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High-Gradient Wakefield Acceleration

CERN Accelerator School

ARIES

Date published:

Wednesday, March 25, 2020

Author:

Bernhard Holzer (CERN)

Article Category:

ARI

Issue:

Issue 32

Teaser:

The Spring 2019 edition of the CERN Accelerator School took place in Tecnico Lisboa and focused on High-Gradient Wakefield Acceleration.

Accelerators for Science and Society

Daniela Antonio — Thu, 11 Jul 2019 14:15:48 +0000

Professor Welsch and experts from Amsterdam Scientific Instruments discussing during the event. (Image: University of Liverpool)

Particle accelerators have numerous applications across many fields including fundamental research, healthcare, electronics, environment and energy… However, despite the vast benefits of accelerators for our everyday life, the whole research area is still nearly unknown to the majority of people.

Developing and building a large accelerator can take several decades and there is a well-documented shortage of engineers and scientists with relevant skills in this area. So the accelerator industry is particularly keen in promoting this career among young people.

World-leading European researchers presented talks on a range of topics from big data to cancer treatment.
(Image: University of Liverpool)

The Symposium 'Accelerators for Science and Society', an international science event that took place at the Liverpool Arena and Convention Centre on Friday 28 June 2019, aims to inspire students with the possibilities of this rapidly evolving field and provide an insight into the economic, scientific and societal benefits of particle accelerators.

The event was organised by the University of Liverpool and supported by the H2020 Marie Skłodowska-Curie training networks AVA and OMA, as well as the Liverpool Big Data Science Centre for Doctoral Training (LIV.DAT). Early stage researchers from all three training initiatives presented their research in the form of posters and gave young delegates the opportunity to experience science up close, through a number of interactive demonstrations that the researchers who are involved in the above schemes developed specifically for this event.

The symposium featured a number of interactive demonstrations developed specifically for this event.
(Image: University of Liverpool)

Renowned speakers addressed the wider public and provided a unique insight into cutting-edge research. All talks were live-streamed to institutions across Europe and are now available to watch in the event website.

Medical accelerators

Despite the huge social and economic impact of cancer, global diagnosis rates are increasing and new therapy methods are required to combat the disease effectively. Although there have been a number of recent advances in radiotherapy, more research is needed to maximise the effectiveness of this promising treatment. The Optimisation of Medical Accelerators (OMA) project, a collaborative research network funded by the EU, is developing upon these advances with the ultimate goal of improving cancer patient outcomes.

In his talk 'Proton Beam Therapy: how the Large Hadron Collider cures cancer' Dr Simon Jolly, Associate Professor at the University College London and the leader of the UCL High Energy Physics proton therapy research group, introduced some of the ways particle accelerators are used in cancer treatment, from the most common radiotherapy gantries to the more advanced technology needed for proton beam therapy.

Dr Simon Jolly discussed the link between the Large Hadron Collider and cutting edge cancer treatments.
(Image: University of Liverpool)

Antimatter research

According to our current understanding of the laws of physics, the Big Bang should have created equal amounts of matter and antimatter that should have instantly obliterated each other – and left the universe filled with nothing but light. Physicists are keen to discover the reasons why this didn’t happen.

The EU-funded Accelerators Validating Antimatter Research (AVA) project enables an interdisciplinary and cross-sector program on antimatter research. The three scientific work packages within the project cover facility design and optimization, advanced beam diagnostics, and novel low energy antimatter experiments. Dr Michael Doser, senior research physicist at CERN, and Steering Committee member within the AVA project, has specialized in working with antimatter. He presented a fascinating talk on ‘Antimatter matters’ that gave insight into the mystery of the missing antimatter and how antimatter affects our daily life.

Big Data

The academic pursuit of knowledge has driven human progress and technological evolution down the centuries, as practical applications often arise from fundamental research.

The World Wide Web is a perfect example of this. Originally developed by Sir Tim Berners-Lee in the 1980s as a way for particle physicists at CERN to share their large data sets remotely around the world, this information system now pervades almost every aspect of our daily lives.

Thirty years on from this first data revolution, the Centre for Doctoral Training LIV.DAT is training the next generation of data scientists.

Professor Maria Fasli, Director for the Institute for Analytics and Data Science at the University of Essex, presented a talk about ‘The power of data’, which discussed some of the trends in the domains of data science, big data and artificial intelligence, and provided examples of applications.

This event aimed to inspire students with the possibilities of this rapidly evolving research field.
(Image: University of Liverpool)

Science meets creative arts

Fundamental research has helped advance knowledge for thousands of years. In combination with the creative minds of artists and designers, unique opportunities for innovation can be created to the benefit of society.

Bestselling author, illustrator and animation creator Curtis Jobling, best known as the designer of the worldwide hit television show 'Bob the Builder', shone a light on the importance of thinking creatively and how the inquiring mind can become the leader in industry. His fun and engaging talk ‘Full STEAM ahead’ was a highlight for the audience – young and old alike.

Training the next generation

Finally, Professor Carsten Welsch, Head of Liverpool Physics and coordinator of the AVA, OMA and LIV.DAT training programmes gave a talk on ‘Accelerating Researcher Careers’ and showed how innovative training programmes in accelerator science have successfully trained more than 100 early-stage researchers over the past decade. “It is fantastic to see the outstanding research results from our three most recent initiatives and how our Fellows are engaging with the next generation of scientists and engineers at the event today,” he said. “Science is a global endeavour and Fellows are perfect ambassadors for the collaborative and interdisciplinary skills that modern research requires.”

More information and all talks can be accessed via the event homepage

Tags:

Accelerators for Science and Society

Event

Date published:

Thursday, July 11, 2019

Author:

Ricardo Torres and Alexandra Welsch (University of Liverpool)

Article Category:

Issue:

Issue 29

Teaser:

International event in Liverpool showcases benefits of accelerator R&D and engages the next generation of researchers.

Academia-industry collaboration drives innovation

Panagiotis Charitos — Wed, 27 Mar 2019 15:06:24 +0000

A new particle collider requires pushing numerous technologies beyond their state of the art. This situation provides industry with powerful test-beds for future markets that come with a high publicity factor. Novel technologies and processes can be piloted with controlled effort engagement. Well-controlled environments allow advancing technologies under conditions that extend beyond conventional product requirements. SMEs are ideal partners to bring these technologies to maturity on the quality level, generating new markets and leading to improved products.

Around 100 researchers, academics and industry delegates from the UK and other EU countries joined an academia-industry Co-Innovation workshop in Liverpool, UK on 22 March 2019. The event explored the exciting opportunities that the technology R&D around the FCC study presents for industry involvement and joint R&D programmes and was supported by the EU-funded EuroCirCol project and that MSCA training networks of EASITrain, OMA and AVA.

Image 1. Workshop participants discussing a range of key technologies. (Image: University of Liverpool)

Discussions across a number of working groups were motivated by the Future Circular Collider (FCC) study, but not limited to this study or even particle accelerators at all – the aim was to identify common ground for joint R&D across disciplinary boundaries.

Working groups were formed to discuss specific opportunities for co-innovation and funding and included for example superconducting magnet technologies which are also two key topics for EASITrain, cryogenics, civil engineering, detector development, radiofrequency technology, energy efficiency, novel materials and material processing techniques.

Image 2. An industry exhibition took place before the workshop to showcase latest technologies. (Image: University of Liverpool)

Short talks about FCC-related areas for innovation, examples of successful technology transfer projects at CERN, as well as current funding opportunities stimulated interesting discussions amongst the participants. All of these presentations are now available via the workshop homepage.

The workshop served as an ideal platform for networking across sector boundaries and opened a number of interesting discussions. Several areas were identified that provide an excellent basis for co-innovation, including resource-efficient tunnelling, transferring optimised purpose-built machine learning soft- and hardware from particle physics to industry, and detector R&D in terms of high speed, power and material constraints, cooling, and data maximization. Notes from all working groups are currently being finalized and will be used to follow up on agreed R&D lines with the aim to setup joint funding bids between participants.

It is anticipated that the final applications of the new technologies that are being developed for a next generation collider will stretch far beyond the applications initially targeted. The World Wide Web, originally invited to support particle physics experiments, has just celebrated its 30th anniversary and is an outstanding example of how these technologies can impact on everyday lives.

There are many other successful examples of where innovations made for fundamental research are benefiting society - most of the time in completely unforeseen ways. The FCC study illustrates this in the brand-new film “Busy bees and might magnets – From the Higgs to Honey: What's all the Buzz about Particle Accelerators?” which was produced between CERN and the University of Liverpool.

The film was launched at the event in Liverpool is now available on YouTube.

Tags:

Date published:

Wednesday, March 27, 2019

Author:

Constantinos Astreos (University of Liverpool)

Article Category:

FCC

ESI

Issue:

Teaser:

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.

Accelerating News Readers Survey

Daniela Antonio — Mon, 25 Mar 2019 17:02:09 +0000

Thank you for your time, we welcome your contribution.

The Editorial Team

Tags:

Accelerator Communication and Outreach

Date published:

Monday, March 25, 2019

Author:

Editorial Team

Article Category:

ACO

Issue:

Issue 31

Teaser:

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!

Seamless accelerating cavities

Sabrina El Yacoubi — Wed, 20 Mar 2019 15:50:42 +0000

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.

Tags:

FCC

issue 28

Date published:

Wednesday, March 20, 2019

Author:

Cristian Pira, Oscar Azzolini, Giorgio Keppel, Silvia Martin, Fabrizio Stivanello (INFN)

Article Category:

FCC

Issue:

Teaser:

Superconducting radiofrequency accelerating cavities are the heart of modern particle accelerators and one of the key challenges for the FCC study.

How to slice a proton beam

Sabrina El Yacoubi — Wed, 20 Mar 2019 15:39:23 +0000

Small proton bundles are needed to separate the charges in the plasma, thus creating surfable waves for the electrons.

Plasma wakefield acceleration technology has the potential to revolutionize linear lepton colliders. Plasma can sustain accelerating fields that are many orders of magnitude higher than the fields of conventional radio-frequency cavities. Thus, plasma-based acceleration could substantially decrease the length (and possibly cost) of a future linear accelerator.

Plasma wakefields can be excited by a highly relativistic particle bunch, the so-called drive bunch. As the bunch enters the plasma, plasma electrons respond to its electric field and start oscillating at the plasma frequency; their oscillations sustain the wakefield. The wakefield’s longitudinal and transverse components accelerate and focus a witness bunch. Similar to a surfer on a water-wave, the witness bunch gains energy from the wakefield.

The drive bunch excites large-amplitude plasma wakefields, when it is about one plasma wavelength long (typically < 3 mm) and its density similar to the plasma electron density (> 10¹⁴/cm³). Such short dense particle bunches are available at facilities such as SLAC, but their energy content is small (<100 J) and when exciting wakefields, their energy depletes over a short distance.

Proton bunches at CERN carry much larger amounts of energy, in excess of 10 kJ. This is enough to drive several GV/m field amplitudes over hundreds of meters. Unfortunately, their bunch length is on the order of 6-12 cm, at least 20 times too long. Additionally, their particle density is approximately 10-100 times too low.

The AWAKE experiment at CERN recently demonstrated for the first time that - using the seeded self-modulation process - one can use those long proton bunches to excite high amplitude wakefields. As the long bunch enters the plasma, it drives low amplitude seed wakefields (~10 MV/m). The transverse wakefields act back on the bunch and periodically focus and defocus it. Defocused protons leave the bunch. After all defocused protons have left, focused regions form a train of ‘micro-bunches’. Each micro-bunch drives its own wakefield and these fields add resonantly, resulting in a large amplitude wave.

Figure 1. As the long bunch enters the plasma, it drives low amplitude seed wakefields (~10 MV/m). (Image: AWAKE)

The plasma itself modulates the proton bunch. Thus, micro-bunches are spaced at the plasma wavelength. This is a fundamental physics property of the process. AWAKE measured the proton micro-bunch structure using a streak camera with pico-second time resolution and showed directly that the self-modulation occurs. Measurements of the micro-bunch spacing (or frequency) are in good agreement with the theoretically predicted value for various plasma densities.

Figure 2. Streak camera measurement of the self-modulated proton bunch. (Image: AWAKE)

Further, AWAKE measured the transverse deflection of the protons that were defocused during the self-modulation process on a screen after the plasma exit. It was shown that such a large transverse displacement can only be achieved if the transverse wakefield amplitudes exceed the amplitude driven by the unmodulated proton bunch. This proves that – as expected - the wakefields have grown along the bunch. Time-resolved measurements of the defocused protons confirm that the displacement of the defocused protons increases along the bunch.

This is clear evidence of proton bunch self-modulation and excitation of high amplitude wakefields in plasma. AWAKE also accelerated externally injected ~18 MeV witness electrons to 2 GeV in these wakefields as published in a Nature article last year. The longitudinal wakefield amplitude reached values comparable to the transverse one. All physics concepts required for proton-driven wakefield acceleration have now been validated, paving the way for more in-detailed studies.

The path to a plasma-based collider is still long as there are many challenges that need to be overcome. But the outstanding success of this proof-of-principle experiment now opens the door for further breakthroughs: demonstration of good witness bunch quality after acceleration, scalability of the plasma and acceleration process and very high witness electron bunch energy. These will the primary goals of AWAKE Run 2 which will start in 2021.

Further information:

Experimental Observation of Plasma Wakefield Growth Driven by the Seeded Self-Modulation of a Proton Bunch, M. Turner et al. (AWAKE Collaboration); Phys. Rev. Lett. 122, 054801 (2019), https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.054801
Experimental Observation of Proton Bunch Modulation in a Plasma at Varying Plasma Densities, AWAKE Collaboration; Phys. Rev. Lett. 122, 054802 (2019), https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.054802

Tags:

Proton

AWAKE

Date published:

Wednesday, March 20, 2019

Author:

Marlene Turner and Karl Rieger

Article Category:

Issue:

Teaser:

First clear evidence of proton bunch self-modulation and excitation of high amplitude wakefields in plasma acceleration.

Highlights from CLIC Week 2019

Daniela Antonio — Wed, 20 Mar 2019 13:22:48 +0000

Figure 1: the CLIC collaboration in January 2019. (Image: M Volpi)

The physics opportunities brought by of a high-luminosity linear electron-positron collider

The annual Compact Linear Collider (CLIC) workshop brings together the full CLIC community, this year attracting more than 200 participants to CERN on 21-25 January 2019. The workshop covered accelerator and detector R&D, as well as detailed studies of the physics opportunities at a high-luminosity linear electron-positron collider. The programme also included civil engineering aspects, infrastructure studies, industrial involvement, and technology spin-off activities.

CLIC occupies a unique position in both the precision and energy frontiers, combining the benefits of electron-positron collisions with the possibility of multi-TeV collision energies. The CLIC project covers the design and parameters for a collider built and operated in three stages, from 380 GeV to 3 TeV, with a diverse physics programme spanning 30 years. CLIC uses an innovative two-beam acceleration scheme, in which high-gradient X-band accelerating structures are powered via a high-current drive beam, thereby reducing the size and cost of the accelerator complex significantly.

Figure 2: The main electron beam is produced in a conventional radio frequency (RF) injector, which allows polarisation and is accelerated to 2.86 GeV. The beam emittance is then reduced in a damping ring. To produce the positron beam, an electron beam is accelerated to 5 GeV and sent into a crystal target to produce energetic photons, which hit a second target and produce electron-positron pairs. The positrons are captured and accelerated to 2.86 GeV. Their beam emittance is reduced in a series of damping rings. In the final injection step, a booster linac system accelerates both beams to 9 GeV, the bunch length is compressed, and the beams are delivered to the main linacs where they are accelerated to 190 GeV, using a unique and innovative two-beam accelerating scheme featuring 12 GHz X-band accelerating structures that reach accelerating gradients of 100 MV/m. The beam delivery system removes transverse tails and off-energy particles with collimators, and compresses the beam to the small size required at the interaction point (IP). After collision, the beams are transported by the post collision lines to their respective beam dumps. (Image: CLIC/CERN)

In Wednesday’s open plenary session, Steinar Stapnes, the CLIC project leader at CERN, reported that the key CLIC concepts, such as drive beam production, operation of high-efficiency radio-frequency cavities, and other enabling technologies, had all been successfully demonstrated. The afternoon session also included detailed presentations on the accelerator and detector status, and of the CLIC physics potential, including key motivations for an electron-positron collider that can be extended to multi-TeV energies.

“The CLIC project offers a cost-effective and innovative technology and is ready to proceed towards construction with a Technical Design Report. Following the technology-driven timeline, CLIC would realise electron-positron collisions at 380 GeV as soon as 2035,” says Stapnes.

A major focus in 2018 was the completion of a Project Implementation Plan (PiP), as well as several comprehensive Yellow Reports describing the CLIC accelerator, detector, and detailed physics studies. These reports were further distilled into the two formal input documents, submitted to the European Strategy for Particle Physics Update 2018 - 2020 (ESPP), which can be found at: https://clic.cern/european-strategy

A central point of the workshop was an updated cost and power estimate, which for the first stage amount to around 5.9 billion CHF and 168 MW, respectively. The energy upgrade to 1.5 TeV adds a cost of approximately 5.1 billion CHF, including an upgrade of the drive-beam radiofrequency power. Further, the energy upgrade to 3 TeV would add approximately 7.3 billion CHF, including the construction of a second drive-beam complex. With the proposed staged approach these costs can be distributed over two or three decades.

Looking to the future, the workshop also discussed the next important step for the CLIC project: an initial five-year preparation phase focusing on further design, technical and industrial developments, with a focus on cost, power and risk reduction. Civil engineering aspects and infrastructure preparation, including site authorisation, will become increasingly detailed during the preparation phase. At the same time, system verifications will be made in dedicated CLIC prototype setups, as well as in other facilities, which have similar high-power radiofrequency linac systems and low emittance beams. These include normal-conducting Free Electron Laser (FEL) linacs and compact photon sources such as those based on Inverse Compton Scattering.

These facilities will provide powerful demonstrations and new benchmarks for reliability, technical parameters, simulation and modelling tools. The goal is to produce a Technical Design Report (TDR), enabling the start of construction for the first CLIC stage by 2026.

The technology-driven schedule is shown in Figure 2, showing the construction and commissioning period and the three stages for data taking, including the corresponding goal for integrated luminosity. The schedule for construction and installation shows that the CLIC project can be implemented well in time for first collisions in 2035, which would allow the exploration of Higgs physics at CLIC immediately after the end of the high-luminosity LHC programme.

2018 saw several significant achievements, including extensive X-band structure development and testing at CERN and in collaborating institutes; further developments of high-efficiency radiofrequency systems; overall system verification studies in CERN Linear Electron Accelerator for Research (CLEAR), Accelerator Test Facility (ATF2) at KEK, free-electron lasers and low emittance rings; comprehensive civil engineering and infrastructure studies; and numerous technical developments, optimising the most critical and cost/power-driving components of the CLIC accelerator.

In parallel, a systematic overview of potential industrial involvement in the CLIC core technologies is being compiled. Several agreements with collaboration partners support technical developments for smaller X-band based accelerators and elements with similar parameters. These include the CompactLight European Commission Design Study for an X-band based free-electron laser design, and the recently proposed eSPS project that aims to study dark sector physics with an Super Proton Synchrotron (SPS)-based primary electron beam facility at CERN, comprising a compact X-band electron injector linac using CLIC technology. These efforts, and many others, were highlighted throughout the week and the subject of a dedicated session on applications of high-gradient X-band technology and of advanced uses of electron beams.

The workshop also discussed interesting developments in plasma- and dielectric-based acceleration. The laser straight linear tunnel of CLIC can provide a natural infrastructure for long-term future projects that might use such novel acceleration techniques.

In the CLIC detector R&D session focusing on silicon pixel technologies, several new and refined test-beam analysis and simulation results were presented. These results enabled the design of two new monolithic detector technology demonstrators targeting the challenging vertex and tracker requirements at CLIC. Final design features for both chips, as well as plans for future tests, were presented and discussed. Many of these tests will take place at the test-beam facilities of DESY in Hamburg, where the CLICdp vertex and tracker group will be welcomed for several weeks during the second planned long shutdown of CERN’s accelerators in 2019/20.

The workshop heard reports on recent developments for Standard Model precision tests in the Higgs boson and top-quark sector, as well as on the broad sensitivity to effects from physics beyond the Standard Model. Updates were presented on benchmark scenarios with challenging signatures such as boosted top quarks and Higgs bosons, numerously produced at the higher-energy stages of CLIC. Further, the Higgs self-coupling, which determines the shape of the Higgs potential, can be directly accessed at the multi-TeV collisions at CLIC through the measurement of double Higgs production. This measurement benefits from the excellent jet resolution and flavour tagging capabilities of the CLIC detector as well as the clean collision environment in electron-positron collisions. The workshop reported projections of the Higgs self-coupling, in a full simulation study, reaching a precision of 10%, an accuracy that is preserved in a global fit of the full Higgs programme of CLIC.

The CLIC physics programme continues to attract interest from the theory community. A series of talks in a dedicated mini-workshop, joint between theorists and experimentalists, reported on the CLIC potential to extend our knowledge of physics beyond the Standard Model. New results were presented showing the CLIC potential to probe the possible composite nature of the Higgs boson at the scale of tens of TeVs, to discover dark matter candidates such as the thermal Higgsino, and to study axion-like particles in a unique mass range. It was also shown how searching for neutral scalar particles coupled through the Higgs will allow CLIC to explore models relating to the nature of the Electroweak Phase Transition and with non-minimal supersymmetric models addressing the Naturalness Problem. The workshop also saw discussions of first studies of stub-tracks and long-lived particles searches, a domain in which CLIC has promising potential for future exploration.

There is widespread support for a lepton collider for high-precision Higgs boson and top-quark physics. CLIC is a mature contender that, in addition, can be extended to multi-TeV collisions, providing unique sensitivity to physics beyond the Standard Model.

Further reading:

https://clic.cern/european-strategy
CLIC 2018 Summary Report (CERN-2018-005-M)
CLIC Project Implementation Plan (CERN-2018-010-M)
The CLIC Potential for New Physics (CERN-2018-009-M)

Tags:

CLIC

linear accelerators

Date published:

Wednesday, March 20, 2019

Author:

Rickard Ström (CERN)

Article Category:

CLIC

Issue:

Teaser:

The physics opportunities brought by of a high-luminosity linear electron-positron collider

Ultra-high energy heavy ion testing

Daniela Antonio — Wed, 12 Dec 2018 15:56:15 +0000

Radiation environments such as space or high-energy accelerators pose a serious threat to the reliable operation of electronic components and systems. Therefore, in order to ensure a suitable operation, semiconductor devices need to be qualified in a radiation environment representative of that to be encountered in operation. The Radiation to Electronics (R2E) project at CERN is focusing on the development, study and testing of electronic components and systems, critical in view of the high luminosity LHC upgrade. To that end, in the past two years the ultra-high energy heavy ion beams of the PS and SPS have been exploited.

In the case of accelerator applications, heavy ions are typically not a concern for radiation effects on electronics, provided the respective environment is constituted by lighter particles, such as neutrons, protons and pions. Despite this fact, heavy ions can still be used to qualify electronics for high-energy accelerator applications, provided that being resistant to ions of a large enough Linear Energy Transfer (LET) also implies being insensitive to the mixed hadron field characteristic of the LHC machine.

The testing of electronics for Single Event Effects (SEEs, one of the main concerns for electronics in radiation) is typically carried out using protons in the 20-200 MeV range and heavy ions with LET values of up to 60 MeVcm2/mg. For space applications, these types of radiation mimic the trapped proton belt environment and Galactic Cosmic Rays, respectively.

Heavy ion tests are typically carried out in cyclotron facilities (such as the UCL and RADEF laboratories, frequently used by the European Space Agency), and some of the ions traditionally employed are Argon, Krypton and Xenon. The energy and penetration in silicon of ions in these facilities is of the order of 10 MeV/n and 100 µm, respectively. Even though their energy is significantly lower than that of Galactic Cosmic Rays (that have fluxes typically peaking at 500 MeV/n and extending to much larger values), the cyclotron provided beams have the key advantage of an ionization capability (described through their LET, and used as a figure-of-merit of potential SEE induction) which covers the full range of what may be encountered in space.

Chip Intel Myriad2 tested at CERN

The main shortcoming of the energies used in ground-level experimental heavy ion facilities is the limited ion penetration: in order for ions to access the sensitive volume of a device before ranging out in the surroundings, the tests need to be performed in vacuum and with unpackaged or thinned devices. For modern, complex devices (e.g. 3D structures), opening the parts to make their sensitive areas accessible at a sub-100 µm scale while keeping them operational can be from very complex and costly to even unfeasible.

Moreover, even if the Linear Energy Transfer is regarded as the main parameter to describe the probability of inducing an SEE, it does not at all account for potential energy effects such as the radial structure of the ionization track in the passage of particles through matter or the probability and nature of their nuclear interactions.

Motivated by the practical and scientific reasons above, during the past two years, the CERN R2E project in collaboration with the beam physicists and facility experts, has been working towards being able to use the very-high energy ion beams in the CERN accelerator complex to test electronic components. In 2018 and profiting from the LHC end-of-year lead ion run, ion beams from two of the LHC injectors (the PS and SPS) were adapted to the characteristics needed to carry out irradiations on electronics.

The main objectives of such experiments with unprecedented ion energies were first of all, to determine the impact of the ion energy on the induced radiation effects and identify possible related shortcomings of the LET figure-of-merit; and secondly, to irradiate complex component structures that cannot be qualified with heavy ions in standard facilities. Within the second category of experiments, a broad set of components and boards for space applications have been tested with ultra-high energy ion beams at CERN in collaboration with the European Space Agency (ESA). Among the ESA devices which took advantage of these very special CERN beams stand the Intel artificial intelligence Myriad 2 chip, the Timepix-3 detector and the Micron 3D NAND flash memories.

A team of experts preparing the experimental setup for testing the space-worthiness of the Intel Myriad2 system-on-chip for space applications.

The results are presently under analysis and are already providing a very interesting insight into the behaviour of the irradiated systems in the harsh radiation environment of an accelerator like the LHC and the proposed future machines, and in test conditions more faithfully mimicking those encountered in space.

During the Long Shutdown 2 (LS2), the CERN R2E project will work on possible upgrades of the ion testing infrastructure for post 2021 irradiations, as well as in modelling through simulation tools the interaction of such ions with electronic components in order to improve the understanding and implications of the experimental observations.

Tags:

Chip Intel Myriad2

Date published:

Wednesday, December 12, 2018

Author:

Ruben Garcia Alia, Pablo Fernandez Martinez ‎and Maria Kastriotou (CERN)

Article Category:

Issue:

Issue 27

Teaser:

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

Accelerating Learning

Sabrina El Yacoubi — Mon, 08 Oct 2018 10:30:03 +0000

The Optimisation of Medical Accelerators (OMA) and Accelerators Validating Antimatter physics (AVA) projects organised several training events this summer at the fascinating research environment of CERN. The events were coordinated by the Quantum Systems and Accelerator Research (QUASAR) Group from the University of Liverpool, based at the Cockcroft Institute. The Group has a unique track record in organising international training events and has organised more than 50 Schools and Topical Workshops for the accelerator community over the past decade.

The OMA project held its 2^nd Topical Workshop on ‘Diagnostics for Beam and Patient Monitoring’ at CERN on 4-5 June. Over 40 delegates attended the two-day event. The workshop brought together experts specialised in monitoring patients with those developing technologies for imaging the particle beam used for the treatment to address some challenging questions in ion beam therapy. It identified common challenges and synergies between both communities.

Fig.1: Participants at the 2nd OMA Topical Workshop. (Credit: QUASAR Group)

The programme included a mix of invited and contributed talks. Technologies for non-invasive particle beam imaging were presented, as well as innovations based on prompt gamma imaging and associated simulation techniques.

Lectures given by leading researchers linked R&D with state-of-the-art clinical treatments. Several industry talks gave insight into the latest developments in clinical hadron therapy. Along the main workshop topic there was also a session on knowledge exchange, discussing how expertise at CERN and in wider research can be developed into partnerships with Industry.

All talks can be accessed via the following link: https://indico.cern.ch/event/716062

The workshop was followed by an academy organised by COSYLAB, from 6-8 June 2018, specifically for the OMA Fellows. This hands-on event introduced them to a control system architecture widely used in research institutes and proton treatment facilities across the world.

Fig.2: OMA Fellows at the COSYLAB academy. (Credit: QUASAR Group)

The participants received training in EPICS control software. This is a software developed by a collaboration that shares designs, software tools, and expertise for implementing large-scale control systems.

This training was a good opportunity to better understand the interface between diagnostic devices and their integration into the control system of a large-scale research facility.

Defining new training standards in antimatter research is the declared goal of AVA. AVA’s training programme is paramount as “Antimatter research boldly goes towards Physics Final frontier”, says Professor Carsten P Welsch, AVA Coordinator.

Fig. 3: Participants at the AVA School. (Credit: QUASAR Group)

AVA’s latest training event was an International School on ‘Low Energy Antimatter Physics’, attended by more than 60 participants. This international event took place over 5 days at CERN from 25-29 June 2018.

The week’s activities included lectures from experts working at the Antiproton Decelerator (AD). They covered the fundamentals of accelerator design and operation, invasive and non-invasive diagnostic techniques, spectroscopy measurements, antimatter gravity studies, as well as electron cooling. Study sessions were in place to allow follow-up discussions and encourage the attendees to ask questions

Fig.4 : AVA Fellows discussing with Dr Gerard Tranquille, one of the lecturers at the AVA School. (Credit: Indrajeet Prasad)

One seminar by Professor Hubert Reeves, a well-known science communicator, was organised in CERN’s Globe of Science and Innovation and was open to the general public. It was a great success with all of the 250 places booked and can now be watched via the event webpage in French or English.

In addition to lectures and seminars, the attendees also received tours around CERN’s unique AD and Synchro Cyclotron (SC) facilities, enabling them to see accelerators first-hand. A poster session encouraged networking and allowed for one to one discussions with other researchers.

Companies involved in AVA presented the particular research challenges they have been facing in a dedicated industry sessions. This gave School participants a better insight into how cutting-edge R&D is carried out in different sectors.

“Research within AVA has the potential to open up an entirely new realm of unseen Physics. Our School provided an excellent overview of the numerous challenges this community is currently facing and was an excellent addition to the long list of international training events we have organized over the years.”, says Professor Welsch.

All talks given during the School can be accessed via the following link: https://indico.cern.ch/event/677170/

The School was followed by hands-on training days on Detectors and Beam Diagnostics offered by Stahl Electronics and Bergoz Instrumentation, respectively. These bespoke trainings allowed Fellows to build up a deep understanding of cutting edge detector technology and obtain hands-on experience in working with them.

Fig.5 : AVA Fellows during training day with Stahl Electronics. (Credit: Indrajeet Prasad)

These summer trainings have set high standards for future events. The various contributions of industry partners ensured that participants received insight into both academic and industry aspects.

A project video, produced by the AVA Fellows during a bespoke Media Training earlier this year, is only one example of successful industry-academia collaboration.

The majority of the workshops and schools organised by the training networks are open for external participants. To learn more about upcoming events, please visit the AVA and OMA webpages or follow the QUASAR Group’s Twitter channel.

Tags:

beam

patient monitoring

Date published:

Monday, October 8, 2018

Author:

Alexandra Welsch, Samantha Colosimo, Javier Resta López (University of Liverpool)

Article Category:

Issue:

Issue 26

Teaser:

Summer events held at CERN boost knowledge and collaboration. The events were coordinated by the QUASAR Group.

First experimental results from the CLEAR facility at CERN

Daniela Antonio — Tue, 03 Jul 2018 12:47:42 +0000

The plasma lens experiment after being fully installed in the CLEAR beamline (Credit: Wilfrid Farabolini - Wilfrid.Farabolini@cern.ch)

The continuous development of high gradient technologies (e.g. X-band, THz radiation, plasma acceleration) makes compact linear electron accelerators attractive for many applications, e.g.such as photon sources (Free Electron Lasers and Inverse Compton), medical application, and components irradiation studies.

Linear accelerators are also the only viable solution for electron-positron colliders at the high-energy frontier. In this case, high gradient technologies allow for cost optimisation and/or for maximizing the energy reach of such machines.

The CERN Linear Electron Accelerator for Research (CLEAR) facility at CERN was set up to expand the testing capabilities of those ideas and technologies and to provide on top the possibility to perform direct measurement with beam of machine components and training of young scientists.

The new CLEAR facility at CERN started its operation in fall 2017. CLEAR results from the conversion of the probe beam line of the former CLIC Test Facility (CTF3) into a new testbed for general accelerator R&D and component studies for existing and possible future accelerator applications, such as X-band structures, plasma and THz technology, nm- and fs-resolution beam instrumentation, sub-ps bunches production, but also for investigating possible use of electron beams for medical purposes or electrical component sensitivity to radiation.

The hardware modifications implemented in 2017 to the existing infrastructure allowed to provide stable and reliable electron beams with energies between 60 and 220 MeV in single or multi bunch configuration at 1.5 GHz.

CLEAR inherited not only the equipment, but also the experience of from operating the previous CTF3 facility: the first beam was set up in August 2017 and, after only a few weeks of commissioning, users could take the first beams to perform experiments in September.

The first CLEAR beam was used for the continuation of the irradiation tests performed on the Very energetic Electron facility for Space Planetary Exploration missions in harsh Radiative environments (VESPER), which was set up at the end of the CALIFES beamline already during the CTF3 era.

VESPER was initially set up to characterise electronic components for the operation in a Jovian environment – as foreseen in the JUpiter Icy Moon Explorer mission (JUICE) of ESA, in which trapped electrons of energies up to several hundred MeVs are present with very large fluxes.

Initial measurements showed the first experimental evidence of electron-induced single event upsets (SEU) on electronic components, pointing to the necessity of extending such an investigation to different electron energies. The CLEAR flexibility allowed to continue the study, showing a dependency of SEU cross-section with energy. Instead, no dependency was observed on radiation flux, suggesting that such components do not suffer from prompt dose effects.

A wider range of devices has also been tested, showing a strong dependency on the device process technology. Preliminary test on a set of memories sensitive to latch-up, a type of short circuit which disrupts the proper functioning of the memory, has also shown that electrons can cause destructive events. Further tests on 16 nm FinFET technology devices were performed by ESA and their contractors IROC in March 2018 and the data are now being analysed.

The CLEAR beam line seen by the final dump. (Credit: Davide Gamba - davide.gamba@cern.ch)

The scope of VESPER was extended to dosimetry for medical applications.

Recent advances in compact high-gradient accelerator technology, largely prompted by the CLIC study, renewed the interest in using very-high energy electrons (VHEE) in the 50 – 250 MeV energy range for radiotherapy of deep-seated tumours.

Understanding the dosimetry of such beams is essential in order to assess their viability for treatment. For this reason a group from the University of Manchester carried out studies in the VESPER installation on energy deposition using a set of EBT3 Gafchromic films submerged in water. The measured dose deposition profile was in agreement with Monte Carlo tracking simulations within 5%. At the same time, the possible aberration of crossing in-homogenous bodies was investigated by measuring the longitudinal dose profiles with and without inserts of various density material. The results confirmed the expectation from simulations that electron beam are relatively unaffected by both high-density and low-density media.

The obtained results indicated that VHEE has the potential to be a reliable mode of radiotherapy for treating tumors also in highly inhomogeneous and mobile regions such as lungs.

Further studies on the dose distribution of a converging beam as opposed to a parallel wide beam, and possibly on multi-angle irradiation are planned for the future.

View of the VESPER test stand set up for irradiation of electronics tests. (Credit: Davide Gamba - davide.gamba@cern.ch)

Water phantom being installed on the VESPER test stand by Agnese Lagzda – Manchester University. (Credit: Kyrre Ness Sjobaek - kyrre.ness.sjoebaek@cern.ch)

CLEAR opened the possibility of exploring also new accelerator technologies, one being active plasma lenses which are a promising technology for strongly focusing particle beams. Their compact size is a plus for potential use in novel accelerators. However, transverse field uniformity and beam excitation of plasma wake-fields may turn out to be significant limitations.

Lead by the University of Oslo, a collaboration between CERN, DESY and Oxford University was set up to develop a novel low-cost, scalable plasma lens. The developed setup consists of a 1 mm diameter, 15 mm long sapphire capillary installed in the middle of a 20x20x20 cm3 aluminum vacuum chamber. The capillary is filled with He or Ar at a controllable pressure. The gas is ionized by a 500 A peak current discharge with a duration of up to a few hundred ns, provided by a 20 kV spark-gap compact Marx bank generator. The longitudinal discharge current is responsible as well for the transverse focusing force in both transverse planes.

The experimental set-up was installed in the CLEAR beamline in September 2017 and after a fast commissioning it was possible to show a clear focusing effect. Extensive measurements were taken during December 2017 and March 2018. Transverse position scans of a pencil beam revealed gradients as high as 350 T/m, which would be compatible with its use for a staged plasma accelerator. More studies are now being conducted for measuring the uniformity of the field and beam emittance preservation also employing different gas species.

Moreover, evidence of non-linear self-focusing at relatively high bunch charge (∼50 pC/bunch) was observed when the beam goes throw the plasma after the discharge. This opens another branch of possible studies on passive plasma lenses that will be further developed.

Overview of the CLEAR plasma lens setup. The actual plasma lens, a 1 mm diameter, 15 mm long sapphire capillary, is installed inside the cubic vacuum chamber. (Credit: Kyrre Ness Sjobaek - kyrre.ness.sjoebaek@cern.ch)

Another technology being explored at CLEAR is the possibility of producing terahertz radiation (1 THz corresponds to 4 meV photon energy, or 300 µm radiation wavelength). This technology has a strong impact in many areas of research, spanning the quantum control of materials, plasmonics, and tunable optical devices based on Dirac-electron systems to technological applications such as medical imaging and security.

The aim at CLEAR is to characterize a LINAC-based THz source, exploiting relativistic electron bunches which emit coherent radiation in the THz domain. For such a source sub-picosecond electron bunches are needed. This triggered a study and optimisation of the CLEAR injector in collaboration with the “Laboratoire de l'Accélérateur Linéaire” (LAL), thanks to which sub-ps bunches down to 200 fs rms have been demonstrated in the machine, paving the way to the THz radiation generation.

The current studies at CLEAR are focused on the production of (sub-)THz radiation by Coherent Transition Radiation (CTR), i.e. making the electron beams passing through thin metal foils and collecting the emitted radiation. With this technique, a peak power of about 1 MW at 0.3 THz have been measured, in agreement with theoretical expectations.

Further experimental tests have been started for producing THz radiation by Coherent Smith-Purcell Radiation (CSPR) targets, where the electron beam passes nearby a periodic structure, emitting radiation at harmonics of its period.

At the same time, investigations are ongoing for producing THz radiation using the Coherent Cherenkov Radiation (CCR) mechanism.

Set up for studies on CTR, CSPR and CCR installed in CLEAR. (Credit: Alessandro Curcio - alessandro.curcio@cern.ch)

CLEAR allows to continue the R&D for CLIC technologies, for example by measuring the resolution of CLIC cavity Beam Position Monitor prototypes and by verifying the behavior of the Wake Field Monitor installed on the present design of the CLIC accelerating structures.

Additionally, CLEAR serves as unique opportunity for fast verification of beam instrumentation, e.g. it was possible to perform first calibration of the scintillator screen used in the electron spectrometer of the AWAKE experiment.

Finally, CLEAR offers also a unique playground for young accelerator physics. During march 2018 part of the students from the Joint Universities Accelerator School (JUAS) had the opportunity of spending one day at the facility performing hands on experiments.

Tags:

CLEAR