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Milestone for HTS coil at UNIGE

Panagiotis Charitos — Fri, 16 Sep 2016 10:48:49 +0000

New milestone for High Temperature Superconductors at UNIGE
by Carmine Senatore & Panos Charitos

Details of the innovative superconducting coil, conceived and manufactured by researchers from UNIGE and Bruker BioSpin. (Image: © L. Windels, UNIGE)

High field superconducting magnets are the enabling technology for particle colliders, modern magnetic medical imaging, magnetic resonance spectroscopy and fusion reactors. To further push the boundaries of science, enhancing resolution or energy, these devices call for ever increasing magnetic fields. However, solenoidal coils built with the Low Temperature Superconductors (LTS) NbTi and Nb3Sn are limited to around 23.5 T while accelerator dipole magnets based on LTS will most likely reach their ultimate performance at about 16 T.

Recent progresses in the technology of High Temperature Superconductors (HTS) and, in particular, in REBa2Cu3O7-x (REBCO, RE = rare earth) coated conductors (CCs) have paved a way for the development of all-superconducting solenoids capable of generating fields in the range of 30 T, i.e. well beyond the limits of the present technology. However, the development of REBCO magnets still poses several fundamental and engineering challenges.

Carmine Senatore, Professor at the University of Geneva (UNIGE) is actively working in the study of applied superconductivity and through EuroCirCol is working for the development of high-field magnets for a future circular collider based on Nb3Sn under the scope of the FCC Study and EuroCirCol project. Senarore, also works on the development of HTS magnets. He is deputy leader of one of the working packages of EuCARD2 (WP 10.2) exploring different HTS conductor concepts and aiming to manufacture conductor prototypes to feed the HTS accelerator magnet demonstration program, which is the scope of WP10.

Recently his research group in the University of Geneva achieved the goal of generating a magnetic field of 25 T and, thus, obtaining the European record of highest superconducting generated magnetic field. Researchers at UNIGE worked closely with Bruker BioSpin to combine a Bruker laboratory magnet producing 21 T, already installed at UNIGE, with an innovative superconducting insert coil that allowed to increase the field by an additional 4 T. This means that in total, a field well beyond the 23.5 T reachable with conventional superconducting coils could be generated.

Piotr Komorowski, R&D engineer at Bruker and Professor Carmine Senator (UNIGE) pointing to the record field of 25T (Credits: UNIGE)

Concerning the scope of the project, Senatore says: «high magnetic fields are an indispensable tool for research in physics and material science as well as medical applications. This technological need represents the driver for the development of HTS, as they are the only means to generate fields well above 20 T». Riccardo Tediosi, manager of Bruker BioSpin’s Superconducting Technologies group adds: "the successful test of the 25 T coil represents a positive test-bench of ideas that we are developing for the next-generation HTS-based NMR magnets. We see that commercial breakthroughs in this field are at reach and 2017-2018 is going to be a very exciting period for Bruker and the NMR community."

The REBCO tapes used to achieve the 25 T in the solenoidal magnet are also studied under EuCARD-2 to build a dipole demonstrator able to generate 5 T in standalone configuration. It is then planned to use the same dipole demonstrator in a background field allowing to reach fields of up to 20 T. The 20 T target in the dipole compared to the 25 T reached in the solenoid should not generate confusion. Compared to solenoids, accelerator magnets are different “animals”: they need compact windings for reason of efficiency and cost, very high currents to ease protection, and they experience large forces transverse to the cable. Simple electromagnetics tells us, they require the double of ampere-turns to generate the same field.

However, there is much in common between the 25 T development based on REBCO coils and the goals of EuCARD-2. Senatore explains: We investigated the electrical, mechanical and thermo-physical properties of commercial REBCO tapes from all over the world. The results of these studies guided the choice of the commercial tape to be used for our insert coil and at the same time provided important inputs to the development of the conductor for the dipole prototype of EuCARD-2. The EuCARD-2 dipole will use these tapes in the form of a Roebel cable, a century old technology used for electrical machines. First winding tests have been performed, in various geometries, and a small coil is presently in test at CERN to validate the manufacturing process that will be used for the final magnet, planned for 2017.

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First hardware for FCC: Designing novel beam screen system

Panagiotis Charitos — Tue, 21 Jun 2016 11:00:40 +0000

First hardware for FCC: Designing novel beam screens system
by Panos Charitos and Cedric Garion (CERN)

For most people vacuum refers to “nothing”, but for an experimental particle physicist it is what enables a particle beam to travel through an accelerator without being scattered away, therefore it has an utmost importance in the performance of a particle collider.

The vacuum pipes of the FCC-hh not only have to maintain an ultrahigh vacuum over 100 km of underground tunnel but must also be able to shield the cold masses from unprecedented levels of synchrotron radiation in proton accelerators.

This radiation may extract electrons and gas molecules from the pipe wall, and so, deteriorate the vacuum, increasing the scattered particles which could lead to heat up or damage the ultra-cold superconducting magnets that keep the high-energy particle beams on track.

Francis Perez, head of accelerators division at ALBA synchrotron, and Paolo Chiggiato, head of the CERN Vacuum, Surfaces and Coatings group, are leading the cryogenic vacuum work package in the EuroCirCol project that gathers different institutes (ALBA, ANKA, CERN, CIEMAT, INFN and STFC).

Similarly to the LHC, the FCC-hh will have a beam screen inserted in the vacuum pipes to intercept the synchrotron light at cryogenic temperatures, with a flow of helium gas circulating in cooling channels to evacuate the heat load. However, the higher power density of the synchrotron radiation expected in the FCC-hh calls for a radically different design.

The team have proposed a novel vacuum system with improved heat transfer, lower impedance, improved pumping, and feasible manufacturing. The design also integrates a new method to mitigate the formation of electron clouds in the proton beam. This method, developed by the STFC and University of Dundee in the UK, consists on modifying the morphology of the beam screen surface by laser treatment to minimize the multipacting of electrons on the screen wall. The team has modelled the new design with dynamic vacuum, thermal and mechanical simulations, it is currently producing a prototype and investigating the process to manufacture the beam screens in the large scale.

The next steps include experimental tests of the new beam screens in the ANKA synchrotron in Karlsruhe. Providing a good approximation of the expected FCC-hh photon spectra, the measurements at ANKA , carried out at room temperature in a first step, will help to determine the heat load distribution, the desorption yield as a function of photon dose, and the photoelectron yield.

The first measurements will probably take place in 2017. However, important challenges remain ahead, like measuring the electron cloud density and the beam impedance. Further tests will assess the mechanical integrity of the beam screens after a magnet quench, the low-temperature gas adsorption on the laser treated surfaces, the generation of dust, etc.

In summary, the new concept for the beam screen of the FCC-hh fulfils the stringent vacuum requirements, easily removes the much higher than LHC synchrotron light power, and integrates e-cloud suppression. The preliminary design has been tested with mechanical, thermal, and gas density simulations, and the first prototype is ready for further tests while a two meter long version will be manufactured by end 2016.

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Highlights from FCC Week 2016

Panagiotis Charitos — Tue, 21 Jun 2016 10:51:00 +0000

Highlights from FCC Week 2016

by Panos Charitos (CERN)

From 11 to 15 April, more than 450 participants from all over the world met in Rome during the 2016 Future Circular Collider (FCC) Week.
The future of high-energy physics on the timescale of the 21st century hinges on designing and building future colliders that could take us at least one order of magnitude beyond the present energy and intensity frontiers. Reaching this goal in an efficient way calls for a large circular collider. The FCC study explores different options for a post-LHC research infrastructure.

The discovery of the Higgs boson, a particle profoundly different from all other elementary particles, calls for further studies of its properties. Moreover, a number “known unknowns” like the observed asymmetry between matter and antimatter, the dark matter content of our Universe and the non-zero neutrino masses are only a few of the indicators that point to physics that possibly lies beyond the Standard Model. There are several questions related to physics at the TeV scale, exacerbated by the lack of evidence (so far) of new physics whose answer is critical for our understanding of the Universe.

The next results from the LHC may shatter some of our previous theories while they could call for a profound change of scientific paradigm signalling an exciting state for modern physics. Whether marked by a major discovery or not they are probably going to question our present understanding of fundamental theories. Gian Guidice, Head of CERN’s TH department in his talk “the FCC and the present physics landscape” concluded: “We live in one of the most fruitful periods in physics facing a number of challenges and new opportunities”.

With the LHC programme underway, the global particle physics community works to prepare a common vision for the future. The full exploitation of the LHC including its high-luminosity phase (HL-LHC) sets a timescale of 20 years. Given the long lead times in the field of high-energy physics, the FCC study is exploring possible options for the post-LHC era. "As one of the high-priority items on CERN's agenda, the FCC design study is exploring a potential post-LHC accelerator project that will ensure the continuation of the world’s particle physics programme” noted Frédérick Bordry, CERN Director for Accelerators and Technology. "The post-LHC accelerator calls for breakthrough technologies to afford the beam energy, intensity and brightness which are required for a future 'discovery machine'." he affirms. This timescale along with the complexity of the FCC project and the desire to profit from other international studies for future accelerators make the FCC study a timely effort.

The physics potential for each of the FCC-study scenarios (proton-proton, electron-positron or electron-proton) was reviewed during the meeting. Each of the scenarios has its specific virtues though there is also a strong complementarity while they set certain challenges for the design of the machine and the experiments. Detector-design concepts for all three scenarios were also presented while areas where further theoretical or experimental input is needed were identified. The FCC physics programme shows that this research infrastructure is not a mere follow up of past machines but could open new horizons in our quest to understand nature.

Among the main R&D programs launched as part of the FCC study are those investigating new superconducting magnets and cryogenic systems, new superconducting RF cavities, innovative vacuum systems as well as innovation in detector technologies to meet the physics challenges. The latest results in these fronts were discussed during the FCC Week 16 and the next steps in R&D activities defined.

Substantial progress has been made on infrastructure and operation studies. Civil engineering studies for a 90-100 km tunnel in the Geneva area were presented. In addition, operational aspects become crucial for FCC; controls and machine protection, as well as energy-consumption, reliability and safety were some of the topics covered during the meeting.

Finally, the FCC week also featured the work of younger researchers. More than 100 of them presented their latest research in the poster sessions. Three of them received the FCC Innovation award that distinguishes early stage researchers or engineers for outstanding work carried out in the scope of the study.

The efforts presented during the 2016 FCC week will culminate into a Conceptual Design Report by 2019. This will serve as a decision aid for a future particle research infrastructure. Michael Benedikt, FCC study leader, concluded: “We have a high responsibility to keep the present momentum and attract more collaborators in our efforts to design future circular machines that will serve the global scientific community”. Following the hard efforts of the last two years: “we must now focus on the established parameters and use them as basis for further optimization that can be done for the machines, detectors, and technologies required to realize such a large-scale research infrastructure.”

The next FCC Week will take place in Berlin from 27 May to 02 June, 2017. This meeting will mark a major review of the study and will be an important step in the launch of the preparation of the FCC Conceptual Design Report.

You can find more information about FCC and the FCC Week 2016 and read more stories in the FCC storify channel.

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issue 17

16.2 T peak field reached in RMC racetrack test magnet

Alessia Barachetti — Thu, 19 Nov 2015 10:48:07 +0000

16.2 T peak field reached in RMC racetrack test magnet

by Luca Bottura, Juan Carlos Perez, Paolo Ferracin, Gijs de Rijk (CERN)

The RMC_03 racetrack test magnet. Credits: CERN

This September, experts from the CERN Magnet Group in the Technology Department celebrated the achievement of a 16.2T peak field in the Racetrack Model Coil (RMC). This is twice the nominal field of the LHC dipole and the highest field ever reached with this configuration. The result, which pushes forward existing boundaries for high-energy accelerators, is the product of a successful cooperation between several R&D programmes within the physics community.

Tested in the CERN SM18 vertical test station at a temperature of 1.9 K, the RMC, which consists of two racetrack coils, trained up to a maximum current of 18.5 kA, within less than 5% of the projected critical current of the cable. Based on the calculation of the field, this current corresponds to peak fields of 16 T on the 33-turns Powder-In-Tube (PIT) coil and 16.2 T on the 35-turns Rod Restack Process (RRP) coil. Three major ingredients made this achievement possible. First, such high fields are only possible thanks to the use of Nb₃Sn, a intermetallic and brittle compound which withstands a much higher magnetic field intensity compared to the previously-used Nb-Ti alloy. Secondly, RMC uses new technologies that allow the coil to resist increasingly high electromagnetic forces. An example of this is the “bladder-and-keys” structure developed at LBNL (USA). The third and perhaps most important ingredient was the close relationship with European and overseas R&D programmes, which joined efforts and synergies to push through existing technology barriers.

The RMC result feeds in a larger objective shared by most high-energy accelerator projects: reaching high magnetic fields to permit higher beam energies – in the case of dipoles - or to squeeze the beam in the experiments, which is the case for high-gradient quadrupoles. RMC-type tests are now a part of the technology programme that supports the EU-funded EuroCirCol design study, which, in turn, is part of the Future Circular Collider study. This aims to be a conceptual design study for a post-LHC research infrastructure focuses on an energy frontier 100 TeV circular hadron collider. The test setup and measurement provide evidence for the feasibility of a 16 T dipoles based on low-temperature Nb₃Sn superconductors. For this reason, the personnel in charge of setting up the testbed, working with industry and performing the test, are also working for the FCC 16 T magnet R&D programme.

RMC tests are a major step for many other R&D projects. In fact, they serve as technology support for the new High Luminosity LHC Interaction Region quadrupole QXF and for the 11 T dispersion suppressor dipoles. Finally, RMC is using wires and cables of the same class as those being used to build FRESCA2, a 13 T dipole magnet with a 100 mm aperture that will be used to upgrade the CERN cable test facility (FRESCA). FRESCA2 coils are currently under construction and will be ready for testing by summer 2016.

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FCC baseline layout and parameter set

Alessia Barachetti — Thu, 19 Nov 2015 09:07:03 +0000

FCC baseline layout and parameter set
by Daniel Schulte (CERN) with Alexandra Welsch (UNILIV)

Figure 1: Schematic layout of the FCC-hh collider ring.

The core of the Future Circular Collider (FCC) project is a hadron collider called "FCC-hh" which aims at colliding proton beams with a centre of mass energy of 100 TeV - more than seven times the energy that can be reached in the LHC.

A team of experts from a large number of collaborating institutes and led by Daniel Schulte from CERN is designing FCC-hh and has reached the first important milestone at the end of September: a baseline for the machine layout and the main parameters of this collider. This will now form the basis for a more detailed design and in particular for a conceptual design report that is foreseen in 2018.

The dimensions of this collider are impressive; it would be hosted in a 100 km-long tunnel and consists of eight straight sections connected by arcs, as illustrated in Figure 1. It is currently planned that two of these sections accommodate high-luminosity experiments, two others could house additional, lower-luminosity experiments, whilst the other insertions would be used to inject fresh beams, clean the beams during operation, and extract the used beams.

The collider parameters have been chosen to fulfil the requests from the theoretical and experimental physics community. The collider layout permits using the LHC as an injector, and is compatible with CERN’s existing accelerator chain, though other options will also be explored.

The collider layout sets demanding goals for the designers of each subsystem. To meet these goals the R&D in the coming years will push a variety of technology frontiers to come to a feasible technical design. This includes for example very high field magnets, a powerful cryogenic vacuum system and a beyond state-of-the-art beam collimation system.

To achieve the envisioned high beam energies the magnets in the storage ring arcs need to reach twice the field strength of the magnets used in the LHC. This requires the use of novel superconducting materials and magnet designs. The synchrotron radiation emitted by the beams when forced on their circular orbit will be 100 to 1,000 times larger than in the LHC. This will require a new approach to the design of the beam pipes and associated cooling systems. Finally, the energy stored in the two beams will be about 16 GJ. The collimation system will need to clean these beams and protect the machine from an accidental beam loss.

In addition, in the FCC-hh scenario, the rate of proton-proton collisions is very high to provide a large number of interesting events to the detectors. The debris of these collisions has a power of 500 kW. An efficient shielding is being designed to protect the detector and machine components. Two sets of machine parameters that have now been determined are summarized in Table 1.

Table 1: Key beam parameters, comparing FCC-hh to LHC and the planned LHC luminosity upgrade

The column “Baseline” describes the initial performance whilst the column “Ultimate” represents the performance that could be expected after several years of operation.

The collaboration will now design and optimise the different systems of the collider to present a conceptual design in 2018 that reaches the target performances.

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Highlights from the FCC week

Livia Lapadatescu — Tue, 14 Apr 2015 08:18:44 +0000

Highlights from the FCC week
by Cristina Martin Perez (CERN), Charlotte Houghton (STFC)

Opening session by US congressman Bill Foster
Image credit: FCC

The FCC Week 2015 took place in Washington DC (USA) from 23 to 27 march 2015 and drew the attention of 340 participants from science and industry. The first annual meeting of this visionary study marked a milestone of the first exploratory study phase. 290 contributions from all domains of the study give impressive evidence of the progress achieved and the challenges ahead.

The FCC-hh and FCC-ee machine studies are progressing in all units and are preparing to make the critical choices to achieve the performance and availability goals. The teams are now focusing on baseline parameters and a preliminary layout. First integrated lattices have been shown. It became clear that designing machines that can meet the required parameters calls for considerable R&D efforts far beyond the current state-of-science. Consensus between scientists, engineers and industry is that significant advances in superconducting magnets, in SRF technologies and RF power sources and other key technologies are needed; and that these need to be launched now to be ready for new machines by the mid 2030ies. The EuroCirCol EU Horizon 2020 project targets the core aspects of the hadron collider design, such as the arc & IR optics and the feasibility studies of key technologies like a 16 T accelerator magnet.

Industry participation - exhibitor stand
Image credit: FCC

With the current developments in accelerator design and technology there has been substantial progress on the geology studies for a tunnel in the Geneva area. These studies have been linked to the CERN accelerator complex, based on 93 km and 100 km scenarios, which fit well the geographical conditions. First ideas discussed are on installation aspects, global computing infrastructures beyond the Grid, controls and machine protection, as well as operational aspects such as energy consumption and safety, were addressed.

Looking forward to an intense year 2015 aiming at substantial progress for the study to be reported during the FCC Week 2016, unique physics capabilities and discovery potentials will be documented in the near future. FCC working groups have scanned the physics panorama both beyond and within the Standard Model and have identified the main areas where new methods for theoretical calculations or experimental inputs are needed. The implementation of a common environment for physics and detector simulations has progressed. This allows performing detailed event simulations to help match and understand better requirements of the detectors.

An inspiring talk by US congressman Bill Foster reminded the audience how high-energy physicists should “never be shy for standing up for the unique nature of their field, and never be afraid of big numbers”. The FCC the week witnessed significant eagerness from the US particle and accelerator community to collaborate in the global R&D effort, focusing on studies of superconducting materials and designs for high-field magnets suitable for a 100 TeV c.m. proton-proton collider. Technological and manufacturing breakthroughs are needed here to meet both, performance and cost goals.

Michael Benedikt, FCC Study leader, pointed out that 2015 should be the year in which the world-wide collaboration reaches consensus agreement on the baseline parameters and concepts and fleshes out the collider layout, injector and infrastructure concepts. “It is time to put a Nb₃Sn 16 Tesla magnet program on solid feet, to define and launch other selected technology R&D programs”, says Benedikt. The FCC community will reinforce physics and detector simulations, and will pursue MDI and experiment studies. The 2016 annual FCC Week will take place in Rome, Italy.

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