Praxis Archives – Page 88 of 181

Allegro Neutrino ou L’attrape-temps

De François Vannucci
L’Harmattan
Broché: €27

Paris, dans les années 1950. Michel a 11 ans et voit des bulles, ce dont il est très fier. Terme résolument non scientifique, le mot ” bulle ” désigne pour le narrateur – Michel – ” une myriade de points lumineux dansant dans tous les sens “, points lumineux qui se révèleront être, au fil des pages, des ” neutrinos “. Nous y voilà.

Vous l’aurez compris, bien qu’écrit par un physicien des particules spécialisé en physique des neutrinos, ce livre est un roman. L’objectif n’étant pas de vous en apprendre des kilomètres sur ces fameux neutrinos, mais de vous embarquer dans une histoire dont ils sont les protagonistes. Et si l’histoire est contée par un jeune narrateur passionné de physique, il n’en reste pas moins qu’il s’agit d’un enfant, et non pas (encore) d’un physicien des particules.

L’intrigue, si je puis donner à l’histoire cette connotation très romanesque, est somme toute assez simple. Michel, écolier plutôt mauvais en maths mais bon en imagination, vit dans un minuscule appartement parisien avec ses parents. Il va à l’école à pied, troue ses chaussettes, accompagne sa mère au marché le jeudi et à la messe le dimanche, passe ses vacances d’été à la campagne, collectionne les timbres, adore les truffes au chocolat, et se délecte des histoires de science de son oncle Albert, fonctionnaire tire-au-flanc et lecteur assidu de magazines de vulgarisation scientifique. Mais ce qui anime surtout Michel, moins son histoire, c’est cette étrange capacité à voir des neutrinos.

Mais ne vous méprenez pas, les neutrinos de Michel sont loin de coller à l’idée que l’on s’en fait au CERN. Pour Michel, ce ne sont en effet ni plus ni moins que les constituants de l’âme des êtres vivants, ou, comme les décrit encore le narrateur, ” notre carburant spirituel “. Ce qui explique d’ailleurs que les jeunes en émettent plus que les vieux, et que ceux qui n’en émettent plus sont morts. CQFD.

Au final, ce livre est un long voyage dans la tête d’un gamin de 11 ans, à la rencontre de ses idées farfelues, de ses expérimentations et déductions scientifiques, de ses découvertes triomphantes et de ses confrontations au monde des adultes. Certains passages sont franchement réjouissants, et l’on finit par se prendre d’affection pour le jeune Michel, qui garde précieusement au fond de sa poche, un marron, une bille et une boîte pleine de neutrinos.

Reviews of Accelerator Science and Technology: Volume 5 – Applications of Superconducting Technology to Accelerators

By Alexander W Chao and Weiren Chou (eds.)
World Scientific
Hardback: £98
E-book: £74

Reviews of Accelerator Science and Technology is a journal series that began in 2008 with the stated aim “to provide readers with a comprehensive review of the driving and fascinating field of accelerator science and technology” – in a “journal of the highest quality”. It made an excellent start, with the first volume presenting the history of accelerators, followed by one that focused on medical applications. With one volume published a year, there are now five in the series, which appears to show no signs of failing in its original goals. Each has communicated a specific topic through the words of highly respected experts in articles that are well illustrated and presented. The books they form hold the promise of becoming an unrivalled encyclopaedia of accelerators.

This latest volume is no exception. It looks at the role of superconductivity in particle accelerators and how this intriguing phenomenon has been harnessed in the pursuit of ever-increasing beam energy or intensity. It also considers the application of superconducting technology beyond the realm of accelerators, for example in medical scanners and fusion devices. As well as containing much technical detail it is also full of fascinating facts.

Exactly 100 years ago, Heike Kamerlingh Onnes speculated that a 10 T superconducting magnet “ought not to be far away”. The first contributions to this volume, in particular, outline some of the steps to 10 T – and why it took longer than Onnes had originally hoped for the industrial-scale production of high-field superconducting magnets to become reality. A major problem lay in finding superconducting materials with physical properties that allow large-scale fabrication into wires. The first commercially produced wires were of niobium-zirconium, as used in early superconducting magnets for bubble chambers. However, this alloy was soon superceded by niobium-titanium (NbTi) – the material of choice in high-energy physics for the past 40 years, culminating today in the superconducting magnets for the LHC, as well as the huge toroidal and solenoidal magnets for the ATLAS and CMS detectors. Now, R&D effort is turning to Nb₃Sn, which can allow higher magnetic fields, for example for the High Luminosity LHC project.

In this context, it is worth realizing that the biggest market for superconducting magnets is for nuclear magnetic-resonance spectroscopy – and it is here that a field as high as 23.5 T has been reached in a magnet based on Nb₃Sn. There is also interest in high magnetic fields for magnetic resonance imaging (MRI) in medicine. In MRI the signal strength is related to the polarization of the protons in whatever is being scanned. Increasing the magnetic field from the 1.5 T that is currently used routinely to 10 T results in a polarization that is almost seven times higher, as well as improved signal-to-noise, leading to a clear improvement in image quality. Upcoming developments include 6 T magnets based on Nb₃Sn.

The application of superconductivity in particle accelerators extends of course to the acceleration system, with the use of superconducting RF technology, first proposed in 1961. In this case, an important part of the R&D has focused on the physics and materials science of the surface – the surface resistance being a key parameter. So far there are no commercial applications for superconducting RF, but it has a role in many types of particle accelerators, from high-current storage rings at light sources to the high-energy machines of the future, such as the International Linear Collider (ILC).

Jefferson Lab’s Continuous Electron-Beam Accelerator Facility (CEBAF) is in a sense the “LHC” of superconducting RF, employing originally 360 five-cell 1.5 GHz cavities. It is currently undergoing an upgrade to 12 GeV with cavities that will operate at 19.2 MV/m. The European X-ray free-electron laser project, XFEL at DESY, will use 800 nine-cell 1.3 GHz cavities operating at more than 22 MV/m, but it would be dwarfed by an ILC with more than 15,000 cavities.

Besides the contributions on the major topics of superconducting magnets and RF, others are dedicated to cryogenic technology, industrialization and applications in medicine. In addition, following the journal’s tradition, there are articles that are not related to the overall theme but are of concern to the accelerator community worldwide. In this case, one article discusses the education and training of the next generation of accelerator physicists and engineers, while another reviews the history of the KEK laboratory in Japan. Altogether, this makes for more than a journal volume – in my opinion, it is a book, well worth reading.

Doing Physics: How Physicists Take Hold of the World (2nd edition)

By Martin H Krieger
Indiana University Press
Paperback: £16.99 $24.00
E-book: £14.99 $21.99

First published over two decades ago, Doing Physics has recently been released as a second edition. The book relates the concepts of physics to everyday experiences through a carefully selected series of analogies. It attempts to provide a non-scientific description of the methods employed by physicists to do their work, what motivates them and how they make sense of the world.

Martin Krieger began his academic career in experimental particle physics but quickly realised that he was not suited to working in large groups on experiments. Following his PhD, he moved into the social sciences and began working on computing models for city planning. He uses this experience to reflect on the way science is done from a social science viewpoint. His aim is to explain how doing physics is part of familiar general culture.

Krieger claims that physicists employ a small number of everyday notions to “get a handle on the world” experimentally and conceptually. He argues further that these models and metaphors describe the way physicists actually view the world and that to see the world in such terms is to be trained as a physicist. The analogies he chooses to support his ideas are drawn from the diverse areas of economics, computing, anthropology, theatre and engineering. Each of the first five chapters of the book is devoted to exploring each of the analogies in detail.

The book begins with a discussion on division of labour according to the economist Adam Smith’s model of a pin factory. The description of physical situations in terms of interdependent particles and fields is analogous to the design of a factory with its division of labour among specialists. The second chapter considers physical degrees of freedom as the parts of a complex model such as a clockwork mechanism or a computer. Chapter three is devoted to the anthropological theory of kinship and marriage, comparing the rules of relationships to the rules of interaction for the families of elementary particles or for chemical species – who can marry whom is like what can interact with what. The conclusion is that anything that is not forbidden will happen. The theatrical world provides an analogy to creation, where a vacuum is represented by a simple stage setting on which something arises out of nothing. Finally, machine-tool design is used to describe the physicist’s toolkit, where the work of doing physics is like grasping the world with handles and probes.

In the second edition, Krieger has provided some minor revisions to the text and has added a brief chapter on the role of mathematics and formal models in physics. This additional discussion is based on work from two other books he has written in the intervening years. It is questionable whether the second edition is warranted. In this highly technical chapter Krieger goes so far as to discern an analogy of analogies in physics and mathematics – a so-called syzygy.

Krieger claims that the book is for high-school students and upwards. However, it seems more appropriate for a specialized audience. Doing Physics is aimed at sociologists and philosophers of science, rather than at the science community itself. Indeed, for some the experience of reading the book could bring to mind a well known quote by Richard Feynman: “Philosophy of science is about as useful to scientists as ornithology is to birds.” For others, however, the book might provide some useful insights into patterns or relationships between physics and the everyday world that they have not previously considered.

Breaking news: The 2013 Nobel Prize in Physics

François Englert, left, and Peter W Higgs have been awarded the 2013 Nobel Prize in Physics “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN’s Large Hadron Collider”. The announcement by the ATLAS and CMS collaborations took place at CERN on 4 July last year.

LBNE gains new partners from Brazil, Italy and UK

In mid-September, the Long Baseline Neutrino Experiment (LBNE) collaboration, based at Fermilab, welcomed the participation of 16 additional institutions from Brazil, Italy and the UK. The new members represent a significant increase in overall membership of more than 30% compared with a year ago. Now, more than 450 scientists and engineers from more than 75 institutions participate in the LBNE science collaboration. They come from universities and national laboratories in the US, India and Japan, as well as Brazil, Italy and the UK.

The swelling numbers strengthen the case to pursue an LBNE design that will maximize its scientific impact. In mid-2012, an external review panel recommended phasing LBNE to meet the budget constraints of the US Department of Energy (DOE). In December the project received the DOE’s Critical Decision 1 (CD-1) approval on its phase 1 design, which excluded both the near detector and an underground location for the far detector. However, the CD-1 approval explicitly allows for an increase in design scope if new partners are able to contribute additional resources. Under this scenario, goals for a new, expanded LBNE phase 1 bring back these excluded design elements, which are crucial to execute a robust and far-reaching neutrino, nucleon-decay and astroparticle-physics programme.

Our universe was yours

The open-days’ poster welcomed the public to the CERN sites with the phrase “Our Universe is Yours”.

CERN Open Days 2013 saw 70,000 people visit more than 40 activities on the surface across CERN’s Meyrin and Prévessin sites, with 20,000 of them able to see something of the accelerators and detectors underground. Highlights for visitors included seeing one of the large experiments on the LHC – ALICE, ATLAS, CMS or LHCb – or operating robotic arms and forklift trucks, or even making superconducting magnets levitate. A taskforce of 2300 volunteers acted as guides and helpers, explaining the variety of activities at CERN – from particle physics and computing to logistics and firefighting – to enthusiasts young and old.

Rolf Heuer at Point 6 — The LHC was a key theme for the open days. Here, visitors to Point 6 are lucky enough to have CERN’s director-general explain its workings.

As well as the public open days on Saturday and Sunday, events before and after made this a weekend to remember. On Friday 27 September, CERN welcomed local officials and industrial contacts from throughout its member states for exclusive tours of the laboratory. In the evening – and to celebrate European Researchers’ Night – CERN and the Istituto Nazionale di Astrofisica organized “Origins 2013”, an event that included simultaneous activities at CERN, Paris and Bologna, with participation from UNESCO, ESA, ESO and INFN. During a webcasted event in the Globe of Science and Innovation at CERN, those onstage took questions both from the audience and online.

In the “Fun zone!” children played with science, technologies, robots and more, including constructing a miniature LHC.

There was also a flurry of activity on social media. Online events began with a CERN tweetup on Friday, when 12 lucky people visited CERN as citizen journalists to share their exclusive preview of the open days with the world via Twitter.

Picture yourself. A visitor to the ALICE cavern captures herself and the experiment on camera.

Lastly, on the following Monday, the whirlwind of events culminated with “Bosons and More” – a celebration for CERN people.

ATLAS experimental cavern — Holders of underground visit tickets were able to descend around 100 m to see the different experimental caverns, including that of ATLAS, shown here.

• Max Brice, the CERN photographer, led a team of 26 photographers recording the open-days’ events, with Anna Pantelia, Fons Rademakers, Laurent Egli, Mike Struick, Didier Steyaert, Mathieu Augustin, Pierre Gildemyn, Matthias Schroder, Dmytro Kovalskyi, Lelia Laureyssens, Sylvain Chapeland, Jan Fiete Grosse-Oetringhaus, Antonella Vitale, Jean-Francois Marchand, Neli Ivanova, Olga Driga, Doris Chromek-Burckhart, Sebastian Lopienski, Tomek photographe, Nicolas Voumard, Erwin van Hove, Stephan Russenschuck, Ilknur Colak, Laura Rossi and Alban Sublet. A selection of photographs is shown here, for many more, see http://cds.cern.ch/collection/Open Days 2013 Photos.

Transport and handling activities provided the opportunity to try out CERN’s heavy-lifting equipment, including getting behind the wheel to move a model magnet.

The Synchrocyclotron, now a visitor point, was CERN’s first accelerator, commissioned in 1957 and in operation until 1990.

Visitors, next to the ATLAS mural, on their way to the experiment cavern.

A CERN volunteer demonstrates levitation with superconducting magnets cooled with liquid nitrogen.

A visitor takes a photo of the LHC tunnel with his smartphone.

The fire service — Thanks to the fire service – who were also on call – visitors could find out what it takes to be a firefighter.

A 360° image of the LHCb experiment underground cavern.

Higgs. Le boson manquant

Par Sean Carroll
Belin
Broché: €22

Translated by Bertrand Nicquevert, a research engineer at CERN, this French edition also contains a preface by Lyn Evans, former LHC project leader, and a postface written by the translator together with ATLAS physicist Pauline Gagnon, Indiana University. For a review of the English edition see CERN Courier July/August 2013 p52.

Le boson et le chapeau mexicain – Un nouveau grand récit de l’Univers

Par Gilles Cohen-Tannoudji et Michel Spiro. Postface de Michel Serres.
Gallimard
Broché: €9.90
Format numérique: €9.40

Gilles Cohen-Tannoudji et Michel Spiro revisitent plusieurs siècles de physique, en s’attardant bien sûr sur le XX^e, qui a vu les révolutions de la théorie de la relativité et de la mécanique quantique. Si la partie consacrée au passage de la mécanique quantique à la théorie quantique des champs n’est pas de lecture vraiment aisée pour le non-spécialiste, celui-ci peut vite retrouver le rythme grâce à l’introduction des diagrammes et amplitudes de Feynman, qui sont une mise en musique de la théorie dynamique des interactions fondamentales. Le Modèle standard est évoqué rapidement, ainsi que les théories de jauge. La nécessité de mécanisme de BEH (pour Brout, Englert et Higgs) est alors introduite avec l’émergence des masses. Il faut noter que jamais les auteurs ne se laissent aller au raccourci facile de l’expression ” boson de Higgs ” ni ne parlent de ” particule de Dieu ” : tout au long de l’ouvrage, le boson est nommé, à juste titre, ” BEH “.

Le non-physicien devra s’armer de courage pour parcourir le chapitre sur la chromodynamique quantique mais en sera récompensé en découvrant l’explication de l’énigmatique titre du livre, qui associe le boson et le chapeau mexicain.

L’histoire du CERN, de sa compétition avec les laboratoires à accélérateurs d’outre-Atlantique et de ses succès, tient une grande place dans ce livre. Les auteurs n’hésitent pas à développer les aspects techniques de l’aventure. Le plaisir que j’ai eu à lire ce livre a été d’autant plus grand que j’ai eu le privilège d’interagir avec Michel Spiro durant son mandat de président du Conseil du CERN. Il m’appelait souvent tôt le matin afin d’avoir des nouvelles de la santé du LHC et voulait savoir pourquoi on ne poussait pas plus rapidement les performances de cette fantastique machine à découvertes. C’est dire l’importance qu’il attache à la découverte du boson BEH, annoncée le 4 juillet 2012 au CERN : consécration d’une longue traque mondiale qui n’a pu être obtenue que grâce à la conception, à la construction et à la mise en service de l’accélérateur LHC.

Les aspects politiques du CERN ne sont pas oubliés : ils sont décrits comme des ingrédients essentiels du succès de l’organisation, et cette description est magistralement développée dans la postface de Michel Serres, ode au CERN et à son mode de gouvernance, o¥ le philosophe défend l’idée que le modèle fonctionne si bien qu’il devrait être reproduit dans d’autres domaines des sciences. Cette postface remarquable de clarté et de richesse aurait pu être mieux valorisée – si le texte avait servi de préface, il aurait permis au lecteur de mesurer encore mieux le rôle du CERN dans la découverte du boson.

Ce livre, que les auteurs ont voulu à moins de 10 €, est écrit dans la langue de Louis de Broglie et François de Rose, pères fondateurs du CERN. Il décrit avec précision et passion la quête du boson BEH qui ouvre les portes la physique au-delà du Modèle standard. Ne boudons pas cette chance de pouvoir lire un tel ouvrage en français !

Il précise que l’aventure n’est pas terminée. Le boson BEH n’est qu’une étape et de nombreuses questions demeurent : le Modèle standard ne décrit que 4% de la matière de l’Univers. Comme le mentionnent les auteurs, il faut dès maintenant semer les graines des prochaines technologies des accélérateurs et des détecteurs afin d’être en mesure de construire les machines post-LHC. En fonction des résultats du LHC quand il fonctionnera à une énergie de 13–14 TeV après le long arrêt technique de 2013–2014, il faudra financer et construire un accélérateur capable d’atteindre des énergies proches de 100 TeV.

Gauge Theories in Particle Physics: A Practical Introduction, Fourth Edition – 2 Volume Set

By Ian J R Aitchison and Anthony J G Hey
CRC Press
Hardback: £82

The fourth edition of this well-established, highly regarded two-volume set continues to provide a fundamental introduction to advanced particle physics while incorporating new experimental results, especially in the areas of CP violation and neutrino oscillations. It offers an accessible and practical introduction to the three gauge theories included in the Standard Model of particle physics: QED, QCD and the Glashow-Salam-Weinberg (GSW) electroweak theory.

In the first volume, a new chapter on Lorentz transformations and discrete symmetries presents a simple treatment of Lorentz transformations of Dirac spinors. Along with updating experimental results, this edition also introduces Majorana fermions at an early stage, making the material suitable for a first course in relativistic quantum mechanics.

Covering much of the experimental progress made in the past 10 years, the second volume remains focused on QCD and the GSW electroweak theory – the two non-Abelian quantum gauge field theories of the Standard Model – and includes a new chapter on CP violation and oscillation phenomena. This new edition also discusses the exciting discovery of a boson with properties consistent with those of the Standard Model Higgs boson. It also updates many other topics, including jet algorithms, lattice QCD, effective Lagrangians, and three-generation quark mixing and the Cabibbo-Kobayashi-Maskawa matrix.

ILC candidate site in Japan announced

The ILC site evaluation committee of Japan has announced the result of the assessment of the two candidate sites for an International Linear Collider (ILC). In a press conference held at the University of Tokyo on 23 August, the committee recommended the Kitakami mountains in the Iwate and Miyagi prefectures as the preferred location.

The search for an appropriate candidate site for the construction of an ILC in Japan has been ongoing since 1999, with more than 10 candidates announced in 2003. In 2010, the list was further reduced to two, consisting of Kitakami in the north-east of the main island of Japan and Sefuri in Kyushu, on Japan’s south-west island. The process to assess these two remaining candidates to narrow them down from a scientific point of view began in January this year.

A site-evaluation committee of eight members was formed within Japan. In addition, two sub-committees of 16 technical experts and 12 socio-environmental experts were created separately to provide expertise on issues such as geological conditions, environmental impact, possible problems during construction and the social infrastructure of each candidate site.

After more than 300 hours of meetings, the site-evaluation committee made a tentative choice in early July. This choice was then submitted and reviewed by an international review committee. The committee recognized that the process to choose the site had been conducted with great care and that the selected site has excellent geological conditions for tunnelling and stability.

• For more information, see the Japanese ILC Strategy Council website http://ilc-str.jp/.

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