Tagged: CERN Courier Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 9:24 am on October 17, 2016 Permalink | Reply
    Tags: , , CERN Courier, 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 .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

     
  • richardmitnick 5:18 pm on October 14, 2016 Permalink | Reply
    Tags: , CERN Courier, , , ,   

    From CERN Courier: “First physics at HIE-ISOLDE begins” 

    CERN Courier

    Oct 14, 2016

    1
    HIE-ISOLDE cryomodules

    In early September, the first physics experiment using radioactive beams from the newly upgraded ISOLDE facility got under way: a study of tin, which is a special element because it has two double magic isotopes. ISOLDE is CERN’s long-running nuclear research facility, which for the past 50 years has allowed many different studies of the properties of atomic nuclei. The upgrade means the machine can now reach an energy of 5.5 MeV per nucleon, making ISOLDE the only Isotope Separator On-Line (ISOL) facility in the world capable of investigating heavy and super-heavy radioactive nuclei.

    HIE-ISOLDE (High Intensity Energy-ISOLDE) is a major upgrade of the ISOLDE facility that will increase the energy, intensity and quality of the beams delivered to scientific users.

    CERN ISOLDE New
    CERN ISOLDE

    “Our success is the result of eight years of development and manufacturing,” explains HIE-ISOLDE project-leader Yacine Kadi. “The community around ISOLDE has grown a lot recently, as more scientists are attracted by the possibilities that new higher energies bring. It’s an energy domain that’s not explored much, since no other facility in the world can deliver pure beams at these energies.”

    The first run of the facility took place in October last year, but because the machine only had one cryomodule, it operated at an energy of 4.3 MeV per nucleon. Now, with the second cryomodule in place, the machine is capable of reaching up to 5.5 MeV per nucleon and therefore can investigate the structure of heavier isotopes. The rest of 2016 will be a busy time for HIE-ISOLDE, with scheduled experiments studying nuclei over a wide range of mass numbers – from 9Li to 142Xe. When two additional cryomodules are installed in 2017 and 2018, the facility will operate at 10 MeV per nucleon and be capable of investigating nuclei of all masses.

    HIE-ISOLDE will run until mid-November, and all but one of the seven different experiments planned during this time will use the Miniball detection station.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

     
  • richardmitnick 5:11 pm on October 14, 2016 Permalink | Reply
    Tags: , CERN Courier, , , ,   

    From CERN Courier: “All systems go for the High-Luminosity LHC” 

    CERN Courier

    Oct 14, 2016

    1
    Model quadrupole magnet

    On 19 September, the European Investment Bank (EIB) signed a 250 million Swiss francs (€230 million) credit facility with CERN in order to finance the High-Luminosity Large Hadron Collider (HL-LHC) project.

    CERN HL-LHC bloc

    The finance contract follows recent approval from CERN Council, and will allow CERN to carry out the work necessary for the HL-LHC within a constant CERN budget.

    The HL-LHC is expected to produce data from 2026 onwards, with the overall goal of increasing the integrated luminosity recorded by the LHC by a factor 10. Following approval of the HL-LHC as a priority project in the European Strategy Report for Particle Physics, this major upgrade is now gathering speed together with companion upgrade programmes of the LHC injectors and detectors. Engineers are currently putting the finishing touches to a full working model of an HL-LHC quadrupole, which will eventually be installed in the insertion regions close to the ATLAS and CMS experiments in order to focus the HL-LHC beam. Built in partnership with Fermilab, the magnets are based on an innovative niobium-tin superconductor (Nb3Sn) that can produce higher magnetic fields than the niobium-titanium magnets used in the LHC.

    The contract signed between CERN and EIB falls under the InnovFin Large Projects facility, which is part of the new generation of financial instruments developed and supported under the European Union’s Horizon 2020 scheme. It’s the second EIB financing for CERN, following a loan of €300 million in 2002 for the LHC. “This loan under Horizon 2020, the EU’s research-funding programme, will help keep CERN and Europe at the forefront of particle-physics research,” says the European commissioner for research, science and innovation, Carlos Moedas. “It’s an example of how EU funding helps extend frontiers of human knowledge.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

     
  • richardmitnick 12:00 pm on August 13, 2016 Permalink | Reply
    Tags: , , CERN Courier, Light sources, , ,   

    From CERN Courier: “MAX IV paves the way for ultimate X-ray microscope” 

    CERN Courier

    Sweden’s MAX IV facility is the first storage ring to employ a multi-bend achromat. Mikael Eriksson and Dieter Einfeld describe how this will produce smaller and more stable X-ray beams, taking synchrotron science closer to the X-ray diffraction limit.

    Aug 12, 2016

    Mikael Eriksson, Maxlab, Lund, Sweden,
    Dieter Einfeld, ESRF, Grenoble, France.

    1
    http://www.lightsources.org/facility/maxiv

    Since the discovery of X-rays by Wilhelm Röntgen more than a century ago, researchers have striven to produce smaller and more intense X-ray beams. With a wavelength similar to interatomic spacings, X-rays have proved to be an invaluable tool for probing the microstructure of materials. But a higher spectral power density (or brilliance) enables a deeper study of the structural, physical and chemical properties of materials, in addition to studies of their dynamics and atomic composition.

    For the first few decades following Röntgen’s discovery, the brilliance of X-rays remained fairly constant due to technical limitations of X-ray tubes. Significant improvements came with rotating-anode sources, in which the heat generated by electrons striking an anode could be distributed over a larger area. But it was the advent of particle accelerators in the mid-1900s that gave birth to modern X-ray science. A relativistic electron beam traversing a circular storage ring emits X-rays in a tangential direction. First observed in 1947 by researchers at General Electric in the US, such synchrotron radiation has taken X-ray science into new territory by providing smaller and more intense beams.

    Generation game

    First-generation synchrotron X-ray sources were accelerators built for high-energy physics experiments, which were used “parasitically” by the nascent synchrotron X-ray community. As this community started to grow, stimulated by the increased flux and brilliance at storage rings, the need for dedicated X-ray sources with different electron-beam characteristics resulted in several second-generation X-ray sources. As with previous machines, however, the source of the X-rays was the bending magnets of the storage ring.

    The advent of special “insertion devices” led to present-day third-generation storage rings – the first being the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, and the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory in Berkeley, California, which began operation in the early 1990s.

    ESRF. Grenoble, France
    ESRF. Grenoble, France

    2
    LBL/ALS

    Instead of using only the bending magnets as X-ray emitters, third-generation storage rings have straight sections that allow periodic magnet structures called undulators and wigglers to be introduced. These devices consist of rows of short magnets with alternating field directions so that the net beam deflection cancels out. Undulators can house 100 or so permanent short magnets, each emitting X-rays in the same direction, which boosts the intensity of the emitted X-rays by two orders of magnitude. Furthermore, interference effects between the emitting magnets can concentrate X-rays of a given energy by another two orders of magnitude.

    Third-generation light sources have been a major success story, thanks in part to the development of excellent modelling tools that allow accelerator physicists to produce precise lattice designs. Today, there are around 50 third-generation light sources worldwide, with a total number of users in the region of 50,000. Each offers a number of X-ray beamlines (up to 40 at the largest facilities) that fan out from the storage ring: X-rays pass through a series of focusing and other elements before being focused on a sample positioned at the end station, with the longest beamlines (measuring 150 m or more) at the largest light sources able to generate X-ray spot sizes a few tens of nanometres in diameter. Facilities typically operate around the clock, during which teams of users spend anywhere between a few hours to a few days undertaking experimental shifts, before returning to their home institutes with the data.

    Although the corresponding storage-ring technology for third-generation light sources has been regarded as mature, a revolutionary new lattice design has led to another step up in brightness. The MAX IV facility at Maxlab in Lund, Sweden, which was inaugurated in June, is the first such facility to demonstrate the new lattice. Six years in construction, the facility has demanded numerous cutting-edge technologies – including vacuum systems developed in conjunction with CERN – to become the most brilliant source of X-rays in the world.

    3
    Iron-block magnets

    Initial ideas for the MAX IV project started at the end of the 20th century. Although the flagship of the Maxlab laboratory, the low-budget MAX II storage ring, was one of the first third-generation synchrotron radiation sources, it was soon outcompeted by several larger and more powerful sources entering operation. Something had to be done to maintain Maxlab’s accelerator programme.

    The dominant magnetic lattice at third-generation light sources consists of double-bend achromats (DBAs), which have been around since the 1970s.

    DBAs
    4
    MAX IV undulator

    A typical storage ring contains 10–30 achromats, each consisting of two dipole magnets and a number of magnet lenses: quadrupoles for focusing and sextupoles for chromaticity correction (at MAX IV we also added octupoles to compensate for amplitude-dependent tune shifts). The achromats are flanked by straight sections housing the insertion devices, and the dimensions of the electron beam in these sections is minimised by adjusting the dispersion of the beam (which describes the dependence of an electron’s transverse position on its energy) to zero. Other storage-ring improvements, for example faster correction of the beam orbit, have also helped to boost the brightness of modern synchrotrons. The key quantity underpinning these advances is the electron-beam emittance, which is defined as the product of the electron-beam size and its divergence.

    Despite such improvements, however, today’s third-generation storage rings have a typical electron-beam emittance of between 2–5 nm rad, which is several hundred times larger than the diffraction limit of the X-ray beam itself. This is the point at which the size and spread of the electron beam approaches the diffraction properties of X-rays, similar to the Abbe diffraction limit for visible light. Models of machine lattices with even smaller electron-beam emittances predict instabilities and/or short beam lifetimes that make the goal of reaching the diffraction limit at hard X-ray energies very distant.

    Although it had been known for a long time that a larger number of bends decreases the emittance (and therefore increases the brilliance) of storage rings, in the early 1990s, one of the present authors (DE) and others recognised that this could be achieved by incorporating a higher number of bends into the achromats. Such a multi-bend achromat (MBA) guides electrons around corners more smoothly, therefore decreasing the degradation in horizontal emittance. A few synchrotrons already employ triple-bend achromats, and the design has also been used in several particle-physics machines, including PETRA at DESY, PEP at SLAC and LEP at CERN, proving that a storage ring with an energy of a few GeV produces a very low emittance.

    DESY Petra III interior
    DESY Petra III

    4
    PEP II at SLAC. http://www.sciencephoto.com/media/613/view

    5
    CERN LEP

    To avoid prohibitively large machines, however, the MBA demands much smaller magnets than are currently employed at third-generation synchrotrons.

    In 1995, our calculations showed that a seven-bend achromat could yield an emittance of 0.4 nm rad for a 400 m-circumference machine – 10 times lower than the ESRF’s value at the time. The accelerator community also considered a six-bend achromat for the Swiss Light Source and a five-bend achromat for a Canadian light source, but the small number of achromats in these lattices meant that it was difficult to make significant progress towards a diffraction-limited source. One of us (ME) took the seven-bend achromat idea and turned it into a real engineering proposal for the design of MAX IV. But the design then went through a number of evolutions. In 2002, the first layout of a potential new source was presented: a 277 m-circumference, seven-bend lattice that would reach an emittance of 1 nm rad for a 3 GeV electron beam. By 2008, we had settled on an improved design: a 520 m-circumference, seven-bend lattice with an emittance of 0.31 nm rad, which will be reduced by a factor of two once the storage ring is fully equipped with undulators. This is more or less the design of the final MAX IV storage ring.

    In total, the team at Maxlab spent almost a decade finding ways to keep the lattice circumference at a value that was financially realistic, and even constructed a 36 m-circumference storage ring called MAX III to develop the necessary compact magnet technology. There were tens of problems that we had to overcome. Also, because the electron density was so high, we had to elongate the electron bunches by a factor of four by using a second radio-frequency (RF) cavity system.

    Block concept

    MAX IV stands out in that it contains two storage rings operated at an energy of 1.5 and 3 GeV. Due to the different energies of each, and because the rings share an injector and other infrastructure, high-quality undulator radiation can be produced over a wide spectral range with a marginal additional cost. The storage rings are fed electrons by a 3 GeV S-band linac made up of 18 accelerator units, each comprising one SLAC Energy Doubler RF station. To optimise the economy over a potential three-decade-long operation lifetime, and also to favour redundancy, a low accelerating gradient is used.

    The 1.5 GeV ring at MAX IV consists of 12 DBAs, each comprising one solid-steel block that houses all the DBA magnets (bends and lenses). The idea of the magnet-block concept, which is also used in the 3 GeV ring, has several advantages. First, it enables the magnets to be machined with high precision and be aligned with a tolerance of less than 10 μm without having to invest in aligning laboratories. Second, blocks with a handful of individual magnets come wired and plumbed direct from the delivering company, and no special girders are needed because the magnet blocks are rigidly self-supporting. Last, the magnet-block concept is a low-cost solution.

    We also needed to build a different vacuum system, because the small vacuum tube dimensions (2 cm in diameter) yield a very poor vacuum conductance. Rather than try to implement closely spaced pumps in such a compact geometry, our solution was to build 100% NEG-coated vacuum systems in the achromats. NEG (non-evaporable getter) technology, which was pioneered at CERN and other laboratories, uses metallic surface sorption to achieve extreme vacuum conditions. The construction of the MAX IV vacuum system raised some interesting challenges, but fortunately CERN had already developed the NEG coating technology to perfection. We therefore entered a collaboration that saw CERN coat the most intricate parts of the system, and licences were granted to companies who manufactured the bulk of the vacuum system. Later, vacuum specialists from the Budker Institute in Novosibirsk, Russia, mounted the linac and 3 GeV-ring vacuum systems.

    Due to the small beam size and high beam current, intra beam scattering and “Touschek” lifetime effects must also be addressed. Both are due to a high electron density at small-emittance/high-current rings in which electrons are brought into collisions with themselves. Large energy changes among the electrons bring some of them outside of the energy acceptance of the ring, while smaller energy deviations cause the beam size to increase too much. For these reasons, a low-frequency (100 MHz) RF system with bunch-elongating harmonic cavities was introduced to decrease the electron density and stabilise the beam. This RF system also allows powerful commercial solid-state FM-transmitters to be used as RF sources.

    When we first presented the plans for the radical MAX IV storage ring in around 2005, people working at other light sources thought we were crazy. The new lattice promised a factor of 10–100 increase in brightness over existing facilities at the time, offering users unprecedented spatial resolutions and taking storage rings within reach of the diffraction limit. Construction of MAX IV began in 2010 and commissioning began in August 2014, with regular user operation scheduled for early 2017.

    On 25 August 2015, an amazed accelerator staff sat looking at the beam-position monitor read-outs at MAX IV’s 3 GeV ring. With just the calculated magnetic settings plugged in, and the precisely CNC-machined magnet blocks, each containing a handful of integrated magnets, the beam went around turn after turn with proper behaviour. For the 3 GeV ring, a number of problems remained to be solved. These included dynamic issues – such as betatron tunes, dispersion, chromaticity and emittance – in addition to more trivial technical problems such as sparking RF cavities and faulty power supplies.

    As of MAX IV’s inauguration on 21 June, the injector linac and the 3 GeV ring are operational, with the linac also delivering X-rays to the Short Pulse Facility. A circulating current of 180 mA can be stored in the 3 GeV ring with a lifetime of around 10 h, and we have verified the design emittance with a value in the region of 300 pm rad. Beamline commissioning is also well under way, with some 14 beamlines under construction and a goal to increase that number to more than 20.

    Sweden has a well-established synchrotron-radiation user community, although around half of MAX IV users will come from other countries. A variety of disciplines and techniques are represented nationally, which must be mirrored by MAX IV’s beamline portfolio. Detailed discussions between universities, industry and the MAX IV laboratory therefore take place prior to any major beamline decisions. The high brilliance of the MAX IV 3 GeV ring and the temporal characteristics of the Short Pulse Facility are a prerequisite for the most advanced beamlines, with imaging being one promising application.

    Towards the diffraction limit

    MAX IV could not have reached its goals without a dedicated staff and help from other institutes. As CERN has helped us with the intricate NEG-coated vacuum system, and the Budker Institute with the installation of the linac and ring vacuum systems, the brand new Solaris light source in Krakow, Poland (which is an exact copy of the MAX IV 1.5 GeV ring) has helped with operations, and many other labs have offered advice. The MAX IV facility has also been marked out for its environmental credentials: its energy consumption is reduced by the use of high-efficiency RF amplifiers and small magnets that have a low power consumption. Even the water-cooling system of MAX IV transfers heat energy to the nearby city of Lund to warm houses.

    The MAX IV ring is the first of the MBA kind, but several MBA rings are now in construction at other facilities, including the ESRF, Sirius in Brazil and the Advanced Photon Source (APS) at Argonne National Laboratory [ANL] in the US.

    ANL APS
    ANL/APS

    The ESRF is developing a hybrid MBA lattice that would enter operation in 2019 and achieve a horizontal emittance of 0.15 nm rad. The APS has decided to pursue a similar design that could enter operation by the end of the decade and, being larger than the ESRF, the APS can strive for an even lower emittance of around 0.07 nm rad. Meanwhile, the ALS in California is moving towards a conceptual design report, and Spring-8 in Japan is pursuing a hybrid MBA that will enter operation on a similar timescale.

    Indeed, a total of some 10 rings are currently in construction or planned. We can therefore look forward to a new generation of synchrotron storage rings with very high transverse-coherent X-rays. We will then have witnessed an increase of 13–14 orders of magnitude in the brightness of synchrotron X-ray sources in a period of seven decades, and put the diffraction limit at high X-ray energies firmly within reach.

    One proposal would see such a diffraction-limited X-ray source installed in the 6.3 km-circumference tunnel that once housed the Tevatron collider at Fermilab, Chicago. Perhaps a more plausible scenario is PETRA IV at DESY in Hamburg, Germany. Currently the PETRA III ring is one of the brightest in the world, but this upgrade (if it is funded) could result in a 0.007 nm rad (7 pm rad) emittance or even lower. Storage rings will then have reached the diffraction limit at an X-ray wavelength of 1 Å. This is the Holy Grail of X-ray science, providing the highest resolution and signal-to-noise ratio possible, in addition to the lowest-radiation damage and the fastest data collection. Such an X-ray microscope will allow the study of ultrafast chemical reactions and other processes, taking us to the next chapter in synchrotron X-ray science.

    Further reading

    E Al-Dmour et al. 2014 J. Synchrotron Rad. 21 878.
    D Einfeld et al. 1995 Proceedings: PAC p177.
    M Eriksson et al. 2008 NIM-A 587 221.
    M Eriksson et al. 2016 IPAC 2016, MOYAA01, Busan, Korea.
    MAX IV Detailed Design Report http://www.maxlab.lu.se/maxlab/max4/index.html.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 2:02 pm on April 23, 2014 Permalink | Reply
    Tags: , , CERN Courier, , , , ,   

    From CERN Courier: “MINERvA searches for wisdom among neutrinos” 

    CERN Courier

    Mar 28, 2014
    Emily Maher, Massachusetts College of Liberal Arts, Deborah Harris, Fermilab, and Kevin McFarland, University of Rochester

    Fermilab Tevatron
    Ye Olde Tevatron

    Fermilab Wilson Hall
    The ever youthful Wilson Hall

    Fermilab NUMI Tunnel project
    Fermilab NUMI Tunnel project

    Neutrino physicists enjoy a challenge, and the members of the MINERvA (Main INjector ExpeRiment for v-A) collaboration at Fermilab are no exception. MINERvA seeks to make precise measurements of neutrino reactions using the Neutrinos at the Main Injector (NuMI) beam on both light and heavy nuclei. Does this goal reflect the wisdom of the collaboration’s namesake? Current and future accelerator-based neutrino-oscillation experiments must precisely predict neutrino reactions on the nuclei if they are to search successfully for CP violation in oscillations. Understanding matter–antimatter asymmetries might in turn lead to a microphysical mechanism to answer the most existential of questions: why are we here? Although MINERvA might provide vital assistance in meeting this worthy goal, neutrinos never yield answers easily. Moreover, using neutrinos to probe the dynamics of reactions on complicated nuclei convolutes two challenges.

    fig 1

    The history of neutrinos is wrought with theorists underestimating the persistence of experimentalists (Close 2010). Wolfgang Pauli’s quip about the prediction of the neutrino, “I have done a terrible thing. I have postulated a particle that cannot be detected,” is a famous example. Nature rejected Enrico Fermi’s 1933 paper explaining β decay, saying it “contained speculations too remote from reality to be of interest to readers”. Eighty years ago, when Hans Bethe and Rudolf Peierls calculated the first prediction for the neutrino cross-section, they said, “there is no practical way of detecting a neutrino” (p23). But when does practicality ever stop physicists? The theoretical framework developed during the following two decades predicted numerous measurements of great interest using neutrinos, but the technology of the time was not sufficient to enable those measurements. The story of neutrinos across the ensuing decades is that of many dedicated experimentalists overcoming these barriers. Today, the MINERvA experiment continues Fermilab’s rich history of difficult neutrino measurements.

    Neutrinos at Fermilab

    Fermilab’s research on neutrinos is as old as the lab itself. While it was still being built, the first director, Robert Wilson, said in 1971 that the initial aim of experiments on the accelerator system was to detect a neutrino. “I feel that we then will be in business to do experiments on our accelerator…[Experiment E1A collaborators’] enthusiasm and improvisation gives us a real incentive to provide them with the neutrinos they are waiting for.” The first experiment, E1A, was designed to study the weak interaction using neutrinos, and was one of the first experiments to see evidence of the weak neutral current. In the early years, neutrino detectors at Fermilab were both the “15 foot” (4.6 m) bubble chamber filled with neon or hydrogen, and coarse-grained calorimeters. As the lab grew, the detector technologies expanded to include emulsion, oil-based Cherenkov detectors, totally active scintillator detectors, and liquid-argon time-projection chambers. The physics programme expanded as well, to include 42 neutrino experiments either completed (37), running (3) or being commissioned. The NuTeV experiment collected an unprecedented million high-energy neutrino and antineutrino interactions, of both charged and neutral currents. It provided precise measurements of structure functions and a measurement of the weak mixing angle in an off-shell process with comparable precision to contemporary W-mass measurements (Formaggio and Zeller 2013). Then in 2001, the DONuT experiment observed the τ neutrino – the last of the fundamental fermions to be detected (CERN Courier September 2000 p6).

    fig 2
    Fig. 2.

    While much of the progress of particle physics has come by making proton beams of higher and higher energies, the most recent progress at Fermilab has come from making neutrino beams of lower energies but higher intensities. This shift reflects the new focus on neutrino oscillations, where the small neutrino mass demands low-energy beams sent over long distances. While NuTeV and DONuT used beams of 100 GeV neutrinos in the 1990s, the MiniBooNE experiment, started in 2001, used a 1 GeV neutrino beam to search for oscillations over a short distance. The MINOS experiment, which started in 2005, used 3 GeV neutrinos and measured them both at Fermilab and in a detector 735 km away, to study oscillations that were seen in atmospheric neutrinos. MicroBooNE and NOvA – two experiments completing construction at the time of this article – will place yet more sensitive detectors in these neutrino beamlines. Fermilab is also planning the Long-Baseline Neutrino Experiment to be broadly sensitive to resolve CP violation in neutrinos.

    A spectrum of interactions

    Depending on the energy of the neutrino, different types of interactions will take place (Formaggio and Zeller 2013, Kopeliovich et al. 2012). In low-energy interactions, the neutrino will scatter from the entire nucleus, perhaps ejecting one or more of the constituent nucleons in a process referred to as quasi-elastic scattering. At slightly higher energies, the neutrinos interact with nucleons and can excite a nucleon into a baryon resonance that typically decays to create new final-state hadrons. In the high-energy limit, much of the scattering can be described as neutrinos scattering from individual quarks in the familiar deep-inelastic scattering framework. MINERvA seeks to study this entire spectrum of interactions.

    To measure CP violation in neutrino-oscillation experiments, quasi-elastic scattering is an important channel. In a simple model where the nucleons of the nucleus live in a nuclear binding potential, the reaction rate can be predicted. In addition, an accurate estimate of the energy of the incoming neutrino can be made using only the final-state charged lepton’s energy and angle, which are easy to measure even in a massive neutrino-oscillation experiment. However, the MiniBooNE experiment at Fermilab and the NOMAD experiment at CERN both measured the quasi-elastic cross-section and found contradictory results in the framework of this simple model (Formaggio and Zeller 2013, Kopeliovich et al. 2012).

    fig 3
    Fig. 3.

    One possible explanation of this discrepancy can be found in more sophisticated treatments of the environment in which the interaction occurs (Formaggio and Zeller 2013, Kopeliovich et al. 2012). The simple relativistic Fermi-gas model treats the nucleus as quasi-free independent nucleons with Fermi motion in a uniform binding potential. The spectral-function model includes more correlation among the nucleons in the nucleus. However, more complete models that include the interactions among the many nucleons in the nucleus modify the quasi-elastic reaction significantly. In addition to modelling the nuclear environment on the initial reaction, final-state interactions of produced hadrons inside the nucleus must also be modelled. For example, if a pion is created inside the nucleus, it might be absorbed on interacting with other nucleons before leaving the nucleus. Experimentalists must provide sufficient data to distinguish between the models.

    The ever-elusive neutrino has forced experimentalists to develop clever ways to measure neutrino cross-sections, and this is exactly what MINERvA is designed to do with precision. The experiment uses the NuMI beam – a highly intense neutrino beam (CERN Courier November 2013 p5). The MINERvA detector is made of finely segmented scintillators, allowing the measurement of the angles and energies of the particles within. Figures 1 and 2 show the detector and a typical event in the nuclear targets. The MINOS near-detector, located just behind MINERvA, is used to measure the momentum and charge of the muons. With this information, MINERvA can measure precise cross-sections of different types of neutrino interactions: quasi-elastic, resonance production, and deep-inelastic scatters, among others.

    fig 4
    Fig. 4.

    The MINERvA collaboration began by studying the quasi-elastic muon neutrino scattering for both neutrinos (MINERvA 2013b) and antineutrinos (MINERvA 2013a). By measuring the muon kinematics to estimate the neutrino energies, they were able to measure the neutrino and antineutrino cross-sections. The data, shown in figure 3, suggest that the nucleons do spend some time in the nucleus joined together in pairs. When the neutrino interacts with the pair, the pair is kicked out of the nucleus. Using the visible energy around the nucleus allowed a search for evidence of the pair of nucleons. Experience from electron quasi-elastic scattering leads to an expectation of final-state proton–proton pairs for neutrino quasi-elastic scattering and neutron–neutron pairs for antineutrino scattering. MINERvA’s measurements of the energy around the vertex in both neutrino and antineutrino quasi-elastic scattering support this expectation (figure 3, right).

    A 30-year-old puzzle

    Another surprise beyond the standard picture in lepton–nucleus scattering emerged 30 years ago in deep-inelastic muon scattering. The European Muon Collaboration (EMC) observed a modification of the structure functions in heavy nuclei that is still theoretically unresolved, in part because there is no other reaction in which an analogous effect is observed (CERN Courier May 2013 p35). Neutrino and antineutrino deep-inelastic scattering might see related effects with different leptonic currents, and therefore different couplings to the constituents of the nucleus (Gallagher et al. 2010, Kopeliovich et al. 2012). MINERvA has begun this study using large targets of active scintillator and passive graphite, iron and lead (MINERvA 2014). Figure 4 shows the ratio of lead to scintillator and illustrates behaviour that is not in agreement with a model based on charged-lepton scattering modifications of deep-inelastic scattering and the elastic physics described above. Similar behaviour, but with smaller deviations from the model, is observed in the ratio of iron to scintillator. MINERvA’s investigation of this effect will benefit greatly from its current operation in the upgraded NuMI beam for the NOvA experiment, which is more intense and higher in (the beamline’s on-axis) energy. Both features will allow more access to the kinematic regions where deep-inelastic scattering dominates. By including a long period of antineutrino operation needed for NOvA’s oscillation studies, an even more complete survey of the nucleons can be done. The end result of these investigations will be a data set that can offer a new window on the process behind the EMC effect.

    Initially in the history of the neutrino, theory led experiment by several decades. Now, experiment leads theory. Neutrino physics has repeatedly identified interesting and unexpected physics. Currently, physics is trying to understand how the most abundant particle in the universe interacts in the simplest of situations. MINERvA is just getting started on answering these types of questions and there are many more interactions to study. The collaboration is also looking at what happens when neutrinos make pions or kaons when they hit a nucleus, and how well they can measure the number of times a neutrino scatters off an electron – the only “standard candle” in this business.

    Time after time, models fail to predict what is seen in neutrino physics. The MINERvA experiment, among others, has shown that quasi-elastic scattering is a wonderful tool to study the nuclear environment. Maybe the use of neutrinos, once thought to be impossible to detect, as a probe to study inside the nucleus, would make Pauli, Fermi, Bethe, Peierls and the rest chuckle.

    See the full article, with notes, here.


    The upstart LHC


    ScienceSprings is powered by MAINGEAR computers

     
  • richardmitnick 4:04 pm on April 27, 2012 Permalink | Reply
    Tags: , , CERN Courier, , , ,   

    From CERN Courier – May 2012 – Important Articles 


    LHC yields data rapidly at new collision energy of 8 TeV

    “At 12.38 a.m. on 5 April, the LHC shift crew declared “stable beams” as two 4 TeV proton beams were brought into collision at the LHC’s four interaction points. This signalled the start of physics data-taking by the LHC experiments for 2012. The collision energy of 8 TeV is a new world record. By 11 April the LHC had already delivered a total integrated luminosity of 0.2 fb–1 to the experiments. Last year, it took six weeks achieve the same number.” Read the rest.

    The rarest B decay ever observed
    “As announced at the “Moriond” conference on 10 March, the LHCb collaboration has made the first observation of the decay B+ → π+μ+μ–. With a branching ratio of about 2 per 100 million decays, this is the rarest decay of a B hadron ever observed.

    The LHCb experiment is designed to search for new physics in the rare decays and CP-violation of particles with heavy flavour, i.e. those containing the c or b quark. Such decays have previously been studied by the B-factory experiments BaBar and Belle, but LHCb is taking the field further as a result of two major advantages: not only are all of the varieties of heavy-flavour hadrons produced in the LHC’s high-energy collisions, but they are also produced at an enormous rate.” Read the rest.

    ATLAS and CMS search for new gauge bosons
    The ATLAS and CMS collaborations are carrying out a large-scale hunt for hypothetical heavy partners of the Standard Model gauge bosons, the W and the Z. The two experiments were designed to be sensitive to the decays of such particles, which are called, appropriately, W’ and Z’. The latest findings presented at the recent winter conferences show that so far these searches probe for W’ and Z’ particles with masses more than 20 times larger than those of their well known Standard Model counterparts.” Read the rest.


    New developments in the search for SUSY

    “Although no sign of supersymmetry (SUSY) has been observed so far, it is still the front-runner as a signal for new physics that could be discovered at the LHC. Not only does it neatly solve several shortcomings of the Standard Model, it also provides a candidate for the as-yet undiscovered dark-matter particle. Unfortunately, the masses of the SUSY particles are not constrained by theory, but it does provide some interesting hints. For SUSY to solve in a natural way the fine-tuning problems that arise in the Standard Model from the presence of a low-mass Higgs, the lightest of the two supersymmetric partners of the top quark (stop quarks) should have a mass not too much beyond that of the Standard Model counterpart, and the mass of the gluon’s superpartner (gluino) should not be too far above that of the stop quarks.

    Both the ATLAS and CMS collaborations have made significant progress in searching for possibly light third-generation squarks (stop and sbottom), produced either directly or in the decays of gluinos, and first results based on the full data set recorded in 2011, equivalent to about 5 fb–1, have been released. CMS has presented a search for events containing multiple b-quarks and two leptons of the same charge, thus effectively eliminating most of the Standard Model backgrounds. ATLAS has released a novel interpretation of its updated multi-jet analysis, which explores events with up to nine high-transverse-momentum jets.” Read the rest.

     
  • richardmitnick 1:37 pm on November 23, 2011 Permalink | Reply
    Tags: , , CERN Courier, , ,   

    CERN Courier: Important Articles 

    From CERN Courier, Some interesting and important articles:

    ALICE measures multi-strange baryons

    Strangeness and heavy flavours in Krakow

    NA61/SHINE: more precision for neutrino beams

    SUSY: the search continues

    Gravity on large scales

    Hadron therapy: collaborating for the future

     
  • richardmitnick 3:41 pm on October 24, 2011 Permalink | Reply
    Tags: , , CERN Courier   

    From CERN Courier: A Bunch of Great Articles 

    This issue of CERN Courier is just loaded with important articles. Here is a list:

    Dewi M Lewis, CERN, and Antonis Kalemis, Philips Healthcare
    October 14, 2011

    PET and MRI: providing the full picture

    Compiled by Marc Türler, INTEGRAL Science Data Centre and Observatory of the University of Geneva.
    October 14, 2011

    Herschel favours quiet galaxy build-up theory

    Akira Yamamoto, KEK
    October 14, 2011

    Progress in applied superconductivity at KEK

    No Writer Credit
    October 14, 2011

    ALICE revolutionizes TOF systems

    No Writer Credit
    October 14, 2011

    ATLAS looks at vector bosons plus jets…

    No Writer Credit
    October 14, 2011

    New results from CMS on top quarks

    Meet CERN in a variety of places:

    Cern Courier

    ATLAS

    i2

    ALICE

    CMS

    i3

    LHCb
    i4

    LHC

    i1

     
  • richardmitnick 3:10 pm on October 24, 2011 Permalink | Reply
    Tags: , , CERN Courier, ,   

    From Cern Courier: “The Discovery of Type II Superconductors” 

    From Cern Courier

    Oct 14, 2011
    Anatoly Shepelev, Kharkov Institute of Physics and Technology, and David Larbalestier, National High Magnetic Field Laboratory, Florida State University.

    Read about Type II Superconductors and their significance at CERN in the LHC.

    The full article is here.

    Meet CERN in a variety of places:

    Cern Courier

    ATLAS

    i2

    ALICE

    CMS

    i3

    LHCb
    i4

    LHC

    i1

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: