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  • richardmitnick 9:24 am on October 17, 2016 Permalink | Reply
    Tags: , CERN CLIC, , Electron–positron collider, , ,   

    From CERN Courier: “CLIC steps up to the TeV challenge” 

    CERN Courier

    Oct 14, 2016
    Philipp Roloff
    Daniel Schulte
    CERN

    1
    The CTF3 test facility at CERN

    CLIC

    2
    Compact Linear Collider layout for nominal 3 TeV version
    Date 3 February 2012
    Author Gerbershagen

    One of CERN’s main options for a flagship accelerator in the post-LHC era is an electron–positron collider at the high-energy frontier. The Compact Linear Collider (CLIC) is a multi-TeV high-luminosity linear collider that has been under development since 1985 and currently involves 75 institutes around the world. Being linear, such a machine does not suffer energy losses from synchrotron radiation, which increases strongly with the beam energy in circular machines. Another option for CERN is a very high-energy circular proton–proton collider, which is currently being considered as the core of the Future Circular Collider (FCC) programme. So far, CLIC R&D has principally focused on collider technology that’s able to reach collision energies in the multi-TeV range. Based on this technology, a conceptual design report (CDR) including a feasibility study for a 3 TeV collider was completed in 2012.

    With the discovery of the Higgs boson in July of that year, and the fact that the particle turned out to be relatively light with a mass of 125 GeV, it became evident that there is a compelling physics case for operating CLIC at a lower centre-of-mass energy. The optimal collision energy is 380 GeV because it simultaneously allows physicists to study two Higgs-production processes in addition to top-quark pair production. Therefore, to fully exploit CLIC’s scientific potential, the collider is foreseen to be constructed in several stages corresponding to different centre-of-mass energies: the first at 380 GeV would be followed by stages at 1.5 and 3 TeV, allowing powerful searches for phenomena beyond the Standard Model (SM).

    While a fully optimised collider at 3 TeV was described in the CDR in 2012, the lower-energy stages were not presented at the same level of detail. In August this year, however, the CLIC and CLICdp (CLIC detector and physics study) collaborations published an updated baseline-staging scenario that places emphasis on an optimised first-energy stage compatible with an extension to high energies. The performance, cost and power consumption of the CLIC accelerator as a function of the centre-of-mass energy were addressed, building on experience from technology R&D and system tests. The resulting first-energy stage is based on already demonstrated performances of CLIC’s novel acceleration technology and will be significantly cheaper than the initial CDR design.

    CLIC physics

    An electron–positron collider provides unique opportunities to make precision measurements of the two heaviest particles in the SM: the Higgs boson (125 GeV) and the top quark (173 GeV). Deviations in the way the Higgs couples to the fermions, the electroweak bosons and itself are predicted in many extensions of the SM, such as supersymmetry or composite Higgs models. Different scenarios lead to specific patterns of deviations, which means that precision measurements of the Higgs couplings can potentially discriminate between different new-physics scenarios. The same is true of the couplings of the top quark to the Z boson and photon. CLIC would offer such measurements as the first step of its physics programme, and full simulations of realistic CLIC detector concepts have been used to evaluate the expected precision and to guide the choice of collision energy.

    The principal Higgs production channel, Higgstrahlung (e+e– → ZH), requires the centre-of-mass energy to be equal to the sum of the Higgs- and Z-boson masses plus a few tens of GeV. For an electron–positron collider such as CLIC, Higgsstrahlung has a maximum cross-section at a centre-of-mass energy of around 240 GeV and decreases as a function of energy. Because the colliding electrons and positrons are elementary particles with a precisely known energy, Higgsstrahlung events can be identified by detecting the Z boson alone as it recoils against the Higgs boson. This can be done without looking at the decay of the Higgs boson, and hence the measurement is completely independent of possible unknown Higgs decays. This is a unique capability of a lepton collider and the reason why the first energy stage of CLIC is so important. The most powerful method with which to measure the Higgsstrahlung cross-section in this way is based on events where a Z boson decays into hadrons, and the best precision is expected at centre-of-mass energies around 350 GeV. (At lower energies it is more difficult to separate signal and background events, while at higher energies the measurement is limited by the smaller signal cross-section and worse recoil mass resolution.)

    The other main Higgs-production channel is WW fusion (e+e− → Hveve). In contrast to Higgsstrahlung, the cross-section for this process rises quickly with centre-of-mass energy. By measuring the rates for the same Higgs decay, such as H → bb, in both Higgsstrahlung and WW-fusion events, researchers can significantly improve their knowledge of the Higgs decay width – which is a challenging measurement at hadron colliders such as the LHC. A centre-of-mass energy of 380 GeV at the first CLIC energy stage is ideal for achieving a sizable contribution of WW-fusion events.

    So far, the energy of electron–positron colliders has not been high enough to allow direct measurements of the top quark. At the first CLIC energy stage, however, properties of the top quark can be obtained via pair-production events (e+e− → tt). A small fraction of the collider’s running time would be used to scan the top pair-production cross-section in the threshold region around 350 GeV. This would allow us to extract the top-quark mass in a theoretically well-defined scheme, which is not possible at hadron colliders. The value of the top-quark mass has an important impact on the stability of the electroweak vacuum at very high energies.

    3
    Centre-of-mass energy dependencies

    With current knowledge, the achievable precision on the top-quark mass is expected to be in the order of 50 MeV, including systematic and theoretical uncertainties. This is about an order of magnitude better than the precision expected at the High-Luminosity LHC (HL-LHC).

    The couplings of the top quark to the Z boson and photon can be probed using the top-production cross-sections and “forward-backward” asymmetries for different electron-beam polarisation configurations available at CLIC. These observables lead to expected precisions on the couplings which are substantially better than those achievable at the HL-LHC. Deviations of these couplings from their SM expectations are predicted in many new physics scenarios, such as composite-Higgs scenarios or extra-dimension models. It was recently shown, using detailed detector simulations, that although higher energies are preferred, this measurement is already feasible at an energy of 380 GeV, provided the theoretical uncertainties improve in the coming years. The expected precisions depend on our ability to reconstruct tt- events correctly, which is more challenging at 380 GeV compared to higher energies because both top quarks decay almost isotropically.

    Combining all available knowledge therefore led to the choice of 380 GeV for the first-energy stage of the CLIC programme in the new staging baseline. Not only is this close to the optimal value for Higgs physics around 350 GeV but it would also enable substantial measurements of the top quark. An integrated luminosity of 500 fb–1 is required for the Higgs and top-physics programmes, which could take roughly five years. The top cross-section threshold scan, meanwhile, would be feasible with 100 fb–1 collected at several energy points near the production threshold.

    Stepping up

    After the initial phase of CLIC operation at 380 GeV, the aim is to operate CLIC above 1 TeV at the earliest possible time. In the current baseline, two stages at 1.5 TeV and 3 TeV are planned, although the exact energies of these stages can be revised as new input from the LHC and HL-LHC becomes available. Searches for beyond-the-SM phenomena are the main goal of high-energy CLIC operation. Furthermore, additional unique measurements of Higgs and top properties are possible, including studies of double Higgs production to extract the Higgs self-coupling. This is crucial to probe the Higgs potential experimentally and its measurement is extremely challenging in hadron collisions, even at the HL-LHC. In addition, the full data sample with three million Higgs events would lead to very tight constraints on the Higgs couplings to vector bosons and fermions. In contrast to hadron colliders, all events can be used for physics and there are no QCD backgrounds.

    4
    CLIC footprints in the vicinity of CERN

    Two fundamentally different approaches are possible to search for phenomena beyond the SM. The first is to search directly for the production of new particles, which in electron–positron collisions can take place almost up to the kinematic limit. Due to the clean experimental conditions and low backgrounds compared to hadron colliders, CLIC is particularly well suited for measuring new and existing weakly interacting states. Because the beam energies are tunable, it is also possible to study the production thresholds of new particles in detail. Searches for dark-matter candidates, meanwhile, can be performed using single-photon events with missing energy. Because lepton colliders probe the coupling of dark-matter particles to leptons, searches at CLIC are complementary to those at hadron colliders, which are sensitive to the couplings to quarks and gluons.

    The second analysis approach at CLIC, which is sensitive to even higher mass scales, is to search for unexpected signals in precision measurements of SM observables. For example, measurements of two-fermion processes provide discovery potential for Z´ bosons with masses up to tens of TeV. Another important example is the search for additional resonances or anomalous couplings in vector-boson scattering. For both indirect and direct searches, the discovery reach improves significantly with increasing centre-of-mass energy. If new phenomena are found, beam polarisation might help to constrain the underlying theory through observables such as polarisation asymmetries.

    The CLIC concept

    CLIC will collide beams of electrons and positrons at a single interaction point, with the main beams generated in a central facility that would fit on the CERN site. To increase the brilliance of the beams, the particles are “cooled” (slowed down and reaccelerated continuously) in damping rings before they are sent to the two high-gradient main linacs, which face each other. Here, the beams are accelerated to the full collision energy in a single pass and a magnetic telescope consisting of quadrupoles and different multipoles is used to focus the beams to nanometre sizes in the collision point inside of the detector. Two additional complexes produce high-current (100 A) electron beams to drive the main linacs – this novel two-beam acceleration technique is unique to CLIC.

    5
    Reconstructed particles

    The CLIC accelerator R&D is focused on several core challenges. First, strong accelerating fields are required in the main linac to limit its length and cost. Outstanding beam quality is also essential to achieve a high rate of physics events in the detectors. In addition, the power consumption of the CLIC accelerator complex has to be limited to about 500 MW for the highest-energy stage; hence a high efficiency to generate RF power and transfer it into the beams is mandatory. CLIC will use high-frequency (X-band) normal-conducting accelerating structures (copper) to achieve accelerating gradients at the level of 100 MV/m. A centre-of-mass energy of 3 TeV can be reached with a collider of about 50 km length, while 380 GeV for CLIC’s first stage would require a site length of 11 km, which is slightly larger than the diameter of the LHC. The accelerator is operated using 50 RF pulses of 244 ns length per second. During each pulse, a train of 312 bunches is accelerated, which are separated by just 0.5 ns. To generate the accelerating field, each CLIC main-linac accelerating structure needs to be fed with an RF power of 60 MW. With a total of 140,000 structures in the 3 TeV collider, this adds up to more than 8 TW.

    Because it is not possible to generate this peak power at reasonable cost with conventional klystrons (even for the short pulse length of 244 ns), a novel power-production scheme has been developed for CLIC. The idea is to operate a drive beam with a current of 100 A that runs parallel to the main beam via power extraction and transfer structures. In these structures, the beam induces electric fields, thereby losing energy and generating RF power, that is transferred to the main-linac accelerating structures. The drive beam is produced as a long (146 μs) high-current (4 A) train of bunches and is accelerated to an energy of about 2.4 GeV and then sent into a delay loop and combiner-ring complex where sets of 24 consecutive sub-pulses are used to form 25 trains of 244 ns length with a current of about 100 A. Each of these bunch-trains is then used to power one of the 25 drive-beam sectors, which means that the initial 146 μs-long pulse is effectively compressed in time by a factor of 600, and therefore its power is increased by the same factor.

    6
    CLIC-design energy stages

    To demonstrate this novel scheme, a test facility (CTF3) was constructed at CERN since 2001 that reused the LEP pre-injector building and components as well as adding many more. The facility now consists of a drive-beam accelerator, the delay loop and one combiner ring. CTF3 can produce a drive-beam pulse of about 30 A and accelerate the main beam with a gradient of up to 145 MV/m. A large range of components, feedback systems and operational procedures needed to be developed to make the facility a success, and by the end of 2016 it will have finished its mission. Further beam tests at SLAC, KEK and various light sources remain important. The CALIFES electron beam facility at CERN, which is currently being evaluated for operation from 2017, can provide a testing ground for high-gradient structures and main-beam studies. More prototypes for CLIC’s main-beam and drive-beam components are being developed and characterised in dedicated test facilities at CERN and collaborating institutes. The resulting progress in X-band acceleration technology also generated important interest in the Free Electron Laser (FEL) community, where it may allow for more compact facilities.

    To achieve the required luminosities (6 × 1034 cm–2 s–1 at 3 TeV), nanometre beam sizes are required at CLIC’s interaction point. This is several hundred times smaller than at the SLC, which operated at SLAC in the 1990s and was the first and only operational linear collider, and therefore requires novel hardware and sophisticated beam-based alignment algorithms. A precision pre-alignment system has been developed and tested that can achieve an alignment accuracy in the range of 10 μm, while beam-based tuning algorithms have been successfully tested at SLAC and other facilities. These algorithms use beams of different energies to diagnose and correct the offset of the beam-position monitors, reducing the effective misalignments to a fraction of a micron. Because the motion of the ground due to natural and technical sources can cause the beam-guiding quadrupole magnets to move, knocking the beams out of focus, the magnets will be stabilised with an active feedback system that has been developed by a collaboration of several institutes, and which has already been demonstrated experimentally.

    7
    Integrated luminosity

    CLIC’s physics potential has been illustrated through the simulation and reconstruction of benchmark physics processes in two dedicated detector concepts. These are based on the SiD and ILD detector concepts developed for the International Linear Collider (ILC), an alternative machine currently under consideration for construction in Japan, and have been adapted to the experimental environment at the higher-energy CLIC. Because the high centre-of-mass energies and CLIC’s accelerator technology lead to relatively high beam-induced background levels for a lepton collider, the CLIC detector design and the event-reconstruction techniques are both optimised to suppress the influence of these backgrounds. A main driver for the ILC and CLIC detector concepts is the required jet-energy resolution. To achieve the required precision, the CLIC detector concepts are based on fine-grained electromagnetic and hadronic calorimeters optimised for particle-flow analysis techniques. A new study is almost complete, which defines a single optimised CLIC detector for use in future CLIC physics benchmark studies. The work by CLICdp was crucial for the new staging baseline (especially for the choice of 380 GeV) because the physics potential as a function of energy can only be estimated with the required accuracy using detailed simulations of realistic detector concepts.

    The new staged design

    To optimise the CLIC accelerator, a systematic design approach has been developed and used to explore a large range of configurations for the RF structures of the main linac. For each structure design, the luminosity performance, power consumption and total cost of the CLIC complex are calculated. For the first stage, different accelerating structures operated at a somewhat lower accelerating gradient of 72 MV/m will be used to reach the luminosity goal at a cost and power consumption similar to earlier projects at CERN – while also not inflating the cost of the higher-energy stages. The design should also be flexible enough to take advantage of projected improvements in RF technology during the construction and operation of the first stage.

    When upgrading to higher energies, the structures optimised for 380 GeV will be moved to the beginning of the new linear accelerator and the remaining space filled with structures optimised for 3 TeV operation. The RF pulse length of 244 ns is kept the same at all stages to avoid major modifications to the drive-beam generation scheme. Data taking at the three energy stages is expected to last for a period of seven, five and six years, respectively. The stages are interrupted by two upgrade periods each lasting two years, which means that the overall three-stage CLIC programme will last for 22 years from the start of operation. The duration of each stage is derived from integrated luminosity targets of 500 fb–1 at 380 GeV, 1.5 ab–1 at 1.5 TeV and 3 ab–1 at 3 TeV.

    An intense R&D programme is yielding other important improvements. For instance, the CLIC study recently proposed a novel design for klystrons that can increase the efficiency significantly. To reduce the power consumption further, permanent magnets are also being developed that are tunable enough to be able to replace the normal conducting magnets. The goal is to develop a detailed design of both the accelerator and detector in time for the update of the European Strategy for Particle Physics towards the end of the decade.

    Mature option

    With the discovery of the Higgs boson, a great physics case exists for CLIC at a centre-of-mass energy of 380 GeV. Hence particular emphasis is being placed on the first stage of the accelerator, for which the focus is on reducing costs and power consumption. The new accelerating structure design will be improved and more statistics on the structure performance will be obtained. The detector design will continue to be optimised, driven by the requirements of the physics programme. Technology demonstrators for the most challenging detector elements, including the vertex detector and main tracker, are being developed in parallel.

    Common studies with the ILC, which is currently being considered for implementation in Japan, are also important, both for accelerator and detector elements, in particular for the initial stage of CLIC. Both the accelerator and detector parameters and designs, in particular for the second- and third-energy stages, will evolve according to new LHC results and studies as they emerge.

    CLIC is the only mature option for a future multi-TeV high-luminosity linear electron–positron collider. The two-beam technology has been demonstrated in large-scale tests and no show stoppers were identified. CLIC is therefore an attractive option for CERN after the LHC. Once the European particle-physics community decides to move forward, a technical design will be developed and construction could begin in 2025.

    See the full article here .

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  • richardmitnick 12:44 pm on February 1, 2015 Permalink | Reply
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    From CERN: “The Compact Linear Collider” 

    CERN New Masthead

    30 Jan 2015
    Cian O’Luanaigh

    Cern Compact Linear Collider
    CERN

    Physicists and engineers at CERN are pursuing advanced accelerator research and development for a machine to exploit the Large Hadron Collider’s discoveries at the high-energy frontier. The Compact Linear Collider (CLIC) study is an international collaboration working on a concept for a machine to collide electrons and positrons (antielectrons) head-on at energies up to several teraelectronvolts (TeV). This energy range is similar to the LHC’s, but using electrons and their antiparticles rather than protons, physicists will gain a different perspective on the underlying physics.

    The aim is to use radiofrequency (RF) structures and a two-beam concept to produce accelerating fields as high as 100 MV per metre to reach a nominal total energy of 3 TeV, keeping the size and cost of the project within reach. The CLIC test facility, CTF3, provides the electron beam for the studies.

    In the two-beam acceleration concept, the high RF power needed to accelerate the main beam is extracted from a second high-intensity electron beam – the “drive beam” – that runs parallel to the main beam. This drive beam is decelerated in special power extraction structures and the generated RF power is used to accelerate the main beam.

    In a related project, the CLIC detector and physics collaboration is developing a detector to record collisions at the future high-energy Compact Linear Collider.

    ——————————————————–

    At the Compact Linear Collider (CLIC) test facility you see none of the heavy-duty steel pipes that characterise the dipole magnets of the LHC. Instead – true to the acronym– you find a compact accelerator module, fed by high-power waveguides, cables and cooling tubes, which sits elegantly on a custom-made mechanical structure that can be moved in all directions to ultra-high precision. The module will test out all the little details that turn a metal structure into a functioning accelerator part – frequency, losses, damping, acceleration, deceleration.

    CERN CLIC Connections
    CERN

    CLIC is one of the potential follow-up projects to the LHC, alongside the International Linear Collider and the Future Circular Collider [FCC] studies. It is designed to produces head-on collisions between electrons and positrons accelerated in a 50-kilomtre-long straight line using a unique acceleration technique where one particle beam drives another like a gigantic power converter. The project published its Conceptual Design Report in 2012, proving that the technologies planned for this ultra-precise machine are working. Now it is in a project preparation phase, where these technologies are tested, improved, made more efficient and more reliable, and where physicists and engineers take a closer look at the cost of the individual components. All this is where the new module comes in.

    ILC schematic
    ILC

    CERN Future Circular Collider
    FCC

    It’s the first module that has been integrated into the test facility and has all the functions of future CLIC modules. Many of the different techniques and technologies needed for CLIC’s sophisticated drive-beam acceleration – where one beam of electrons pushes another by transferring its energy – have been tested individually in the past. The CLIC researchers have proven that they can generate the high-current drive beam; that they can accelerate it and slow it right down again for the energy transfer to the main beam; that the beam can have the designated gradient and quality; and that the energy from the drive beam can actually be transferred to the main beam at the right frequency through the power-extraction and transfer structures. They have also shown that the accelerating structure can reach a gradient of 105 MV/m at a pulse length of 240 nanoseconds and with a low breakdown rate in separate high-power tests.

    Now the CLIC team have put it all together in the prototype module, added CLIC-type alignment systems, accelerating structures with higher-order-mode damping, and integrated diagnostics tools such as wakefield monitors – and they are testing it with beam. “It’s a complex system, and our very first experiments look promising,” says CERN’s Steffen Doebert, who is part of the team that developed the module. “We have to check all the connections and calibrate the module before installing a second super accelerating structure consisting of two accelerator units.”

    The two super structures will be installed on the same girder and then tested with beam (another two modules are being built and will be tested without beam). With the help of the diagnostic tools integrated into the module, which can detect very small fields, the researchers know where the beam is at any time within the structure. They can also make beam-based corrections thanks to a very precise alignment system developed by the CERN Metrology Group and a silicon carbide support that can be adjusted in all directions. “After all we need to be precise down to ten microns,” says Doebert.

    The module development has been a large effort within the CLIC collaboration with contributions from outside institutions and CERN groups. Their annual collaboration meeting took place at CERN this week, 26 – 30 January 2015.

    See the full article here.

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  • richardmitnick 1:16 pm on June 12, 2014 Permalink | Reply
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    From Symmetry: “Researchers imagine the accelerators of the future” 

    Symmetry

    June 12, 2014
    Sarah Charley

    At the LHC Physics Conference in New York, experts looked to the next steps in collider physics.

    In the late 1800s, many scientists thought that the major laws of physics had been discovered—that all that remained to be resolved were a few minor details.

    Then in 1896 came the discovery of the first fundamental particle, the electron, followed by the discovery of atomic nuclei and revolutions in quantum physics and relativity. Modern particle physics had just begun, said Natalie Roe, the Director of the Physics Division at Lawrence Berkeley National Laboratory, at the recent Large Hadron Collider Physics Conference in New York.

    Since then, physicists have discovered a slew of new elementary particles and have developed a model that accurately describes the fundamental components of matter. But this time, they know that there is more left to find—if only they can reach it. In a presentation and a panel discussion chaired by New York Times science reporter Dennis Overbye, experts at the LHCP Conference discussed the future of collider-based particle physics research.

    The discovery of a Higgs boson bolstered physicists’ confidence in the Standard Model—our best understanding of matter at its most fundamental level. But the Standard Model does not answer important questions such as why the Higgs boson is so light or why neutrinos have mass, nor does it account for dark matter and dark energy, which astronomical observations indicate make up the majority of the known universe.

    sm
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    “We know that the Standard Model is not a complete theory because many outstanding questions remain,” said CERN physicist Fabiola Gianotti, the former head of the ATLAS experiment at the LHC, at the LHCP Conference. “We must ask, at what energy scales do these questions find their answers?”

    CERN ATLAS New
    ATLAS at the LHC

    CERN LHC Grand Tunnel

    CERN LHC Map
    LHC at CERN

    The LHC will access an energy level higher than any previous accelerator, up to 13 trillion electronvolts, when it restarts in 2015. Scientists are already thinking about what could come next, such as the proposed International Linear Collider or hadron colliders under discussion in Europe and Asia.

    ILC schematic
    ILC design

    CERN CLIC
    CLIC design at CERN

    Building any proposed future accelerator will not be easy, “and none of them are cheap,” Gianotti said. However, one should not discount the opportunities that technological advances can afford.

    Gianotti pointed out that, in a 1954 presentation to the American Physical Society, Nobel Laureate Enrico Fermi estimated that an accelerator capable of accessing up to an energy of 3 trillion electronvolts would need to encircle the Earth and would cost about $170 billion.

    Thanks to the development of colliders and superconducting magnets, the 17-mile-long LHC has reached an energy level more than twice as high for a small fraction of Fermi’s estimated cost.

    Whatever the next step may be, physicists must look toward the future as an international community, panelists said.

    “The world has become more global, and we have contributed to that,” said Sergio Bertolucci, research director at CERN. “Things have changed.”

    According to scientists at the LHCP Conference, the discovery of the Higgs boson by a large international collaboration marked an era in which the big questions are tackled not by one nation, but by a global community.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.



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  • richardmitnick 9:46 pm on May 22, 2014 Permalink | Reply
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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
    ILC schematic proposal

    CERN CLIC
    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.

    Fermilab Campus

    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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  • richardmitnick 6:41 pm on March 11, 2014 Permalink | Reply
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    From SLAC: “SLAC Accelerator Physicists Help Make Sure ILC Will Hit Target” 

    March 7, 2014
    Lori Ann White

    An international team of scientists at Japan’s high-energy accelerator research facility KEK has successfully demonstrated a key component of a future high-power linear collider, such as the International Linear Collider (ILC) under consideration in Japan or the Compact Linear Accelerator (CLIC) being developed at the European facility CERN.

    ILC schematic
    ILC

    CERN CLIC
    CLIC

    The component, called the final focus optics, will help produce precise beams of particles at these future research facilities, said Glen White, the SLAC accelerator physicist who is lead author on a recent paper in Physical Review Letters.

    Optics for an accelerator that boosts charged particles to near light speed aren’t lenses in the typical sense of eyeglass lenses or magnifying lenses. Instead, “optics” refers to the magnets that steer the particles. The final focus optics for an accelerator are a sequence of powerful magnets that concentrate particles into tight beams. The optics demonstrated by the Accelerator Test Facility 2 (ATF2) focused an electron beam down to only a few tens of nanometers tall.

    This special sequence of magnets was developed by former SLAC accelerator physicists Andrei Seryi and Pantaleo Raimondi nearly 15 years ago. Many more SLAC physicists are members of the ATF2 collaboration, an international group of scientists that built and continue to test the structure at the KEK accelerator facility in Japan.

    The optics for a future linear collider must take many different issues into account, said White, including the physics and the economics of extremely energetic beams of tiny particles.

    For example, a magnet will focus charged particles that have slightly different energies to slightly different places.”No bunch of particles in an accelerator is perfectly uniform,” said White. Thus, the particles can “fuzz out” around the focal point, resulting in fewer collisions and less data, unless such differences in position, called chromatic aberrations, are accounted for.

    Previous methods for correcting chromatic aberration, such as those tested during the Final Focus Test Beam experiment at SLAC, required additional lengthy sections of tunnel for the magnets used, thus adding considerable cost, White said. The design the ATF2 collaboration tested involved adding magnets called sextupoles to the focusing magnets, called quadrupoles, already in use. “The sextupoles refocus the particles according to their positions, which are determined by their energies,” he said – essentially reversing the errors introduced by the quadrupoles.

    sextupole
    Sextupole electromagnet as used within the storage ring of the Australian Synchrotron to focus and steer the electron beam

    quad
    A quadrupole electromagnet as used in the storage ring of the Australian Synchrotron

    Seryi, who left SLAC in 2010 to become director of the John Adams Institute for Accelerator Science at Oxford University, is a member of the ATF2 collaboration. “It is extremely gratifying to see the idea realized in practice and know that it works,” he said. “I am also tremendously happy that the ATF2 experiment has trained many young accelerator physics experts. This was actually one of the goals – to create the team who will be able to work on the linear collider’s final focus when the real project starts.”

    Now that they know it works, said White, the next steps are to work on stabilizing the beam and train more young physicists for the real thing.

    See the full article here.

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
    i1


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  • richardmitnick 12:24 pm on February 14, 2014 Permalink | Reply
    Tags: , , CERN CLIC   

    From CERN: “Some CLIC with your free-electron laser?” 

    CERN New Masthead

    14 Feb 2014
    Barbara Warmbein

    Particle physics has a long tradition of technologies serendipitously making their way into other realms of science or even everyday life. Think of the web or particle detectors for medical diagnostics. The scientists working on the CLIC accelerator, one of the potential successors of the Large Hadron Collider, LHC, held a “High Gradient Day” specially targeted at industry during their workshop last week in order to catalyse the transfer of knowledge gathered over years of R&D.

    team
    Happy scientists at the end of acceptance-testing a new X-band klystron at SLAC in January. The testing team consists of people from CERN, SLAC, PSI, Trieste and the klystron manufacturer CPI (Image: SLAC)

    clic
    Proposed CLIC design

    During the day, several light-source operators from Switzerland, Turkey, Italy, China, Australia and Sweden exchanged their specs, wishes and future plans with the CLIC team. For Walter Wuensch, head of the X-band R&D for CLIC, and his colleagues, a light-source free-electron laser driven by CLIC technology would be a dream come true. Wuensch says that both the technology and beam diagnostic tools have been tested to the core. “We are confident we can build linear accelerators for free-electron lasers according to the desired specifications,” he says.

    The planned CLIC accelerator would use a unique way of accelerating its electrons and their anti-particles, positrons: two accelerators would sit side by side, one, the main linear accelerator or “linac”, getting the beams of particles from source to collision, and the other, the “drive beam”, passing as much power as possible on to the main beams. This gives them a big push, it increases the rate at which they accelerate – their gradient.

    In order to test the accelerating structures, CLIC scientists build test stands that are not powered by the CLIC drive beam but by power sources called klystrons that provide radiofrequency power in the X-band range. They believe that these klystron test stands (combined with high-gradient accelerating structures) could be useful for future free-electron lasers, special accelerator-driven lasers that provide very particular laser light for studying materials, biological samples, molecular processes and much more. “The high gradient means that the accelerator can be very short because beams reach the designated energy much more efficiently,” explains Wuensch. “We have done a lot of research on getting the gradient for CLIC, we have a lot of experience with X-band systems and sources are now available commercially. All this makes an X-band accelerator comparatively affordable.” This means labs or companies can build or upgrade free-electron lasers and make them available for all sorts of applications.

    Another topic at the High Gradient Day was the involvement of CLIC expertise medical projects. One of these, TERA TULIP, looks into operating a proton accelerator for cancer therapy. CLIC’s high-gradient experience could help make the gantry through which the beam is passed to the patient shorter and lighter by installing the accelerator on the gantry itself, thus reducing the number of bending magnets needed for the proton beam and making the gantry more compact. If it could move around the patient and provide high-precision beams, damage to non-cancerous tissue could be avoided.

    A few other potential applications which might benefit from X-band and high-gradient technology were discussed at the industry day, “but these are further down the line,” says Wuensch. We’ll make sure to let you know when the first free-electron laser using CLIC technology comes online.

    See the full article here.

    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New
    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries


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  • richardmitnick 8:26 am on April 22, 2013 Permalink | Reply
    Tags: , , CERN CLIC, , ,   

    From CERN: “Two-beam module to drive particle beams” 

    CERN New Masthead

    22 Apr 2013
    Cian O’Luanaigh

    “It may look like a steampunk locomotive, but this first prototype module for the Compact Linear Collider (CLIC) won’t be carrying any passengers. CLIC is a concept for a two-beam linear accelerator to collide electrons and positrons (antielectrons) head-on at energies up to several teraelectronvolts (TeV).

    two
    The first prototype module for the Compact Linear Collider is being tested at CERN (Image:Anna Pantelia/CERN)

    The module above – the first of its kind – is being tested at CERN, with neither beam nor radiofrequency (RF) system. The CLIC two-beam module team is checking the feasibility of the engineering designs for the different technical systems, such as the RF structures, the support structures, the alignment, stabilization and vacuum.”

    In the CLIC machine, energy is extracted from a low-energy, high-intensity electron beam to drive a parallel beam of particles The main linear accelerators (linacs) have a modular design based on 2-metre long two-beam modules, and will operate under ultra-high vacuum conditions required for beam physics.

    clic
    CLIC

    See the full article here.

    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New
    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries


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  • richardmitnick 7:33 am on November 21, 2012 Permalink | Reply
    Tags: , , , CERN CLIC, , , , ,   

    From Symmetry- “A bouquet of options: Higgs factory ideas bloom” 

    November 20, 2012
    Signe Brewster

    Now that a Higgs-like boson has been discovered at the Large Hadron Collider, proposals to build colliders that churn out the new particle are gathering momentum.

    higgs
    One possible signature of a Higgs boson from a simulated collision between two protons. It decays almost immediately into two jets of hadrons and two electrons, visible as lines.

    “If you hurl two oranges together at close to the speed of light, there’s going to be a lot of pulp. But, somewhere in the gooey mess will be the rare splinters left over from two seeds colliding.The Large Hadron Collider at CERN works in a similar way. Protons, each made of quarks and gluons, collide and produce other particles. Roughly once every 5 billion proton collisions, everything aligns and a Higgs-like boson pops out.

    Now that a boson with Higgs-like qualities has been found, physicists are calling for something more precise: a Higgs factory that would collide elementary particles to produce Higgs bosons in droves without all the distracting pulp. By colliding particles that don’t break down into composite parts as they produce Higgs-like particles, a Higgs factory could allow a more precise view of the new boson.

    Now that the Higgs-like particle is known to have a mass of about 125 billion electronvolts, scientists know that it is within reach of a variety of proposed colliders, both small and large. As a result, proposals for Higgs factories have emerged for colliders that smash electrons with positrons, muons with muons, or photons with photons.

    Linear electron–positron colliders are among the largest and most expensive Higgs factories because they are designed to be versatile. Two proposed machines, known as the International Linear Collider and the Compact Linear Collider, would be 3.4 miles and 1.35 miles long respectively. It would cost at least $5 billion to build the ILC or CLIC…

    lic
    A view of the two beam lines in the CLIC experimental hall.

    Electron–positron colliders can also be circular. The LHC tunnel was originally built for the Large Electron–Positron collider, which produced the first precise measurements of the W and Z bosons in the 1980s. One proposal, called LEP3, would build a Higgs factory in the LHC tunnel, most likely after the LHC shuts down. It would cut costs by using existing infrastructure, such as some of the particle detectors and the cryogenics system.”

    lep
    LEP, preceded the LHC at CERN

    See the full article here. There is much more important material here.

    Symmetry is a joint Fermilab/SLAC publication.

     
  • richardmitnick 1:56 pm on November 23, 2011 Permalink | Reply
    Tags: , , CERN CLIC, , , ,   

    From isgtw: “New accelerators, now just a CLIC away” 

    Neasan O’Neill
    November 23, 2011

    “In high energy physics bigger is usually better. Now a team at CERN in Geneva, Switzerland, has decided to look at different instead of big. The Compact Linear Collider (CLIC) team are investigating the potential of a new kind of particle accelerator, and to help them they are simulating their designs using grid resources, such the UK computing grid for particle physics, GridPP.

    Accelerators can be split into two broad categories, linear and circular. The circular ones are known as discovery machines, the experiments where new physics/particles are seen, while the linear machines are about accuracy and really nailing down specific properties and information.

    The 27 kilometer-long Large Hadron Collider at CERN is probably the best known of the discovery machines and CLIC is being designed to complement it (and others) by allowing researchers to flesh out the discoveries made and providing the detail needed for future discoveries/experiments.”

    i1
    General design of CLIC. Image courtesy CLIC.

    See the full article here.

     
  • richardmitnick 1:22 pm on October 27, 2011 Permalink | Reply
    Tags: , , CERN CLIC, ,   

    From CERN Bulletin via ILC Newsline: “Detectors on the drawing board” 

    Katarina Anthony
    Monday 24 October 2011

    ” ‘While the LHC experiments remain the pinnacle of detector technology, you may be surprised to realise that the design and expertise behind them is well over 10 years old,’ says Lucie Linssen, CERN’s Linear Collider Detector (LCD) project manager whose group is pushing the envelope of detector design. “The next generation of detectors will have to surpass the achievements of the LHC experiments. It’s not an easy task but, by observing detectors currently in operation and exploiting a decade’s worth of technological advancements, we’ve made meaningful progress.”

    The LCD team is currently working on detectors for the CLIC experiment. “Electron-positron colliders like CLIC demand detectors with significantly more precision than those at the LHC,” explains Lucie. “We’ve studied a variety of techniques to cope with this precision and other CLIC-specific issues. Many of these were pioneered for earlier linear colliders, but have since been adapted to fit CLIC’s unique parameters.” The team’s work has culminated in two detector designs, published in the CLIC Conceptual Design Report.

    i1
    A simulated event display in one of the new generation detectors.

    There is a lot of interesting information in this post. See the full article here. This article at ILC newsline is a bit of a surprise to me, as the CLIC is in direct competition with the ILC itself for future funding ans use.

     
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