Jobs – Page 212 of 527

Inflation and String Theory

By D Baumann and L McAllister Cambridge University Press

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This complete and accessible text, written by two of the leading researchers in the field, provides a modern treatment of inflationary cosmology and its connection to string theory and elementary particle theory.

The past two decades of advances in observational cosmology have brought about a revolution in our understanding of the universe. In particular, deeper studies of the cosmic microwave background have revealed strong evidence for a period of inflationary expansion in the very early universe. At the same time, new developments in string theory have led to a better understanding of inflation in a framework that unifies quantum mechanics and general relativity.

After a brief introduction about observations in favour of the inflationary hypothesis, the volume provides an overview of effective field theory, string theory, and string compactifications. Finally, several classes of models of inflation in string theory are examined in detail.

The background material in geometry and cosmological perturbation theory included in the appendices makes the book self-contained and accessible not only to experienced researchers, but also to graduate students and readers who are new to the field.

Nuclear and Particle Physics

By Claude Amsler
IOP Publishing

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This textbook provides an introductory course on nuclear and particle physics for undergraduate and early graduate students. It originated from a series of lectures given at the Physics Institute of the University of Zurich by the author. The subjects are presented following their historical development. The explanations are experimentally and phenomenologically orientated, and often make use of intuitive arguments. In addition, many concepts and phenomena are derived with inductive rather than deductive thinking.

Originally published in German, this new version in English has been enriched with several modern topics, such as the Higgs boson, updates on neutrinos, the top quark and bottom-quark physics.

Supersymmetric Field Theories: Geometric Structures and Dualities

By Sergio Cecotti
Cambridge University Press

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An unconventional and elegant geometrical approach is adopted in this book to explain supersymmetric field theories, and describe intuitive methods for understanding the logic underlying such concepts. Aimed at graduate students and researchers, the collection of lectures provides an advanced course in supergravity and supersymmetry, which requires knowledge of the basic concepts and fundamental tools of these fields. The author shows how complex results and formulae obtained from the more classical approaches to SUSY can be simplified dramatically when translated to a geometric setting.

Covering a wide range of topics and offering rigorous, in-depth explanations, this text would be an extremely valuable resource for theoretical physicists.

Particle and Astroparticle Physics, Gravitation and Cosmology: Predictions, Observation and New Projects – Proceedings of the XXXth

International Workshop on High Energy Physics
By V Petrov and R Ryutin (eds)
World Scientific

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The most interesting talks delivered at the XXXth International Workshop on High Energy Physics, held in Protvino, Russia, in June 2014, are collected in this volume, along with the minutes of the six panel discussions. As the full title suggests, this conference not only focused on high-energy physics, but addressed a wide range of fundamental issues of modern particle and astroparticle physics, gravitation and cosmology.

The major subjects presented included the discovery and interpretation of the Brout–Englert–Higgs boson at the LHC, heavy-quark physics, quark–gluon plasma studies, diffractive scattering at high energies, neutrino oscillations, and theoretical interpretations of cosmological data on the evolution of the universe.

The panel discussions, in turn, highlighted difficult points in the various domains of modern physics, and identified possible research paths.

General Relativity and Gravitation: A Centennial Perspective

By A Ashtekar et al (eds)
Cambridge University Press

On the occasion of the centennial of Einstein’s discovery of general relativity, the International Society on General Relativity and Gravitation commissioned a team of leading international researchers to write about the advances that have occurred in all of the branches of physics during the last three decades. Through 12 comprehensive chapters, the volume gives an overview of key topics in relativistic astrophysics, cosmology and gravitational-wave theories, as well as mathematics and computational science. The book in intended both for beginners, who could use it as an introduction to the entire field, and for more advanced researchers, especially if they are interested in subjects that are outside of their field of expertise. Organised in four parts, each of about five chapters, the book guides the reader on a journey from the triumph of Einstein’s theory of relativity through the phenomenon of gravitational waves, to quantum gravity.

QCD and Heavy Quarks: In Memoriam Nikolai Uraltsev

By I I Bigi, P Gambino and T Mannel (eds)
World Scientific

The book collects together articles on QCD and heavy-quark physics written in memory of Nikolai Uraltsev, who passed away unexpectedly in February 2013. Uraltsev was an excellent theorist with acute intuition, who dedicated his career to the study of phenomenological particle physics, in particular quantum chromodynamics and its non-perturbative properties. He is also considered one of the fathers of heavy-quark expansion. By writing this book, Uraltsev’s closest colleagues and friends intended to honour his groundbreaking work, as well as give testimonies of their personal relationships with him.

The text gives an overview of some aspects of QCD, including CP violation in hadronic processes and hadronic matrix elements in weak decays. Three selected works by Uraltsev are also reproduced in the appendix.

Quantum Field Theory and the Standard Model

By Matthew D Schwartz
Cambridge University Press
Also available at the CERN bookshop

Providing a comprehensive and modern introduction to quantum field theory, this textbook covers the development of particle physics from its foundations to the recent discovery of the Brout–Englert–Higgs boson. Based on a course taught by the author at Harvard University for many years, the text starts from the principle that quantum field theory (QFT) is primarily a theory of physics and, as such, it provides a set of tools for performing practical calculations. The book develops field theory, quantum electrodynamics, renormalisation and the Standard Model, including modern approaches and state-of-the-art calculation techniques.

With a combination of intuitive explanations of abstract concepts, experimental data and mathematical rigour, the author makes the subject accessible to students with different backgrounds and interests.

Gaseous Radiation Detectors: Fundamentals and Applications (Cambridge Monographs on Particle Physics, Nuclear Physics and Cosmology)

By Fabio Sauli
Cambridge University Press
Also available at the CERN bookshop

In the last few decades, fast revolutionary developments have taken place in the field of gaseous detectors. At the start of the 1970s, multiwire proportional chambers were invented. These detectors and their descendants (drift chambers, time-projection chambers, ring-imaging Cherenkov detectors, etc) rapidly replaced cloud and bubble chambers, as well as spark counters, in many high-energy physics experiments. At the end of the last century, resistive-plate chambers and micropattern detectors were introduced, which opened up new avenues in applications.

Ironically, for a long time, no books had been published on gaseous detectors and their fast evolution. For this reason, in spite of thousands of scientific publications covering the rapid and exciting developments in the field of gaseous detectors, no simple and analytical description has been made available for a wide audience of non-professionals, including, for example, students.

Suddenly “an explosion” took place: several books dedicated to modern gaseous detectors and their applications appeared on the market, almost all at the same time.

Sauli’s book is certainly one of the best of these. The author, a leading figure in the field, has succeeded in writing a remarkable and charming book, which I strongly recommend to anyone interested in learning about recent progress, open questions and future perspectives of gaseous detectors. Throughout its 490 pages, it offers a broad coverage of the subject.

The first five chapters focus on fundamentals: the interaction of charged particles and photons with matter, the drift and diffusion of electrons and ions, and avalanche multiplications. This first part of the book offers a refreshing mix of basic facts and up-to-date research, but avoids giving too much space to formulas and complicated mathematics, so non-specialists can also gain from the reading.

The remaining eight chapters are dedicated to specific detectors, from single-wire proportional counters to state-of-the-art micro-pattern gaseous detectors. This latter part of the book gives exhaustive detail and describes the design and operational features, including signal development, time and position resolutions, and other important characteristics. The last chapter deals with degeneracy and ageing – serious problems that detectors can experience if the gas composition and construction materials are not chosen carefully.

This fascinating book is easy to read, so it is suitable for everyone, and in particular, I believe, for young people. I was especially impressed by the care with which the author prepared many figures, which in some cases include details that I have not seen in previous texts of this kind. The high-quality figures and photographs contribute significantly to making this book well worth reading. In my opinion, it is not only remarkably complementary to other recently published monographs, but it can also serve as a main textbook for those who are new to the field.

The only omission I have observed in this otherwise wide-ranging and well-researched book, is the lack of discussion on secondary processes and ion back flows, which are very important in the operation of some modern photosensitive detectors, including, for example, ALICE and COMPASS ring-imaging detectors.

There could be a few other improvements in a future edition. For instance, it would be useful to expand the description of the growing applications of gaseous detectors, especially resistive-plate chambers and micropattern detectors.

All in all, this is a highly recommendable book, which provides an interesting guided tour from the past to present day of gaseous detectors and the physics behind their operation.

High Luminosity LHC moves forward

New technologies for the high-luminosity LHC.
Image credit: CERN.

October 2015 was a turning point for the High Luminosity LHC (HL-LHC) project, marking the end of the European-funded HiLumi LHC Design Study activities, and the transition to the construction phase, which is also reflected in the redesigned logo that was recently presented.

Artistic shot of the light show that celebrated the HiLumi LHC milestone and the International Year of Light.
Image credit: Mike Struik, CERN.

So far, the LHC has only delivered 10% of the total planned number of collisions. To extend its discovery potential even further, the LHC will go through the HL-LHC major upgrade around 2025, which will increase the luminosity by a factor of 10 beyond the original design value (from 300 to 3000 fb^–1). The HL-LHC machine will provide more accurate measurements and will enable the scientific community to study new phenomena discovered by the LHC, as well as new rare processes. The HiLumi upgrade programme relies on a number of key innovative technologies, such as cutting-edge 12 Tesla superconducting magnets, very compact and ultra-precise superconducting cavities for beam rotation, and 100 m-long high-power superconducting links with zero energy dissipation. In addition, the higher luminosities will make new demands on vacuum, cryogenics and machine protection, and will require new concepts for collimation and beam diagnostics, advanced modelling for the intense beam and novel schemes of beam crossing to maximise the physics output of these collisions.

From design to construction

The green light for the beginning of this new HL-LHC phase, marked by main hardware prototyping and industrialisation, was given with the approval of the first version of the Technical Design Report – the document that describes in detail how the LHC upgrade programme will be carried out. This happened at the 5th Joint HiLumi LHC-LARP Annual Meeting, which took place at CERN from 26 to 30 October and saw the participation of more than 200 experts from all over the world to discuss the results and achievements of the HiLumi LHC Design Study. In the final stage of the more than four-year-long design phase, an international board of independent experts worked on an in-depth cost-and-schedule review. As a result, the total cost of the project – amounting to CHF 950 million – will be included in the CERN budget until 2026.

In addition to the project management work-package (WP), a total of 17 WPs involving more than 200 researchers and engineers addressed the technological and technical challenges related to the upgrade. During the 48 months of the HiLumi Design Study, the accelerator-physics and performance team defined the parameter sets and machine optics that would allow HiLumi LHC to reach the very ambitious performance target of an integrated luminosity of 250 fb^–1 per year. The study of the beam–beam effects confirmed the feasibility of the nominal scenario based on the baseline β* levelling mechanism, providing sufficient operational margin for operation with the new ATS (Achromatic Telescopic Scheme) at the nominal levelling luminosity of 5 × 10³⁴ cm^–2s^–1, with the possibility to reach up to 50% more. The magnet design activity, focusing on the design of the insertion magnets, launched the hardware fabrication of short models of the Nb₃Sn quadrupoles’ triplet (QXF), separation dipole, two-in-one large aperture quadrupole and 11 T dipole for Dispersion Suppressor collimators. Single short coils in the mirror configuration have already been successfully tested for the triplet. The first model of the QXF triplet containing two CERN and two LARP coils was assembled in the US in the summer, and is being tested this autumn, while a short model of the 11 T dipole fabricated at CERN reached 12 T. To protect the magnets from the higher beam currents, the collimation team focused on the design and verification of the new generation of collimators. The team presented a complete technical solution for the collimation in and around the insertions in HL-LHC, providing improved flexibility against optics changes. The crab-cavities activity finalised and launched the manufacturing of the crab-cavity interfaces, including the helium vessels and the cryo-module assembly. All cavity parts stamped in the US will be assembled and surface processed in the US, in addition to electron-beam welding and testing. Last but not least, as part of their efforts to develop a superconducting transmission line, the cold powering activity hit a world-record current of 20 kA at 24 K in a 40 m-long MgB₂ electrical transmission line. The team has finalised the development and launched the procurement of the first MgB₂ PIT round wires. This is an important achievement that will enable the start of large cabling activity in industry, as required for the production of a prototype cold-powering system for the HL-LHC.

In addition to the technological challenges, the HL-LHC project has also seen an important expansion of the civil-engineering and technical infrastructure at P1 (ATLAS) and P5 (CMS), with new tunnels and underground halls needed to house the new cryogenic equipment, the electrical power supply and various plants for electricity, cooling and ventilation.

A winning combination

Such an extensive technical, technological and civil endeavour would not be possible without collaboration with industry. To address the specific technical and procurement challenges, the HL-LHC project is working in close collaboration with leading companies in the field of superconductivity, cryogenics, electrical power engineering and high-precision mechanics. To enhance the co-operation with industry on the production of key technologies that are not yet considered by commercial partners due to their novelty and low production demand, the newly launched QUACO project, recently funded by the EU, is bringing together several research infrastructures with similar technical requirements in magnet development to act as a single buyer group.

A new record for the RMC test magnet at CERN

The RMC_03 racetrack test magnet.
Image credit: CERN.

High magnetic fields are the Holy Grail of high-energy accelerators. The strength of the dipole field determines the maximum energy the beam can achieve on a given orbit, and large-aperture, high-gradient quadrupoles, with high peak field, govern the beam collimation at the interaction points. This is why, this September, members of the CERN Magnet Group in the Technology Department had big grins on their faces when the RMC racetrack test magnet attained a peak field of 16.2 T, twice the nominal field of the LHC dipoles, and the highest field ever reached in this configuration.

This result was achieved thanks to a different superconductor –the intermetallic and brittle compound Nb₃Sn – used for the coils and the new “bladder-and-keys” technology developed at LBNL to withstand the extremely powerful electromagnetic forces.

The beginning of this success story dates back more than 10 years, when experts started to realise that Nb–Ti alloy, the workhorse of the LHC (and of all superconducting accelerators until then), and the conventional collar structure enclosing the superconducting coils in a locked, laminated assembly, would soon run out of steam. A technological quantum leap was needed.

Seeds sown

The first seeds of a European programme were sown in 2004, when a group of seven European laboratories and universities (CCLRC RAL, CEA, CERN, CIEMAT, INFN, Twente University and Wrocŀław University), under the co-ordination of CEA Saclay, decided to join forces to develop the technologies for the next-generation high-field magnets. Initially conceived to develop a 15 T dipole with a bore of 88 mm, the NED JRA EU-funded programme subsequently became an R&D programme to develop a new conductor. Its main result was an industrial Nb₃Sn powder-in-tube (PIT) conductor with high current densities, designed to reach fields up to 15 T.

Three of the NED JRA partners – CEA, CERN and RAL – saw the importance of exploiting the new technology and continued the R&D beyond the NED JRA programme. Inspired by programmes at neighbouring laboratories, in particular LBNL, they started to develop a sub-scale model magnet with racetrack coils: the short model coil (SMC). This intermediate step led the partners to learn the basic principles of Nb₃Sn coil construction. In fact, the SMC became a fast-turnaround test-bed for medium-sized cables, and is still in use at CERN. In 2011, the second SMC assembly successfully achieved 12.5 T. In a subsequent SMC assembly in 2012, the field went up to 13.5 T. With these results, CERN and its European partners demonstrated that they were on track to master Nb₃Sn magnet technology.

Towards high fields

Since 2009, CERN and CEA have continued work on the technology, initially under the FP7-EuCARD project activities, and today within the scope of the CEA/CERN magnet collaboration. The focus of the FP7-Eucard high-field magnet (HFM) work package became the construction of a 13 T dipole magnet with a 100 mm aperture, which will be used to upgrade the FRESCA facility at CERN: FRESCA2. To achieve the 13 T objective, the CERN-CEA team designed the magnet for a field of 15 T using the state-of-the-art Nb₃Sn technology: a 1 mm wire supplied by the only two manufacturers in the world capable of meeting the critical current specification, one in Germany (powder-in-tube, or PIT wire) and one in the US (rod restack process, or RRP wire). The cable for FRESCA2, was designed to have 40 strands and to carry nearly 20 kA at 1.9 K for a magnetic field of 16 T. This is an impressive set of values compared with the LHC, where the dipole cables can carry 13 kA at 1.9 K for a magnetic field of 9 T.

Samples of the two cables used to wind the RMC_03 coils.
Image credit: CERN.

In spite of the engineering margins in the design, FRESCA2 proved to be a challenging goal. CERN therefore decided to design and construct an intermediate step, consisting of two racetrack, flat coils and no bore, made with the same 40 strand cable and fabrication procedures as for FRESCA2. This magnet was named the “racetrack model coil” (RMC).

Two initial assembly configurations were built using either RRP and PIT cables, and then a third one – called RMC_03 – was trained up to a maximum current of 18.5 kA at a temperature of 1.9 K. Based on the calculation of the field, this current corresponds to peak fields of 16 T in the coil wound with PIT cable and 16.2 T in the coil wound with RRP cable. With this result – a new record in this configuration – CERN has reached LBNL in the domain of high dipole fields.

Nb₃Sn will be used to build the IR QXF quadrupoles and the 11 T dispersion suppressor dipoles for the high-luminosity upgrade of the LHC (CERN Courier January/February 2013 p28). The RMC record paves the way for a promising demonstration of this technique for future developments. In particular, cables of the same type as for FRESCA2 are also being considered for the Future Circular Collider (FCC) studies (CERN Courier April 2014 p16).

A lot of hard work remains before CERN and its collaborating partners will be able to achieve a 16 T field inside a beam aperture with the required field quality for an accelerator, so the development work on FRESCA2 continues. The coils are under construction and a test station is being built in SM18 to host the giant magnet, which should be ready for testing by next summer.

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From design to construction

A winning combination

Seeds sown

Towards high fields