CERN Accelerating science

A novel beam screen technology for FCC-hh

3rd Prototype of the FCC-hh beam screen, manufactured according to the current base line design, during alignment procedure at BESTEX. (Image: CERN)

 

The Future Circular Collider Study, supported through the EU-funded H2020 EuroCirCol project, was conceived as a conceptual design study for a post-LHC research infrastructure combining an energy-frontier 100 TeV circular hadron collider (FCC-hh) with a lepton collider (FCC-ee) as a first step, both housed in a new 100km tunnel. The EuroCirCol project was divided in five work packages (WP) with the goal to develop the necessary key technologies to go beyond the current state–of-the-art. Among them, the “Cryogenic vacuum system” Work Package (WP4) was established to develop the technical design concept for the FCC-hh vacuum beam-pipe, based on the requirements and constraints derived from the design of the overal 100km ring and the bending magnets. 

Such challenge was successfully overcome by the different tasks under WP4: the smooth cooperation among the different teams contributing to this goal resulted in the development of an overall integrated design for the cryogenic beam vacuum system that could cope with the requirements posed by the very energetic beams of FCC-hh.

A critical component of the cryogenic beam vacuum system is the so-called beam screen. It protects the cryogenic (1.9K) dipole magnets from the direct irradiation of the synchrotron photons. This radiation is originated when the hadron beam trajectory is bent as it passes through the dipole’s magnetic field. During its operation, the hadron beams stored at the collider FCC-hh would originate unprecedented levels of radiation for hadron machines, in such way that the accelerator power and flux will be orders of magnitude higher than those of the LHC. These facts made the design of the FCC-hh beam screen a very challenging task for WP4 of the EuroCirCol project. The working temperature, dynamic vacuum pressure, as well as the photo- and secondary electron population are just some of the many parameters that were optimized by intensive engineering studies, to satisfy the required conditions for the correct operation of FCC-hh.

In such framework, the necessity of studying the vacuum and cryogenic performance of the actual FCC-hh beam screen prototypes arose as a key step for the design validation. To this end, a Beam Screen Testbench EXperiment (BESTEX) was build and put in operation by the collaboration.

Fig.1: Schematic description of BESTEX and its functionality.

The goal of the measurement setup was to determine the synchrotron radiation photodesorpotion yield, reflectivity, heat loads, and photoelectron yields inside the FCC-hh beam screen prototypes.  In order to perform the experimental work under conditions similar to those foreseen for the real machine, BESTEX was designed to be installed at the synchrotron radiation source KARA (previously known as ANKA) at the Karlsruhe Institute of Technology (KIT) in Karlsruhe, Germany. KARA was chosen due to its similarity with FCC-hh’s photon flux and power spectra. KARA’s synchrotron critical energy at its nominal 2.5 GeV operation is 4.2 KeV while for FCC-hh, at nominal operation (50 TeV per beam), it is expected to be 6.2 KeV. Such similarity results in a high resemblance of flux and power across the whole photon energy spectrum.

Fig.2: Left Luis Antonio González, Right Left Miguel Gil-Costa during installation of the first FCC-hh beam screen prototype for commissioning at BESTEX. (Image: FCC)

In October 2015, the conceptual design of BESTEX started at CERN by two project associates at the Vacuum Studies and Measurements (VSM) and Design Logistics and Methods (DLM) sections from the Vacuum, Surfaces and Coatings (VSC) Group at CERN. On 19 July 2017, the irradiation of the first FCC-hh beam screen prototype took place at BESTEX (see Fig.2). Between these two dates, all the components were designed and manufactured. The control system of BESTEX, as well as its data acquisition software, were also developed. BESTEX was assembled, aligned and fully commissioned at CERN before being disassembled and shipped to KARA for the final installation. A strategy was developed, allowing its re-assembly the setup after transportation to KARA without compromising the accuracy of the alignment. Such capability was achieved by developing a system formed by fiducialized callipers and vacuum compatible linear actuators. Since its first run, BESTEX has performed measurements of synchrotron radiation-related effects on several samples. As the design of FCC-hh evolved after each improvement iteration, new prototypes have been manufactured according to each different design.

The processes performed at CERN, as well the installation of BESTEX at KARA, were carried out in close collaboration with the Institute for Beam Physics and Technology (IBPT) team at KIT, allowing to efficiently synchronize and optimize the tasks succeed in such challenging project.

The measurements performed at BESTEX have allowed to optimise the beam screen design process by confirming the performance foreseen by simulations. Moreover, data acquired after acquisition of high photon doses makes possible to predict the vacuum performance of the FCC-hh beam screen during machine operation. Such measurements have been a key input for the development of the FCC Conceptual Design Report (CDR) published in July 2019.

BESTEX remains now an extremely valuable R&D experimental setup from CERN. It provides the necessary resources to perform numerous synchrotron-related experiments, not only on FCC-hh technical samples, but also to perform fundamental material properties’ studies on materials of interest for the realm of the particle accelerators.

 
P. Ferracin, E. Todesco (CERN)
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Matthew Chalmers (Editor, CERN Courier)
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Ch. Bracco, D. Carbajo Perez and A. Perillo Marcone
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Demonstrator racetrack dipole magnet produces record peak field

The enhanced Racetrack Model Coil (eRMC) is a magnet consisting of two racetrack (block) coils assembled without midplane gap and featuring a straight section of approximately 750 mm allowing the study of the design and assembly parameters relevant for full-length accelerator magnets. The magnet produced a 16.36 T central field at 1.9 K and a 16.5 T peak field on the coil. This is the highest dipole field ever reached for a magnet of this configuration. The magnet was also tested at 4.5 K and reached a field of 16.3T, corresponding to 98% of the estimated conductor limit at this temperature as measured from witness strands.

The enhanced Racetrack Model Coil (eRMC). (Image: CERN)

The magnet uses Nb3Sn superconducting wires, the superconductor used for the High Luminosity LHC Project (HL-LHC). The same material (Nb3Sn) in an identical cable configuration, was used for FRESCA2, a 100 mm aperture dipole magnet also built with block coils, to be installed in a test facility at CERN. In 2018, FRESCA2 has set a world record field for a bore-free dipole magnet of 14.6 T.

It is worth recalling the result recently achieved with the MDPCT1 magnet at FNAL by the US-MDP (Magnet development Program), a US-DOE program with objectives comparable to the FCC Project Study. MDPCT1, with an aperture of 60 mm, was tested at FNAL in June 2019 and achieved 14.1 T at 4.5K, a world record for a cos-theta model magnet (see previously on Accelerating News).

These results, and the recent advances on Nb3Sn conductors, demonstrate the potential of this technology for a next step hadron collider such as the FCC-hh. In the past year, the FCC 16T magnet development programme has attracted global interest, supported also by the EU-funded EuroCirCol project, allowing to establish a rigorous collaboration to carry on further R&D on the domains of superconducting technologies and mechanical design (see also “Towards 16T magnets for future particle colliders”).

After the success of this test, the next step is to dis-assemble eRMC, and re-assemble it adding an additional racetrack coil in the midplane, opening a cavity of 50 mm diameter. This configuration will reproduce, in its central part, the same coil geometry as that of an accelerator dipole magnet built with block coils. 

Alexandra Welsch (University of Liverpool)
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Giovanni Iadarola (CERN)
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A novel beam screen technology for FCC-hh

3rd Prototype of the FCC-hh beam screen, manufactured according to the current base line design, during alignment procedure at BESTEX. (Image: CERN)

 

The Future Circular Collider Study, supported through the EU-funded H2020 EuroCirCol project, was conceived as a conceptual design study for a post-LHC research infrastructure combining an energy-frontier 100 TeV circular hadron collider (FCC-hh) with a lepton collider (FCC-ee) as a first step, both housed in a new 100km tunnel. The EuroCirCol project was divided in five work packages (WP) with the goal to develop the necessary key technologies to go beyond the current state–of-the-art. Among them, the “Cryogenic vacuum system” Work Package (WP4) was established to develop the technical design concept for the FCC-hh vacuum beam-pipe, based on the requirements and constraints derived from the design of the overal 100km ring and the bending magnets. 

Such challenge was successfully overcome by the different tasks under WP4: the smooth cooperation among the different teams contributing to this goal resulted in the development of an overall integrated design for the cryogenic beam vacuum system that could cope with the requirements posed by the very energetic beams of FCC-hh.

A critical component of the cryogenic beam vacuum system is the so-called beam screen. It protects the cryogenic (1.9K) dipole magnets from the direct irradiation of the synchrotron photons. This radiation is originated when the hadron beam trajectory is bent as it passes through the dipole’s magnetic field. During its operation, the hadron beams stored at the collider FCC-hh would originate unprecedented levels of radiation for hadron machines, in such way that the accelerator power and flux will be orders of magnitude higher than those of the LHC. These facts made the design of the FCC-hh beam screen a very challenging task for WP4 of the EuroCirCol project. The working temperature, dynamic vacuum pressure, as well as the photo- and secondary electron population are just some of the many parameters that were optimized by intensive engineering studies, to satisfy the required conditions for the correct operation of FCC-hh.

In such framework, the necessity of studying the vacuum and cryogenic performance of the actual FCC-hh beam screen prototypes arose as a key step for the design validation. To this end, a Beam Screen Testbench EXperiment (BESTEX) was build and put in operation by the collaboration.

Fig.1: Schematic description of BESTEX and its functionality.

The goal of the measurement setup was to determine the synchrotron radiation photodesorpotion yield, reflectivity, heat loads, and photoelectron yields inside the FCC-hh beam screen prototypes.  In order to perform the experimental work under conditions similar to those foreseen for the real machine, BESTEX was designed to be installed at the synchrotron radiation source KARA (previously known as ANKA) at the Karlsruhe Institute of Technology (KIT) in Karlsruhe, Germany. KARA was chosen due to its similarity with FCC-hh’s photon flux and power spectra. KARA’s synchrotron critical energy at its nominal 2.5 GeV operation is 4.2 KeV while for FCC-hh, at nominal operation (50 TeV per beam), it is expected to be 6.2 KeV. Such similarity results in a high resemblance of flux and power across the whole photon energy spectrum.

Fig.2: Left Luis Antonio González, Right Left Miguel Gil-Costa during installation of the first FCC-hh beam screen prototype for commissioning at BESTEX. (Image: FCC)

In October 2015, the conceptual design of BESTEX started at CERN by two project associates at the Vacuum Studies and Measurements (VSM) and Design Logistics and Methods (DLM) sections from the Vacuum, Surfaces and Coatings (VSC) Group at CERN. On 19 July 2017, the irradiation of the first FCC-hh beam screen prototype took place at BESTEX (see Fig.2). Between these two dates, all the components were designed and manufactured. The control system of BESTEX, as well as its data acquisition software, were also developed. BESTEX was assembled, aligned and fully commissioned at CERN before being disassembled and shipped to KARA for the final installation. A strategy was developed, allowing its re-assembly the setup after transportation to KARA without compromising the accuracy of the alignment. Such capability was achieved by developing a system formed by fiducialized callipers and vacuum compatible linear actuators. Since its first run, BESTEX has performed measurements of synchrotron radiation-related effects on several samples. As the design of FCC-hh evolved after each improvement iteration, new prototypes have been manufactured according to each different design.

The processes performed at CERN, as well the installation of BESTEX at KARA, were carried out in close collaboration with the Institute for Beam Physics and Technology (IBPT) team at KIT, allowing to efficiently synchronize and optimize the tasks succeed in such challenging project.

The measurements performed at BESTEX have allowed to optimise the beam screen design process by confirming the performance foreseen by simulations. Moreover, data acquired after acquisition of high photon doses makes possible to predict the vacuum performance of the FCC-hh beam screen during machine operation. Such measurements have been a key input for the development of the FCC Conceptual Design Report (CDR) published in July 2019.

BESTEX remains now an extremely valuable R&D experimental setup from CERN. It provides the necessary resources to perform numerous synchrotron-related experiments, not only on FCC-hh technical samples, but also to perform fundamental material properties’ studies on materials of interest for the realm of the particle accelerators.

 
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A workshop on the energy-sustainable future for research infrastructures

 

 

Group photo from the 5th Energy for Sustainable Science at Research Infrastructures workshop. (Image: PSI)

On 28 and 29 November, CERN took part in the 5th Energy for Sustainable Science at Research Infrastructures workshop at the Paul Scherrer Institute – PSI, in Villigen, Switzerland.

The Energy for Sustainable Science at Research Infrastructures workshop series was established in 2011 by CERN, the European Spallation Source – ESS (Sweden), and the Association of European-Level Research Infrastructures Facilities – ERF. It brings delegates from research institutes together with policymakers from around the world to discuss energy sustainability.

The fifth edition was organised by PSI in collaboration with CERNERFESS and the H2020 project ARIES (Accelerator Research and Innovation for European Science and Society). The goals of this year’s workshop were to discuss energy management, efficiency, storage and savings, to pinpoint and share good practice and identify potential future technological solutions. In addition to that, the workshop stimulates new initiatives and cooperation amongst institutes.

Among the highlights was a presentation from Stefan Oberholzer, Head of Photovoltaics and Central Solar Power at the Swiss Federal Office of Energy – SFOE. He spoke about the Swiss Energy Strategy 2050, explaining that the strategy’s priorities are efficiency, increasing energy from renewable sources, security of supply, and strengthening energy research. Oberholzer also discussed the opportunities and challenges with energy storage and renewable sources, such as photovoltaics. Large storage systems were also the subject of a presentation from Michel Düren, a Professor at the Justus-Liebig-Universität Gießen. He concluded that the scientific community could play a leading role in demonstrating best practice for the energy transition that we are now facing.

Among the presentations from CERN was one from Laurent Tavian, High-Luminosity Project Office Coordinator, who presented a project for energy efficient refrigeration for the Future Circular Collider (FCC). Instead of conventional cryoplants, where helium is the refrigerant, the project found that a mix of helium and neon makes a more energy efficient cooling system. Over 10 years, this could save up to 3 TWh of energy.

Amalia Ballarino, CERN’s Head of Superconducting Devices, presented a project on magnesium diboride (MgB2) based power transmission lines for powering the High-Luminosity LHC superconducting magnets. Magnesium diboride is superconducting at 39K, the highest temperature among conventional superconductors, making it interesting from an energy efficiency perspective both for accelerator applications and for potential electricity distribution systems in towns and cities.

Serge Deleval, Deputy Group Leader for cooling and ventilation at CERN, gave a talk on water consumption and its environmental impacts, a first for this workshop series. He presented recent studies on minimising the increase of water consumption and reducing the environmental impact of cooling tower effluents.

In summing up the workshop, Frédérick Bordry, CERN’s Director for Accelerators and Technology, concluded very succinctly that: “Research infrastructures don’t want to represent an energy issue for society. We wish to contribute to good practices and find solutions for the future”.

The next workshop on Energy for Sustainable Science will be held in 2021 in Grenoble, France.

All the presentations from this year’s workshop can be found here.

News item also published in the CERN Bulletin.

 
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Unfolding the full potential of a future circular lepton collider

 

 

A next-generation lepton collider should offer an attractive physics programme, including a detailed study of the Higgs boson and ushering in a new era of high-precision studies in the electroweak sector, along with numerous possibilities to unveil new physics beyond the framework of the Standard Model.

After many earlier design studies for linear machines (VLEPP, TESLA, NLC, JLC, GLC, and more recently ILC and CLIC), in 2018, the Future Circular Collider (FCC) collaboration submitted the Conceptual Design Report (FCC CDR, Vol.II) for a circular lepton collider (FCC-ee) spanning the energy range from the Z pole (90 GeV) up to the top quark production threshold (365 GeV), promising extremely high luminosities at multiple interaction points. The FCC-ee design profits from new concepts, like beam operation with strong radiation damping, double rings, and a crab-waist collision scheme, which were demonstrated at other past, recent and present colliders - notably at LEP, the B-factories, and DAFNE - and from technological advances such as superconducting radiofrequency cavities based on thin-film technology or energy-efficient twin-aperture magnets. These and other innovations paved the way towards extremely high luminosities at future circular lepton colliders.

The FCC-ee, housed in a new 100 km circumference tunnel, offers two interaction points – upgradeable to four – and thus deliver twice (or consequently four times) as much luminosity as a single interaction point which is another substantial advantage when precision is the name of the game. In fact, the FCC-ee luminosity could be five orders of magnitude higher than LEP, thus enabling ultraprecise tests of the Standard Model and extremely sensitive searches for rare processes. 

FCC-ee could run at different energies, as an electroweak, flavour, Higgs and top factory, respectively. The 15-year operation programme of the FCC-ee aims at covering the full energy regime from the Z pole over the WW threshold, and the energy of maximum Higgs production rate up to the top quark threshold. This approach allows high precision studies of the Z and W bosons, and offers a smooth profile for the machine evolution to harness the most important physics opportunities. For example, the FCC-ee’s high-precision measurements of the Higgs boson could be combined with HL-LHC results, removing many of the model dependencies. According to the baseline design, FCC-ee delivers to each of its two interaction points - at a centre-of-mass energy of 240 GeV where the Higgs-boson production rate is maximum -- a luminosity more than ten times larger compared to linear colliders thus allowing to collect at least an order of magnitude more Higgs bosons per year. Another advantage of a circular collider like FCC-ee is the accurate beam calibration offered thanks to the availability of transverse polarisation expected at a beam energy of 80 GeV or higher allowing energy calibration at the 100 keV level; a unique feature in a precision physics programme. The experimental accuracy offered by FCC-ee allows detecting very rare processes and tiny violations in the measured quantities of the electroweak key observables.

FCC-ee design is based throughout on energy-efficient technology such as thin-film superconducting radiofrequency cavities (RF), efficient radiofrquency power sources, and twin-aperture arc magnets. As a consequence, over its full energy range  (from 90 to 385 GeV c.m.) FCC-ee offers an extremely high energy-to-luminosity efficiency at low energy consumption as demonstrated also in the following figure of merit from the EPPSU Physics Briefing Book.

 

Figure 1: One possible figure of merit for future colliders: luminosity per supplied primary energy (from the Physics Briefing Book of the EPPSU 2019).

Despite the significant progress of the past years, circular lepton colliders still struggle to reach even higher centre-of-mass energies, e.g. in excess of 400 or 500 GeV, due to limitations from synchrotron radiation that, at constant beam current, rapidly increases with energy. In a recent preprint, Vladimir Litvinenko (Stony Brook), Thomas Roser and Maria Chamizo-Llatas (Brookhaven National Laboratory) suggest the use of a novel approach that could potentially provide an attractive upgrade path for a future circular lepton collider towards even higher energies or luminosities.

The proposed acceleration scheme is based on the use of Energy Recovery Linacs (ERLs) that could reduce the total energy loss from synchrotron radiation, and especially the beam emittance at the collision point, and consequently extend the centre-of-mass energy reach of a future circular collider while still allowing for extremely high luminosities and reducing overall power consumption. In the case of FCC-ee this approach, if successfully demonstrated, could potentially extend its energy reach up to 600 GeV.

The concept of the ERL was first proposed in 1965 by Maury Tigner, as a key ingredient of a linear electron-positron collider. In recent years, ERLs have been considered as important drivers both for future light sources. The basic idea is to accelerate a high-power electron beam, without spending too much on radiofrequency (RF) power generation, by recovering the spent-beam energy after the collision. More specifically, an electron beam from the injector is accelerated through a time-varying RF field stored in superconducting linear accelerators. The two beams after the interaction are injected at opposite phase into the accelerating structures for deceleration. During this stage, the beams lose their energy, that is converted back into RF field energy, and can be reused to accelerate the succeeding electron bunches. In addition to an excellent conversion efficiency from electric power to electron beam power, ERLs also allow for higher-brightness beams of electrons and positrons at the collision point.

About 20 years ago, the ERL concept was first demonstrated at Jefferson Lab in the US and, a few years later, by ALICE at Daresbury Laboratory in the UK. Presently a team at the Cornell–Brookhaven ERL Test Accelerator (CBETA) facility is attempting to demonstrate a four-turn ERL based on single large-aperture fixed-field alternating-gradient magnets, thus fueling the discussion about the feasibility of such a cost-saving technique for a future circular lepton collider.

Figure 2: The FCC-ee baseline layout (left) and the possible options for an ERL-based energy upgrade of the FCC-ee (right). Both schemes can fit in the same tunnel with 100km circumference thus providing a diverse programme of for exploring the electroweak sector and studying the Higgs boson.

In their paper, Litvinenko, Roser and Chamizo-Llatas suggest the installation of the ERLs in the FCC tunnel; a natural extension of an earlier idea developed for an ERL-based electron-ion collider at Brookhaven National Laboratory (eRHIC). The use of ERLs in the FCC-ee could indeed offer significant advantages for exploring the regime up to 600 GeV compared to linear colliders, as it offers much higher luminosities, while reducing the power consumption. In particular, the ERL approach also allows maintaining an ultra-low beam emittance at high energy. As a consequence, the use of ERLs for a potential energy upgrade of FCC-ee will allow for much relaxed optics parameters at the collision point, compared to current requirements for linear machines. On the other hand, at lower energy, e.g. on the Z pole or at the WW threshold, the ERL might not offer any advantage compared with the FCC-ee baseline. Here, instead, the FCC-ee storage-ring collider enables an extremely precise beam energy calibration, as discussed before, which would no longer be available for the ERL mode of operation.

According to the authors of the Stony-Brook/Brookhaven paper, their suggested scheme could allow for a low electric power consumption even at the highest energies considered. Thereby, their approach is much in line with the emphasis that the FCC-ee study has placed on delivering a “green” collider by boosting the efficiency of the key collider components, documented in the FCC-ee CDR.

 

Figure 3: Luminosities for various options of an FCC ee. The thick green line and green squares show our estimated luminosities for the ERL-based collider consuming 10 MW of RF power (Green option) while the red dash-line shows a linear scaling of the luminosities with 100 MW RF (Credits: Litvinenko, Roser and Chamizo-Llatas).

ERLs could find numerous applications in other particle physics accelerators, like the suggested FCC-eh proposal for an electron-positron interaction region for detailed PDF measurements, in future light sources with high average brilliance, as well as in industry. To understand the actual gain and the limitations of the new scheme, further research is needed. This would include advanced cavity-design concepts, surface treatments, higher-order-mode damping, and emittance preserving optics, along with beam diagnostics for multiple passes and with a high dynamic range.

Today, ERLs remain a topic of great worldwide interest with efforts presently underway at Cornell, Jefferson Lab, KEK, Mainz, and Orsay. However, significant further research appears needed to demonstrate the overall feasibility of this concept with the proposed parameters, and to quantify the financial burden implied, before the ERL option can be considered a realistic upgrade path for the FCC-ee.

A better understanding of the achievable ERL beam parameters could render the proposed scheme an attractive option for a future upgrade of the FCC-ee either to achieve much higher luminosity at the top quark pair-production threshold or to extend the FCC-ee operation to 500 GeV c.m and beyond. The ERL approach could further boost the versatility of the post-LHC research infrastructure proposed by the FCC collaboration adding to the physics opportunities offered by the integrated FCC programme.

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FCC Week 19: Towards 16T magnets for future particle colliders

 

 

 

 

In the past decades, the development of high-field superconducting accelerator magnets received a strong boost from high-energy physics. The current state-of-the-art are the LHC dipole magnets operating in the LHC at around 8T. Exploring higher energies, up to 100 TeV, requires higher magnetic fields to steer the more energetic hadron beams at a future circular collider (FCC). The goal is to double the field strength compared to the LHC dipole magnets, reaching up to 16 Tesla. This goal can only be achieved with a different superconductor technology compared to the Nb-Ti used in LHC. Currently niobium tin (Nb3Sn) is explored as a viable candidate for reaching this goal. Other superconducting technologies, like High-Temperature Superconductors (HTS), MgB2 and iron-based materials, are also under study: REBCO tapes are being used in HTS development coils, whilst MgB2 and iron-based materials are under investigation as part of the FCC conductor development programme.

The first magnets using the Nb3Sn technology, the so-called 11T dipole magnets and the final focusing magnets are developed for HL-LHC. Designing, manufacturing and operating such high-field accelerator magnets is not a trivial task while it should be noted that the strength of the field is only one of the parameters that inform the design of accelerator magnets. In the case of FCC, more than 5000 dipole superconducting magnets will be needed for the 100 km tunnel. These magnets will have to be powered in series and operate continuously over long time periods. Therefore a reliable and efficient magnet design is key for the sustainable operation of this machine. 

The FCC study explores a number of critical aspects that underlie the design, cost-efficient manufacturing and reliable operation of 16T dipole magnets for future particle colliders. Among them is the improvement of the state-of-the-art Nb3Sn performance towards a target critical current density of 1500 A/mm2 at 16 T and 4.2 K, i.e almost a 50% increase compared to the HL-LHC specifications. Moreover, the industrialisation of such high-performing wire for large scale production and the achievement of a target cost for the Nb3Sn wire andurthermore, the design of cost-effective 16 T dipole magnets with adequate electromagnetic and structural designs as well as the improvement of magnet training.

To meet this goal, the FCC collaboration has launched a rigorous R&D conductor development programme and a R&D magnet programme. The conductor development programme focuses on the development of Nb3Sn wire with a target performance exceeding that of state of the art conductors. The world-wide community, including leading companies and laboratories from Europe, Korea, Japan and Russia, has enthusiastically taken on  the challenge. All collaborators have reached impressive achievements. Unit lengths of Nb3Sn wires with performance at least comparable to that of the HL-LHC conductor have been produced in industry and cabled at CERN. 

Very promising achievements reached in the USA with the production of R&D Nb3Sn wire via new technologies were presented during the FCC week 2019. At Fermilab, multi-filamentary wire produced with the Internal Oxidation process has already exceeded the FCC target critical current density – reaching values of up to about 1600 A/mm2 at 16 T and 4.2 K. Moreover, work at the Applied Superconductivity Centre of Florida State University has demonstrated the beneficial influence in improving the high-field performance of Nb3Sn via Hafnium addition to Nb-Ta.

In contribution to the FCC Conductor Development Programme, the Applied Superconductivity group at the University of Geneva has demonstrated that a combination of high upper critical field and enhanced critical current density can be obtained by grain refining in Ta-doped Nb3Sn with internally oxidised Zr. With a record-high value of 28.8 T at 4.2 K, the upper critical field of the samples based on Nb-Ta-Zr alloys even surpasses the values of industrial state-of-the art Nb3Sn conductors. Moreover, under the EuroCirCol conductor programme, the effect of the transverse load on the performance of Nb3Sn cables and wires was quantified following a successful collaboration with the Universities of Geneva and Twente. The effect becomes more relevant in higher fields and the results will inform the design of the final magnets.

“The enthusiasm of the world-wide superconductors’ community and the achievements are impressive”, says Amalia Ballarino, leader of the conductor activity at CERN. “The FCC conductor development targets are very challenging. The demonstration of the possibility of reaching the target critical current density in development Nb3Sn wires is a milestone in the history of Nb3Sn conductor and a reassuring achievement for the FCC magnet development programme”.     

The magnet programme includes three main activities covering the required R&D on superconducting cable, magnet cross section, iron yoke, collars and the magnet structure. Key components of the programme are CERN’s magnet development programme beyond HL-LHC  (which sets a milestone for the FCC high-field magnets), an ongoing R&D effort involving a network of academic institutes and industrial partners firmly supported by the EU-funded  Horizon 2020 EuroCirCol project, the FCC Conductor Development Programme and connection with other programmes taking place around the world, with first and foremost the US Magnet Development Programme as well as partners from Russia and Asia. These programmes have attracted partners, both from the academia and industry, who collaborate to tackle the complex challenges for the more powerful magnets needed for an energy-frontier collider. More innovative and better-integrated activities between academia and industry led to a cost optimised magnet design and the availability of different conductor options. The outcome of this joint effort is documented in the FCC Conceptual Design Report (CDR) and was extensively discussed during the 2019 FCC week. 

The FCC CDR included design and cost models for the magnets, based on the results of the EU supported EuroCirCol WP5. These showed that several different design options have the potential, to deliver 16 T in a reliable and cost-efficient way, once properly developed.

The efforts focused on the integration of the electromechanical characteristics of the conductor. Nb3Sn is a brittle material, which can crack easily, so specific care and attention are required  starting from the initial design phase on the electromechanical properties. The magnet design was treated as one integrated task including the structural, the magnetic and the magnet protection design. All collaborators used the same set of parameters for their simulations. Davide Tommasini (leader of the FCC magnet R&D) stresses that: “The impact of the programme in the relevant community has been extremely important. A considerable effort has been made, by all parties, in cultivating an environment in which information is openly shared throughout the whole duration of the programme”.

To this end, EuroCirCol WP5 has organised about 40 collaboration video-meetings and around 30 topical meetings, many of them with the enlarged participation of the US laboratories engaged in the US MDP. A number of national research laboratories including CEA (France), CIEMAT (Spain), INFN (Italy) and CHART (Switzerland) have recently signed agreements in the framework of the CERN FCC 16T programme with the aim of manufacturing around 1 m long prototypes of the designs developed within EuroCirCol, as a step towards building full scale models. The Swiss Chart-II roadmap for applied superconductivity is also planning significant contributions towards the high-field magnets required for FCC. CERN is coordinating these efforts through an international high-field magnet forum. Daniel Schoerling, the coordinator of the high-field magnet forum, states that ‘this forum shall continue providing a platform for the different institutes, as successfully cultivated during the EuroCirCol programme.’ 

An eRMC magnet structure was assembled at CERN using instrumented aluminium dummy coils and its mechanical structure has been characterised at cryogenic temperature. Moreover, three superconducting Nb3Sn coils are produced and ready for assembly for the first cold powering tests scheduled for the end of this year. 

Finally, the recent success of the test of the US MDP cosine-theta dipole, which achieved its target of 14T was announced during the FCC week 2019. Daniel Schoerling, coordinator of the International High-Field Magnet Forum, and some other key speakers highlighted in their talks the importance of the MDP 15 T dipole program and how the latest results that considerably strengthen the FCC Design Report.

Following this successful test, the magnet pre-stress will be increased in order to reach its design limit of 15 T. This result, obtained on a very early stage of a tailored R&D for high-field accelerator magnets, puts future closer in time. This project was initiated four years ago at Fermilab by Alexander Zlobin and the Fermilab Supeconducting Magnet team, in response to the P5 and HEPAP Accelerator R&D subpanel recommendations. In June 2016, after the Office of High Energy Physics at US-DOE created MDP to integrate accelerator magnet R&D in the United States and coordinate it with the international effort, this project became a key task of the MDP. A year later this effort received support also by the EuroCirCol program, making it a truly International endeavor. The next step of this project is to re-assemble the magnet with higher coil pre-load to achieve its design goal of 15 T.

Fig 1.  15 T dipole demonstrator MDPCT1 with project leader A.V. Zlobin and 15 T project team (Fermilab).

In addition to the baseline design of the cosine-theta coil type, other design options have been studied in detail and will be experimentally tested in the coming years. The elaboration of the FCC conceptual electro-magnetic designs for the other arc and interaction region magnets largely profited from the long-standing tradition of collaboration at CERN. Most of the involved institutes had already been  responsible for the design and procurement of similar magnet types for LHC and HL-LHC, and also took on the responsibility for magnet types with similar functions for the FCC study. They contributed in a great collaborative spirit to the development of the challenging arc and interaction magnets for FCC (see Fig. 2), as presented in the CDR. 

Fig 2. Electromagnetic baseline designs of the FCC arc and interaction region magnets. The institute taking the lead in the design is indicated in brackets.

Two examples of this collaborative effort for the design of the ‘other’ magnets is the finalisation of a comprehensive design optimisation for the arc quadrupole magnets performed under the lead of CEA. To validate this design, the first winding trials are currently performed by CEA. Another example is the conceptual design established by FNAL for low-luminosity (LL) and high-luminosity (HL) quadrupole triplet magnets with large apertures and gradients. FNAL is continuing their efforts with work on the structural and thermal design, and on a quench protection study. 

The above results prove the value of a strong R&D programme for the successful but also sustainable operation of post-LHC frontier colliders. The FCC collaboration provides a platform for creativity and innovation to flourish in collaboration with research centres and industrial partners from all over the globe. Coordinated R&D efforts can lead towards better technological capabilities for future accelerators that will push further the energy and intensity frontiers in particle physics while they can pave the way for new products and innovation processes.

 
 
 
Constantinos Astreos (University of Liverpool)
Academia-industry collaboration drives innovation
27 Mar 2019

Academia-industry collaboration drives innovation

Co-innovation workshop focused on strategic R&D programme of future collider and the benefits for industry in terms of project involvement and product commercialisation.

Panagiotis Charitos (CERN)
Science transcends boundaries
8 Dec 2017

Science transcends boundaries

European and Japanese collaboration in the framework of the FCC study was highlighted during Science Agora 2017

Philippe Lebrun, JUAS Director
25th edition of Joint Universities Accelerator School
13 Mar 2018

25th edition of Joint Universities Accelerator School

Twenty-five years of training accelerator scientists and going from strength to strength

FCC Week 2019 accelerates progress towards post-LHC colliders

CERN’s Director-General, Fabiola Gianotti, welcomes participants to the FCC Week 2019 in Brussels, Belgium. The event also marks the final event of the EU-funded Horizon 2020 EuroCirCol project. (Image: Nicolas Lobet/CERN)

 

From 24 to 28 June 2019, academic and research institutes, industrial partners and funding agencies met in Brussels for the Future Circular Collider (FCC) study annual meeting. Through its proposed ambitious projects, the FCC Week 2019 bolstered the interest of the international research community in preparing for the post-LHC era.

More than 400 researchers and industrial partners from around the world met to discuss innovations in key enabling technologies (i.e. superconductivity, high-field magnets, superconducting radio-frequency systems, vacuum and cryogenics) and review the diverse experimental programme offered by the proposed future accelerator facility. By providing, in a first stage, highest luminosity electron-positron collisions and, in a second stage, highest energy hadron collisions, the FCC will push the exploration of the fundamental laws of nature to unprecedented limits.

CERN’s Director General Dr. Fabiola Gianotti and Dr. Wolfgang Burtscher, the European Commission Deputy Director General for Research & Innovation, opened the conference stressing the role of fundamental research and the importance of this endeavour for strengthening Europe’s leading role in the global landscape. Moreover, in his keynote speech Mr Herman van Rompuy (President Emeritus of the European Council and former Prime Minister of Luxemburg) discussed the challenges lying ahead for Europe and the value of investments in fundamental science to tackle them.

Dr. Wolfgang Burtscher, the European Commission's Deputy Director General for Research & Innovation, opens the Future Circular Collider (FCC) week 2019 in Brussels, Belgium. (Image: CERN)

 

This year’s meeting marks the final event of the Horizon 2020 EuroCirCol project, tightly integrated with the FCC study research programme. EuroCirCol focused on key enabling technologies for an energy-frontier 100 TeV collider (FCC-hh). Results from the ongoing R&D programme were presented, demonstrating the feasibility of this new machine, identifying future research paths, and stimulating global collaborations to successfully pursue these goals.

More specifically, the EuroCirCol Work Package 5 has successfully achieved the objective of feeding the FCC Conceptual Design Report (CDR) with a design and cost model for magnets that could meet the FCC requirements, once properly developed, by taking into account the electromechanical characteristics of the conductor. The FCC magnet development programme, strongly supported by the EU Horizon 2020 programme, has been extremely important in boosting worldwide efforts, fostering strong collaborations with USA, Japan and Russian institutes. Furthermore, impressive progress has been made in the performance of the Nb3Sn superconducting wires, as shown in numerous sessions during the FCC week. Two promising developments have been the 14T magnetic field achieved at Fermilab, surpassing the previous record of 13.8 Tesla for accelerator niobium-tin magnets, and the reach of the critical current density Jc = 1500 A mm-2 required for the FCC wires.

The successful implementation of the FCC also relies on the work of the so-called infrastructures and operation group (IO, in short), which covers a wide field of different aspects, comprising civil engineering, integration, cryogenics, electricity distribution, cooling, ventilation, safety, and many others. Three parallel sessions were devoted to IO related matters. One complete session dealt with cryogenics; one was devoted to implementation aspects, comprising civil engineering, as well as administrative activities; and one session focused on matters of safety and technical infrastructure. The focus of the latter was on optimizing the footprint, getting the administrative processes underway, and planning preparatory works like geodetic modeling and site investigations, among various others.

A number of parallel sessions and a dedicated poster session offered the opportunity for liverly and fruitful discussion during the FCC week 2019. (Image: CERN)

 

A wide range of presentations focused on a future circular lepton collider (FCC-ee). Results testify to the technological readiness of FCC-ee. These, combined with progress in the design of beam optic and interactions regions, confirm the feasibility of this new machine, which could be operational by the mid-2030s. Recent studies contribute to further boost its performance, for example, by increasing the number of collision points or by introducing concepts of energy recovery and positron recycling. The time window opened by FCC-ee will also enable the research community to push the limits of novel technologies to steer the more energetic beams of FCC-hh, reaching energies eight times higher than LHC, in an affordable way, within the 21st century.

The FCC week offered an in-depth review of the work done since the kick-off meeting in 2013. These results have been documented in the four-volume FCC Conceptual Design Report published earlier in 2018. The four volumes of the FCC CDR were presented during the FCC Week 2019 in Brussels, Belgium. In a special ceremony, on the first day of the conference, Christian Caron (Executive Editor for the European Physical Journal (EPJ) at Springer Nature) handed over the four volumes to Fabiola Gianotti (CERN’s Director General), Frédérick Bordry (CERN’s Director of Accelerators & Technologies) and Michael Benedikt (FCC study leader).

“The FCC design report is the outcome of the common effort of more than 1.350 contributors from 34 countries including academic and industrial partners. I would like to thank each and every participant for helping to develop a global vision and preparing the construction of this unique facility, which will serve the worldwide high-energy physics community throughout the 21st century. Together, we will continue reviewing the experimental challenges and exploiting opportunities for technological breakthroughs towards the realisation of these machines,” said Michael Benedikt (FCC study leader).

Precision studies of the Higgs boson, along with a number of other electroweak observables, set a clear experimental challenge for a post-LHC collider. In his keynote talk on “FCC and the Future of Fundamental Physics”, Nima Arkani Hamed from Princeton’s Institute of Advanced Studies highlighted the importance of scrutinizing the Higgs boson properties, given its unique nature compared to all other known particles of the Standard Model. Finally, a number of presentations also highlighted the potential for studying the strong interaction through heavy-ion collisions and for detailing the parton distribution inside protons with a proton-electron interaction point.

The socio-economic impact of RIs was another key point of the conference, given the required large-investments necessary to these facilities. A dedicated workshop on the “Economics of Science” was held during the second day of the FCC week. Experts on cost-benefit analysis shared lessons with representatives from CERN and other major European research organisations, including SKA, ESA and ESS.

Thierry Lagrance, Head of CERN's Industry, Procurement and Knowledge Transfer department, opened the dedicated workshop on the Economics of Science, stressing the role of fundamental science for the future of our society. (Image: CERN)

 

Further interactions on how to maximise the benefits of large-scale research facilities took place throughout the day. The workshop concluded with a round-table discussion “Investing in Fundamental Science: For whom?” with the participation of Dr. Philip Amisson (STFC), Professor Massimo Florio (University of Milano), Professor Michela Massimi (University of Edinburgh), and Professor Carsten Welsch (University Liverpool). The workshop attracted a large, particularly diverse audience, creating a new space for future collaboration in this field.

You can watch the recording of the Opening and Plenary sessions of the FCC week HERE

Alexandra Welsch (University of Liverpool) , Panagiotis Charitos (CERN)
Marie Skłodowska-Curie's legacy inspires young scientists
11 Dec 2017

Marie Skłodowska-Curie's legacy inspires young scientists

A multi-site event to celebrate twice Nobel Prize winner’s 150th birth anniversary held in Geneva, Munich and Liverpool

Daniela Antonio (CERN)
A reverse hackathon with CERN
8 Oct 2018

A reverse hackathon with CERN

What if we selected a few CERN Technologies and put them in the hands of professionals that help create highly successful start-ups?

Outi Heloma (CERN), Isabel Bejar Alonso (CERN)
Education for innovation in Hilumi and FCC
6 Mar 2018

Education for innovation in Hilumi and FCC

What’s in it for innovators in Hilumi and FCC? Twenty young researchers interested in innovation and entrepreneurship participated in this two-day course.

Seamless accelerating cavities

Header Image: The teamwork with the first copper seamless 400 MHz cavity. (Image: C. Pira)

Superconducting radiofrequency accelerating cavities are the heart of modern particle accelerators. One of the key challenges for FCC is the development of more efficient superconducting RF cavities. Any progress on substrate manufacturing and preparation will have an immediate impact on the final RF performance, as it was demonstrated by the seamless cavities produced for the HIE-ISOLDE project. The welded ISOLDE Quarter Wave Resonators show the typical Q-slope of thin films cavities (decrease of the Cavity Quality Factor at high accelerating fields). The issue was substantially reduced substituting the welding cavities with seamless ones.

Seamless construction helps to reduce the performance limitations arising from defects and irregularities of the welding seams and the area in their vicinity, as well to reduce possible contamination originating from them. FCC studies push in this direction, exploring the seamless cavity production by spinning and electro-hydraulic forming. The cavities will be made both in bulk niobium and in copper coated with a thin film of superconductive niobium.

Spinning is a well-known forming technique since the Middle Ages, however, the SRF community needed to wait for Enzo Palmieri who produced the first seamless elliptical cavity spun and presented it during the SRF conference of 1993 at CEBAF.

Figure 1. The aluminum seamless 400 MHz cavity prototype realized under the supervision of Enzo Palmieri. (Image: O. Azzolini)

In particular, he showed the possibility to spin a copper and niobium monocell, complete with cut-off tubes, starting from planar blanks. The technique is now mature, and it has demonstrated the feasibility to produce a 1.5 GHz nine cell elliptical resonant cavity. For its cheapness, today the spinning technique is largely used by the SRF community for the production of R&D cavities, both in niobium and copper. However, in the production of cavities for accelerators, the standard technique is still preferred. Elliptical cavities traditional fabrication methods consist in the spinning, or deep drawing, of the half-cells and a further electron beam welding on the equator. This protocol guarantees the required dimensional tolerance in a large-scale production, which is a mandatory parameter in the RF design of the accelerator. Due to the non-symmetrical nature of the seamless spinning fabrication method, to guarantee the dimensional tolerance in a large-scale production of thousands cells required from FCC is one of the challenges of this research.

Figure 2. Image featured in the Proceedings of 6th International Conference on RF Superconductivity (SRF1993). Set-up for monocell cavity spinning using a simple hand tool applied as a pry bar. (Image: E. Palmieri)

Moreover, since in FCC the 400 MHz cavities are demanded, the cell diameter increases almost 4 times compared to the standard 1.3 and 1.5 GHz produced up to now by seamless spinning methods. The seamless spinning process increases the surface, from the sheet to a final cavity shape, more or less of a factor of 1.5, independently on the cavity frequency and dimension. This means that the increment in surface during the spinning, in absolute values is 15 times higher in a 400 MHz cavity than the same increment in a 1.3 GHz cavity!

When the seamless spinning technique was proposed for the FCC cavities studies, no one knew if the large amount of cold work generated during the spinning of such a huge cavity, could allow to close the cavity without producing any cracks.

Figure 3. Image featured in the Proceedings of 8th International Workshop on RF Superconductivity (SRF1997). Development of work sone and material stress during intermediate stage of spinning. (Image: E. Palmieri)

In 2017 the aluminum prototype was realized. Aluminum cavity is the first step in seamless spinning production, since aluminum is very machinable compared to copper and niobium and the prototype is used to test the mandrel and the metrology of the cavity. For us, this piece of metal has got a special meaning: it was the last seamless cavity realized by Enzo Palmieri.

During the last year the INFN-LNL SRF group has been carrying out the R&D of the seamless 400 MHz cavities, following the road traced by Enzo, but without benefiting of his genius and his 30 year’s experience.

The first 400 MHz copper cavity spun showed deep cracks near the cell iris, but was fundamental to understand how to improve the process. For a 1.3 GHz a single intermediate annealing between the spinning of the first half cell and the second one allows a complete closure of the cavity. For the 400 MHz cavity, at least three intermediate annealings in ultra high vacuum furnace, at three different stages of spinning process, are necessary for the complete closure.

In November 2018, the first seamless 400 MHz copper cavity in the world was produced. The cavity required three months of work to be finalized, but the more difficult part starts now: to optimize the process and transform a hand-made technology into an industrialized one capable to produce the thousands of cells required by FCC.


References

  • Figure 2. V. Palmieri, R. Preciso, and S. Y. Stark, “Seamless 1.5 GHz cavities obtained by spinning a circular blank of copper or niobium,” in Proceedings of 6th International Conference on RF Superconductivity (SRF1993), CEBAF, Newport News, Virginia, USA, 1993.
  • Figure 3. V. Palmieri, “Seamless cavities: the most creative topic in RF Superconductivity,” in Proceedings of 8th International Workshop on RF Superconductivity (SRF1997), Abano Terme (Padova), Italy, 1997, vol. 3.
Isabel Bejar Alonso & Francisco Sanchez Galan (CERN)
A new JTT shielding adapting ATLAS to Hilumi configuration
20 Mar 2019

A new JTT shielding adapting ATLAS to Hilumi configuration

A report/word from HL-LHC Collider-Experiment Interface Work Package

Panagiotis Charitos (CERN)
EASIschool '18: A summer to remember
8 Oct 2018

EASIschool '18: A summer to remember

A unique learning experience for the participants of the first school organized by EASITrain, this summer in Vienna.

Editorial Team
Accelerating News Readers Survey
25 Mar 2019

Accelerating News Readers Survey

With this survey we are trying to learn more about our audience and how we can improve in the future. It should take less than 5 minutes. Thank you!

A big step towards the superconducting magnets of the future

Last April, the FRESCA2 dipole magnet reached a field of 14.6T. This field value sets a new world record for dipole magnets with a free aperture, and breaks the old record established in 2008 of 13.8T by LBNL with the HD2 dipole magnet.

The development of magnets with fields beyond 10T started in Europe in 2004 with the FP6-CARE-NED project where the basic technologies were developed and specifically the Nb3Sn conductor which is the workhorse for the HL-LHC 11 T magnet, the LHC luminosity upgrade programme and baseline option for the more powerful 16T magnets for the Future Circular Collider study.

“FRESCA2 has already played an important role in the development of the new magnets for the High Luminosity LHC and will soon help develop the next generation of magnets." says Gijs de Rijk, head of the FRESCA2 programme.

The FRESCA2 dipole magnet design and construction was started in the framework of the FP7-EuCARD-HFM project in 2009 and has been co-financed by HL-LHC. The FRESCA2 magnet is much larger than a LHC magnet, measuring 1.5 m in length and 1 m in diameter. This allows the magnet to have a large aperture, measuring 10 centimetres, so that it can house the cables being tested, as well the sensors to monitor their behaviour. 

The FRESCA2 magnet before the start of the tests. (Image: Maximilien Brice/CERN). 

The magnet is the outcome of a successful collaborative effort between CERN and CEA-Saclay. The technology developments for FRESCA2 were essential for the new Nb3Sn magnets of HL-LHC. Formed by the superconducting niobium-tin compound and cooled to 1.9 kelvin (-271°C), it had already reached a field of 13.3 teslas in August 2017. Then, with a modification of the mechanical pre-stressing, it started a new series of tests in April before reaching its record intensity.

FRESCA2 will also be used to test coils formed from high-temperature superconductors. The goal is to test not only the maximum electrical current but also study in depth the effects of so high magnetic fields and the behaviour of the coil. Results from these measurements feed current efforts to design high-field magnets for future energy-frontier colliders. 

The magnet was tested to the nominal operating field, and achieved 13.3T in August 2017 after a very rapid training of 5 quenches. As a second step, the mechanical preload was increased and the magnet was retested in April 2018 to explore the ultimate operating limit. In this configuration FRESCA2 reached a maximum bore field of 14.6T at a temperature of 1.9K with additional 6 training quenches. The tests are currently being performed in the new purposely built test cryostat of the SM18 cryogenic test station at CERN.

This result is a major milestone in the progression towards high field accelerator magnets beyond HL-LHC. The future of FRESCA2 is to provide background fields for tests of cables and small coils, a new facility that will provide unique test capabilities.

Rama Calaga (CERN)
World’s first crabbing of a proton beam
26 Jun 2018

World’s first crabbing of a proton beam

The first test of the HL-LHC crab cavities to rotate a beam of protons was performed last month at CERN.

Fiona Harden, Yacine Kadi, Nikolaos Charitonidis, Aymeric Bouvard
International HiRadMat Workshop
30 Sep 2019

International HiRadMat Workshop

The much-antecipated event took place in the summer of 2019 at CERN, with great success.

Jim Clarke (STFC)
CLARA Update: First Accelerated Beam
8 Dec 2017

CLARA Update: First Accelerated Beam

UK’s Free Electron Laser Test Facility reached another significant milestone.

The first 802 MHz prototype cavities for CERN’s future circular collider

A general memorandum of understanding between JLab and CERN has been established to cooperate in the development of superconducting radio frequency (SRF) accelerator technologies for the future circular collider (FCC). Both partner laboratories agreed to build a small series of 802 MHz prototype cavities. A key element is the design of a high current, five-cell Energy Recovery Linac (ERL) SRF cavity to support R&D efforts for the Large Hadron electron Collider (LHeC) and the FCC electron-hadron collider (FCC-he). For both machines it is proposed to use five-cell 802 MHz SRF cavities in a 60 GeV three-pass racetrack ERL for a linac-ring hadron-electron collider configuration. At the same time, the development addresses the need for five-cell 802 MHz SRF cavities required for the ttbar configuration of the FCC lepton-lepton collider (FCC-ee).

JLab’s SRF institute houses a complete set of infrastructures covering cavity design, mechanical fabrication, chemical surface post-processing of the delicate cavity interior, clean-room assembly, as well as high-field characterization of SRF cavities. The latter is facilitated in JLab’s test area housing dedicated liquid helium dewars for so-called ‘vertical’ tests. This capability provides a rather quick turnaround time from a ‘paper’ design towards the realization and high power testing of an SRF cavity prototype. The main goal of the 802 MHz development was to validate the basic RF cavity design in a vertical test setup at 2 K temperature for both a single-cell and a five-cell cavity made from fine-grain, high purity niobium sheets. 

First, the conceptual ERL cavity design was finalized with extensive use of numerical analyses resulting in a five-cell cavity that balances key performance parameters with regard to RF, mechanical and beam-dynamical aspects. A single-cell cavity is simply made up of end half-cells attached to beam tubes.  Manufacturing of production tools commenced based on the conceptual design, starting with deep-drawing of metal discs into cavity half-cells as well as rolling of metal plates into beam tubes. Cavity sub-assemblies were joined by the standard, yet critical, electron beam welding process to complete the mechanical fabrication.

Though the focus of the project was on the bulk niobium cavity development, JLab also produced two single-cell cavities from OFHC copper to support ongoing Nb thin-film coating R&D at CERN. In addition, an OFHC copper cavity was built for low power bench measurements, in which multiple half-cells can be mechanically clamped together. Presently, a mock-up can be created with up to two full cells. This can be used for example for higher-order-mode (HOM) coupler development.

The first metal sheets were pressed in April 2017, and the fabrication of the cavities was completed in March 2018 (see figure below), including successful vertical tests of the single-cell and five-cell niobium cavities.

Standard interior surface post-processing methods were applied to the niobium cavities, including bulk buffered chemical polishing, high temperature vacuum annealing, light electropolishing, ultrapure high-pressure water rinsing, and low temperature bake-out.

The test results were extremely encouraging, since both cavities reached accelerating fields, Eacc, slightly above 30 MV/m ultimately limited by thermal breakdown (quench). Moreover, the RF losses were rather small due to the relatively low RF frequency, which provides a small BCS surface resistance. This resulted in unloaded quality factors, Q0, as high as ~5e10 at 2 K at low fields, while Q0-values of 3e10 could be maintained for the five-cell cavity up to ~27 MV/m (see plot below).

These performance values already exceed present specifications for the LHeC, FCC-he and FCC-ee machines that are set at Eacc ≤ 20 MV/m and Q0 ≤ 2e10, respectively. This provides generous headroom for a potential reduction in performance when the cavities are equipped with all the ancillary components and installed in cryomodules. More R&D is envisioned with the single-cell niobium cavity to explore the recently developed N-infusion technique that can further lower the BCS resistance as well as chemical vapor deposition of Nb3Sn onto the niobium surface.

Meanwhile, the five-cell cavity design has been adopted for the Powerful ERL for Experiments (PERLE) facility at Orsay/France, which is proposed as a test bed to demonstrate LHeC and FCC-he principles. With the successful completion of the prototyping effort, future work must concentrate on the development towards a fully-equipped cavity production unit for installation in a cryomodule, i.e. a five-cell cavity dressed with a helium tank and featured with all ancillary components such as an input power coupler, HOM couplers, and a pickup probe.

 

D. Gamba, A. Curcio, R. Corsini (CERN)
First experimental results from the CLEAR facility at CERN
3 Jul 2018

First experimental results from the CLEAR facility at CERN

Flexibility and versatility, together with a dynamic and experienced team of researchers, are key ingredients for the growing success of the new CLEAR facility, exploring novel accelerator concepts at CERN.

Lucio Rossi (CERN)
ARIES consortium produces world-class HTS tapes
24 Mar 2020

ARIES consortium produces world-class HTS tapes

REBCO conductor tapes reached a world-record critical current at 20T, strengthening the possibilities for a demonstrator of high-level accelerator magnets. Lucio Rossi, leader of the HL-LHC project, explains.

Adriana Rossi (CERN) & Sergey Sadovich (CERN)
Electron Lens Test Stand at CERN
20 Mar 2019

Electron Lens Test Stand at CERN

The new electron lens test stand paves the way for the HL-LHC upgrade.

Education for innovation in Hilumi and FCC

HiLumi and FCC organised their first innovation course in collaboration with IdeaSquare and CERN Knowledge Transfer (KT) on 31 January and 1 February, 2018. Twenty students and young professionals from HiLumi and FCC interested in innovation and entrepreneurship participated in the two-day course and will continue working on their ideas for a few weeks. The purpose of the induction session was twofold: to let the participants explore potential ways to apply their knowledge and skills outside the CERN context, and to familiarize them with established innovation practices. The aim was to inspire students/young professionals to think “outside the box” and teach them basic skills on how to think like an innovator and an entrepreneur thus offering them new skills and competences, which they may find useful later on in their careers. “It has been a real pleasure to host the course at IdeaSquare”, says Markus Nordberg who is a recognised expert in open innovation and manages other innovation courses such as the Challenge Based Innovation CBI.

During the two days, the participants gained insight into how to deliver innovation, assess knowledge transfer opportunities and identify different applications of CERN technologies from presentations given by the IdeaSquare team and distinguished visiting presenters. Harri Toivonen from Aalto University introduced the participants to the design thinking philosophy, opening minds on how to approach challenges with no clear solution. Giovanni Anelli from KT demonstrated how CERN technologies have turned into applications that benefit society in sectors such as medicine, safety and environment. He also put a focus on the innovation opportunities offered by KT. Philipp Topic from Vienna University of Economics and Business introduced Technological Competence Leveraging, a systematic, proactive and crowdsourcing-based method to identify new application fields for technologies. Marcello Losasso presented the QUACO project as a case study of a Pre-Commercial Procurement initiative, a mechanism that boosts innovation and attracts potential industrial partners. Creating a network of like-minded people is also a key to success in innovation and this is why Laure Esteveny presented the CERN Alumni activities and IdeaSquare and KT student programs were presented to open up ideas on how to reach to peers.

The participants were encouraged to bring their own innovation topics to the course, and if so had the chance to display them in an elevator pitch on both days. Using the knowledge and tools introduced during the course, the participants then worked in four groups, developing and refining their ideas. During the group sessions, some ideas were dropped, and the groups  developed detailed presentations for 10 ideas they most believed in, to defend their views. At the end of the second day, three ideas were subsequently voted as most promising and three groups were put in place to further refine and work on them. At the time of publication of this article each group is developing their ideas with expert support.

The results will be presented in an award ceremony to an invited audience on 21 March. “It has been extremely impressive how the participants have used the information received during the course”, says Isabel Bejar Alonso, organizer of the course. “From the first presentation to the last there has been a complete revolution moving from vague ideas to credible proposals.” This innovation course has demonstrated how important it is for young researchers to see that entrepreneurship can be an option for their careers. Even more so as they realised that there is no real frontier between industrial innovation and the work they do every day.

 

Header image: The participants refined their ideas during group workshops in the HiLumi FCC Innovation course at IdeaSquare (photo by Isabel Bejar Alonso, CERN)  

Giovanni Iadarola (CERN)
Parallel computing boosts e-cloud studies for HL-LHC
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Parallel computing boosts e-cloud studies for HL-LHC

Parallel computing techniques allow the processing of heavy e-cloud simulations for HL-LHC.

Steinar Stapnes (CERN)
Updates to the CLIC performance studies
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The CLIC study collaboration proposes new ways of increasing the luminosity performance at 380 GeV at modest additional cost and power consumption. These updates are summarized in a recent CLIC note.

P. Ferracin, E. Todesco (CERN)
Power tests of HL-LHC quadrupole
8 Oct 2018

Power tests of HL-LHC quadrupole

Successful results from the power test of the fourth short model of a Nb3Sn quadrupole for the High Luminosity upgrade.

Science transcends boundaries

For a third year, the European Union (EU) Delegation to Japan, together with EU Member State embassies, European and Japanese research laboratories organized a number of events during the Science Agora 2017, Japan’s largest science fair. Every year, Science Agora offers a unique opportunity for scientists to interact with policymakers and the general public to discuss how science and technology transform our daily lives and occupy a central place in economic growth and societal change.

The key theme of the 2017 Science Agora was “Beyond the Boundaries”. In this regard, international collaboration and geographical diversity are just as important as diversity of disciplines. The FCC study, supported through EC’s H2020 EuroCirCol programme, was presented as an example of how international scientific collaboration transcends different boundaries and could help us address a number of inter-connected global challenges. In total five projects were selected to showcase how collaboration between European and Japanese institutes boosts frontiers in particle physics, sustainable energy sources, the internet of things, nuclear fusion, smart cities and climate change.

EU's "participation in Science Agora is thus driven by our twofold desire to show in a tangible manner some of the best science and innovation which are being developed in Europe, and to demonstrate the diverse ways in which European and Japanese researchers and scientists are cooperating", said EU Ambassador Viorel Isticioaia-Budura.

The opening ceremony of EU's participation to Science Agora 2017 in Tokyo. EU Ambassador to Japan Viorel Isticioaia-Budura (right) and Leonidas Karapiperis, Head of S&T Section, Delegation of the EU to Japan (left) (Image Credits: EU delegation to Japan).

Frank Zimmermann (Deputy FCC-study leader) discussed how the FCC study strengthens the role of global collaboration in science, technology and innovation, leveraging the competencies of experts from different fields and countries. “We are facing a changing reality that not only opens up the opportunity for collaboration, but which actually necessitates the latter, as it becomes increasingly difficult for individual scientists or even individual countries to conduct groundbreaking research on their own. We have witnessed how scientific research has evolved over the past decades, requiring R&D efforts beyond institutes and even countries to develop novel enabling technologies.” International cutting-edge research helps us cross the boundary between the present and the future, and allows us to envisage a much more powerful post-LHC collider.

Moreover, Zimmermann presented the joint efforts with KEK and University of Tokyo in developing a new generation of superconductors that will meet the requirements of the high-field magnets needed for a 100 TeV energy frontier collider. It is key to the success of any high-tech project to involve the entire scientific and engineering community from the very early days onwards.

Frank Zimmermann (CERN) presenting the scope of the study for a Future Circular Collider and highlighting aspects of the collaboration with Japanese research institutes and universities.

The European Union’s participation in the Science Agora also included lively demonstrations of superconductors, a video illustration of the FCC collider, poster presentations, and small tokens for the young visitors! This event offered the opportunity for European and Japanese researchers to present their joint projects and, conversely, to listen to the voices of the general public, including Japanese high-school, middle-school and primary-school students fascinated by science. This next generation will eventually provide the researchers to work on the proposed future accelerator complex. At the Agora, the participating scientists also shared their original motivation and the questions they are trying to address through their research, thereby inspiring many young students who were curious about a researcher’s life.

The stand of the EU delegation in the Science Agora 2017 giving information about a number of EC supported projects.

The FCC study along with the other collaborative projects that were presented at the Science Agora 2017 are helping to expand the area of world-leading scientific and technological collaboration between Japan and Europe – an area that will create growth and that will offer to young people, from around the world, the space to dream, to aspire and to develop.

Ruben Garcia Alia, Pablo Fernandez Martinez ‎and Maria Kastriotou (CERN)
Ultra-high energy heavy ion testing
12 Dec 2018

Ultra-high energy heavy ion testing

The ultra-high energy heavy ions at accelerators allows to test electronic components.

Stéphanie Vandergooten
Apply now to the Joint Universities Accelerator School
23 Sep 2019

Apply now to the Joint Universities Accelerator School

Interested to learn more about Particle Accelerators? Apply now to the 2020 JUAS School in Archamps to follow 5-week courses on particle accelerators.

Livia Lapadatescu (CERN)
Shaping the future of accelerators: the new innovation pilot project
16 Jul 2019

Shaping the future of accelerators: the new innovation pilot project

Take part in the new Accelerator Innovation Pilot project by submitting your proposal to the open call launched by TIARA and ARIES until 31 August 2019.