From ILC : Several articles From International Linear Collider Newsline

From International Linear Collider Newsline

Laboratories and industry in tune for particle physics detector R&D in Europe

19 April 2021
Perrine Royole-Degieux

10 million euros. This will be the amount granted to members of the AIDAinnova project (advancement and innovation for Detectors at Accelerators programme) funded by the European Commission Horizon 2020 programme, under a special ‘Innovation Pilots’ call. As particle physics requires highly-specialised detection equipment, often on an industrial scale, the project will be strongly marked by the collaboration between industry and academic institutions.

AIDAinnova [no link] builds on the success of its predecessor projects AIDA [no link] and AIDA 2020-Advanced European Infrastructures for Detectors at Accelerators (EU), both of which boosted infrastructure at research labs for the development of new detector technologies. Coordinated by CERN, the successor project receives 10 million Euros for four years and features nine industrial companies, three research and technology organisations and 34 academic institutions in 15 countries. ‘Having companies directly involved in detector development is a novelty that aims at faster turnaround and more innovation both for research and industry,’ said Felix Sefkow (DESY, Germany), AIDAInnova coordinator, and scientific coordinator for the previous project AIDA-2020.

AIDAinnova will provide state-of-the-art upgrades to research infrastructures, such as test beams, in order to exploit the scientific potential of detector technologies. Among well-defined R&D work packages, scientists have opened the door to ‘greenfield’ projects. A call for tenders will be launched which will allow funding innovative and ‘off-axis’ projects.

There will be two levels of participation for industry. Companies may simply participate as associates of AIDAInnova member laboratories. Other companies – nine in total – signed to join as full members of the collaboration. They will use the EC funds to design and test detector parts or to employ dedicated staff. A new kind of collaboration with industry, more constraining but also with more benefits.

‘The nine industrial companies involved in AIDAInnova will benefit in many ways, first and foremost in terms of visibility,’ said Giovanni Calderini, AIDAInnova coordinator at CNRS/IN2P3, France. Being a full member of the project demonstrates a strong link with the scientific community and is also a heavy responsibility. ‘Collaborating with major institutions or laboratories such as CERN, IN2P3 or DESY to name a few, is a guarantee of quality for their future clients,’ said Calderini. ‘They may become later privileged partners for other scientific experiments, opening up new sectors and new markets.’ And the benefit is mutual. ‘In a collaboration, there is a deeper level of exchange. Sometimes this leads scientists to play an actual role within the company. Getting to know an industrial company in great detail is extremely valuable for us, the exchanges are sincere and transparent,’ concludes Calderini.

AIDAInnova will cover a wide range of experiments from the second round of upgrades of the LHC detectors, at the mid of the high-luminosity phase (foreseen to be ready around 2030s) to CLIC, FCC and of course ILC detectors. Most work packages may contribute to any of these projects. For the ILC, one challenge will be to design mechanical structures and electronics as thin and light as possible so that incoming particles barely interact with them. Another crucial area of R&D will be the calorimetry, where scientists will try to increase detector granularity and time resolution for a more precise reconstruction of particle showers. Another promising technology for the ILC are monolithic sensors, where sensors and front end electronics are realised on a common silicon structure. ‘We’ve made a lot of progress in this area in the last years, and I’m convinced that these technologies will play a major role in the construction of the ILC detectors,’ says Calderini.

For all these technological challenges, collaboration with industry will be crucial, as the real difficulty will be to find a compromise between the most advanced technology to date and a reasonable cost for the scientific community. The AIDAInnova kick-off meeting, gathering all partners from academia to industry, will take place from 13 to 16 April 2021.

See the full article here .

Call for participation in Physics & Detector WG3

19 April 2021
Hitoshi Murayama

Two detector concepts- SiD(left) and ILD(right)
Image: Rey.Hori

The IDT Working Group on Physics & Detector activities (WG3) would like to invite the community to engage in the ILC studies.

WG3 aims to raise awareness and interest in the ILC development and expand the community, support newcomers to get involved in physics and detector studies, encourage new ideas for experimentations at the ILC.

The WG3 Steering Group consists of the coordinator (WG3 Chair), two deputy coordinators, subgroup conveners, and additional members of the Steering Group.

The four subgroups of WG3 are: (1) Machine-Detector Interface Subgroup, (2) Detector and Technology R&D Subgroup, (3) Software and Computing Subgroup, (4) Physics Potential and Opportunities Subgroup.

The studies provide crucial information about the physics and detectors to the final engineering design of the machine as well as infrastructure and lead up to Expressions of Interest for collider and non-collider experiments. The participation is completely open to anybody interested in the particle physics community.

You can find the mandate adopted for the WG3 at https://linearcollider.org/idt-wg3-mandate/. The members of the leadership are listed at https://linearcollider.org/team/. You are encouraged to contact convenors of the subgroup of your interest. We look forward to having you involved!

See the full article here .

LCWS2021- the community focuses on an ILC Pre-Lab as the next step

19 April 2021
Steinar Stapnes

The table showing the session time slots in 3 time zones; Pacific Daylight Time (PDT) – US West Coast
Central European Time (CET) – Geneva
Japan Standard Time (JST) – Tokyo

The 2021 International Workshop on Future Linear Colliders (LCWS2021), arranged by Europe as an online conference with more than 900 registered participants, took place from 15 to 18 March. As earlier conferences in this series it was primarily devoted to the physics, detector, and accelerator studies for the Compact LInear Collider (CLIC) and the International Linear Collider (ILC).

Since the last workshop in the series (LCWS2019), many new international developments have taken place. The European Strategy for Particle Physics (ESPP) Update 2020 places an electron-positron Higgs factory as the highest-priority next-generation collider. A linear collider – CLIC or ILC – will operate as a Higgs factory during its initial stage, while maintaining a clear path for future energy upgrades. The CLIC programme and associated high-gradient R&D for 2021-26 have been defined in accordance with the ESPP outcome.

Preparations for the ILC in Japan have changed gear with the International Committee for Future Accelerators (ICFA) announcing the establishment of the ILC International Development Team (IDT) hosted by KEK. ILC is currently the focus of a general and broad effort in Japan involving several Ministries as well as the Diet, in close connection with industry, academia and the Tohoku region, the potential construction site. This progress has been summarised in a recent document issued by the ILC Steering Panel established under Japan Association of High Energy Physicists (JAHEP). Besides the progress achieved in Japan, 2020 also saw the emergence and focused effort of the IDT towards defining the ILC Pre-Lab programme – a four-year preparatory phase to bring the ILC project to construction readiness, and the organisational structures and processes needed to start the Pre-Lab. In the US, the Snowmass process is on-going with ILC as the most prominent Higgs-factory possibility on the timescale considered.

The LCWS2021 started Monday morning with an online version of the 8th Linear Collider Physics school where some 160 students participated. From Monday afternoon to Thursday afternoon plenary and parallel sessions were used to review the progress on accelerator design for linear colliders, detector developments and physics studies and, equally important, looking ahead towards the next steps. ILC topics were overlapping with similar CLIC activities whenever possible.

The main plenaries were on Monday and Thursday. The Monday plenary session featured reports on technical/scientific aspects on ILC and CLIC, status reports from Japan (KEK, the JAHEP ILC Steering Panel and Tohoku) and North America, and recent progress from IDT. The Thursday plenary included CERN and European perspective talks, an update on the linear-collider-related Snowmass preparation and documentation, and summaries of some of the parallel working group sessions. The Tuesday and Wednesday plenary sessions focused on accelerator and physics & detector studies, respectively.

With a wide programme of 51 parallel sessions, the workshop provided ample opportunities to present ongoing work as well as getting informed and involved. The Physics and Detector parallel sessions alone attracted 144 submitted abstracts. Altogether 292 talks were given during the four days.

Besides these sessions, the programme also included a special ‘New Research and Opportunities Tracks’ to discuss ideas of complementary programmes beyond the ILC Higgs factory (e.g. fixed-target and beam-dump experiments – relevant for example for dark sector physics, lower energy beams for accelerator and detector R&D, irradiation possibilities, electron-laser collisions, etc.). In addition, a session on ‘New Technologies & Ideas for Collider Detectors’ was included. These sessions represent a first step towards ILC Expressions of Interest, and these topics will be further pursued in a dedicated ILC workshop, planned to be held in Tsukuba from 26 to 29 October.

A new feature was a session on advanced and novel accelerator (ANA) technologies prepared by the ICFA-ANA panel. Not only can these technologies be of interest to deploy in the longer term in an LC tunnel to reach multi-TeV energies, but an LC facility can also in the shorter term provide interesting and unique beams and opportunities for developing such novel technologies.

A very interesting session with around 70 participants was devoted to the industrial aspects of the ILC, offering an opportunity to highlight the expertise and innovation capabilities of national laboratories and their related industrial partners for the ILC Pre-Lab activities and the main ILC technologies.

Overall the workshop highlighted the large and increasing international community and efforts pursuing a future linear collider, and the community is now very focused on an ILC Pre-Lab as the immediate next step towards an operational Higgs factory by 2035.

Steinar Stapnes on behalf of – and with sincere thanks to – the Organising Committee
Europe | European Strategy for Particle Physics | Higgs factory | ILC

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New joint French-Japanese laboratory in Tokyo for physics at the largest and smallest scales

April 01, 2021
Véronique Etienne

The French National Centre for Scientific Research [Centre national de la recherche scientifique, CNRS] (FR) and the University of Tokyo[(東京大学; Tōkyō daigaku](JP) have set up a laboratory for physics research at the largest and smallest scales of the Universe.

ILANCE is the CNRS’s seventh International Research Laboratory in Japan.

From neutrinos to dark matter, and from particle accelerators to gravitational wave detectors and the first light of the Universe1: the ILANCE laboratory (International Laboratory for Astrophysics, Neutrino and Cosmology Experiments), bringing together the CNRS and the University of Tokyo, will conduct physics research at the very smallest and largest scales of our Universe. Set up on 1 April 2021, the CNRS’s seventh International Research Laboratory in Japan is also the third to be jointly run with the University of Tokyo2. It will be headed by Michel Gonin, Research Professor at the CNRS, who has long been involved in neutrino experiments in Japan3, and co-directed by Takaaki Kajita, Professor at the University of Tokyo and winner of the Nobel Prize in Physics in 2015.

Based on the Kashiwa campus located in the north-east of the Greater Tokyo Area, the laboratory will permanently host scientists from the University of Tokyo and the CNRS, focusing on five research topics in which both institutions are at the cutting edge: neutrinos (in connection with the Super-Kamiokande and Hyper-Kamiokande projects); the primordial Universe (in connection with the Japanese LiteBIRD satellite, which will follow on from Europe’s Planck spacecraft); gravitational waves (in connection with the Kagra gravitational wave detector4); the dark Universe (dark matter and energy); and particle physics (in connection with the ATLAS experiment at CERN and a particle accelerator project in Japan, the International Linear Collider).

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Stem Education Coalition

The International Linear Collider (ILC) is a proposed linear particle accelerator.It is planned to have a collision energy of 500 GeV initially, with the possibility for a later upgrade to 1000 GeV (1 TeV). The host country for the accelerator has not yet been chosen and proposed locations are Japan, Europe (CERN) and the USA (Fermilab). Japan is considered the most likely candidate, as the Japanese government is willing to contribute half of the costs, according to a representative for the European Commission on Future Accelerators.Construction could begin in 2015 or 2016 and will not be completed before 2026.

ILC schematic, being planned for the Kitakami highland, in the Iwate prefecture of northern Japan.

From LC Newsline: “Linear collider technology checks LHC lumi”

Linear Collider Collaboration

5 March 2015
Barbara Warmbein

The luminometer was installed in the CMS detector in January. Image: CERN

There’s a piece of linear collider detector technology that is getting ready to take real collision data. The linear collider may be at planning stage, but right in the middle of the CMS detector, a luminometer based on work done for the forward region of the ILC’s ILD detector is very much a working piece of kit. It will measure the luminosity in CMS, ie the rate of collisions that the LHC produces per second, and the beam-induced background.

CMS

The luminometer, part of the beam radiation instrumentation and luminosity (BRIL) project at CMS, consists of the so-called pixel luminosity telescope PLT and another part called BCM1F. It’s the BCM1F, a DESY-CERN coproduction, that has its roots in the forward calorimeter. The forward calorimeter is located in a tough area that needs radiation-hard equipment in order to survive. Already several years ago the FCAL collaboration tested several different technologies and settled on diamond sensors. It was actually during one of the test beam periods at CERN that the collaboration for the CMS luminometer was born when the LC FCAL started chatting to CERN experts on beam halo monitoring.

The BCM1F sets itself apart thanks to diamonds and speed. Image: Wolfgang Lohmann, DESY

Radiation-hardness isn’t the only thing that sets the BCM1F lumi tool apart: its sensors use diamond crystals that deliver ultra-short signals when a particle passes through. The application-specific integrated circuit (ASIC) to amplify the signal, developed and commissioned by a team from AGH-UST Cracow, CERN and DESY (Zeuthen), takes only a few nanoseconds to be back online, making it possible to count particles that pass through at very short intervals. Physics can deduce whether the particle comes from a collision or from beam background based on the time they passed through.

The luminometers were installed in CMS in January. The setup consists of two semi circles with an outside radius of 10 centimetres. They sit at 1,8 metres distance from the interaction point and, once the LHC starts up again, send their information about luminosity and particle count from the beam-induced background to the CMS and LHC control rooms every second.

Meanwhile, over at the linear collider’s FCAL, the FCAL collaboration will use the experience acquired in the operation of the CMS luminometers in the LHC’s run 2 for the construction of prototypes of forward calorimeters. ASICs experts will get to work on FCAL-specific integrated circuits with the help of funds from the AIDA2020 programme. So in true particle physics cross-fertilisation tradition the technology that started in the linear collider community will give its first performance in the LHC only to to be developed further with the experience gained from that first performance.

The BRIL collaboration. Image: CERN

See the full article here.

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The Linear Collider Collaboration is an organisation that brings the two most likely candidates, the Compact Linear Collider Study (CLIC) and the International Liner Collider (ILC), together under one roof. Headed by former LHC Project Manager Lyn Evans, it strives to coordinate the research and development work that is being done for accelerators and detectors around the world and to take the project linear collider to the next step: a decision that it will be built, and where.

Some 2000 scientists – particle physicists, accelerator physicists, engineers – are involved in the ILC or in CLIC, and often in both projects. They work on state-of-the-art detector technologies, new acceleration techniques, the civil engineering aspect of building a straight tunnel of at least 30 kilometres in length, a reliable cost estimate and many more aspects that projects of this scale require. The Linear Collider Collaboration ensures that synergies between the two friendly competitors are used to the maximum.

From LC Newsline: “What does the P5 report mean for the International Linear Collider?”

Linear Collider Collaboration

21 August 2014
Joykrit Mitra

Since the last Particle Physics Project Prioritization Panel (P5) report in 2008, an even stronger case has emerged for building the long heralded International Linear Collider. The latest P5 report, released this year, recommends that the US Department of Energy and the National Science Foundation make provisions, among other things, for significant US participation in the ILC construction, should the project move forward.

ILC

P5 is an advisory panel that is periodically initiated by the Department of Energy’s Office of High Energy Physics and the National Science Foundation. Although P5 has no final say in the allocation of funding, it represents the American particle physics community’s viewpoint, and produces a report that is the culmination of a community driven process. It comprised well-known experts in the field, who sifted through the science and charted the field’s priorities over the next 10 years, keeping in mind the overall progress the field hopes to make in the next two decades. It also streamlined the particle physics community’s expectations according to fiscal realities of varying abundance.

The panel was also advised by scientists involved in the ILC project, regarding the scale in terms of costs, manpower, technology and how it would all fit into a global high-energy physics research programme. After deliberation, it recommended support for the ILC on some level under all budgetary scenarios, as the physics case was extremely strong.

“Such a recommendation is a very important step because the ILC is a high-risk high-return project,” said Dmitri Denisov, Americas region representative on the Linear Collider Physics and Detector’s executive board. “It confirms there is really important physics to be done.”

The report, published in May, comes as a coherent plan for American high-energy physics. Funding for high-energy physics had been shrinking for some time. Even though expectations were mixed, the 2014 P5 report has injected substantial optimism, both for national projects and international collaborations.

“I think the LHC has the highest priority in the report,” said Harry Weerts, High Energy Physics Division director of Argonne National Laboratory and Americas regional director for the Linear Collider Collaboration. “But compared to 2008, the ILC is more recognised as a higher priority because we now know what the mass of the Higgs particle is.”

In a field that is already quite global, the technical and fiscal scale of the ILC requires unprecedented global cooperation. It is projected to cost around 7.8 billion ILCU (2012 US Dollar) and is designed to be a staggering 31 kilometers long. The ILC’s latest Technical Design Report, which has been nearly 10 years in the making, was created by the world community of high-energy physicists. In Europe, many scientists are already working full time on research and development for the ILC. In the United States, there was a strong push for many years starting in the early 2000s, to host the ILC. But the Omnibus Spending Bill laid that to rest in 2008.

Currently, there are significant resources the United States can provide for the ILC. For instance, while Japan, as the most likely host country is expected to arrange for a significant portion of the infrastructure and funds, the accelerators—accounting for a large portion of the building cost— will require around two thousand accelerating cryo-modules. This is beyond the scope of a single nation to produce, and the United States already has the experience and infrastructure in place for producing at least a significant fraction of them.

A clear case for the ILC emerged after CERN’s historic announcement on 4 July, 2012 of the Higgs discovery, and has grown even stronger since Japan took ensuing political steps to make the ILC happen. The lowest budgetary scenario recommends engaging personnel in R&D on the ILC accelerator and detectors for the next 3 years. The particle physics community recognises the imperative for US participation in this global project to maintain its leadership position in high-energy physics.

Meanwhile, in July, members of the Japanese Diet visited Washington to meet with members of Congress, and to be briefed by scientists. Once Japan green lights the ILC project, a formal collaboration will proceed. Enabling the U.S. to play a world leading role is a high-priority option.

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From Fermilab: “International Linear Collider makes progress in siting, R&D”

Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

Friday, May 16, 2014
No Writer Credit

This week, members of the Linear Collider Collaboration met at Fermilab to discuss the progress and future of the proposed International Linear Collider, as well as of CERN’s Compact Linear Collider, during the Americas Workshop on Linear Colliders.

ILC schematic proposal

CERN’s CLIC

At the workshop, scientists and engineers involved in the ILC discussed both their recent successes and the work still to be done to make the 18-mile-long electron-positron collider a reality.

One recent breakthrough took place at KEK. At the Japanese laboratory’s Accelerator Test Facility, scientists achieved an electron beam height of 55 nanometers at the final focus, or the point where the collision would occur. This is the smallest electron beam ever produced. It was a demonstration that the techniques scientists used to shrink the beam would be transferable to the ILC, whose aim is an electron beam height of 5 nanometers.

“The ATF at KEK is an essential element in the R&D activity toward a linear collider,” said Linear Collider Collaboration Director Lyn Evans. “The latest results give great confidence that the design parameters of a linear collider can be reached.”

That electron beam would travel through accelerator cavities — long, hollow niobium structures that look like strings of pearls. Scientists at Fermilab have made significant advancements on this front, achieving world-record quality factors. The so-called quality factor is a measure of how effectively the cavities store energy. The more efficient they are, the lower the cost of refrigeration, which is needed to keep the superconducting cavities cold.

“This workshop at Fermilab gives us the perfect opportunity to interact with the SRF community here at the lab,” said ILC Director Mike Harrison. “We take advantage of the workshop to catch up on the latest results at the lab.”

For the first time, ILC researchers actively discussed the International Linear Collider in the context of a precise, geographical home — the Kitakami mountains in the Japan’s Iwate prefecture. Site pictures and films at the workshop included actual accelerator and detector locations among hills and trees.

“This really gives a sense of reality to the project,” said Fermilab Director Nigel Lockyer. “Now the site-specific design work needed to put the ILC in that location can begin in earnest. This has been a long time coming, and we are very pleased with this step forward.”

See the full article here.

Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

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From LC Newsline: “The ILC design evolves”

17 April 2014
Mike Harrison

The ILC baseline design as described in the Technical Design Report and its associated cost estimate was finalised in 2012. Since that time the design has been relatively static while the global high-energy physics community absorbed and responded to this information. During the past 12 months, significant progress in Japan has resulted in the choice of a preferred site together with a proposal to consider implementing the ILC project in a series of discrete energy stages rather than an initial 500- gigaelectronvolt (GeV) centre-of-mass energy. Thus the time is fitting to evolve the TDR baseline in response to these new eventualities. An initial step in this direction was taken recently in a three-day meeting at the University of Tokyo, which involved a joint team from the conventional facilities and accelerator design and integration groups.

Projected design of the Linear Collider

The goals of the meeting were described thus: “This meeting will examine the scope of the pre-project CFS work, the schedule, and necessary resources. The detector hall concept at the proposed site, and the impact of energy phasing will also be addressed. The pre-project CFS timeline will likely drive many aspects of the accelerator design work in the next few years thus it is important to understand these constraints. In order to derive a site dependent ILC design and address long lead-time CFS activities then we need to assess what design information needs to be available to the CFS group and when. The ILC technical design in the TDR relied on a generic site description which is inadequate to proceed much further in the site specific design.”

During the LCWS13 meeting last November, it became apparent that in order to be consistent with a construction project which can start in 2018, a multi-year pre-construction programme centred around the conventional facilities work in Japan needed to start soon. In turn, this programme would need timely input from the site-specific accelerator design. Although three days is insufficient time to finalise anything, a consensus was achieved on many items which provides the necessary framework for how to proceed during the next few years. Next month’s Americas Workshop on Linear Collider to be held at Fermilab will build on this work.

Conventional facilities preparation for a construction project covers not only the detailed design of the tunnel, associated enclosures and the interaction region/damping ring complex but also such green-field related topics as land acquisition, environmental impact, geological and topographical studies. The schedule for this work depends to a certain degree on the available resources but it will require a minimum of several years. The meeting discussed the work scope and how best to proceed but there was little dissent from the conclusion that we need to start soon to remain consistent with a construction start in 2018 or thereabouts. This topic will provide the basis of a funding request for the long lead-time elements.

Intermediate energy operation at values less than 500 GeV is based on a partial installation of the main linac and has ramifications on many aspects of the project execution including such programme aspects as the cryomodule production rate, funding profiles and minor design changes to best accommodate lower energies. The exact details depend on the desired energy points and the associated integrated luminosity at these values. These specifications are currently under study by the parameters working group, but one critical conclusion from the meeting was the recognition that all the major convention construction needs to be completed as part of the first phase of any project. This result will now be used as input for subsequent planning.

A partial linac can be implemented in several ways. The basic variants consist of “missing” cryomodules at the upstream end, the downstream end or interspersed along the length. All of these approaches require the full injector complex, the complete beam delivery system and transport sections in the main tunnel. Emittance growth minimisation requires an initial accelerating section of at least 50 Ge,V which argues against a missing linac on the upstream end. Most discussions involved a solution which has the location of the accelerating sections determined by the baseline cryogenic infrastructure which satisfies the beam dynamics requirements and allows for some operational flexibility. This approach will be used for the future energy scaling discussions.

The preferred site has re-opened debate on the possibility of a vertical access shaft (or shafts) for the detector hall as opposed to, or in addition to, the baseline design which involved a horizontal access tunnel. This is complicated issue involving the detector construction technique, personnel safety, and exact location of interaction point as well as old favourites such as cost and schedule. More work is necessary before an optimal decision can be made but in order to start to restrict the potential phase space of solutions we decided to use the TDR baseline (horizontal) and the so-called Hybrid A (CMS
-like) as the models for further study. The goal in this area is to converge on a solution by the end of this calendar year.

Several other topics such as the role of the central campus, safety issues arising from the tunnel design, and short-term activities were also part of the meeting. The looming LC NewsLine deadline suggests that these items be left for a later date – the talks are posted on the aforementioned web site for those of you who can’t bear to wait. The upcoming Fermilab workshop will provide the next forum for further face-to-face dialogue.

On behalf of the meeting participants I would like to thank the University of Tokyo and the support staff for arranging the meeting, the facilities, the excellent weather, the cherry blossom in bloom, and a damn good meal which appeared to materialise in a mysterious and spontaneous fashion courtesy of the physics department.

See the full article here.

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From CERN Courier: “The case for a circular e+e– Higgs factory”

Jul 12, 2013
John Ellis, King’s College London and CERN.

“Options for a future facility to study Higgs bosons in detail include a larger, more powerful reincarnation of LEP.

lep

The discovery of a Higgs boson by the ATLAS and CMS collaborations at the LHC has opened new perspectives on accelerator-based particle physics. While much else might well be discovered at the LHC as its energy and luminosity are increased, one item on the agenda of future accelerators is surely a Higgs factory capable of studying this new particle in as much detail as possible. Various options for such a facility are under active consideration and circular electron–positron (e+e–) colliders are now among them.

In a real sense, a Higgs factory already exists in the form of the LHC, which has already produced millions of Higgs bosons and could produce hundreds of millions more with the high-luminosity upgrade planned for the 2020s. However, the experimental conditions at the LHC restrict the range of Higgs decay modes that can be observed directly and measured accurately. For example, decays of the Higgs boson into charm quarks are unlikely to be measurable at the LHC. On the one hand, decays into gluons can be measured only indirectly via the rate of Higgs production by gluon–gluon collisions and it will be difficult to quantify accurately invisible Higgs decays at the LHC. On the other hand, the large statistics at the LHC will enable accurate measurements of distinctive subdominant Higgs decays such as those into photon pairs or ZZ*. The rare decay of the Higgs into muon pairs will also be accessible. The task for a Higgs factory will be to make measurements that complement or are even more precise than those possible with the LHC.

Attractive options

Cleaner experimental conditions are offered by e+e– collisions. Prominent among other contenders for a future Higgs factory are the design studies for a linear e+e– collider: the International Linear Collider (ILC) and the Compact Linear Collider (CLIC). In addition to running at the centre-of-mass energy of 240 GeV that is desirable for Higgs production, these also offer prospects for higher-energy collisions, e.g. at the top–antitop threshold of 350 GeV and at 500 GeV or 1000 GeV in the case of the ILC, or even higher energies at CLIC. These would become particularly attractive options if future, higher-energy LHC running reveals additional new physics within their energy reach. High-energy e+e– collisions would also offer prospects for determining the triple-Higgs coupling, something that could be measured at the LHC only if it is operated at the highest possible luminosity.

ilc

There has recently been a resurgence of interest in the capabilities of circular e+e– colliders being used as Higgs factories following a suggestion by Alain Blondel and Frank Zimmermann in December 2011 (Blondel and Zimmermann 2011). It used to be thought that the Large Electron–Positron (LEP) collider would be the largest and highest-energy circular e+e– collider and that linear colliders would be more cost-efficient at higher energies. However, advances in accelerator technology since LEP was designed have challenged this view. In particular, the development of top-up injection at B factories and synchrotron radiation sources, as well as advances in superconducting RF and in beam-focusing techniques at interaction points, raise the possibility of achieving collision rates at each interaction point at a circular Higgs factory that could be more than two orders of magnitude larger than those achieved at LEP. Moreover, it would be possible to operate such a collider with as many as four interaction points simultaneously, as at LEP.

One attractive option would be to envisage a future circular e+e– collider as part of a future, very large collider complex. For example, a tunnel with a circumference of 80–100 km could also accommodate a proton–proton collider capable of collisions at 80–100 TeV in the centre of mass, which would also open up the option of very-high-energy electron–proton collisions. This could be an appealing vision for accelerator particle physics at the energy frontier for much of the 21st century. Such a complex would fit naturally into the updated European Strategy for Particle Physics, which has recently been approved.”

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From CERN: “International Linear Collider ready for construction”

12 Jun 2013
Cian O’Luanaigh

“Today the Linear Collider Collaboration published its Technical Design Report [PDF] for the International Linear Collider (ILC) – a proposed 31-kilometre electron-positron collider that will both complement and advance beyond the physics of the Large Hadron Collider.

ilc
A schematic of the layout of the International Linear Collider – note the soccer pitch for scale (Image: Pablo Vazquez )

In three consecutive ceremonies in Asia, Europe and the Americas, the authors officially handed the report over to the international oversight board for projects in particle physics, the International Committee for Future Accelerators (ICFA). The report presents the latest, most technologically advanced and most thoroughly scrutinized design for the ILC.

The ILC will accelerate and collide electrons and their antiparticles, positrons. Collisions will occur roughly 7000 times per second at the collision energy of 500 GeV. Some 16,000 superconducting cavities will be needed to drive the ILC’s particle beams. The report also includes details of two state-of-the-art detectors that will record the collisions, as well as an extensive outline of the geological and civil engineering studies conducted for siting the ILC.

‘The Technical Design Report is an impressive piece of work that shows maturity, scrutiny and boldness,’ says Lyn Evans, director of the Linear Collider Collaboration. ‘The International Linear Collider should be next on the agenda for global particle physics.'”

See the full article here.

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From Symmetry: “Linear collider focus gets down to size”

In a display of timing worthy of a blockbuster movie, a multinational team of accelerator physicists focused a beam of electrons down to the tiny size needed for a future linear collider the same week that the linear collider board formed.

March 11, 2013
Lori Ann White

“In late 2012, Toshiaki Tauchi clicked the send button on an email with the subject line ’70nm achieved at ATF2!’ It signaled a major success for Tauchi, an accelerator physicist at KEK, and his colleagues at the Japanese lab’s Accelerator Test Facility 2: They had shown they could focus a beam of electrons down to the tiny size required by a future linear collider.

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Photo: Nobu Toge, KEK

Tauchi is a member of the executive committee overseeing the global design effort for the International Linear Collider, and the timing of his announcement could not have been better.

Just the day before, Fermilab Director Pier Oddone, in his role as chair of the International Committee for Future Accelerators, announced the formation of a Linear Collider Board to shepherd the global effort to build a linear collider capable of pushing back the frontiers of high-energy physics revealed by the Large Hadron Collider at CERN. With Japan expressing interest in hosting such a facility and the even more recent formation of a Linear Collider Collaboration to coordinate and advance global plans, momentum seems to be building for the construction of the giant electron-positron collider.”

See the full article here.

Symmetry is a joint Fermilab/SLAC publication.

From ilc newsline: “Superconducting radio-frequency”

9 August 2012
Daisy Yuhas

“How do you accelerate particles in a particle collider? One answer is superconducting radio-frequency (SCRF) cavities. To give particles energy as they move through an accelerator, physicists use cavities containing electric fields that oscillate. The changes in electric field help push the particles from one cavity to the next. These oscillations occur with the same frequency as radio waves, which is why this form of acceleration is called radio-frequency.

Image: Rey.Hori

Superconducting refers to the way in which electric current is carried through these accelerating cavities. Electric current in a cavity may create friction—unless the cavity is created using special metals called superconductors. ‘Some metals have no resistance below a critical temperature,’ says Fermilab scientist Camille Ginsburg. This means that these metals conduct electricity perfectly. Even in a superconductor, if electric current passing through a cavity encounters any bumps or impurities, the flow of electricity is interrupted and energy can be lost as heat. This is why cavities must be very clean and polished to a smooth finish. In proposed accelerators such as the ILC, the metal used is niobium, which becomes superconducting at temperatures below 9.2 Kelvin (-264°C). Keeping cool isn’t easy, however. To do this, each cavity is kept in a large thermos structure holding frigid liquid helium, typically at 2 Kelvin (-271°C).”

See the full post here.

ilc

From ILC Newsline: “Doing the cryomodule shuffle”

ilc – International Linear Collider

Leah Hesla
19 April 2012

“Fermilab researchers will soon take a quantum step towards the realisation of an ILC-type cryomodule.

Next week the newly assembled cryomodule RFCA002, familiarly referred to as CM2, will replace CM1 in the Advanced Superconducting Test Accelerator at the laboratory’s NML test facility. The change-out is a rung up on the R&D ladder, and not only because it is the second eight-cavity cryomodule to come out of the laboratory. Far more than the first, CM2 resembles an ILC-type cryomodule in its components and cavity test performance.

‘The hope for CM2 is that it will be the first cryomodule to reach the average ILC specification gradient at Fermilab,” said lead engineer Tug Arkan. The so-called S1 goal of the ILC programme is to achieve an average gradient of 31.5 megavolts per metre over eight metre-long cavities. “That’s the goal to demonstrate. We haven’t yet proved it at Fermilab.’”

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Cryomodule 2 in the Fermilab Industrial Center Building. Image: Reidar Hahn

See the full article here.