Kim J.J.,SLAC |
Kim M.S.,SLAC |
Nam I.H.,SLAC |
Nam I.H.,Accelerator Laboratory |
And 2 more authors.
IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference | Year: 2016
Generation of tunable coherent radiation is numerically investigated via the two-dimensional particle-in-cell (2DPIC) code developed by UNIST  and SIMPLEX developed by Spring-8. The electron beams can be produced by the laser-driven wakefield acceleration technique. The electron beam energy can be easily adjusted between 450 MeV and 800 MeV with a tapered density plasma on the order of 1×1018 cm-3 while the driving laser power is fixed, and the high-energy electron beams can be sent through the undulator arrays for the coherent light emission. The energycontrollable electron bunches can provide an opportunity to control the radiation wavelength with the fixed gap undulators. For the tapered density profile, a capillary cell with two gas inlets can be used. In this paper, we show some simulation and numerical research results regarding these issues, which reveal the possibility for a tunable light source in the soft X-ray regime. Copyright © 2016 CC-BY-3.0 and by the respective authors.
News Article | April 17, 2017
Bernard Degrange, emeritus director of research at CNRS, has been awarded the 2016 André Lagarrigue Prize in acknowledgement of his exemplary career in experimental particle physics. Co-financed by the CNRS, the University Paris Sud, Linear Accelerator Laboratory (LAL), Eʹcole Polytechnique, CERN and CEA, with the support of the French Physical Society, the prize was created in 2005 in honour of André Lagarrigue. Director of LAL from 1969 to 1975, Lagarrigue played a leading role in the discovery of weak neutral currents in the Gargamelle bubble-chamber experiment at CERN, thus paving the way for electroweak theory. After completing his thesis in 1969, Degrange joined the Gargamelle collaboration where he contributed to the first measurement of the ratio of the neutrino and antineutrino cross-sections on nucleons and studied exclusive channels produced in neutral or charged-current interactions. In the early 1980s he moved into the study of cosmic rays and high-energy gamma-ray astronomy, helping to discover several “blazars” in the Crab Nebula with the CAT experiment. For the simultaneous observation of gamma and X-rays during the major bursts of these extragalactic sources, Degrange was awarded the silver medal of the CNRS in 1997. Anticipating the detection power of stereoscopy associated with fast high-granularity imagery, he made major contributions to the design and the results of the HESS experiment. The Czech Republic’s Academia Film Olomouc has decided to give its 2017 Award for Contribution to Science Communication to CERN, for its “long-lasting commitment not only to research in the edge of science but also to communication of its results and science in general to broader public”. The committee described CERN as a pioneer in developing new ways to communicate science via social media, film, traditional media and events such as CineGlobe. The award ceremony will take place on 29 April at Palacký University Interactive Science Centre in Olomouc. On 2 March, in collaboration with CERN and 20th Century Fox, the Pathé cinema in Geneva hosted an advance screening of the film Hidden Figures, followed by a debate on the position of women in science. The film tells the story of three African-American female scientists who played key roles in the US space conquest, contributing in particular to the preparations for putting astronaut John Glenn into orbit. After the film, Maite Barroso Lopez of CERN’s IT department, Stéphanie Beauceron and Anne-Marie Magnan from CMS, and Andry Rakotozafindrabe from ALICE shared their experiences of science careers with the audience in a debate. They answered questions about the alleged rivalry among women, about whether there is a link between CERN and NASA as pictured in the film, and about their mentors. The 2017 Rencontres de Moriond conference took place in La Thuile, Italy, from 18 March to 1 April, with around 270 participants attending the two-week-long event. The four main LHC experiments presented many fresh results, ranging from precise measurements of the Standard Model (SM) to searches for new physics, including the first obtained with the full 13 TeV data set collected during 2016. Numerous results from experiments outside CERN were also presented, especially in the neutrino field, and participants heard some of the latest developments in theory. Analyses of the Higgs boson presented by CMS included a precise new measurement of the Higgs mass. CMS also showed results from searches for associated Higgs-top production in final states with multiple leptons, which provides direct evidence for the existence of a top-quark Higgs coupling with a measured signal strength consistent with the SM. Both CMS and ATLAS showed new measurements of total and differential cross-sections of the Higgs boson decaying into four leptons or two photons, which agree with the SM. ATLAS also showed preliminary results from searches for the rare Higgs-boson decay to two muons, which are now approaching the sensitivity required to observe a signal. Concerning other SM particles, ATLAS presented its first measurement of the mass of the W boson with similar precision to the previous best result from a single experiment. The D0 and CDF collaborations at the former Tevatron collider, meanwhile, presented precise measurements of the top-quark mass. Among the highlights of searches for physics beyond the SM were new limits on supersymmetric particles from ATLAS, which now exclude models with particle masses above 2 TeV (see "ATLAS pushes SUSY beyond 2 TeV"). ATLAS also showed searches for new heavy particles decaying to jets of hadron particles, excluding non-elementary quarks with masses as large as 6 TeV. Both ATLAS and CMS are also looking for new heavy resonances decaying to a vector and a Higgs boson: ATLAS sees a 3.3 standard deviation local excess for a W´ → WH decay at masses around 3 TeV, whereas CMS sees a similar local excess but at a lower mass. Exotic searches from CMS using the full 2016 data sample place new limits on many scenarios including dark matter, new types of quarks, vector bosons and gravitons. No significant deviations from SM predictions have been observed so far by CMS and ATLAS. Results of searches for bottonium states at the Belle experiment and charmonium-like states at BESIII were also shown. In particular, the analysis of the Y(4260) appears to be inconsistent with a single peak at more than seven standard deviations. The heavy-flavour field also saw several new results presented by LHCb. Besides an update of the measurement of the rarest decay of a particle containing a b quark ever observed, and the recent observation of a new system of five particles all in a single analysis, LHCb presented the most precise single measurement of the CP-violating phase φ . The LHCb collaboration is also putting in place new analyses to shed light on two flavour anomalies: R(D*) and R(K), which remain around three standard deviations away from their SM values. A measurement of the angular coefficient P ´ in the flavour-changing neutral current decay of B mesons was also presented by ATLAS, CMS and Belle, and was found to be compatible with previous LHCb results. In the dedicated heavy-ion session, ALICE showed recent results from large samples of proton–proton, lead–lead, and proton–lead collisions collected in 2015 and 2016. One of the new results, concerning the azimuthal asymmetry of the production of J/ψ mesons, shows that heavy quarks directly “feel” the shape and size of the asymmetric quark–gluon plasma produced in the interaction region. With LHC Run 2 about to get under way with a similar integrated-luminosity target as achieved in 2016, the search for new physics is in full swing at CERN and elsewhere. The 8th High-Energy Physics (HEP) Madagascar International Conference (HEPMAD 2016) was held in Antananarivo, Madagascar, from 13 to 18 October. It was the event’s 15th anniversary and some 50 participants – including 15 invited high-energy physicists from abroad – were present. It is the only conference series in high-energy physics and indeed across all science held in sub-Saharan countries, and aims to be both pedagogical and topical, reviewing the latest experimental and theoretical results in high-energy physics. Recent results from the LHC, including precision tests of the Standard Model, Higgs properties and searches for new physics, were presented by ATLAS and CMS. Theory talks, meanwhile, covered topics including the status of the muon anomalous magnetic moment and determinations of the masses and couplings of charmonium and bottomium states using QCD spectral sum rule. The high-energy physics talks were complemented by national contributions about climate science and sustainable technologies for energy. The next HEPMAD event will take place in Antananarivo on 21–27 September 2017. In the digital era, where we are surrounded by ever more technological innovations, it is interesting to reflect on the enormous progress that modern physics has made following the quantum-mechanics revolution 90 years ago. The story began in 1900, with Max Planck’s suggestion that light is quantised, which Albert Einstein was the first to fully comprehend and exploit. Then, in the mid 1920s, a revolution in physics took place: quantum mechanics was formulated by Werner Heisenberg, Erwin Schrödinger, Paul Dirac and a handful of other young geniuses under the supervision of Niels Bohr and with Einstein as a critical voice. At the famous Fifth Solvay Conference in 1927, where 17 of the participants either already were or were to be Nobel laureates, much of the basic elements of quantum mechanics were ready and discussed. Never in the history of physics has so much been achieved by so few in such a short time. To commemorate the beginning of this revolution and its impact on the modern world, a special conference titled 90 Years of Quantum Mechanics was held at the Institute of Advanced Study at Nanyang University in Singapore on 23–26 January. The event gathered leading experts in the foundations of quantum mechanics, quantum cosmology, quantum gravity, quantum field theory, quantum condensed matter, quantum optics, quantum information and technology, and quantum chemistry. Altogether there were 30 talks, with six speakers being Nobel laureates. Some 300 participants attended from all over the world, with a strong emphasis on South East Asia and China. The Standard Model of particle physics has proved to be a consistent description of natureʼs fundamental constituents and their interactions, and its predictions have been confirmed by numerous experiments, most recently with the discovery of the Higgs boson at the LHC. However, the model fails to explain several phenomena in particle physics, astrophysics and cosmology, and it is expected that yet unknown particles or interactions are needed to explain these puzzles. Our inability to observe new particles possibly lies in their extremely feeble interactions. If true, this would imply that experiments are needed not just at the high-energy frontier but also at the “intensity frontier”, by increasing the number of collisions to search for rare events. In 2016, CERN created a Physics Beyond Colliders study group with a mandate to explore opportunities offered by the CERN accelerator complex to address outstanding questions in particle physics through projects complementary to high-energy colliders (CERN Courier November 2016 p28). A two-week-long “theory institute” took place at CERN from 20 February to 3 March to discuss the theory and phenomenology of possible new physics at low energy scales. More than 100 participants from 21 countries discussed the theoretical landscape, predicting new light particles and “dark forces”. The potential for the new physics reach of existing and planned intensity-frontier experiments – SHiP, NA62, DUNE, MATHUSLA and many others – was discussed. These future experiments are at different stages today, ranging from the preparation of a comprehensive design report (SHiP) to a letter of intent (MATHUSLA). The time is therefore ripe to ensure that any necessary changes to the experiment designs can still be made to the physics reach of intensity-frontier experiments. The annual Compact Linear Collider (CLIC) workshop took place at CERN on 6–10 March, attracting 220 collaborators from 26 countries to discuss the latest status of the CLIC accelerator and detector studies. CLIC is a future multi-TeV electron–positron linear collider at CERN envisaged for the era beyond the High-Luminosity LHC (HL-LHC). First beams in CLIC could be foreseen in 2035 and be the starting point of a 20–25 year-long physics programme. During the workshop particular focus was placed on the recently published updated staging scenario for the CLIC accelerator, where construction and operation are pursued in three stages with collision energies of 0.38, 1.5 and 3 TeV, respectively (CERN Courier November 2016 p20). At its initial energy, CLIC is optimised for Higgs and top measurements and enables a scan at the top-quark pair-production threshold, while the higher-energy stages provide the best sensitivity to new physics through direct and indirect searches. High-energy operation also provides access to rare processes such as double Higgs production, which is sensitive to the important Higgs self-coupling. CLIC week 2017 hosted a variety of sessions with 150 speakers, covering the activities of both the accelerator and detector-and-physics studies. The workshop also included meetings among the CLIC accelerator institutes and the detector-and-physics institutes. In both meetings the focus was on the steps necessary to submit a project-implementation plan in time for the European Strategy update in 2019–2020. Particular priority is given to the studies where cost and power can be reduced, presenting the initial CLIC project and further upgrades as a realistic option that is compatible with the level of resources available at CERN. Another highlight was the summary of the successful demonstration of key CLIC concepts obtained by the recently completed CTF3 test programme at CERN. Part of the CFT3 facility has now been approved for conversion into an electron accelerator facility called CLEAR (CERN Linear Electron Accelerator for Research), providing an open user facility for accelerator R&D, irradiation and training. The future CLEAR programme will include CLIC high-gradient and instrumentation studies. The successful operation of high-gradient accelerating structures and experience with advanced beam-dynamics techniques, developed for the small dimensions of these structures, have inspired a growing number of applications outside of particle physics. Applications of high-gradient and X-band technology include compact linacs and advanced diagnostics for photon sources, as well as medical applications. Many of the technologies under study for the CLIC detector are also of interest to the HL-LHC, where the high granularity and time-resolution needed for CLIC are equally crucial. Other communities also benefit: for example, software reconstruction techniques developed for particle flow at linear colliders have been applied to current and next-generation neutrino experiments. For many years the biennial Russian conference on accelerator physics and technology, RuPAC, was viewed by the international accelerator community as an internal event for representatives of the Soviet accelerator school. Although representatives of the latter have actively been working in accelerator centres around the world since the beginning of perestroika in the late 1980s, it is indeed rare to see a foreign specialist invited to a prominent position in Russia. But that situation is changing, and RuPAC16 held at St Petersburg State University (SPbSU) in November last year saw the worldʼs largest accelerator projects represented and more than 60 reports by participants from outside Russia. For the first time, the event also provided simultaneous translation from Russian to English. Today, RuPAC has become an excellent platform for information exchange between researchers working in accelerator science and technology and related issues. More than 40 reports from SPbSU students were presented at RuPAC16, and the geographical reach of the event extended to 260 participants from 67 institutions in 13 countries. In addition to traditional participants Ukraine, Belarus and Armenia, the event was attended by experts from China, South Africa, UK, Germany, Italy, Canada, US, Japan, Poland, Sweden and Switzerland. CERN’s High-Luminosity LHC and Future Circular Collider projects were presented, and several other reports were devoted to mutual research between Russian and European scientists. A particular focus was the FAIR-NICA collaboration concerning production and testing of superconducting accelerator magnets. Two new facilities have been commissioned at the Joint Institute for Nuclear Research (JINR) in Dubna for the international FAIR and NICA projects in Germany and Russia, respectively. The first is a high-tech assembly and testing hall for superconducting magnets, while the second is a heavy-ion linear accelerator that accelerates ions up to Au31+ to an energy of 3.2 MeV per nucleon. Status reports from all accelerator facilities of JINR were presented, as were activities at other major accelerator centres. The National Research Centre Kurchatov Institute carries out a broad range of activities, among them the development of a synchrotron radiation source and operation of the U-70 facility, Russiaʼs largest accelerator complex, with its new facility for carbon-beam medical applications and plans to attain high-power neutron fluxes. Important work also continues at the Institute for Nuclear Research of the Russian Academy of Sciences and the Budker Institute of Nuclear Physics (BINP). The latter facility has established itself as a manufacturer and supplier of high-tech accelerator facilities to the international market, such as electronic cooling systems, electron accelerators for industrial applications, components and synchrotron systems, magnetic systems and power systems, for example for the European X-FEL. BINP is also actively involved in the construction of FAIR and NICA, while continuing to develop domestic projects including a free electron laser, two electron–positron colliders (VEPP 2000 and VEPP4M) and facilities for radioisotope analysis. The conference concluded with a satellite meeting devoted to NICA, for which most Russian accelerator centres are already involved in manufacturing elements. Backed by the Russian government since 2016, NICA is a major factor driving current trends in the country’s accelerator science and technology. The success of this project will influence government support of other accelerator projects, such as the super C-tau factory project at BINP. Although Russia has a highly developed scientific infrastructure and potential to design complex accelerator facilities, the corresponding market is underestimated. Applied research projects such as medical beams for Russia’s first proton-therapy facility, along with the Russian “mega-science” projects, are thus a vital factor for accelerating Russian industry. As is clear, such projects are reinforcing the international outlook of Russian accelerator science and technology. The next RuPAC event will be held in autumn 2018. Marianne Thyssen, MEP and European commissioner for employment, social affairs, skills and labour mobility, toured CERN on 10 March, during which she visited CMS, ISOLDE and the new MEDICIS facility. She is pictured signing the guestbook with CERN Director-General Fabiola Gianotti. Enrique Cabrero Mandoza, director-general of CONACYT in Mexico, visited CERN on 23 March, immediately following the 9th CERN–Latin American School held in San Juan del Rio. He visited the ALICE experiment and the LHC tunnel before signing the guestbook with CERN’s head of relations with associate members and non-Member States, Emmanuel Tsesmelis, and director of international relations Charlotte Warakaulle. UK minister of state for universities, science, research and innovation Jo Johnson (top) came to CERN on 29 March, during which he visited the underground area at CMS. Two days later, chief scientific adviser to the UK government Mark Walport (bottom) also visited CERN, taking in the computing centre, ATLAS and the Antiproton Decelerator.