Jobs – Page 4 of 505 – CERN Courier

Robert Aymar 1936–2024

Robert Aymar, CERN Director-General from January 2004 to December 2008, passed away on 23 September at the age of 88. An inspirational leader in big-science projects for several decades, including the International Thermonuclear Experimental Reactor (ITER), his term of office at CERN was marked by the completion of construction and the first commissioning of the Large Hadron Collider (LHC). His experience of complex industrial projects proved to be crucial, as the CERN teams had to overcome numerous challenges linked to the LHC’s innovative technologies and their industrial production.

Robert Aymar was educated at Ecole Polytechnique in Paris. He started his career in plasma physics at Commissariat à l’Energie Atomique (CEA), since renamed Commissariat à l’Energie Atomique et aux Energies Alternatives, at the time when thermonuclear fusion was declassified and research started on its application to energy production. After being involved in several studies at CEA, Aymar contributed to the design of the Joint European Torus, the European tokamak project based on conventional magnet technology, built in Culham, UK in the late 1970s. In the same period, CEA was considering a compact tokamak project based on superconducting magnet technology, for which Aymar decided to use pressurised superfluid helium cooling – a technology then recently developed by Gérard Claudet and his team at CEA Grenoble. Aymar was naturally appointed head of the TORE SUPRA tokamak project, built at CEA Cadarache from 1977 to 1988. The successful project served inter alia as an industrial-size demonstrator of superfluid helium cryogenics, which became a key technology of the LHC.

Robert Aymar set out to bring together the physics of the infinitely large and the infinitely small

As head of the Département des Sciences de la Matière at CEA from 1990 to 1994, Robert Aymar set out to bring together the physics of the infinitely large and the infinitely small, as well as the associated instrumentation, in a department that has now become the Institut de Recherche sur les Lois Fondamentales de l’Univers. In that position, he actively supported CEA-CERN collaboration agreements on R&D for the LHC and served on many national and international committees. In 1993 he chaired the LHC external review committee, whose recommendation proved decisive in the project’s approval. From 1994 to 2003, he led the ITER engineering design activities under the auspices of the International Atomic Energy Agency, establishing the basic design and validity of the project that would be approved for construction in 2006. In 2001, the CERN Council called on his expertise once again by entrusting him to chair the external review committee for CERN’s activities.

When Robert Aymar took over as Director-General of CERN in 2004, the construction of the LHC was well under way. But there were many industrial and financial challenges, and a few production crises still to overcome. During his tenure, which saw the ramp-up, series production and installation of major components, the machine was completed and the first beams circulated. That first start-up in 2008 was followed by a major technical problem that led to a shutdown lasting several months. But the LHC had demonstrated that it could run, and in 2009 the machine was successfully restarted. Robert Aymar’s term of office also saw a simplification of CERN’s structure and procedures, aimed at making the laboratory more efficient. He also set about reducing costs and secured additional funding to complete the construction and optimise the operation of the LHC. After retirement, he remained active as scientific advisor to the head of the CEA, occasionally visiting CERN and the ITER construction site in Cadarache.

Robert Aymar was a dedicated and demanding leader, with a strong drive and search for pragmatic solutions in the activities he undertook or supervised. CERN and the LHC project own much to his efforts. He was also a man of culture with a marked interest in history. It was a privilege to serve under his direction.

BWT water dispensers at CERN: a sustainable hydration solution

Since 2011, BWT (Best Water Technology) has been a proud partner of CERN, supplying state-of-the-art water dispensers to various sites and buildings within the vast CERN complex, which spans both Switzerland and France. Our partnership with CERN is rooted in our shared commitment to sustainability, innovation, and exceptional service. Today, we are pleased to report that there are over 150 BWT water dispensers installed and actively serving the CERN community.

Enhancing Hydration at CERN

Our water dispensers provide a range of hydration options to meet the diverse needs of CERN’s staff, visitors, and contractors. With the water dispenser in use, we offer cold water, ambient water, sparkling water, and even hot water. These dispensers are strategically placed throughout CERN’s numerous facilities, ensuring that hydration is always within easy reach.

CERN’s community is a dynamic and international one, with over 17,500 people from around the world working together to push the boundaries of scientific knowledge. This includes approximately 2,500 permanent staff members, as well as countless visitors and collaborators. Ensuring access to high-quality, sustainable hydration solutions is crucial in such an environment, where long hours and intense focus are the norms.

Sustainability at the Core

BWT’s partnership with CERN goes beyond providing high-quality water; it’s about embedding sustainability into everyday practices. Our water dispensers are designed to encourage the use of reusable bottles and cups. By offering easily accessible water stations, we help reduce the reliance on single-use plastic bottles, significantly cutting down on plastic waste.

A BWT water dispenser. Credit: Best Water Technology

The dispensers’ user-friendly design, with spouts specifically engineered to accommodate reusable bottles, further promotes this eco-friendly practice. This is particularly important at CERN, where sustainability is a core value. By choosing BWT, CERN demonstrates its commitment to environmental stewardship and the promotion of sustainable practices within the scientific community.

Technical Excellence and Reliable Service

CERN has trusted BWT not only for the quality of our products but also for our outstanding technical service. Gaining access to CERN’s premises requires authorization, reflecting the high-security environment of the world’s leading particle physics laboratory. Despite these stringent access controls, BWT’s technical team has consistently provided timely and efficient service, ensuring that all water dispensers operate at peak performance.

Our service includes regular maintenance and swift responses to any technical issues, ensuring minimal disruption to CERN’s daily operations. This reliable support has been a key factor in the long-standing relationship between BWT and CERN.

Meeting the Needs of a Diverse Community

The versatility of BWT water dispensers caters to the diverse hydration preferences of CERN’s international community. Whether someone prefers chilled water to stay refreshed during hot summer days, sparkling water for a fizzy treat, or hot water for a quick cup of tea, our dispensers deliver. This flexibility is highly appreciated in a setting as dynamic and varied as CERN.

Moreover, the availability of multiple water options in a single dispenser minimizes the need for separate machines, saving space and reducing energy consumption. This aligns perfectly with CERN’s efforts to optimize resource use and minimize its environmental footprint.

BWT’s water dispensers are more than just hydration stations; they are a testament to our commitment to sustainability, innovation, and excellent service. Our partnership with CERN highlights the importance of providing sustainable, high-quality water solutions in environments where excellence and precision are paramount.

As CERN continues to explore the frontiers of science, BWT is proud to support its mission by ensuring that the people driving these groundbreaking discoveries stay hydrated. Together, we are making strides towards a more sustainable future, one refillable bottle at a time.

GTT supports groundbreaking neutrino research

Over the past 60 years, GTT has established itself as the technology expert in membrane containment systems for the transport and storage of liquefied gases. In 2023, 511 of the world’s 629 liquefied natural gas carriers with a capacity over 100,000 m³ were equipped with GTT technology. Innovation is at the heart of GTT’s strategy, as demonstrated by its 3295 registered patents and its position as the leading medium-sized company for patent filings in 2023. Today, GTT is applying its expertise to the Deep Underground Neutrino Experiment (DUNE), adapting its advanced solutions to support this groundbreaking scientific research.

The project

DUNE is an international research initiative aimed at enhancing the understanding of neutrinos. It is a dual-site experiment for both neutrino science and proton decay studies. The project utilises neutrinos generated by Fermilab’s Long-Baseline Neutrino Facility (LBNF). Once completed, the LBNF will feature the world’s highest intensity neutrino beam. The infrastructure necessary to support the massive cryogenic far detectors will be installed at the Sanford Underground Research Facility (SURF) 1300 km downstream, in Lead, South Dakota, US. These detectors are housed in large instrumented cryostats filled with liquid argon.

The challenge

The experimental facilities will include several individual cryogenic detectors, each housed inside a large, instrumented cryostat filled with 17,500 tonnes of liquid argon. In this context, the liquid argon must be maintained at a stable temperature of –186°C, requiring perfect tightness, material purity and high thermal insulation. To ensure the proper functioning of the projection chamber and allow electrons to drift over long distances, the impurity of the liquid argon must not exceed 0.1 parts per billion.

The solution

GTT provided a solution based on its technology, which is typically used in cargo ships transporting liquefied natural gas stored at –163°C. GTT’s patented membrane containment system uses two cryogenic envelopes to contain and isolate the liquefied gas. This modular system can be assembled to accommodate large volumes. GTT has offered its services to CERN to provide a solution to the LBNF/DUNE challenge. Each DUNE cryostat is a membrane cryostat constructed with an adapted Mark III membrane containment system developed by GTT.

The Mark III membrane system is a containment and insulation system directly supported by the ship’s hull structure. The containment system consists of a corrugated stainless-steel primary membrane, in contact with the fluid, placed on a prefabricated insulating panel made of reinforced polyurethane foam, incorporating a composite secondary membrane made of Triplex (aluminium foil between two glass cloths). This modular system integrates standard prefabricated components designed to be produced on a large scale and easily assembled –and that can be adapted to any tank shape and capacity.

GTT’s technologies are constantly optimised to meet the expectations of ship-owners and shipyards, its usual market, while complying with changes in maritime regulations. Since 2008, GTT has been working on developments of the Mark III concept, dedicated to improving the thermal and structural efficiency of the technology. In 2011, GTT launched the Mark III Flex technology, an improved version of Mark III, which offers a guaranteed boil-off rate of 0.07% volume/day, thanks to an increased thickness of 480 mm.

Why not extend this technology to another field? GTT and CERN have collaborated since 2013 to tailor GTT’s technology to CERN’s requirements, focusing on thermal performance and the containment of ultra-pure liquid argon for the time projection chambers required for DUNE. Leveraging the adaptability of the Mark III system, GTT has designed six tanks with CERN, resulting in a fully tested technology that meets CERN’s requirements. The collaboration began with a 17m³ initial prototype commissioned in 2017, followed by two 600m³ tanks, ProtoDUNE, commissioned in 2018 and 2019. The design showed areas for further improvement and required specific upgrades.

Following this initial set of prototypes, CERN and GTT worked together to propose an improved design. This design, optimised for cryogenic conditions, offers excellent containment tightness and thermal insulation, which helps maintain argon purity. The adapted technology includes:

• approximately 800 mm of insulation thickness;

• specific panel arrangements;

• double containment;

• tightness ensured by a combination of stainless steel (1.2 mm) for the primary barrier, a composite material (0.7 mm) for the secondary barrier and a reinforced polyurethane foam for insulation.

This optimised design has been tested and commissioned for two tanks so far. The first, a 200m³ short-baseline near detector sitting in the Booster Neutrino Beam at Fermilab, was commissioned in January 2023, and the second, a 600m³ dark side tank at the Gran Sasso National Laboratory in Assergi, Italy, was commissioned in June 2024.

The future

In the coming years, CERN and GTT will continue their collaboration with future targets already identified. The construction of two tanks, each with a capacity of 12,500 m³, for the DUNE far detector cryostats, to be installed at SURF in Lead, 1300 km downstream, will be the pinnacle of this collaboration. The design of the containment system has been completed by GTT, and the start of construction is planned for 2025.

Slovak LV cabinets contribute to investigating unresolved questions about the formation of the universe

Michal Cunik with the distribution panels prepared for transport to CERN. Credit: PPA CONTROLL

Slovakia has established itself as a significant player in the nuclear energy sector, primarily due to its nuclear capacities and a strategy focused on sustainability and energy security. Moreover, Slovakia’s commitment to nuclear energy is also evident in its strategic partnerships and collaborations with international organisations, including CERN.

PPA ENERGO, the largest member of the PPA CONTROLL group, specialises in delivering comprehensive solutions in automated control systems, field instrumentation and electrical systems. Our services encompass every stage of the project, ensuring seamless integration and performance across the entire lifecycle. This includes engineering, procurement, installation, testing and commissioning, service and maintenance, and, of course, the manufacturing of LV panels. Our extensive experience in manufacturing low-voltage panels, including their qualification for seismic resistance, EMC, vibration, aging, magnetic field resistance and more, combined with our deep expertise in the nuclear industry, has paved the way for prestigious opportunities, such as collaboration with CERN.

PPA ENERGO has demonstrated its ability to apply extensive expertise and experience in the execution of complex infrastructure projects to support CERN’s initiatives. With a wealth of experience in significant nuclear power plant construction projects, such as Mochovce Units 3 and 4 (Slovakia), Hinkley Point C (UK) and others, we have refined our ability to deliver top-tier solutions in challenging environments. Proven capabilities in managing large-scale, critical projects are expected to bring substantial value to CERN.

From technical design to Switzerland

CERN’s requirement was to design, manufacture and test the control and power distribution cabinets for the ATLAS and CMS 2PACL CO2 detector cooling systems. The cooling modules will circulate liquid CO2 through evaporators specifically designed in the detectors in a “two-phase pumped loop scheme”. Each cooling module will be equipped with a dedicated diaphragm pump for liquid CO2. Our control and power distribution cabinets will be part of this cooling system. After the successful qualification of our distribution panels approved by CERN, the first series was successfully delivered to Switzerland. Based on the positive feedback and personal visits of CERN’s technical team to our production hall, we were then commissioned to manufacture the second batch of distribution panels.

As Michal Cunik (pictured with the distribution panels prepared for transport to CERN), the designer responsible for the production of the cabinets, stated: “The major challenge was that we also had to prepare detailed 3D models, a digital twin of the panel to ensure precise replication and future facility maintenance and upgrades.” At this stage, intensive production of the distribution panels is underway, with planned completion in December 2025.

The successful delivery and ongoing production of the distribution panels has elevated our collaboration with CERN to the highest level.

CERN to insource beam-pipe production

In the Large Hadron Collider (LHC), counter-rotating beams of protons travel in separate chambers under high vacuum to avoid scattering with gas molecules. At four places around the 27-km ring, the beams enter a single chamber, where they collide. To ensure that particles emerging from the high-energy collisions pass into the ALICE, ATLAS, CMS and LHCb detectors with minimal disturbance, the experiments’ vacuum chambers must be as transparent as possible to radiation, placing high demands on materials and production.

The sole material suitable for the beam pipes at the heart of the LHC experiments is beryllium — a substance used in only few other domains, such as the aerospace industry. Its low atomic number (Z = 4) leads to minimal interaction with high-energy particles, reducing scattering and energy loss. The only solid element with a lower atomic number is lithium (Z = 3), but it cannot be used as it oxidizes rapidly and reacts violently with moisture, producing flammable hydrogen gas. Despite being less dense than aluminium, beryllium is six times stronger than steel, and can withstand the mechanical stresses and thermal loads encountered during collider operations. Beryllium also has good thermal conductivity, which helps dissipate the heat generated during beam collisions, preventing the beam pipe from overheating.

But beryllium also has drawbacks. It is expensive to procure as it comes in the form of a powder that must be compressed at very high pressure to obtain metal rods, and as beryllium is toxic, all manufacturing steps require strict safety procedures.

By bringing beam-pipe production in-house, CERN will acquire unique expertise

The last supplier worldwide able to machine and weld beryllium beam pipes within the strict tolerances required by the LHC experiments decided to discontinue their production in 2023. Given the need for multiple new beam pipes as part of the forthcoming high-luminosity upgrade to the LHC (HL-LHC), CERN has decided to build a new facility to manufacture vacuum pipes on site, including parts made of beryllium. A 650 m² workshop is scheduled to begin operations on CERN’s Prévessin site next year.

By insourcing beryllium beam-pipe production, CERN will gain direct control of the manufacturing process, allowing stricter quality assurance and greater flexibility to meet changing experimental requirements. The new facility will include several spaces to perform metallurgical analysis, machining of components, surface treatments, final assembly by electron-beam welding, and quality control steps such as metrology and non-destructive tests. As soon as beryllium beampipes are fabricated, they will follow the usual steps for ultra-high vacuum conditioning that are already available in CERN’s facilities. These include helium leak tests, non-evaporable-getter thin-film coatings, the installation of bakeout equipment, and final vacuum assessments.

Once the new workshop is operational, the validation of the different manufacturing processes will continue until mid-2026. Production will then begin for new beam pipes for the ALICE, ATLAS and CMS experiments in time for the HL-LHC, as each experiment will replace their pixel tracker – the sub-detector closest to the beam – and therefore require a new vacuum chamber. With stricter manufacturing requirements, never accomplishment before now, and a conical section designed to maximise transparency in the forward regions where particles pass through at smaller angles, ALICE’s vacuum chamber will pose a particular challenge. Together totalling 21 m in length, the first three beam pipes to be constructed at CERN will be installed in the detectors during the LHC’s Long Shutdown 3 from 2027 to 2028.

By bringing beam-pipe production in-house, CERN will acquire unique expertise that will be useful not only for the HL-LHC experiments, but also for future projects and other accelerators around the world, and preserve a fundamental technology for experimental beam pipes.

An intricate web of interconnected strings

Strings 2024 participants — **Evolving community** In a break from the past, Strings 2024 emphasised younger speakers and community organisation. Credit: CERN-PHOTO-202406-114-2

Since its inception in the mid-1980s, the Strings conference has sought to summarise the latest developments in the interconnected fields of quantum gravity and quantum field theory, all under the overarching framework of string theory. As one of the most anticipated gatherings in theoretical physics, the conference serves as a platform for exchanging knowledge, fostering new collaborations and pushing the boundaries of our understanding of the fundamental aspects of the physical laws of nature. The most recent edition, Strings 2024, attracted about 400 in-person participants to CERN in June, with several hundred more scientists following on-line.

One way to view string theory is as a model of fundamental interactions that provides a unification of particle physics with gravity. While generic features of the Standard Model and gravity arise naturally in string theory, it has lacked concrete experimental predictions so far. In recent years, the strategy has shifted from concrete model building to more systematically understanding the universal features that models of particle physics must satisfy when coupled to quantum gravity.

Into the swamp

Remarkably, there are very subtle consistency conditions that are invisible in ordinary particle physics, as they involve indirect arguments such as whether black holes can evaporate in a consistent manner. This has led to the notion of the “Swampland”, which encompasses the set of otherwise well-behaved quantum field theories that fail these subtle quantum-gravity consistency conditions. This may lead to concrete implications for particle physics and cosmology.

An important question addressed during the conference was whether these low-energy consistency conditions always point back to string theory as the only consistent “UV completion” (fundamental realisation at distance scales shorter than can be probed at low energies) of quantum gravity, as suggested by numerous investigations. Whether there is any other possible UV completion involving a version of quantum gravity unrelated to string theory remains an important open question, so it is no surprise that significant research efforts are focused in this direction.

Attempts at explicit model construction were also discussed, together with a joint discussion on cosmology, particle physics and their connections to string theory. Among other topics, recent progress on realising accelerating cosmologies in string theory was reported, as well as a stringy model for dark energy.

A different viewpoint, shared by many researchers, is to employ string theory rather as a framework or tool to study quantum gravity, without any special emphasis on its unification with particle physics. It has long been known that there is a fundamental tension when trying to combine gravity with quantum mechanics, which many regard as one of the most important, open conceptual problems in theoretical physics. This becomes most evident when one zooms in on quantum black holes. It was in this context that the holographic nature of quantum gravity was discovered – the idea that all the information contained within a volume of space can be described by data on its boundary, suggesting that the universe’s fundamental degrees of freedom can be thought of as living on a holographic screen. This may not only hold the key for understanding the decay of black holes via Hawking radiation, but can also teach us important lessons about quantum cosmology.

Strings serves as a platform for pushing the boundaries of our understanding of the fundamental aspects of the physical laws of nature

Thousands of papers have been written on this subject within the last decades, and indeed holographic quantum gravity continues to be one of string theory’s most active subfields. Recent breakthroughs include the exact or approximate solution of quantum gravity in low-dimensional toy models in anti-de Sitter space, the extension to de-Sitter space, an improved understanding of the nature of microstates of black holes, the precise way they decay, discovering connections between emergent geometry and quantum information theory, and developing powerful tools for investigating these phenomena, such as bootstrap methods.

Other developments that were reviewed include the use of novel kinds of generalised symmetries and string field theory. Strings 2024 also gave a voice to more tangentially related areas such as scattering amplitudes, non-perturbative quantum field theory, particle phenomenology and cosmology. Many of these topics are interconnected to the core areas mentioned in this article and with each other, both technically and/or conceptually. It is this intricate web of highly non-trivial consistent interconnections between subfields that generates meaning beyond the sum of its parts, and forms the unifying umbrella called string theory.

The conference concluded with a novel “future vision” session, which considered 100 crowd-sourced open questions in string theory that might plausibly be answered in the next 10 years. These 100 questions provide a glimpse of where string theory may head in the near future.

A decider for CERN’s next collider

The third update of the European strategy for particle physics, launched by the CERN Council on 21 March, is getting into its stride. At its June session, the Council elected former ATLAS spokesperson Karl Jakobs (University of Freiburg) as strategy secretary and established a European Strategy Group (ESG), which is responsible for submitting final recommendations to Council for approval in early 2026. The aim of the strategy update, states the ESG remit, is to develop “a visionary and concrete plan that greatly advances human knowledge in fundamental physics through the realisation of the next flagship project at CERN”.

“Given the long timescales involved in building large colliders, it is vital that the community reaches a consensus to enable Council to take a decision on the next collider at CERN in 2027/2028,” Jakobs told the Courier. To reach that consensus it is important that the whole community is involved, he says, emphasising that, compared to previous strategy updates, there will be more opportunities to provide input at different stages. “There is excellent progress with the LHC and no new indication that would change our physics priorities: understanding the Higgs boson much better and exploring further the energy frontier are key to the next project.”

The European strategy for particle physics is the cornerstone of Europe’s decision-making process for the long-term future of the field. It was initiated by the CERN Council in 2005, when completing the LHC was listed as the top scientific priority, and has been updated twice. The first strategy update, adopted in 2013, continued to prioritise the LHC and its high-luminosity upgrade, and stated that Europe needed to be in a position to propose an ambitious post-LHC accelerator project at CERN by the time of the next strategy update. The second strategy update, completed in 2020, recommended an electron–positron Higgs factory as the highest priority, and that a technical and financial feasibility study for a next-generation hadron collider should be pursued in parallel.

Significant progress has been made since then. A feasibility study for the proposed Future Circular Collider (FCC) at CERN presented a mid-term report in March 2024, with a final report expected in spring 2025 (CERN Courier March/April 2024 pp25–38). There is also a clearer view of the international landscape. In December 2023 the US “P5” prioritisation process stated that the US would support a Higgs factory in the form of an FCC-ee at CERN or an International Linear Collider (ILC) in Japan, while also exploring the feasibility of a high-energy muon collider at Fermilab (CERN Courier January/February 2024 p7). Shortly afterwards, a technical design report for the proposed Circular Electron Positron Collider (CEPC) in China was released (C ERN Courier March/April 2024 p39). The ILC project has meanwhile established an international technology network in a bid to increase global support.

Alternative scenarios

In addition to identifying the preferred option for the next collider at CERN, the strategy update is expected to prioritise alternative options to be pursued if the chosen preferred plan turns out not to be feasible or competitive. “That we should discuss alternatives to the chosen baseline is important to this strategy update,” says Jakobs. “If the FCC were chosen, for example, a lower-energy hadron collider, a linear collider and a muon collider are among the options that would likely be considered. However, in addition to differences in the physics potential we have to understand the technical feasibility and the timelines. Some of these alternatives may also require an extension of the physics exploitation at the HL-LHC.”

Given the long timescales involved in building large colliders, it is vital that the community reaches a consensus

The third strategy update will also indicate physics areas of priority for exploration complementary to colliders and add other relevant items, including accelerator, detector and computing R&D, theory developments, actions to minimise environmental impact and improve the sustainability of accelerator-based particle physics, initiatives to attract, train and retain early-career researchers, and public engagement.

The particle-physics community is invited to submit written inputs by 31 March 2025 via an online portal that will appear on the strategy secretariat’s web page. This will be followed by a scientific open symposium from 23 to 27 June 2025, where researchers will be invited to debate the future orientation of European particle physics. A “briefing book” based on the input and discussions will then be prepared by the physics preparatory group, the makeup of which was to be established by the Council in September before the Courier went to press. The briefing book will be submitted to the ESG by the end of September 2025 for consideration during a five-day-long drafting session, which is scheduled to take place from 1 to 5 December 2025. To allow the national communities to react to the submissions collected by March 2025 and to the content of the briefing book, they are offered further opportunities for input both ahead of the open symposium (with a deadline of 26 May 2025) and ahead of the drafting session (with a deadline of 14 November 2025). The ESG is expected to submit the proposed strategy update to the CERN Council by the end of January 2026.

“The timing is well chosen because at the end of 2025 we will have a lot of the relevant information, namely the final outcome of the FCC feasibility study plus, on the international scale, an update about what is going to happen in China,” says Jakobs. “The national inputs, whereby national communities are also invited to discuss their priorities, are considered very important and ECFA has produced guidelines to make the input more coherent. Early-career researchers are encouraged to contribute to all submissions, and we have restructured the physics preparatory group such that each working group has a scientific secretary who is an early-career researcher. We look forward to a very fruitful process over the forthcoming one and a half years.”

Excellence in precision: advanced RF measurement technology for particle accelerators

MXO 5 series oscilloscope — Fig. 1: MXO 5 and MXO 5C series oscilloscopes combined for more available channels.

Radio frequency (RF) systems are central to particle accelerators, and they require a wide variety of test and measurement equipment in both their developmental and operational stages. Precise, dependable instrumentation is essential for monitoring and controlling different aspects of RF systems.

RF systems generate, control and manage the electric fields used for particle acceleration. Central to these systems are RF cavities, which are evacuated metallic structures that support an electric field at a specific (radio) frequency. RF pulses are used to generate electric fields within these cavities, and the cavities have specific resonant frequencies that match the frequency of the pulses. Charged particles gain energy from these fields as they pass through the cavities at precise moments.

Monitoring RF signals in the time domain

Monitoring RF signals in the time domain is crucial for detecting and analysing transients, phase shifts and other dynamic behaviours that can affect system performance. For such time domain analyses, oscilloscopes are essential.

The MXO 5 oscilloscope from Rohde & Schwarz is a true pioneer in test and measurement technology. As the world’s first eight-channel oscilloscope that offers 4.5 million acquisitions/s, the MXO 5 sets a new standard in real time signal capture. The fast Fourier transform (FFT) technology of the MXO 5 is unique: the oscilloscope can show four FFTs in parallel with a maximum update rate of 45,000 FFT/s per channel.

For the same capabilities in a compact form factor, check out the MXO 5C. It is a screenless oscilloscope that occupies significantly lower vertical space compared to the MXO 5. This is great for space efficiency on the rack as well as for connecting with an MXO 5C oscilloscope to increase available channels (figure 1).

Master oscillator in storage ring

The master oscillator is at the heart of the storage ring and serves as the primary source of timing and synchronisation for the entire accelerator system. It generates a stable and precise reference frequency, which is used to ensure that RF cavities operate at a frequency that matches the revolution frequency of the particles.

The R&S®SMA100B RF and microwave signal generator is ideal for this purpose (figure 2). As the world’s leading signal generator, it can handle the most demanding test and measurement tasks on both module and system levels. With the R&S®SMA100B, it is no longer necessary to choose between signal purity and high output power: it is the only signal generator on the market that can supply signals with ultra high output power in combination with extremely low harmonic signal components. It is also capable of generating microwave signals with extremely low close in SSB phase noise, which improves operation efficiency by helping to prevent large energy spreads within particle beams.

Amplifying RF pulses

Broadband amplifiers are used to amplify RF pulses to the required power levels. In a typical setup, an amplifier might be connected to an RF source generating the base signal. The amplifier boosts this base signal to a specified power level before it is fed into the RF cavities of the accelerator.

The Rohde & Schwarz high power transmitter and broadband amplifiers address customer demands for the highest amplitude and phase stability, lowest phase noise, top energy efficiency, small footprint and modular design. The R&S®BBA150 and R&S®BBA300 are robust solid state power amplifiers and cover ultra broad frequency ranges. They have high availability, and their modular designs allow for experimental flexibility that enables quick reconfiguration to support different setups and eliminates the need for multiple dedicated amplifiers.

Minimising phase noise

The phase of the RF cavity electric field must be extremely stable; phase noise can cause particles to experience different levels of acceleration, leading to the energy spread of particles.

An important aspect of minimising phase noise is introducing advanced feedback systems. Accelerators should be equipped with real time monitoring and feedback systems that continuously adjust the phase of the RF pulses to counteract any phase noise that does arise. The R&S®FSWP phase-noise analyser and voltage-controlled oscillator (VCO) tester is the optimum solution for precise phase-noise measurement. It is ideal for pulsed signals and has an internal source for measuring additive phase noise.

Rohde & Schwarz – partner to the global research community

Rohde & Schwarz has 90 years of experience in high-energy RF signal generation, signal amplification and state-of-the-art test and measurement solutions. We have built up long-lasting relationships within the global research community, offering our expertise and market-leading solutions to labs and institutions worldwide. From beam testing to safe particle storage, we have the background to help you address the highly sophisticated requirements of accelerator testing.

Discover more particle-acceleration solutions from Rohde & Schwarz or get in touch with us.

24 years of CERN and WinCC OA: the success story of a groundbreaking technological partnership

This relationship, initiated in 2000, has not only endured but also set a benchmark for managing and evolving complex control systems.

Rigorous selection process

In the late 1990s, CERN undertook an extensive evaluation to choose a SCADA (supervisory control and data acquisition) system for its Large Hadron Collider (LHC) detectors. The process spanned two years and involved 10 person-years of testing and evaluation. Six products were rigorously assessed for functionality, performance, scalability and openness. WinCC OA emerged as the top choice, primarily due to its robust architecture and potential for future development, even though it did not fully meet CERN’s requirements at the time.

Strategic partnership formation

Recognising the need for significant enhancements to WinCC OA, CERN sought more than just a transactional relationship. A symbiotic partnership was formed, focused on mutual growth and adaptation. This collaboration was crucial in ensuring the timely deployment of the LHC detectors in 2009. From the outset, both parties worked closely to evolve WinCC OA to meet the unique demands of the LHC.

Collaboration examples

The first contract for WinCC OA (then known as PVSS2) was signed in 1999, initiating work on scaling the product to meet CERN’s unprecedented requirements. One key area of collaboration was the development of a new UI manager based on Qt, funded by CERN, ensuring compatibility across Linux and Windows while enhancing customisation options. This partnership was vital for the product’s evolution.

Another significant collaboration focused on the archiving system of WinCC OA. CERN required a system capable of storing data from large distributed systems in a central, high-performance database. Over the years, this system evolved through numerous workshops and large-scale tests, ultimately resulting in a substantial performance boost in the Oracle RDB archiver system, delivered on time for the LHC’s launch.

ETM’s (ETM professional control, a Siemens company) sponsorship of the CERN openlab project in 2009 furthered this collaboration, leading to the development of the Next Generation Archiver. This new feature, co-designed with CERN, became a cornerstone of WinCC OA, offering modularity, extendability and support for multiple database technologies. This flexibility allowed CERN to integrate the system into the “O2” physics data flow for the ALICE experiment, providing crucial data for analyses. Ongoing collaboration focuses on advancing the NextGen Archiver’s performance, with promising developments like the TimeScaleDB backend.

CERN’s input has also led to numerous enhancements in WinCC OA, such as improvements to the alarm-summarising engine and the modernisation of the CTRL scripting language. Additionally, the TSPP extension of the S7+ driver was implemented, maximising throughput and enabling precise time-stamped events.

CERN’s innovations, like the WebView widget, have influenced the product’s development, allowing the integration of web technologies within WinCC OA panels. The ongoing collaboration between CERN and ETM is set to continue, with plans to explore web-based interfaces, alternative scripting languages and container orchestration.

Widespread adoption and homogeneity

The success of WinCC OA in managing LHC detectors resulted in its adoption across other CERN systems, including cryogenics, electricity distribution and ventilation. Over time, WinCC OA became the standard SCADA solution at CERN, supporting more than 850 mission-critical applications across its experiments and infrastructure. These applications range from small systems to vast control systems managing millions of hardware IO channels across multiple computers, demonstrating WinCC OA’s scalability and adaptability.

CERN’s development of frameworks like JCOP and UNICOS, based on WinCC OA, has enabled the integration of diverse systems into a vast, homogeneous control environment. These frameworks, centrally maintained by CERN, provide guidelines, conventions and tools for engineering complex control systems, reducing redundancy and maximising the reuse of commonly maintained technologies. This approach has proven efficient, minimising development and maintenance costs while ensuring the integrity of a critical software project despite personnel turnover. The open sourcing of the JCOP and UNICOS frameworks has further strengthened this model, offering a blueprint for other large, complex projects.

A blueprint for future collaborations

WinCC OA’s adoption is growing beyond CERN’s LHC, with other laboratories and experiments, such as GSI and the Neutrino Platform, choosing it as their SCADA solution. Looking ahead, CERN may use WinCC OA for the Future Circular Collider (FCC) project, with feasibility studies already underway. The ongoing CERN ETM partnership demonstrates the power of collaboration in driving technological innovation. By working together, CERN and ETM have not only met the extraordinary demands of the LHC but also continuously evolved WinCC OA to support CERN’s mission-critical applications.

This partnership serves as a model for organisations aiming to implement large-scale, complex systems, underscoring the importance of selecting the right technology and the right partners committed to a shared vision of success.

“We congratulate CERN on 70 years of excellence in particle-physics research and are proud to partner with such an extraordinary organisation. This collaboration continually inspires us to maximise our capabilities and redefine technological boundaries,” Bernhard Reichl, CEO ETM professional control, a Siemens Company.

High-voltage pulse stability measurement of klystron modulators

Klystron modulators are key elements in free electron lasers. They provide high-voltage pulses to bias klystron tubes with energies of several hundred joules. Amplitude variations directly affect the gain and phase of amplified RF pulses and therefore the accelerating fields created by RF cavities. A huge effort is put into minimising these variations with both klystron modulators and RF pulse regulation.

For machines such as the SwissFEL (Swiss Free Electron Laser), the required HV pulse stability is 15 ppm (parts per million). Stability is calculated from measurements of 100 consecutive pulses taken at a repetition rate of 100 Hz as the relative standard deviation of gated averages with respect to a mean pulse amplitude. The measurement gate is located around the maximum plateau of the pulse, the so-called flat-top region, during which the RF pulse is fired.

Figure 2: Waveforms after automatic CVD offset adjustment with a 1 μs measurement gate.

A common technique for measuring such small variations involves pulse offsetting and magnification of the flat-top region in order to achieve a sufficient quantisation resolution. However, signal conditioning requires low-noise analogue electronics in the form of summing amplifiers and clippers with sufficient bandwidth and settling time. Such a set-up has so far involved the use of an external differential amplifier for signal conditioning and a high-end scope with statistical analysis functionality. The resolution of this set-up makes it possible to measure stability down to around 7 ppm, and it is mounted on a trolley so that it can be shared between RF stations.

Starting as an apprentice project, the aim was to consolidate such a bulky and extensive set-up into an embedded unit that could be integrated into any pulse modulator cabinet, allowing permanent live monitoring of pulse stability. As a versatile data-acquisition system with open source firmware / software and small size, the Red Pitaya device is a perfect fit for this application. Figure 1 shows the block diagram of how a Red Pitaya STEMlab 125-14 4-input board, connected to a signal conditioning board developed at PSI, is used to measure the pulse stability of klystron modulators.

Pulse current and voltage are measured simultaneously, while only the voltage signal is used for the stability statistics. The required pulse offset voltage is automatically set by a precision 16-bit DAC before the statistics are calculated. There is a gain factor of 20 (26 dB) between the full range pulse voltage on channel 3 and the flat-top voltage on channel 4, giving a theoretical increase in resolution of 4.3 bits. In principle, this gain can be increased further to give an even higher resolution, but in practice the pulse is not purely rectangular but has a dynamic range due to pulse droop and non-flatness. Figure 2 shows how real waveforms might look in operation. The yellow trace shows the pulse current, while the red and blue traces show the full-range and magnified flat-top pulse voltages, respectively.

The set-up presented here was able to measure pulse stability of 7–8 ppm in operation, with a resolution limit of 5–6 ppm at a 1 µs gate length and 67% of ADC full scale.

To find out more about Red Pitaya STEMlab 125-14 4-input board scan here.

The software running on the Red Pitaya is built around the standard C API and includes the OPC-UA stack from open62541.org to allow communication and data transfer via the server and client approach. The integration into our control system environment (EPICS) is currently on-going.

The complete assembly is called a Pulse Measurement Unit (PMU), and it offers many additional features such as the regulation of a high-voltage charging power supply, interfacing with opto-isolated IOs and a low-jitter PLL in order to lock external synchronisation frequencies to generate a synchronised ADC clock. With an overall size of 160 x 100 mm, the unit fits easily in a Eurocard rack or can be mounted on a DIN rail, as shown in Figure 3.

Velika pot 21, 5250
Solkan, Slovenia
Tel +386 30 322 719
E-mail nicu.irimia@redpitaya.com
www.redpitaya.com

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