accelerating-news-arc.web.cern.ch - issue 22

An interview with Marcela Carena

Jennifer Toes — Tue, 17 Oct 2017 12:40:59 +0000

An interview with Marcela Carena
by Panos Charitos (CERN)

(Image credit: Marcela Carena, Fermilab)

Marcela Carena, born in Buenos Aires in Argentina, completed her PhD at the University of Hamburg in 1989. Carena is the head of the Theoretical Physics Department of Fermilab - the Fermi National Accelerator Laboratory near Chicago, Illinois, and a professor in the Physics Department and the Enrico Fermi Institute at the University of Chicago.

Carena is one of the leading physicists in theoretical high energy physics and has worked particularly on possible extensions of the Standard Model of particle physics, on the explanation of the matter/anti-matter asymmetry in the Universe, and on the origin of dark matter. She works closely with experimental physicists, creating and implementing strategies for testing the possible existence of a new symmetry of nature and new physics models that may imply that the Higgs is a composite of other constituents.

What motivated you to study physics?

I first thought seriously about pursuing a career in math and physics when I was in high school. My math teacher was a charismatic woman whose passion for what she was teaching got me excited about the art of solving challenging problems. She told me about the Balseiro Institute in the mountain city of Bariloche, which is a unique place in Argentina to study physics. A few years later I started studying engineering in Buenos Aires, but during my second year I decided to also take a few courses in philosophy. It was only in my third year of college that physics became the merger of the two. I was fortunate to be admitted to “El Balseiro” that year which I finally attended.

Which is the most exciting aspect of your present role at Fermilab?

Just yesterday our group had an exciting meeting with Fermilab experimental physicist Juan Estrada and his team about novel technologies that they are developing that could allow to detect dark matter in a new way. We brainstormed about what kinds of theories of dark matter could be probed using this breakthrough. It is exciting to be in a lab with such a diverse international community of people brought together by their common interest in science. As head of our theory group, as well as in my international role, I have the opportunity to reach out to brilliant young people who are just starting their research and bring them to Fermilab.

What have we learned from the discovery of the Higgs boson? Does it close a chapter in modern physics?

The Higgs boson discovery was more than the discovery of a new particle; it confirms that there is an invisible force field that permeates our entire universe, and gives mass to the electrons and quarks that make up everything from the stars in the sky to the spoon that you use to eat your cereal. This discovery opens a new door for modern physics, since the Higgs boson is a type of particle never seen before. By studying it now in great detail at the LHC and future experiments, we can probe the answers to many mysteries.

For example, how does the Higgs field communicate directly with dark matter, the dominant form of matter in the universe, whose existence has been so far only established by the gravitational effects of dark matter in the cosmos.

Is the Higgs responsible for the fact that our universe favors the existence of matter over antimatter? To answer this question, we need to probe experimentally how the Higgs boson interacts with itself, which is very challenging.

This is also linked to the “hierarchy problem”, which stems from the fact that there is a large hierarchy of sixteen orders of magnitude distance between the Planck mass (related to gravity) and the electroweak scale (related to the Higgs), while the quantum physics inherent to the Higgs field implies that the two scales should be similar. Only the cosmological constant has perhaps more mystery of such large discrepancies compared to expectations.

Does supersymmetry answer these questions?

The discovery of the Higgs boson and some of the open questions about our Universe point to the existence of new physics. In that sense, supersymmetry is one of the theories that could describe the new physics that lies beyond the Standard Model.

It predicts additional heavier partners for each of the known particles of the Standard Model. Adding these superpartners, effectively doubles the number of particles in nature. This is analogous to the addition of anti-particles in the standard quantum field theory; a move that also doubled the spectrum. The quantum effects of the known particles and their supersymmetric partners on the mass of the Higgs cancel each other out and thus the expected Higgs mass is consistent with the mass observed at the LHC. Hopefully these supersymmetric particles are not too far away from the electroweak scale so that the theory can be tested at colliders.

The particles in the standard model make up the inner circle. Their supersymmetric partners make up the outside ring. (Image Credit:YouTube/Particle Fever)

Dealing with the hierarchy problem has been one of the original motivations for introducing supersymmetry at low energy scales, of the order of a TeV. Moreover, supersymmetry is an attractive extension as it can tackle many other questions in a mathematically elegant way. These include the nature of dark matter, the matter/antimatter asymmetry and the tiny masses of neutrinos.

Are there alternative ways to address these open questions?

Compositeness is the other popular direction to explain the mass of the Higgs boson. Instead of adding extra supersymmetric particles, the theory suggests that the Higgs boson is not a fundamental particle but is instead made of other fundamental particles - like the pions in the case of Quantum Chromodynamics (QCD). Composite Higgs models are speculative extensions of the Standard Model where the Higgs boson is the result of a new strong force.

Composite Higgs theories may materialize in many different realizations of extended global symmetries in nature. Although they may not be at first sight as appealing as the supersymmetric guiding principle one has to look to the data and what nature tells us. Perhaps, one of the main “advantages” of compositeness is that it has many similar characteristics to QCD and we could use similar tools to advance studies for a composite Higgs.

Fermilab recently launched a rigorous research program on neutrino physics through LBNF/DUNE. Which is the key motivation for this and the current status?

Besides the Higgs boson, neutrinos are the most unexplored part of the Standard Model. Fermilab has started construction of the Long-Baseline Neutrino Facility that will be the future home of the Deep Underground Neutrino Experiment (DUNE), which promises to shed new light on neutrinos and seek answers about the evolution of our universe.

Neutrinos have proven to be one of the most surprising subatomic particles, including the discovery that they change between three different “flavours”. That discovery began with a solar neutrino experiment led by physicist Ray Davis (Nobel Prize in Physics, 2002), performed in the 1960s in the same underground mine that will now house LBNF/DUNE.

Once completed, LBNF/DUNE will be the largest experiment ever hosted in the United States to study the properties of the mysterious neutrinos. Unlocking the secrets of neutrinos could help explain more about how the universe works and why matter and not antimatter dominates the universe.

In the experiment, researchers will send a beam of neutrinos 1300 km through the Earth – from Fermi National Accelerator Laboratory near Chicago to Sanford Lab in South Dakota, where a four-story-high, 70,000-ton underground detector will catch the particles. Scientists will study the interactions of neutrinos in the detector, looking to better understand changes the particles undergo as they travel across the country in less than the blink of an eye.

A global neutrino physics community is developing a leading-edge, dual-site experiment for neutrino science and proton decay studies, the Deep Underground Neutrino Experiment (DUNE), hosted at Fermilab in Batavia, IL (Image Credit: Fermilab).

It should be noted of course that this is a global effort involing more than 30 countries. CERN will be providing the first cryostat in South Dakota, the first investment in infrastructure outside of Europe in CERN’s history. Moreover, the new CERN neutrino platform hosts two DUNE detector prototypes for the full-size detectors that will eventually be installed underground in South Dakota.

What is your take on efforts for future colliders that could extend the energy and intensity frontiers?

Today we are facing different options for a post-LHC collider. The community is considering the physics opportunities that new proton and electron colliders can offer, as well as the push for novel technologies to meet the challenges of these machines. I am very supportive of these initiatives, that will allow us to continue the exploration of nature at the fundamental level in the framework of international collaborations.

Does the effort to answer these deep questions about nature also has a societal impact?

Already from the past it has been proven that technologies developed in HEP are extremely beneficial for society, MRI’s, proton cancer therapy and the World Wide Web are just examples. In the end, it is part of human nature to keep continuously inquiring and learning more about the mysteries of our world. The fundamental questions lying ahead seek for a profound understanding but also require new tools; these tools advance technologies which later have a great impact in our daily lives. I think this is a powerful synergy between basic research and technology innovation.

High-energy physics is an amazing field because it aims to understand the deepest secrets of nature while it also has a strong social side. It brings together scientists, engineers and technicians from all around the world, bridging cultural and social differences in a unique way. People work together and learn to collaborate to answer the fundamental questions about nature without the need of complex legal structures that would oblige them to do that; such level of cooperation is highly unusual in human society. This is one of the greatest merits of our field, and I am proud to be part of such an endeavour. Moving forward in the exploration of our universe and continuing fundamental R&D is something we owe to the next generations.

How difficult is for a women to pursue a career in physics and where we should focus our efforts to tract more female scientists?

When I began my career in physics, there were very few women in my field that I could look to for inspiration. Today, this situation has changed, but we are behind other fields of science in terms of achieving gender diversity. Increasing the number of role models would be a necessary step towards engaging young women and other underrepresented groups to pursue careers in physics. The more women you have the more you will attract because you create a more supportive environment.

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Marcela Carena

interview

Fermilab

issue 22

Superconductivity accelerates a sustainable future

Sabrina El Yacoubi — Tue, 17 Oct 2017 08:14:58 +0000

Superconductivity accelerates a sustainable future
By Panos Charitos (CERN)

At the two-and-a-half-day Superconductivity Hackathon that hosted by CERN’s IdeaSquare, students worked side-by-side with scientists, researchers and company representatives, to solve problems in different application fields by using the advantages of superconductivity. Interdisciplinarity, creativity and collaboration are the keys to success and the hackathon offered numerous possibilities of interexchange with several experts thanks to its character and informal setting.In addition, the event highlighted the importance of preparing now the next generation of experts for the challenges that lie ahead.

The phenomenon of superconductivity, discovered around 100 years ago, has yet to find its way everyday life. Particle physics uses superconducting magnets since the late 1960s. These magnets generate stronger magnetic fields to curve particle trajectories, thereby allowing to reach previous unexplored territories at higher energies and higher intensities. Moreover superconductors are used for the detector magnets allowing to study in great detail the debris of very energetic particle collisions. Together with their impact on fundamental research, superconductivity has an unexpected transformative potential that can guarantee a greener and sustainable future. Superconductors are the natural choice for any application where strong magnetic fields are needed including applications as diverse as magnetic resonance imaging (MRI), the magnetic separation of minerals in the mining industry and efficient power transmission lines.

An intensive 3-day Superconductivity Hackathon took place at CERN’s Idea Square (Image Credit: FCC collaboration).

The promise for future technologies is even greater, and overcoming our limited understanding of the fundamental principles of superconductivity and enabling large-quantity production of high-quality conductors at affordable prices will open new business opportunities. In an effort to transfer this leading-edge technology to daily applications and tackle the above challenges, the Marie-Curie training network EASITRAIN together with the FCC study, HL-LHC project and CERN’s KT group established a collaboration with the Vienna University of Economics to research new fields of application that generate socio-economical value.

During the past semester, students identified and evaluated new fields of application. More than 120 qualitative interviews with experts from a broad range of industries were carried and 29 potential application areas were selected that in close consultation with the technology and industry experts were subsequently narrowed down to three specific cases: Uninterruptible Power Supply (UPS) systems, fruit sorting machines to monitor food quality and a visionary rocket launch system that could boost our exploration of the solar system in an energy and cost efficient way compared to current conventional systems.

The three topics informed the work of the six teams that participated in the Hackathon. During an intense 3-day program, they identified the challenges for each application, evaluated its commercial adaptation and developed business strategies. Academic and industrial experts joined the teams to answer their questions and steer their imagination. Industrial experts from Babcock Noell (superconducting flywheels for UPS systems), Equinix (Data Centres) MicroTech (fruit shorting machines) and Swissloop (concepts for Hyperloop in Switzelrnad) worked together with the students to develop applications with short-term or long-term applicability. “We have tried to work out our solutions as practically as possible and always have an eye on their concrete implementation" says Marco Boschett from MicroTech, one of the companies that participated in the SC Hackathon.

The jury prize went to the team who developed a fruit sorting method for avocados that will determine the fruits’ maturity. Tonnes of fruit have to be disposed of worldwide because current technologies based on spectroscopy are not able to determine the maturity level of fruit sufficiently accurately, with techniques also offering limited information about small-sized fruit. Superconductors would enable NMR-based scanning systems that allow producers to accurately and non-destructively determine their valuable properties saving billions every year. "The superconducting technology could present the next innovation in the market for the fruit processing industry and open up new possibilities, which ultimately benefits the consumer", said Microtec CEO Federico Giudiceandrea.

Superconductors could present the next innovation in the market for the fruit processing industry and open up new possibilities (Image Credits: Athina Papageorgiou Koufidou)

The audience award was given for the concept of a novel space transport method. Have you ever considered a global energy crisis in the near future? The team dealt with this potential threat and came up with a futuristic, albeit realistic solution. They developed the concept of a high-innovative transport method to harvest the moon using superconductors technology. The moon holds essential resources, including helium-3 which is a gas that could be used as fuel in future nuclear fusion power plants. By establishing two space module stations on the moon and a futuristic space shuttle it will be possible to transport helium-3 to earth while the same station could be used for future trips to the neighborhood of our solar system.

The audience award went to the team that designed a novel superconducting rocket launch system (Image Credit: Athina Papageorgiou Koufidou)

But it is not only the scientific results that matter. The participant build new networks and they will continue working together to cultivate and expand the newly established contacts from the different academic institutes and industries. As Markus Nordberg, head of IdeaSquare, mentioned in his speech during the award ceremony: “You are all winners and the biggest prize is sharing, the fact that you met and shared your experiences and ideas”.

The time is right for superconductivity to emerge as the next great transformational technology — with far-reaching impact: From building new powerful scientific instruments like a future circular collider reaching unprecedented energy scales but also for paving the way to new applications in medicine, energy and other fields impacting our lives.

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CompactLight: to compact accelerators and beyond

Livia Lapadatescu — Thu, 12 Oct 2017 13:30:25 +0000

CompactLight: to compact accelerators and beyond
by Gerardo D’Auria (Sincrotone Trieste S.C.p.A)

After years of intense R&D carried out at SLAC (USA) and KEK (Japan) for the NLC/JLC (Next Linear Collider / Japan Linear Collider) projects and at CERN with collaborators in the context of the CLIC study (Compact Linear Collider), and following the successful pioneering experience of the Elettra (Italy) and PSI (Switzerland) laboratories, the X-band technology takes an important leap forward.

The Horizon 2020-funded project, CompactLight, will soon begin to design the first hard X-ray Free Electron Laser based on 12 GHz X-band technology. A consortium of 21 leading European institutions, including industries, together with the Shanghai Institute Of Applied Physics, the Australian Synchrotron, and the University of Melbourne, are partnering up to achieve this ambitious goal within the 36-month duration of the recently-awarded grant. The ambition of the CompactLight collaboration goes even beyond compact acceleration, as the consortium aims at simultaneously investigating and developing the next generation of undulators.

Map of CompactLight partners (Image credit: CompactLight consortium)

During the past decades, Synchrotron Radiation facilities have seen an impetuous growth as a fundamental tool for the study of materials in a wide spectrum of sciences, technologies, and applications. The latest generation of light sources, the Free Electron Lasers (FELs), capable of delivering high-intensity photon beams of unprecedented luminosity and quality, provided a substantially novel way to probe matter. Currently, the FELs operating in Europe are three: FERMI @Elettra, FLASH and FLASH II (DESY), operating in the soft X-ray range, and two are under commissioning, SwissFEL (PSI) and EuroXFEL (Germany), which will operate in the hard X-ray scale. Yet, this field still has very high, largely unexplored, potentials for science and innovation.

While most of the worldwide existing FELs use conventional normal conducting 3 GHz S-band linacs, others use newer designs based on 6 GHz C-band technology, increasing the accelerating gradient with an overall reduction of the linac length and cost. CompactLight gathers the world-leading experts both in the domains of X-band acceleration and undulator design, and intends to design a hard X-ray FEL facility beyond today’s state of the art, using the latest concepts for bright electron photo injectors, very high-gradient X-band structures at 12 GHz, and innovative compact short-period undulators. If compared to existing facilities, the proposed facility will benefit from a lower electron beam energy, due to the enhanced undulators performance, be significantly more compact, as a consequence both of the lower energy and of the high-gradient X-band structures, have lower electrical power demand and a smaller footprint.

A successful outcome of CompactLight might have a much wider impact: affirming X-band technology as a new standard for accelerator-based facilities and advancing undulators to the next generation of compact photon sources. This will facilitate the widespread distribution of compact X-band based accelerators, as well as the development of compact X-ray FEL facilities across and beyond Europe.

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EuCARD-2 achievements and prospects

Livia Lapadatescu — Wed, 11 Oct 2017 13:03:41 +0000

EuCARD-2 achievements and prospects
by Panos Charitos (CERN)

Some EuCARD-2 results in numbers, showing the impact on European science and society.
(Image credit: EuCARD-2 collaboration)

Accelerators are our only key to accessing the subatomic world, concentrating huge amounts of energy in tiny particle beams that penetrate deeply into the matter revealing new structures and physics phenomena. By converting energy into matter following Einstein’s famous formula (E=mc²) they can produce new types of matter that may have existed just after the Big Bang, when our Universe was too hot and dense. Moreover, some accelerators can inspect molecular and atomic structures, thus finding many applications outside fundamental research, from material science to medical diagnostics and treatment.

To exploit the potential that particle accelerators can offer in different fields, inside and outside of particle physics, crucial technological advancements are needed. Future accelerators should be more compact, more sustainable and more affordable; these developments could endure their use for particle physics and unlock their huge transformative potential in other fields. Improving the present and future European accelerator-based Research Infrastructures was the main goal of EuCARD-2, the FP7 Integrating Activity project just completed after 4 years full of events and successful accomplishments. Maurizio Vretenar, the EuCARD-2 Project Coordinator, explains: “In exploring societal applications we tried to capitalise on our competences in scientific accelerators, at the same time identifying areas where the impact of accelerators could be the highest”.

EuCARD-2 focused on improving the performance of existing and future accelerators with the goal of making them more compact, economic and energy efficient. On top of that, new applications of accelerators were analysed by EuCARD-2 in collaboration with industry. Accelerator produced isotopes can open new perspectives in medical imaging and in fighting cancer, giving an important contribution to the new generation of personalised cancer therapies. In the environmental field, the treatment with particle accelerators of flue gases from coal plants or of exhaust gases from e.g. large marine engines will reduce the rejection of sulphur and nitrogen oxides in the atmosphere, thus improving the quality of air. The diffusion of industrial processes based on accelerators, like material analysis, inspection, treatment of plastics and ion implantation will increase competitiveness for European industry, resulting in job creation and economic growth.

EuCARD-2 also studied ways to maximise the energy efficiency of accelerator facilities, contributed to the development of new schemes for frontier accelerators and in coordinating the plasma accelerator community in Europe, which resulted in the EuPRAXIA Design Study.

Key scientific achievements of EuCARD-2 include the selection of the conductor, the cable geometry and magnet design for High Temperature superconductors for accelerator magnets that can be used in future colliders, aiming to push further the energy and intensity frontiers: a world record current density of 1338 A/mm² was reached in an YBCO tape. EuCARD-2 produced and tested novel collimation materials that will be used for the High Luminosity upgrade of the LHC. Finally, it played a pivotal role in the demonstration of high-brightness electron beams for laser plasma accelerators and contributed to the initial success of the AWAKE plasma-driven experiment at CERN.

Participants of the final Annual Meeting on 28-30 March 2017, hosted by the University of Strathclyde in Glasgow (Image credit: EuCARD-2 collaboration)

EuCARD-2 brought together 40 European universities, accelerator laboratories and technological institutes on a programme structured in 13 Work Packages. With clear objectives in mind, the EuCARD-2 team focused on obtaining results of direct benefit to both European science and European citizens. Vretenar explains: “We focused in structuring and supporting the existing accelerator community, contributing to the development of new ideas and technologies for the future accelerators for science, and to transferring these technologies to accelerators that could impact our everyday life.”

Reaching these goals called for the formation of a well-balanced international network of partners including research centres, universities and the industry. Modern scientific projects require collaboration and one of the key challenges of EuCARD-2 was to build across Europe a strong network of experts and young researchers who would share the same goal and remain motivated during this project. By promoting complementary expertise, cross-disciplinary fertilisation and a wider sharing of knowledge and technologies on strategic topics, EuCARD-2 succeeded in enhancing multidisciplinary R&D for European accelerators and prepared the ground for other EU funded accelerator projects.

Successful collaboration doesn’t come without problems and the coordination team of EuCARD-2 often had to tackle delicate technical problems. “Research is unforeseeable by definition and delays in the production of prototypes, unavailability of key people, unavailability of testing equipment forced us to change many times the schedule and to look for alternative solutions to keep our work plan and our engagements. Most of the times, the solutions consisted in a redistribution of the work among the partners that was possible only thanks to the good team spirit and to our culture of collaboration and exchange.”

As Vretenar points out, “There is a brave new world of applications in front of us, with many opportunities to exploit, but as well, many challenges to face in promoting scientific innovation in our complex European society”. EuCARD-2 has identified a number of promising technologies that could be exploited to improve European science and to address our societal challenges, such as providing better medicine for an aging population, reducing the environmental impact related to high living standards, and increasing technological content and competitiveness of industry. Some of these steps are part of the successor to EuCARD-2, the new ARIES (Accelerator Research and Innovation for European Science and Society) project that will continue the exploratory work of EuCARD-2, but at the same time will push forward selected key technologies in collaboration with industry.

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More information on the EuCARD-2 results can be found in the Final Project Report.

EuCARD-2

impact

results

Accelerator Applications

issue 22

Corrector magnets for HL-LHC

Livia Lapadatescu — Wed, 11 Oct 2017 12:34:07 +0000

Successful tests of canted correctors for HL-LHC
by Panos Charitos (CERN)

The High-Luminosity upgrade of the LHC (HL-LHC) will extend the discovery potential of the world’s largest accelerator. The upgrade aims to increase its luminosity (rate of collisions) by a factor of five beyond the original design value and the integrated luminosity (total collisions created) by a factor ten.

To reach these goals, a wide range of magnets and new technologies are currently under development. There will be about 100 magnets of 11 new types: four types of main magnets and seven different types of correcting magnets. In addition to the dipole and quadrupole magnets that guide and focus the charged particles, corrector magnets are used to cure imperfections in the magnets and compensate for alignment errors.

Among them, 2-m-long orbit correctors with an ultimate field close to 3 T will be positioned near the insertion region of the ATLAS and CMS experiments. These magnets will be used not only to correct imperfections and alignment, but also to open the crossing angle (between the two beams) avoiding parasitic collisions in the detectors. The team working under the HL-LHC project selected for this intermediate field a “canted cos theta” design with Nb-Ti superconducting wire. This type of winding configuration superposes two concentric and oppositely tilted solenoids, to produce a pure dipole field. “This design has been proposed long time ago, but this will the first time to be used in a high energy physics particle accelerator” – says G. De Rijk, in charge of the magnet laboratory building the corrector.

A 0.5-m-long short model was an essential step to demonstrate the validity of the design and of the technological solutions. It was tested in August 2017 at CERN and successfully reached the ultimate field. The 2-m-long prototype is expected to be tested by the middle of 2018. Even though this design requires about 50% more conductor than usual sector coils, this should be widely compensated by the simplicity of construction. “This magnet has 10 drawings instead of 100, so less components and less tooling to assemble – at the end, a less expensive and a more reliable magnet” explains G. Kirby, in charge of the magnet development.

A 0.5-m-long short model was tested in August at CERN. It was an essential step to demonstrate the validity of the design and of the technological solutions. (Image: Glyn Kirby/CERN)

It is the first time that this design is studied at CERN while Berkley magnet lab and PSI are exploring the applicability of this concept for higher-field magnets based on Nb3Sn. This novel approach has also great potential for intermediate fields required for medical applications - Berkeley National Labs are developing a gantry for cancer therapy.

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ARIES to launch innovation fund

Jennifer Toes — Fri, 06 Oct 2017 15:28:32 +0000

ARIES to launch innovation fund
by Jennifer Toes (CERN)

ARIES Proof-of-Concept fund opens in December 2017 (Image: CERN)

In December 2017, the ARIES project will launch a call for proposals to its Proof-of-Concept (PoC) fund. By offering funding to new and novel projects, the fund aims to foster innovation and enhance the impact of accelerator technology in society.

By bridging the gap between the seed stages of research and their full commercial application, the fund will reduce the financial risks associated with early-stage innovation.

A total of €200,000 will be initially available for up to four projects based on accelerator science, with clear potential to go beyond the realm of scientific research within particle physics.

Selected projects should focus on the possible societal and commercial applications of their ideas within fields such as medicine, energy, security, and any others of relevance where accelerator technology may be of use.

ARIES will manage the fund through a dedicated Work Package, WP14 Promoting Innovation, led by Marcello Losasso of the CERN Knowledge Transfer Group. WP14 will foster technology development in key areas, strengthen relationships with commercial partners, and provide advice to ARIES members on intellectual property (IP) management and licensing.

With this in mind, the PoC funding may be used to investigate the commercial feasibility of a new concept, as well as identifying opportunities for partnerships, licences and IP positions.

Via a competitive two-step selection process, projects will shortlisted for interview based on the quality and potential impact of their project, as demonstrated in their proposal. The Evaluation Panel will make their final recommendations following the presentation and interview of shortlisted candidates.

“The Proof-of-Concept fund is a key component of the ARIES innovation strategy,” says Maurizio Vretenar, ARIES project Scientific Coordinator, based at CERN in Switzerland. “Our community is very creative and it is important to stimulate this talent towards applications that could have an impact on society.”

The fund will officially open its call for proposals as of 14^th December 2017, and will remain open for at least four months. The final deadline for submissions is expected in April 2018.

Further information about the fund will be posted on the ARIES project website soon. Interested parties are invited to check the site regularly for updates.

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Boosting the electron beam brightness: NeXource

Livia Lapadatescu — Fri, 06 Oct 2017 08:19:20 +0000

Boosting the electron beam brightness: NeXource
by Bernhard Hidding (University of Strathclyde)

Particle-in-cell-simulation with VSim: the driver beam propagates to the right and excites the plasma wave, which accelerates the witness bunch while being dechirped by an escort bunch population.(Courtesy: A.F. Habib)

Extremely high-quality electron beams are required to realize knowledge-generating machines in the hard x-ray regime or at the energy frontier. EuPRAXIA, the H2020 project exploring design options for a "European Plasma Research Accelerator with eXcellence In Applications", therefore aims to develop a compact plasma accelerator with superior beam quality. EuPRAXIA researchers at the University of Strathclyde and partners at the University of Hamburg/DESY and UCLA, supported by industry (RadiaBeam, RadiaSoft and Tech-X), have now developed a breakthrough technique which may allow to increase the brightness of electron beams by many orders of magnitude. The study has recently been published in Nature Communications [G. G. Manahan, A. F. Habib, et al., doi: 10.1038/ncomms15705].

While the huge accelerating electric fields of plasma accelerators allow to realize energy gains of many tens of GeV on few cm-scale lengths, the output electron beam quality is also of paramount importance for many key applications. One especially promising approach is the plasma photocathode a.k.a. “Trojan Horse” technique. The concept decouples injection from acceleration, and allows to generate tunable electron beams by controlled ionization injection with a synchronized laser pulse directly inside an electron beam driven plasma wave. This injection mechanism generates witness beams with orders of magnitude better normalized transverse emittance and 5d-brightness, because the laser pulse transfers very low residual transverse momentum to the electrons in statu nascendi. Such plasma photocathodes may have comparable impact as the development of conventional photocathodes, which was a key to realize hard x-ray FEL’s such as the LCLS or the European XFEL in Hamburg. Exploration of the Trojan Horse technique has therefore already been foreseen for large-scale plasma accelerator projects such as SLAC’s FACET-II, BNL’s ATF-II, DESY’s FLASHForward and for EuPRAXIA.

However, it is highly desirable to go even further, and to also tackle the “energy spread” problem. The ultrahigh electric fields in plasmas come at a price: they also produce ultrahigh electric field gradients. Therefore, the head of the accelerated electron beam gains energy at a lower rate than its tail. This leads to an electron beam energy “chirp” which gives rise to various significant problems e.g. during extraction, capture, transport and for applications, where it can be a showstopper e.g. for FEL.

The study in Nature Communications proposes to exploit tailored beam loading by so called “escort” electron bunches, again to be produced by the plasma photocathode technique, in order to flip the accelerating field and hence to obtain longitudinal phase space control over the witness bunch. Most importantly, the technique allows to remove the correlated energy chirp completely, leaving just the uncorrelated, residual energy spread. A discovered scaling law indicates that the relative energy spread of the dechirped bunch can reach sub-0.01%-levels at plasma wavelengths of ~500 µm and electron energies > 2 GeV. This energy spread is approximately two orders of magnitude improved compared to without dechirping.

This would boost the output of plasma accelerators e.g. in terms of 6d-brightness to levels beyond those of even the finest traditional accelerators. For example, the combination of low emittance, ultrahigh brightness and low energy spread may allow to beat the FEL Pellegrini criterion and the FEL Pierce parameter at the same time, and to harness ultrahigh gain.

Claudio Pellegrini (not involved in the study), one of the key figures in the history of the LCLS, said: "The path towards realizing the LCLS required a fundamental improvement of the electron beam quality obtainable from conventional accelerators. The approach Manahan et al. suggest now is very promising as regards obtaining a further step change in electron beam quality, this time to be enabled with plasma accelerators. This holds great prospects for the construction of future compact hard x-ray FEL's".

The combination of ultralow emittance and reduced energy spread may allow to realize next generation electron beam sources with ultrahigh 6D-brightness, an approach which the team calls the “NeXource” technique. Bernhard Hidding, who led the study and presented some of the results at IPAC’17, said that the novel concept could hardly come at a better time: “We have just seen first experimental signatures of the plasma photocathode in the ‘E210: Trojan Horse’ programme at SLAC FACET. Fascinatingly, it looks like the complex beam-plasma physics involved support each other to facilitate the mechanism. This is highly encouraging for future R&D along the NeXource approach.”


Residual energy spread scaling law: reducing the plasma wavelength and increasing the electron energy can reduce the residual relative energy spread to sub-0.01% levels already at 2-3 GeV, an energy which is today routinely reached by plasma accelerators. (Courtesy: A.F. Habib and G.G. Manahan)	The diagram indicates the projected 6d-brightness performance of the plasma-based NeXource approach in a couple of variations and at different energies when compared to state-of-the-art accelerators. (Courtesy: A.F. Habib and G.G. Manahan)

Strathclyde’s Research & Knowledge Exchange Services office has patented the approach and is now working with well-known accelerator product SME RadiaBeam Technologies to further develop and commercialize the technology. The technology may enable future compact free-electron lasers with a shot-by-shot performance substantially better than today obtainable even from the best of today’s large machines, and may have transformative effect on this and other important areas of research in natural, life and material sciences. It may be a unique path forward for EuPRAXIA to realize the goal of compact hard x-ray free-electron-lasers, and to fertilize plasma-based linear collider and high energy physics efforts.