people who work at CERN make the experience unforgettable for visitors, and may give you some surprising benefits, too!

ndinmore Thu, 09/28/2023 - 11:36 Byline Naomi Dinmore Publication Date Thu, 09/28/2023 - 17:30

Accelerator Report: SPS and LHC lead-ion physics: navigating technical hurdles for success The LHC fixed display showing the last verification and validation step before establishing collisions, initially with 119 bunches, which will gradually be increased to up to 1248 bunches in the coming days. (Image: CERN)

On Tuesday 26 September, the Operations team successfully circulated stable beams of lead nuclei in the LHC, ahead of the heavy-ion physics run.

The end of the proton physics run is an excellent time to look back and reflect. The proton physics run for the North Area started on 1 May, 150 days ago. One important criterion for both the accelerators and the experiments is the “beam availability” – i.e. the amount of time the beam was ready for the experiments. This year, the beam was available for the NA experiments 85.8% of the time it was requested, which is more than our target (85%). This represents a significant improvement over the 2022 proton physics run, which reached only 72% of beam availability due to numerous major issues.

The 14.2% of non-availability was caused by a total of 1859 faults, amounting to 495 hours, as documented in the Accelerator Fault Tracking (AFT) system. This system is used across all CERN accelerators to log faults, along with their start and end times. Experts then review these faults to ensure consistency throughout the accelerator complex. The information is used by the equipment groups to address the issues and make decisions on system and equipment consolidation. Approximately half of the beam non-availability (6.7%) was due to issues in the SPS injector chain (Linac 4, PS Booster and PS). The other half (7.5%) resulted from faults within the SPS itself.

The longest fault we experienced this year was the malfunction of a dipole magnet in the SPS on 6 September. While the actual replacement took only a few hours, the time required to restore the vacuum to a level suitable for beam circulation resulted in a 24-hour downtime.

A more comprehensive analysis of the unavailability of each of the accelerators will be conducted at the end of 2023.

In the meantime, the LHC kicked off its lead-ion commissioning earlier than originally planned for 2023 (although still later than anticipated, following the helium circuit and insulation vacuum leak that occurred during the summer). Indeed, despite a swift restart at the end of August, various unrelated technical problems arose in the injectors, the LHC machine and the experiments, leading to additional delays. These issues prevented the planned proton–proton reference run from occurring before the start of the lead-ion collisions.

One significant problem emerged on Thursday, 31 August, when a vacuum leak was detected at Point 8 in a TDIS (target dump injection system), which plays a crucial role in safeguarding the machine against beam losses during the injection process. On Tuesday, 8 September, another leak occurred in a different but identical component of the same system at Point 8. In both cases, the vacuum team took swift action, identified the leaks and successfully sealed them.

Due to these repairs, the affected parts of the system could no longer be repositioned into the machine, limiting the level of protection for beam injection at Point 8, but still guaranteeing a sufficient level of protection for injecting lead ions. If no further issues arise, both the LHC and the experiments are looking forward to a productive and successful lead-ion physics run.

Meanwhile, protons continue to be the primary focus for the rest of the accelerator complex. They are supplied to various areas, including ISOLDE, the PS East Area and n_TOF and the AD and ELENA. AWAKE, situated behind the SPS, will also continue to rely on proton beams in the upcoming weeks.

anschaef Thu, 09/28/2023 - 11:33 Byline Rende Steerenberg Publication Date Thu, 09/28/2023 - 11:29

An exabyte of disk storage at CERN

CERN’s data store has now crossed the remarkable capacity threshold of one exabyte, meaning that CERN has one million terabytes of disk space ready for data!

CERN’s data store not only serves LHC physics data, but also the whole spectrum of experiments and services needing online data management. This data capacity is provided using 111 000 devices, predominantly hard disks along with an increasing fraction of flash drives. Having such a large number of commodity devices means that component failures are common, so the store is built to be resilient, using different data replication methods. These disks, most of which are used to store physics data, are orchestrated by CERN’s open-source software solution, EOS, which was created to meet the LHC’s extreme computing requirements.

“We reached this new all-time record for CERN’s storage infrastructure after capacity extensions for the upcoming LHC heavy-ion run,” explains Andreas Peters, EOS project leader. “It is not just a celebration of data capacity, it is also a performance achievement, thanks to the reading rate of the combined data store crossing, for the first time, the one terabyte per second (1 TB/s) threshold.”

This graph shows the capacity evolution of CERN’s data store. (Image: CERN)

“This achievement marks the accomplishment of a significant target in data-handling capabilities. It sets new standards for high-performance storage systems in scientific research for future LHC runs,” emphasises Joachim Mnich, CERN Director for Research and Computing.

How many bytes is that?
Megabyte = 1 000 000 bytes
Gigabyte = 1 000 000 000 bytes
Terabyte = 1 000 000 000 000 bytes
Petabyte = 1 000 000 000 000 000 bytes
Exabyte = 1 000 000 000 000 000 000 bytes

anschaef Wed, 09/27/2023 - 12:17 Byline Tim Smith Publication Date Fri, 09/29/2023 - 09:45

The LHC lead-ion collision run starts

The LHC is back delivering collisions to the experiments after the successful leak repair in August. But instead of protons, it is now the turn of lead ion beams to collide, marking the first heavy-ion run in 5 years. Compared to previous runs, the lead nuclei will be colliding with an increased energy of 5.36 TeV per nucleon (compared to 5.02 TeV per nucleon previously) and the collision rate has increased by a factor of 10. The primary physics goal of this run is the study of the elusive state of matter known as quark-gluon plasma, that is believed to have filled the Universe up to a millionth of a second after the Big Bang and can be recreated in the laboratory in heavy-ion collisions.

Quark-gluon plasma is a state of matter made of free quarks (particles that make up hadrons such as the proton and the neutron) and gluons (carriers of the strong interaction, which hold the quarks together inside the hadrons). In all but the most extreme conditions, quarks cannot exist individually and are bound inside hadrons. In heavy-ion collisions however, hundreds of protons and neutrons collide, forming a system with such density and temperature that the colliding nuclei melt together, and a tiny fireball of quark-gluon plasma forms, the hottest substance known to exist. Inside this fireball quarks and gluons can move around freely for a split-second, until the plasma expands and cools down, turning back into hadrons.

Event display showing a lead-lead collision in the ATLAS detector. (Image: ATLAS)

The ongoing heavy-ion run is expected to bring significant advances in our understanding of quark-gluon plasma. In addition to the improved parameters of the lead-ion beams, significant upgrades have been performed in the experiments that detect and analyse the collisions. ALICE, the experiment which primarily focuses on studies of quark-gluon plasma, is now using an entirely new mode of data processing storing all collisions without selection, resulting in up to 100 times more collisions being recorded per second. In addition, its track reconstruction efficiency and precision have increased due to the installation of new subsystems and upgrades of existing ones. CMS and ATLAS have also upgraded their data acquisition, reconstruction and selection infrastructure to take advantage of the increased collision rates. ATLAS has installed improved Zero Degree Calorimeters, which are critical in event selection and provide new measurement capabilities. LHCb, in addition to performing studies of lead-lead collisions with an upgraded tracking system, is preparing a unique programme of fixed-target collisions of lead nuclei with other types of nuclei using its unique SMOG2 apparatus that allows various gases to be injected into the LHC collision area.

Event display showing a lead-lead collision in the CMS detector. (Image: CMS)

Studies of quark-gluon plasma in this heavy-ion will focus on rare processes such as the production of heavy quarks, quarkonium states, real and virtual photons and heavy nuclear states. The increased number of collisions is expected to allow measurement of the temperature of the plasma using thermal radiation in the form of photons and electron-positron pairs. Hydrodynamic properties of the near-perfect liquid state of matter will be measured in greater detail and “tomography” using particles such as the charm or beauty quarks that are produced in the initial phase of the collision, pass through the plasma and are detected afterwards. All these measurements will be far more precise than before.

In addition to studies of quark-gluon plasma, the experiments will be looking at so-called ultra-peripheral collisions of heavy ions, in which the beams do not collide directly, but one beam emits a high-energy photon that strikes the other beam. These collisions will be used to probe gluonic matter inside nuclei and to study rare phenomena such as light-by-light scattering and τ lepton photoproduction.

Five years after the previous heavy-ion run, expectations are high.

ptraczyk Tue, 09/26/2023 - 16:59 Byline Piotr Traczyk Publication Date Thu, 09/28/2023 - 09:29

HiLumi News: Recombination dipole prototype successfully tested for the LHC’s high-luminosity upgrade

The LHC requires a variety of different types of magnets to direct the beams around its circular shape. Currently installed in the LHC’s interaction regions are 9.45-m-long double-aperture magnets of 2.8 T, manufactured by BNL for the RHIC. For HL-LHC, the interaction region magnets will be replaced by the recombination dipole D2, the longest of all the HL-LHC interaction region magnets. While also based on the same Nb-Ti technology as the previous magnets, the D2 magnets have a stronger field (4.5 T) and a wider aperture. Thanks to this upgrade, the “kick” given to the beams to bring them on the same path around IP1 and IP5 will increase from 28 to 35 tesla-metres (T·m), allowing space to install the crab cavities.

The HL-LHC will need four units of these magnets, plus two spares. These six magnets are deliverables of a collaboration agreement between INFN-Genova and CERN. The Italian institute was in charge of the design and construction of a short model and a full-size prototype, and is now carrying out the series production. The construction of the magnets took place at ASG Superconductors, Genova.

After the prototype magnet was delivered in late 2021, the team at CERN integrated it in 2022 into a cold mass with two prototype orbit correctors providing 5 T·m dipolar kicks. These correctors are based on a canted cosine theta technology, proposed in the late 60s, which has had an increase in attention in the past decade for its potential wide range of applications. A prototype of these correctors was developed at CERN, a second one in China under the helm of IHEP, and the series magnets are an in-kind contribution of China. These were then assembled alongside the D2 prototype in a 14-m-long cold mass at CERN.

The team at CERN ran power tests of the magnets from late 2022 to June 2023. The prototype D2 reached its performance requirements at 1.9 K, corresponding to operation at 7 TeV in the HL-LHC plus a 0.5 TeV margin (the so-called ultimate current).

“We are extremely satisfied with the performances of the D2 prototype,” says Stefania Farinon, from INFN-Genova, who is in charge of the D2 collaboration agreement. “We are now finishing the construction of the first series unit at ASG, which will be delivered to CERN at the end of September.”

Power test of the D2 prototype. (Image: CERN)

The powering of the correctors, already successfully tested in a standalone mode, showed an electrical issue in one of the circuits that will be analysed by the cold mass integration team. “Debugging these types of problems is one of the reasons to build prototype cold masses and not start directly with the series production,” says Herve Prin, in charge of the cold mass assembly in the Large Magnet Facility at CERN.

As pointed out by Arnaud Foussat, the project engineer in charge of the magnet and of the correctors from CERN: “These results are remarkable, also considering that this complex prototype cold mass, assembling parts from Italy, CERN and China, was manufactured in a period in which collaborations and activities were jeopardised by the pandemic.” 

ndinmore Tue, 09/26/2023 - 10:52 Byline Ezio Todesco Naomi Dinmore Publication Date Fri, 09/29/2023 - 09:48

Computer security: T2U4U2FA* *Thanks to you for using 2FA

One year ago, the CERN Computer Security team and the IT Identity Management team started the CERN-wide roll-out of multifactor authentication to staff and users. The combination of a second “factor”, i.e. something you have, and the primary factor “something you know”1, i.e. your password, provides the ultimate silver bullet for the protection of your CERN computing account: “2-factor authentication” (2FA). This was seriously needed as, in our latest phishing campaign in August 2022, more than 2000(!) people provided their password to a fake login page. 2FA would have protected their accounts from any evil-doing. Hence, many thanks to you ─ T2U!

Technically, this new 2FA protection is not very different from that deployed for your Google mailbox or your bank account. And bear in mind that your CERN account is there not only to give you access to your emails and your money but also potentially provides you with much more power, with much more severe consequences if your account password is lost to an evil, malicious attacker. With your password gone, the attacker might be able to steer particle beams into uncharted territories and create previously unseen damage, delete our precious physics data or manipulate it such that none of our results make sense anymore, misuse data centre computing resources to create crypto-money or manipulate our invoices to extract money, or access confidential and sensitive information owned by or stored within the Organization…

After extensive experience of using 2FA to protect administrator access to CERN’s data centre (using the “AIADM” gateways), expert access to our accelerator control systems (via the so-called “ROG”) and CERN’s VPN service, last summer we started adding 2FA protection to CERN web applications accessible via CERN’s new Single Sign-On (SSO)2. Since then, the new CERN SSO requires your 2FA about every 12 hours when you stay on the same device. That’s all. One quick extra step every half-day when using the same device. And at every login you can choose whether you want to use the one-time password (OTP) generator installed on your Android smartphone or iPhone (top row in the photo below, currently we recommend the privacy-preserving and secure “Aegis Authenticator”; and “Raivo OTP”;), a pocket-style OTP generator (middle row) or a USB hardware dongle (“Yubikey”, bottom row). Easy as pie ─ but also a potential pain in the arm when you are part of the population who regularly forgets their smartphone or keychain at home. In that case, it’s like with your dosimeter: do a U-turn and head back home. So, acknowledged!, 2FA does add another (minor) inconvenience when accessing CERN’s computing facilities. Sorry for that ─ S4T.

On the other hand, as mentioned before, 2FA provides the right industrial-standard state-of-the-art level of access protection that the Organization desperately needed. In fact, more than 5500 account owners from ATS & FHR desktop support, the BE/EN/FAP/IPT/IT/SY/TE departments, the CERN Pension Fund, the DG-IA/LS/TMC services & the Directorate secretariats, the EP-AGS/AID-DC/CMD/CMG/DI/DT/ESE/LBC/LBD/LBO/SFT/SME, HR-DHO/PXE, and RCS-SIS groups, the HSE unit, the IR sector, SCE-SMS/Site Security, SERCO support, and MPEs of the TH department as well as users of the AIADM/AITNADM/CS-CCR-DEV/ROG gateways, have already (been) enrolled for 2FA protection of their accounts. And the numbers of complaints, problems, issues, questions and the like raised with us were few and far between ─ and very appreciated to make 2FA even better. Hence, once more, a big THANKS to you ─ T2U!!!!

And we’re not done yet. We still have some communities at CERN who have not yet been enrolled into 2FA protection. We’ll address this by the end of the year. And we’ll look into enlarging 2FA protection to other means, like CERN’s Terminal Service. And, of course, we’ll follow the evolution of 2FA software and might add new/other 2FA tokens to make your life even easier. If you’re interested in joining and haven’t done so yet, check out our Knowledge Base article here. Thanks to you for using 2FA protection: T2U4U2FA. And S4T ─ sorry for those ─ who aren’t yet enjoying its merits and benefits…

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.

 

[1] The third and last factor is “something you are” like using your fingerprint, an iris scan (like when entering the accelerator complex) or a blood/DNA sample. For obvious reasons, none of these are appropriate for digital access to your CERN account.

[2]  Websites behind the old SSO are not affected as this old SSO has to die and shall RIP by the end of the year.

 

ndinmore Tue, 09/26/2023 - 10:23 Byline Computer Security team Publication Date Tue, 09/26/2023 - 10:12

ALPHA experiment at CERN observes the influence of gravity on antimatter

Isaac Newton's historic work on gravity was apparently inspired by watching an apple fall to the ground from a tree. But what about an “anti-apple” made of antimatter, would it fall in the same way if it existed? According to Albert Einstein’s much-tested theory of general relativity, the modern theory of gravity, antimatter and matter should fall to Earth in the same way. But do they, or are there other long-range forces beyond gravity that affect their free fall?

In a paper published today in Nature, the ALPHA collaboration at CERN’s Antimatter Factory shows that, within the precision of their experiment, atoms of antihydrogen – a positron orbiting an antiproton – fall to Earth in the same way as their matter equivalents.

“In physics, you don't really know something until you observe it,” says ALPHA spokesperson Jeffrey Hangst. “This is the first direct experiment to actually observe a gravitational effect on the motion of antimatter. It’s a milestone in the study of antimatter, which still mystifies us due to its apparent absence in the Universe.”

Gravity is the attractive force between any two objects with mass. It is by far the weakest of the four fundamental forces of nature. Antihydrogen atoms are electrically neutral and stable particles of antimatter. These properties make them ideal systems in which to study the gravitational behaviour of antimatter.

The ALPHA collaboration creates antihydrogen atoms by taking negatively charged antiprotons, produced and slowed down in the Antimatter Factory’s AD and ELENA machines, and binding them with positively charged positrons accumulated from a sodium-22 source. It then confines the neutral – but slightly magnetic – antimatter atoms in a magnetic trap, which prevents them from coming into contact with matter and annihilating.

Until now, the team has concentrated on spectroscopic studies in the ALPHA-2 device, shining laser light or microwaves onto the antihydrogen atoms to measure their internal structure. But the ALPHA team has also built a vertical apparatus called ALPHA-g, which received its first antiprotons in 2018 and was commissioned in 2021. The ‘g’ denotes the local acceleration of gravity, which, for matter, is about 9.81 metres per second squared. This apparatus makes it possible to measure the vertical positions at which the antihydrogen atoms annihilate with matter once the trap’s magnetic field is switched off, allowing the atoms to escape.

This is exactly what the ALPHA researchers did in their new investigation, following a proof-of-principle experiment with the original ALPHA set-up in 2013. They trapped groups of about 100 antihydrogen atoms, one group at a time, and then slowly released the atoms over a period of 20 seconds by gradually ramping down the current in the top and bottom magnets of the trap. Computer simulations of the ALPHA-g set-up indicate that, for matter, this operation would result in about 20% of the atoms exiting through the top of the trap and 80% through the bottom, a difference caused by the downward force of gravity. By averaging the results of seven release trials, the ALPHA team found that the fractions of anti-atoms exiting through the top and bottom were in line with the results of the simulations.

The full study involved repeating the experiment several times for different values of an additional “bias” magnetic field, which could either enhance or counteract the force of gravity. By analysing the data from this “bias scan”, the team found that, within the precision of the current experiment (about 20% of g), the acceleration of an antihydrogen atom is consistent with the familiar, attractive gravitational force between matter and the Earth.

“It has taken us 30 years to learn how to make this anti-atom, to hold on to it, and to control it well enough that we could actually drop it in a way that it would be sensitive to the force of gravity,” says Hangst. “The next step is to measure the acceleration as precisely as we can,” continues Hangst. “We want to test whether matter and antimatter do indeed fall in the same way. Laser-cooling of antihydrogen atoms, which we first demonstrated in ALPHA-2 and will implement in ALPHA-g when we return to it in 2024, is expected to have a  significant impact on the precision.”

CERN’s Antimatter Factory is a unique facility in the world for producing and studying antimatter. Two other experiments at this facility, AEgIS and GBAR, share with ALPHA the goal of measuring with high precision the gravitational acceleration of atomic antimatter. Also at the Antimatter Factory is the BASE experiment. Its main focus is to compare with high precision the properties of the proton with those of its antimatter twin, and it has recently compared the gravitational behaviour of these two particles. 

Click here to download the video news release. 

Further information: 

Collection of videos

Virtual tour of ALPHA

angerard Mon, 09/25/2023 - 17:15 Publication Date Wed, 09/27/2023 - 17:00

Two new members elected to the Senior Staff Advisory Committee (“the Nine”) in 2023

The electronic voting process for the Senior Staff Advisory Committee (known as “the Nine”) closed at midnight on Friday, 25 August 2023.

The Senior Staff Advisory Committee was created in 1981 to serve as a channel of communication between the senior staff (grade 8 and above) and the Director-General. It is made up of nine members elected by the senior staff for a period of three years. The Nine share the ideas and feedback of the senior staff with the Director-General and offer advice on questions concerning scientific activities, organisational matters and use of resources. Elections for the Nine are held every year, ensuring an annual rotation of members.

In August 2023, out of the 576 senior staff members eligible to vote, 326 voted.

Candidates stood for election for Electoral Group 2 (members of IT, RCS, SCE, HSE and ATS, and members of EP and TH who are NOT in Electoral Group 1)*.

Sophie Baron and Giovanna Vandoni were elected to replace the outgoing Nine members, Stefan Lüders and myself. Their mandate is from September 2023 to August 2026.

Christoph Rembser has been appointed as the new spokesperson for one year, starting in September 2023. The Nine now consists of the two newly elected members together with [end of mandate in brackets]:

• Marzia Bernardini [2025]
• Markus Brugger [2025]
• Cécile Curdy [2025]
• Niko Neufeld [2025]
• David Barney [2024]
• Christophe Delamare [2024]
• Christoph Rembser [2024]

I wish to congratulate the newly elected members and warmly thank all the other candidates for having stood for election. Special thanks go to our polling officer, Alberto Pace.

Eric Montesinos, outgoing spokesperson of the Nine

______________________________________

The Nine seek input for topics to be investigated throughout the year, so please feel free to get in touch, either by sending an email to mailto:the-nine@cern.ch or by contacting one of its members. In 2023/2024 we meet once per week, on Thursdays from 12.15 p.m. to 1.45 p.m., and you are welcome to join the first 15–20 minutes of our meeting to raise your topic in person. We would appreciate your contacting one of us, either in person or by phone/email, in advance for more information, e.g. where we meet.
Details of previous topics are available on the Nine pages.

* Electoral Group 1: Research physicists/principal research physicists and applied physicists/principal applied physicists in EP or TH; Electoral Group 2: Members of IT, RCS, SCE, HSE and ATS, and members of EP and TH who are NOT in Electoral Group 1; Electoral Group 3: Members of DG, FAP, HR, IPT, IR and PF.

anschaef Fri, 09/22/2023 - 12:14 Publication Date Tue, 09/26/2023 - 11:09

ATLAS measures strength of the strong force with record precision

Binding together quarks into protons, neutrons and atomic nuclei is a force so strong, it’s in the name. The strong force, which is carried by gluon particles, is the strongest of all fundamental forces of nature – the others being electromagnetism, the weak force and gravity. Yet, it’s the least precisely measured of these four forces. In a paper just submitted to Nature Physics, the ATLAS collaboration describes how it has used the Z boson, the electrically neutral carrier of the weak force, to determine the strength of the strong force with an unprecedented uncertainty of below 1%.

The strength of the strong force is described by a fundamental parameter in the Standard Model of particle physics called the strong coupling constant. While knowledge of the strong coupling constant has improved with measurements and theoretical developments made over the years, the uncertainty on its value remains orders of magnitude larger than that of the coupling constants for the other fundamental forces. A more precise measurement of the strong coupling constant is required to improve the precision of theoretical calculations of particle processes that involve the strong force. It is also needed to address important unanswered questions about nature. Could all of the fundamental forces be of equal strength at very high energy, indicating a potential common origin? Could new, unknown interactions be modifying the strong force in certain processes or at certain energies?

In its new study of the strong coupling constant, the ATLAS collaboration investigated Z bosons produced in proton–proton collisions at CERN's Large Hadron Collider (LHC) at a collision energy of 8 TeV. Z bosons are typically produced when two quarks in the colliding protons annihilate. In this weak-interaction process, the strong force comes into play through the radiation of gluons off the annihilating quarks. This radiation gives the Z boson a “kick” transverse to the collision axis (transverse momentum). The magnitude of this kick depends on the strong coupling constant. A precise measurement of the distribution of Z-boson transverse momenta and a comparison with equally precise theoretical calculations of this distribution allows the strong coupling constant to be determined.

In the new analysis, the ATLAS team focused on cleanly selected Z-boson decays to two leptons (electrons or muons) and measured the Z-boson transverse momentum via its decay products. A comparison of these measurements with theoretical predictions enabled the researchers to precisely determine the strong coupling constant at the Z-boson mass scale to be 0.1183 ± 0.0009. With a relative uncertainty of only 0.8%, the result is the most precise determination of the strength of the strong force made by a single experiment to date. It agrees with the current world average of experimental determinations and state-of-the-art calculations known as lattice quantum chromodynamics (see figure below).

This record precision was accomplished thanks to both experimental and theoretical advances. On the experimental side, the ATLAS physicists achieved a detailed understanding of the detection efficiency and momentum calibration of the two electrons or muons originating from the Z-boson decay, which resulted in momentum precisions ranging from 0.1% to 1%. On the theoretical side, the ATLAS researchers used, among other ingredients, cutting-edge calculations of the Z-boson production process that consider up to four “loops” in quantum chromodynamics. These loops represent the complexity of the calculation in terms of contributing processes. Adding more loops increases the precision.

“The strength of the strong nuclear force is a key parameter of the Standard Model, yet it is only known with percent-level precision. For comparison, the electromagnetic force, which is 15 times weaker than the strong force at the energy probed by the LHC, is known with a precision better than one part in a billion,” says CERN physicist Stefano Camarda, a member of the analysis team. “That we have now measured the strong force coupling strength at the 0.8% precision level is a spectacular achievement. It showcases the power of the LHC and the ATLAS experiment to push the precision frontier and enhance our understanding of nature.”

The new ATLAS value of the strong coupling constant compared with other measurements. (Image: ATLAS/CERN)

 

abelchio Wed, 09/20/2023 - 12:01 Publication Date Mon, 09/25/2023 - 10:00

Quest for the curious magnetic monopole continues

Magnets, those everyday objects we stick to our fridges, all share a unique characteristic: they always have both a north and a south pole. Even if you tried breaking a magnet in half, the poles would not separate – you would only get two smaller dipole magnets. But what if a particle could have a single pole with a magnetic charge? For over a century, physicists have been searching for such magnetic monopoles. A new study from the ATLAS collaboration at the Large Hadron Collider (LHC) places new limits on these hypothetical particles, adding new clues for the continuing search.

In 1931, physicist Paul Dirac proved that the existence of magnetic monopoles would be consistent with quantum mechanics and require — as has been observed — the quantisation of the electric charge. In the 1970s, magnetic monopoles were also predicted by new theories attempting to unify all the fundamental forces of nature, inspiring physicist Joseph Polchinski to claim that their existence was “one of the safest bets that one can make about physics not yet seen.” Magnetic monopoles might have been present in the early Universe but diluted to an unnoticeably tiny density during the early exponential expansion phase known as cosmic inflation. 

Researchers at the ATLAS experiment are searching for pairs of point-like magnetic monopoles with masses of up to about 4 teraelectronvolts (TeV). These pairs could be produced in 13 TeV collisions between protons via two different mechanisms: “Drell-Yan”, in which a virtual photon produced in the collisions creates the magnetic monopoles, or “photon-fusion”, in which two virtual photons radiated by the protons interact to create the magnetic monopoles.

The collaboration’s detection strategy relies on Dirac’s theory, which says that the magnitude of the smallest magnetic charge (gD) is equivalent to 68.5 times the fundamental unit of electric charge, the charge of the electron (e). Consequently, a magnetic monopole of charge 1gD would ionise matter in a similar way as a high-electric-charge object (HECO). When a particle ionises the detector material, ATLAS records the energy deposited, which is proportional to the square of the particle’s charge. Hence, magnetic monopoles or HECOs would leave large energy deposits along their trajectories in the ATLAS detector. Since the ATLAS detector was designed to record low-charge and neutral particles, the characterisation of these high-energy deposits is vital to the search for monopoles and HECOs.

In their new study, the ATLAS researchers combed through the experiment’s full dataset from Run 2 of the LHC (2015–2018) in search of magnetic monopoles and HECOs. The search made use of the detector’s transition radiation tracker and the finely segmented liquid-argon electromagnetic calorimeter. The result places some of the tightest limits yet on the rate of production of magnetic monopoles.

The search targeted monopoles of magnetic charge 1gD and 2gD and HECOs of electric charge 20e, 40e, 60e, 80e and 100e, with masses between 0.2 TeV and 4 TeV. Compared to the previous ATLAS search, the new result benefited from the larger, complete Run-2 dataset. This was also the first ATLAS analysis to consider the photon-fusion production mechanism.

With no evidence of either magnetic monopoles or HECOs in the dataset, the ATLAS researchers established new limits on the production rate and mass of monopoles with a magnetic charge of 1gD and 2gD. ATLAS remains the experiment with the greatest sensitivity to monopoles in this charge range; the smaller LHC experiment MoEDAL-MAPP has previously studied a larger charge range and has also searched for monopoles with a finite size.

ATLAS physicists will continue their quest to find magnetic monopoles and HECOs, further refining their search techniques and developing new strategies to study both Run-2 and Run-3 data.

Find out more on the ATLAS website.

abelchio Fri, 09/15/2023 - 13:38 Byline ATLAS collaboration Publication Date Fri, 09/15/2023 - 13:32

Quest for the curious magnetic monopole continues

Magnets, those everyday objects we stick to our fridges, all share a unique characteristic: they always have both a north and a south pole. Even if you tried breaking a magnet in half, the poles would not separate – you would only get two smaller dipole magnets. But what if a particle could have a single pole with a magnetic charge? For over a century, physicists have been searching for such magnetic monopoles. A new study from the ATLAS collaboration at the Large Hadron Collider (LHC) places new limits on these hypothetical particles, adding new clues for the continuing search.

In 1931, physicist Paul Dirac proved that the existence of magnetic monopoles would be consistent with quantum mechanics and require — as has been observed — the quantisation of the electric charge. In the 1970s, magnetic monopoles were also predicted by new theories attempting to unify all the fundamental forces of nature, inspiring physicist Joseph Polchinski to claim that their existence was “one of the safest bets that one can make about physics not yet seen.” Magnetic monopoles might have been present in the early Universe but diluted to an unnoticeably tiny density during the early exponential expansion phase known as cosmic inflation. 

Researchers at the ATLAS experiment are searching for pairs of point-like magnetic monopoles with masses of up to about 4 teraelectronvolts (TeV). These pairs could be produced in 13 TeV collisions between protons via two different mechanisms: “Drell-Yan”, in which a virtual photon produced in the collisions creates the magnetic monopoles, or “photon-fusion”, in which two virtual photons radiated by the protons interact to create the magnetic monopoles.

The collaboration’s detection strategy relies on Dirac’s theory, which says that the magnitude of the smallest magnetic charge (gD) is equivalent to 68.5 times the fundamental unit of electric charge, the charge of the electron (e). Consequently, a magnetic monopole of charge 1gD would ionise matter in a similar way as a high-electric-charge object (HECO). When a particle ionises the detector material, ATLAS records the energy deposited, which is proportional to the square of the particle’s charge. Hence, magnetic monopoles or HECOs would leave large energy deposits along their trajectories in the ATLAS detector. Since the ATLAS detector was designed to record low-charge and neutral particles, the characterisation of these high-energy deposits is vital to the search for monopoles and HECOs.

In their new study, the ATLAS researchers combed through the experiment’s full dataset from Run 2 of the LHC (2015–2018) in search of magnetic monopoles and HECOs. The search made use of the detector’s transition radiation tracker and the finely segmented liquid-argon electromagnetic calorimeter. The result places some of the tightest limits yet on the rate of production of magnetic monopoles.

The search targeted monopoles of magnetic charge 1gD and 2gD and HECOs of electric charge 20e, 40e, 60e, 80e and 100e, with masses between 0.2 TeV and 4 TeV. Compared to the previous ATLAS search, the new result benefited from the larger, complete Run-2 dataset. This was also the first ATLAS analysis to consider the photon-fusion production mechanism.

With no evidence of either magnetic monopoles or HECOs in the dataset, the ATLAS researchers established new limits on the production rate and mass of monopoles with a magnetic charge of 1gD and 2gD. ATLAS remains the experiment with the greatest sensitivity to monopoles in this charge range; the smaller LHC experiment MoEDAL-MAPP has previously studied a larger charge range and has also searched for monopoles with a finite size.

ATLAS physicists will continue their quest to find magnetic monopoles and HECOs, further refining their search techniques and developing new strategies to study both Run-2 and Run-3 data.

Find out more on the ATLAS website.

abelchio Fri, 09/15/2023 - 13:38 Byline ATLAS collaboration Publication Date Fri, 09/15/2023 - 13:32

ALICE reports new charmonia measurements in LHC Run 3 3D drawing of the ALICE detector. (Image: ALICE)

Earlier this month, almost 700 physicists from all over the world met in Houston, Texas, to attend the 30th edition of the Quark Matter conference, the largest conference in the field of heavy-ion physics. At this meeting, the ALICE collaboration presented its first results based on data collected with the upgraded detector in 2022, the first year of Run 3 of the LHC. Before the start of Run 3, ALICE underwent a major upgrade of its experimental apparatus to allow the recording of 50-100 times more Pb-Pb collisions and up to 500 times more proton-proton collisions than in previous runs. In addition, upgrades of the tracking detectors improved the pointing resolution by a factor 3-6. All in all, many new high-precision results will become available in the coming years.

One of the new results presented at the Quark Matter conference was the measurement of the production of two different states of charmonia in proton-proton collisions. Charmonia are particles that consist of a charm and an anti-charm quark, with a total mass of about 3 GeV, more than 3 times that of the proton. Charmonia have a characteristic decay signature, producing an electron-positron pair or a positive and a negative muon. 

There are a variety of charmonium states, with different binding energies, from the tightly bound J/ψ (binding energy of approximately 650 MeV) to the weakly bound – and two times larger – ψ(2S) (binding energy of 50 MeV). In heavy-ion collisions, these states melt in the quark–gluon plasma (QGP) and a reduced number of them is observed in the final state, a phenomenon known as charm suppression. Physicists can determine the temperature of the plasma by measuring how the different states are suppressed. Such measurements have played an important role in the field over the years, starting from early measurements at the SPS in the 1990s. 

The key to measuring charmonium suppression is knowing the production rates. These rates can be determined by measuring the production of quarkonia in proton-proton collisions, where there is no suppression. This provides the reference for the measurements performed in Pb-Pb collisions. 

The upgraded ALICE detector has a broad kinematic coverage that allows it to study J/ψ and ψ(2S) down to zero transverse momentum in two different and complementary regions. In the central region, charmonium is reconstructed from its decay into an e+e- pair in the central barrel detectors, while in the forward region it is detected in its decay channel µ+µ-, in the muon spectrometer.  

The proton-proton statistics collected in LHC Runs 1 and 2 allowed ALICE to study the ψ(2S) yields in the forward region, but not in the central region. The data from 2022 represents an increase of the total number of collisions by a factor of 300, making it possible to measure the production rate of the ψ(2S) in the central region for the first time. The results, based on 500 billion minimum-bias proton-proton collisions, show that both the excited and the ground charmonium states can be accessed over the whole ALICE kinematic region and this will constrain the models of quarkonium production and open the way for more detailed measurements in the upcoming heavy-ion run. 

Ratio of ψ(2S) to J/ψ in LHC Run 3 proton-proton collisions as a function of transverse momentum, showing ALICE’s capability for measurements of the excited and ground charmonium states in the central (red points) and forward (black points) region. (Image: ALICE) ptraczyk Fri, 09/15/2023 - 12:21 Byline ALICE collaboration Publication Date Fri, 09/15/2023 - 11:52

ALICE reports new charmonia measurements in LHC Run 3 3D drawing of the ALICE detector. (Image: ALICE)

Earlier this month, almost 700 physicists from all over the world met in Houston, Texas, to attend the 30th edition of the Quark Matter conference, the largest conference in the field of heavy-ion physics. At this meeting, the ALICE collaboration presented its first results based on data collected with the upgraded detector in 2022, the first year of Run 3 of the LHC. Before the start of Run 3, ALICE underwent a major upgrade of its experimental apparatus to allow the recording of 50-100 times more Pb-Pb collisions and up to 500 times more proton-proton collisions than in previous runs. In addition, upgrades of the tracking detectors improved the pointing resolution by a factor 3-6. All in all, many new high-precision results will become available in the coming years.

One of the new results presented at the Quark Matter conference was the measurement of the production of two different states of charmonia in proton-proton collisions. Charmonia are particles that consist of a charm and an anti-charm quark, with a total mass of about 3 GeV, more than 3 times that of the proton. Charmonia have a characteristic decay signature, producing an electron-positron pair or a positive and a negative muon. 

There are a variety of charmonium states, with different binding energies, from the tightly bound J/ψ (binding energy of approximately 650 MeV) to the weakly bound – and two times larger – ψ(2S) (binding energy of 50 MeV). In heavy-ion collisions, these states melt in the quark–gluon plasma (QGP) and a reduced number of them is observed in the final state, a phenomenon known as charm suppression. Physicists can determine the temperature of the plasma by measuring how the different states are suppressed. Such measurements have played an important role in the field over the years, starting from early measurements at the SPS in the 1990s. 

The key to measuring charmonium suppression is knowing the production rates. These rates can be determined by measuring the production of quarkonia in proton-proton collisions, where there is no suppression. This provides the reference for the measurements performed in Pb-Pb collisions. 

The upgraded ALICE detector has a broad kinematic coverage that allows it to study J/ψ and ψ(2S) down to zero transverse momentum in two different and complementary regions. In the central region, charmonium is reconstructed from its decay into an e+e- pair in the central barrel detectors, while in the forward region it is detected in its decay channel µ+µ-, in the muon spectrometer.  

The proton-proton statistics collected in LHC Runs 1 and 2 allowed ALICE to study the ψ(2S) yields in the forward region, but not in the central region. The data from 2022 represents an increase of the total number of collisions by a factor of 300, making it possible to measure the production rate of the ψ(2S) in the central region for the first time. The results, based on 500 billion minimum-bias proton-proton collisions, show that both the excited and the ground charmonium states can be accessed over the whole ALICE kinematic region and this will constrain the models of quarkonium production and open the way for more detailed measurements in the upcoming heavy-ion run. 

Ratio of ψ(2S) to J/ψ in LHC Run 3 proton-proton collisions as a function of transverse momentum, showing ALICE’s capability for measurements of the excited and ground charmonium states in the central (red points) and forward (black points) region. (Image: ALICE) ptraczyk Fri, 09/15/2023 - 12:21 Byline ALICE collaboration Publication Date Fri, 09/15/2023 - 11:52

CERN Science Gateway: pre-inauguration for the CERN community CERN Science Gateway (Image: CERN)

In a few weeks, on 7 October, CERN will formally inaugurate CERN Science Gateway. As our Director-General, Fabiola Gianotti, noted in her email to personnel on 11 September, this is a project to which many of you have contributed and which we all look forward to becoming a unique place where visitors of all ages, from near and far, will learn all about CERN’s science and people. She has invited the CERN community and families to a pre-inauguration of Science Gateway on 19 and 20 September.

Please note that, contrary to the original announcement, visitors must be over 18 years of age. This is due to safety reasons, as Science Gateway will still be a construction site. Thank you for your understanding. From 8 October, you will be able to visit with family members of all ages.

Many of you have expressed interest and we have received several questions, which we will address here:

Do family members need a CERN Access card?

Accompanying family members over the age of 18 (see above) will need to have their CERN Access card with them. If they do not have a CERN Access card, they can obtain one at building 55. More details are available in the CERN admin e-guide.

Do I need to register?

You must register for the pre-inauguration talk on Tuesday 19 September at 1.30 p.m. You do not need to register for anything else during the two days. More details here.

Will I be able to see all areas of CERN Science Gateway?

This pre-inauguration, including the visits, will take place during the final, intense stage of preparing for the formal inauguration on 7 October and the opening to the public as of 8 October. Several areas of the building are a worksite, so for safety reasons some areas may be cordoned off. 

Will there be hands-on activities?

The visits will be an experience of looking rather than experimenting with the exhibits and lab activities. This will allow work to carry on, to have everything ready for the opening to the public. Thank you in advance for your understanding.

You can find more information here.

Enjoy this CERN Science Gateway trailer to see what is in store. (Video: CERN) ndinmore Thu, 09/14/2023 - 14:53 Byline Ana Godinho Publication Date Fri, 09/15/2023 - 12:46

CERN Science Gateway: pre-inauguration for the CERN community CERN Science Gateway (Image: CERN)

In a few weeks, on 7 October, CERN will formally inaugurate CERN Science Gateway. As our Director-General, Fabiola Gianotti, noted in her email to personnel on 11 September, this is a project to which many of you have contributed and which we all look forward to becoming a unique place where visitors of all ages, from near and far, will learn all about CERN’s science and people. She has invited the CERN community and families to a pre-inauguration of Science Gateway on 19 and 20 September.

Please note that, contrary to the original announcement, visitors must be over 18 years of age. This is due to safety reasons, as Science Gateway will still be a construction site. Thank you for your understanding. From 8 October, you will be able to visit with family members of all ages.

Many of you have expressed interest and we have received several questions, which we will address here:

Do family members need a CERN Access card?

Accompanying family members over the age of 18 (see above) will need to have their CERN Access card with them. If they do not have a CERN Access card, they can obtain one at building 55. More details are available in the CERN admin e-guide.

Do I need to register?

You must register for the pre-inauguration talk on Tuesday 19 September at 1.30 p.m. You do not need to register for anything else during the two days. More details here.

Will I be able to see all areas of CERN Science Gateway?

This pre-inauguration, including the visits, will take place during the final, intense stage of preparing for the formal inauguration on 7 October and the opening to the public as of 8 October. Several areas of the building are a worksite, so for safety reasons some areas may be cordoned off. 

Will there be hands-on activities?

The visits will be an experience of looking rather than experimenting with the exhibits and lab activities. This will allow work to carry on, to have everything ready for the opening to the public. Thank you in advance for your understanding.

You can find more information here.

Enjoy this CERN Science Gateway trailer to see what is in store. (Video: CERN) ndinmore Thu, 09/14/2023 - 14:53 Byline Ana Godinho Publication Date Fri, 09/15/2023 - 12:46

Accelerator Report: Getting lead ions ready for physics

In about a week, lead ions will be sent from the SPS into the LHC to collide in the accelerator’s four big experiments – ALICE, ATLAS, CMS and LHCb. This is a particular highlight for the ALICE collaboration, which has been eagerly awaiting lead-ion collisions since the end of Long Shutdown 2 (LS2), when its detector was upgraded. ALICE (A Large Ion Collider Experiment) is a detector dedicated to heavy-ion physics. It is designed to study the physics of strongly interacting matter at extreme energy densities, where a phase of matter called quark-gluon plasma forms.

The following week, the SPS will also provide slow-extracted lead-ion beam pulses of 4.5 seconds per cycle to the North Area experiments. The NA61/SHINE experiment is the main user of lead ions in the North Area, but other users will also benefit from these during the short period they are available.

In the last two weeks of the 4-week 2023 run, the PS will provide lead ions to the East Area, where the CHIMERA facility irradiates electronics with high-energy heavy ions to study the effects of cosmic radiation on electronics used in the CERN accelerators and experiments, as well as for space missions and avionics.

Although the lead-ion physics period is relatively short, it is of great importance, and special care is taken by the experts and operations teams to provide high-quality beams.

The origin of lead ions and lead-ion beams
Lead ions are “born” in the source of Linac3, where a pure lead sample is evaporated: oxygen gas and lead vapour are injected into the source plasma chamber. A microwave is applied to create the plasma in which the lead and oxygen atoms are ionised. These ions are then extracted, partially stripped and accelerated. The lead-ion charge after the stripping process is 54+, meaning that 28 of the 82 electrons have been removed (a lead atom originally has 82 electrons).

These lead ions are then transported and injected into the next machine in the chain, LEIR (Low Energy Ion Ring), which can receive single or multiple pulses, depending on the beam intensities needed (the more pulses, the more lead ions accumulated and the higher the intensity).

For the LHC beam, LEIR receives seven pulses from Linac3, each of which is cooled using electron cooling to reduce the beam size. In this process, a “cold” electron beam is sent along over a distance of 2.5 m with the “hot” lead-ion beam. The exchange of energy between the two beams reduces the beam size of the lead-ion beam, leaving space to inject another pulse from Linac3 and repeat the cooling process. Finally, two bunches are accelerated and extracted towards the PS.

The SPS lead-ion beam production cycle for the LHC. In yellow, the beam intensity increases in 14 steps, representing the 14 injections from the PS. (Image: CERN)

The PS further accelerates the two-bunch beam and performs several longitudinal beam manipulations using the radiofrequency (RF) cavities to finally obtain four bunches spaced by 100 ns. After up to 14 cycles, these four bunches of Pb54+ ions are then transported to the SPS. In the transfer line between the PS and the SPS, the ions are fully stripped of their remaining electrons to become Pb82+ ions divided into 56 bunches spaced by 100 ns.

After an initial acceleration in the SPS, the beam is slip-stacked (see box) to reduce the bunch spacing to 50 ns, thus doubling the total lead-ion beam intensity in the LHC. Following a final acceleration phase, the beam is extracted and injected into the LHC, either in a clockwise or counter-clockwise direction. The LHC will be filled with up to 1248 bunches per beam.

As I write this article, the Linac3, LEIR and PS machines are producing lead-ion beams on a routine basis. The focus is now on completing the commissioning of slip-stacking in the SPS; this process is already well advanced and it looks likely that slip-stacked ion beams will be delivered to the LHC in the coming weeks.

A new method to reduce bunch spacing for lead ion beams

Measurement of the bunches during the slip-stacking process. At the bottom of the graph, you can see the two parts of the injected beam. Between the times 53000 and 54000, the bunches on the right-hand side slip along the machine towards the other beam until they are interleaved/stacked. At the bottom of the graph, the bunch spacing is 100 ns; after the slip-stacking, at the top of the graph, the same number of bunches are spaced by only 50 ns. (Image: CERN)

Over the last few years, the CERN ion injector complex has undergone a series of upgrades in preparation for a doubling of the total intensity of the lead-ion beams for the HL-LHC. In the SPS, teams began using a technique known as “momentum slip-stacking”, which involves injecting two batches of four lead-ion bunches separated by 100 nanoseconds to produce a single batch of eight lead-ion bunches separated by 50 nanoseconds.

In this process, the 56 bunches injected into the SPS are divided among two RF systems, which each receive 28 bunches. As there is a small frequency difference between these two RF systems, half of the beam travels slightly faster along the SPS circumference (known as “slipping”). Once the two halves of the beam are placed so that the space between two bunches is 50 ns, the beam is interleaved (or “stacked”). This allows the total number of bunches injected into the LHC to increase from 648 in Run 2 to 1248 in Run 3 and subsequent runs.

anschaef Thu, 09/14/2023 - 12:33 Byline Rende Steerenberg Publication Date Wed, 09/13/2023 - 12:28

Accelerator Report: Getting lead ions ready for physics

In about a week, lead ions will be sent from the SPS into the LHC to collide in the accelerator’s four big experiments – ALICE, ATLAS, CMS and LHCb. This is a particular highlight for the ALICE collaboration, which has been eagerly awaiting lead-ion collisions since the end of Long Shutdown 2 (LS2), when its detector was upgraded. ALICE (A Large Ion Collider Experiment) is a detector dedicated to heavy-ion physics. It is designed to study the physics of strongly interacting matter at extreme energy densities, where a phase of matter called quark-gluon plasma forms.

The following week, the SPS will also provide slow-extracted lead-ion beam pulses of 4.5 seconds per cycle to the North Area experiments. The NA61/SHINE experiment is the main user of lead ions in the North Area, but other users will also benefit from these during the short period they are available.

In the last two weeks of the 4-week 2023 run, the PS will provide lead ions to the East Area, where the CHIMERA facility irradiates electronics with high-energy heavy ions to study the effects of cosmic radiation on electronics used in the CERN accelerators and experiments, as well as for space missions and avionics.

Although the lead-ion physics period is relatively short, it is of great importance, and special care is taken by the experts and operations teams to provide high-quality beams.

The origin of lead ions and lead-ion beams
Lead ions are “born” in the source of Linac3, where a pure lead sample is evaporated: oxygen gas and lead vapour are injected into the source plasma chamber. A microwave is applied to create the plasma in which the lead and oxygen atoms are ionised. These ions are then extracted, partially stripped and accelerated. The lead-ion charge after the stripping process is 54+, meaning that 28 of the 82 electrons have been removed (a lead atom originally has 82 electrons).

These lead ions are then transported and injected into the next machine in the chain, LEIR (Low Energy Ion Ring), which can receive single or multiple pulses, depending on the beam intensities needed (the more pulses, the more lead ions accumulated and the higher the intensity).

For the LHC beam, LEIR receives seven pulses from Linac3, each of which is cooled using electron cooling to reduce the beam size. In this process, a “cold” electron beam is sent along over a distance of 2.5 m with the “hot” lead-ion beam. The exchange of energy between the two beams reduces the beam size of the lead-ion beam, leaving space to inject another pulse from Linac3 and repeat the cooling process. Finally, two bunches are accelerated and extracted towards the PS.

The SPS lead-ion beam production cycle for the LHC. In yellow, the beam intensity increases in 14 steps, representing the 14 injections from the PS. (Image: CERN)

The PS further accelerates the two-bunch beam and performs several longitudinal beam manipulations using the radiofrequency (RF) cavities to finally obtain four bunches spaced by 100 ns. After up to 14 cycles, these four bunches of Pb54+ ions are then transported to the SPS. In the transfer line between the PS and the SPS, the ions are fully stripped of their remaining electrons to become Pb82+ ions divided into 56 bunches spaced by 100 ns.

After an initial acceleration in the SPS, the beam is slip-stacked (see box) to reduce the bunch spacing to 50 ns, thus doubling the total lead-ion beam intensity in the LHC. Following a final acceleration phase, the beam is extracted and injected into the LHC, either in a clockwise or counter-clockwise direction. The LHC will be filled with up to 1248 bunches per beam.

As I write this article, the Linac3, LEIR and PS machines are producing lead-ion beams on a routine basis. The focus is now on completing the commissioning of slip-stacking in the SPS; this process is already well advanced and it looks likely that slip-stacked ion beams will be delivered to the LHC in the coming weeks.

A new method to reduce bunch spacing for lead ion beams

Measurement of the bunches during the slip-stacking process. At the bottom of the graph, you can see the two parts of the injected beam. Between the times 53000 and 54000, the bunches on the right-hand side slip along the machine towards the other beam until they are interleaved/stacked. At the bottom of the graph, the bunch spacing is 100 ns; after the slip-stacking, at the top of the graph, the same number of bunches are spaced by only 50 ns. (Image: CERN)

Over the last few years, the CERN ion injector complex has undergone a series of upgrades in preparation for a doubling of the total intensity of the lead-ion beams for the HL-LHC. In the SPS, teams began using a technique known as “momentum slip-stacking”, which involves injecting two batches of four lead-ion bunches separated by 100 nanoseconds to produce a single batch of eight lead-ion bunches separated by 50 nanoseconds.

In this process, the 56 bunches injected into the SPS are divided among two RF systems, which each receive 28 bunches. As there is a small frequency difference between these two RF systems, half of the beam travels slightly faster along the SPS circumference (known as “slipping”). Once the two halves of the beam are placed so that the space between two bunches is 50 ns, the beam is interleaved (or “stacked”). This allows the total number of bunches injected into the LHC to increase from 648 in Run 2 to 1248 in Run 3 and subsequent runs.

anschaef Thu, 09/14/2023 - 12:33 Byline Rende Steerenberg Publication Date Wed, 09/13/2023 - 12:28

Accelerating stroke prevention

The complex system of the CERN accelerator chain requires immense precision in order to operate. To address this need, CERN researchers developed artificial intelligence (AI) algorithms that predict and diagnose anomalies, minimising failures and keeping our infrastructure working around the clock. The same algorithms have the potential to improve people’s lives when applied to complications that occur in the human body.

The CAFEIN* platform was developed at CERN in collaboration with Consiglio Nazionale delle Ricerche and Politecnico di Milano in Italy to address challenges in both fundamental research and medicine. In particular, in the latter, it enables the detection of pathologies in the human body (such as brain pathologies) and predicts the risk of disease recurrence.

Among brain pathologies, stroke is one of the leading causes of severe disability worldwide. It is associated with a significant social and economic burden, which will dramatically increase over the coming decades due to the ageing population.

By correctly assessing a stroke patient’s risks and potential outcome, it is possible to provide improved and personalised treatment to help prevent relapse. The TRUSTroke project** was developed to ensure that as many patients as possible are treated and to reduce the numbers of patients discharged too early from hospital.

Under the coordination of Vall d'Hebron, a leading healthcare campus in Barcelona, CERN and eleven other partners from across Europe joined forces to assist clinicians, caregivers, and patients by creating AI algorithms using data confined to the hospital environment, which is the key feature of the CAFEIN platform. This approach, which uses local data samples without exchanging them, is known as Federated Learning (FL), and it can guarantee the confidentiality of patient data by sharing only the necessary information without sharing any individual’s personal data.

“AI algorithms trained using FL platforms like CAFEIN are being applied more and more in the medical domain, where privacy prevents the sharing of personal data. In addition to the ongoing TRUSTroke project, CERN’s developments are being used at the Medical School of the National and Kapodistrian University of Athens in brain-pathology screening using MRIs or, more recently, to develop risk-based cancer screening tools with the International Agency for Research on Cancer (IARC).”, says Luigi Serio, principal scientist in the Technology Department at CERN.

Two online public events have been organised to provide more information on the project:

• “TRUSTroke webinar on Federated Learning” on 28 September, 12.00 p.m. More information: https://indico.cern.ch/e/trustrokewebinar.
• “How AI and a CERN federated learning platform can assist clinicians in the management of stroke patients” on 29 September, 9.00 a.m. More information: https://indico.cern.ch/e/trustroke.

* The Computer-Aided deFEcts detection, Identification and classificatioN (CAFEIN) project has received support from the CERN budget for knowledge transfer to medical applications through a grant awarded in 2019. https://kt.cern/kt-fund/projects/cafein-federated-network-platform-development-and-deployment-ai-based-analysis-and

**The TRUSTroke project is funded by the European Union in the call HORIZON-HLTH-2022-STAYHLTH-01-two-stage under grant agreement No. 101080564

 

ndinmore Wed, 09/13/2023 - 11:48 Byline Kristiane Bernhard-Novotny Marzena Lapka Publication Date Wed, 09/13/2023 - 11:42

Accelerating stroke prevention

 

The complex system of the CERN accelerator chain requires immense precision in order to operate. To address this need, CERN researchers developed artificial intelligence (AI) algorithms that predict and diagnose anomalies, minimising failures and keeping our infrastructure working around the clock. The same algorithms have the potential to improve people’s lives when applied to complications that occur in the human body.

The CAFEIN* platform was developed at CERN in collaboration with Consiglio Nazionale delle Ricerche and Politecnico di Milano in Italy to address challenges in both fundamental research and medicine. In particular, in the latter, it enables the detection of pathologies in the human body (such as brain pathologies) and predicts the risk of disease recurrence.

Among brain pathologies, stroke is one of the leading causes of severe disability worldwide. It is associated with a significant social and economic burden, which will dramatically increase over the coming decades due to the ageing population.

By correctly assessing a stroke patient’s risks and potential outcome, it is possible to provide improved and personalised treatment to help prevent relapse. The TRUSTroke project** was developed to ensure that as many patients as possible are treated and to reduce the numbers of patients discharged too early from hospital.

Under the coordination of Vall d'Hebron, a leading healthcare campus in Barcelona, CERN and eleven other partners from across Europe joined forces to assist clinicians, caregivers, and patients by creating AI algorithms using data confined to the hospital environment, which is the key feature of the CAFEIN platform. This approach, which uses local data samples without exchanging them, is known as Federated Learning (FL), and it can guarantee the confidentiality of patient data by sharing only the necessary information without sharing any individual’s personal data.

“AI algorithms trained using FL platforms like CAFEIN are being applied more and more in the medical domain, where privacy prevents the sharing of personal data. In addition to the ongoing TRUSTroke project, CERN’s developments are being used at the Medical School of the National and Kapodistrian University of Athens in brain-pathology screening using MRIs or, more recently, to develop risk-based cancer screening tools with the International Agency for Research on Cancer (IARC).”, says Luigi Serio, principal investigator in the Technology Department at CERN.

Two online public events have been organised to provide more information on the project:

• “TRUSTroke webinar on Federated Learning” on 28 September, 12.00 p.m. More information: https://indico.cern.ch/e/trustrokewebinar.
• “How AI and a CERN federated learning platform can assist clinicians in the management of stroke patients” on 29 September, 9.00 p.m. More information: https://indico.cern.ch/e/trustroke.

----------

* The Computer-Aided deFEcts detection, Identification and classificatioN (CAFEIN) project has received support from the CERN budget for knowledge transfer to medical applications through a grant awarded in 2019. https://kt.cern/kt-fund/projects/cafein-federated-network-platform-development-and-deployment-ai-based-analysis-and

**The TRUSTroke project is funded by the European Union in the call HORIZON-HLTH-2022-STAYHLTH-01-two-stage under grant agreement No. 101080564

ndinmore Wed, 09/13/2023 - 11:48 Publication Date Wed, 09/13/2023 - 11:42

A new generation of iron-dominated electromagnets has been successfully tested at CERN

Many physics experiments at CERN require moderate magnetic fields (around 2 tesla) in a large gap over a large volume. These are currently created by normal-conducting, iron-dominated electromagnets. While robust and reliable, these resistive magnets require significant electrical power – in the MW range – and therefore can be costly to operate.

To combat this, engineers from the CERN TE-MSC group are investigating intermediate temperature superconductors (operating at 20 kelvin and above) to be used in the coil winding of electromagnets with the aim of increasing magnet efficiency. They have now designed, manufactured and successfully tested a conductor for use in these electromagnets. This proof-of-principle demonstrator is a superconducting coil wound from a magnesium diboride (MgB2) cable mounted inside an iron yoke. As a first step, the demonstrator was tested at 4.5 K, where it reached the expected magnetic field. The group designed the demonstrator to be easily scalable to large, iron-dominated electromagnets, such as some of the magnets needed for the Search for Hidden Particles (SHiP) experiment. The innovative design could also be retrofitted to existing magnets by replacing the normal-conducting coils with the new coils.

The MgB2 cable is one of the units manufactured for the Superconducting Link of the High-Luminosity Large Hadron Collider (HL-LHC) at CERN. The MgB2 strands were developed by CERN together with ASG S.p.A during the R&D phase of the HL-LHC Cold Powering work package and were produced by ASG S.p.A. The MgB2 cable was also developed by CERN and then industrialised for production in long lengths by Tratos Cavi S.p.A, a member of the ICAS consortium. The iron yoke and the winding formers were fabricated with the support of CERN EN-MME.

The demonstrator magnet in the horizontal position, during the last stages of assembly (left), as well as when attached to a vertical insert for testing in one of the CERN SM18 cryogenic test stations (right). (Image: CERN)
​​​​​​

For the initial test, the engineers cooled the demonstrator down to 4.5 K with liquid helium and successfully ramped it up to 5 kA, the design current, without any resistive transition or resistive voltage across the coil. They then warmed it up to room temperature and cooled it again to 4.5 K: the magnet again reached the target current of 5 kA after this thermal cycle, with no quench. Magnetic measurements at cryogenic temperature confirmed that the demonstrator met design expectations, both in terms of field strength – the magnetic field in the pole gap is 1.95 T at 5 kA – and field quality.

The measured dipole magnetic field in the centre of the magnet compared to simulations. (Image: CERN)

“These encouraging results demonstrate the robustness of the MgB2 cable and the suitability of its coil design for iron-dominated electromagnets,” explains TE-MSC group leader Arnaud Devred. “The team warmly thank Richard Jacobsson for inspiring this work, Davide Tommasini for his exploratory feasibility study and José Miguel Jimenez for his unconditional support for this project.”

The next step for the team is to work with the CERN TE-CRG group to carry out a test of the demonstrator in gaseous helium at 20 K. Ultimately, the coil will be inserted into a dedicated cryostat to enable its operation at 20 K while keeping the surrounding iron yoke at room temperature.

 

ndinmore Mon, 09/11/2023 - 16:49 Byline TE department Publication Date Mon, 09/11/2023 - 16:27