by B G Sidharth, World Scientific. Hardback ISBN 9789812812346, £29 ($58).
This text examines developments that are leading to a paradigm shift and a new horizon for physics, at a time when the underlying principle of reductionism is being questioned. Presenting the new paradigm in fuzzy space–time, it is based on some 100 published journal papers and two recent books. This work has predicted correctly epoch-turning observations, for example, that the universe is accelerating with a small cosmological constant driven by dark energy – when the prevalent line of thinking was the exact opposite. Regarding a unified description of gravitation and electromagnetism via fluctuations, several other highlighted features presented are in complete agreement with experiments.
by Georges Charpak, Odile Jacob. Paperback ISBN 9782738121844, €23.
Eighty-five years and at least three lives’ worth of living unfold in the three sections of these memoirs by Georges Charpak with the contributions from François Vannucci, Roland Omnès and Richard L Garwin.
Uprooted as a child from his native town on the Polish–Ukrainian border during the anti-Semite persecutions of the Russian civil war, he narrates the tribulations of a central-European immigrant in the first part of the book, entitled “Déraciné” (Uprooted). This is the account of his incredible early destiny, from his arrival in France at the age of seven, through his brilliant secondary studies in Paris to his engagement in the struggle against Fascism and subsequent imprisonment, and finally his survival of deportation to Dachau.
Charpak’s career as a physicist “started at age 24 and was more complex than that of most young French scientists”. This sets off the second part “Physicien”, which is entirely devoted to physics and – through the account of his career – a golden age of physics. After liberation, he first joined the Ecole des Mines (“not the right choice,” he says on p24) before finally moving to the laboratory of Frédéric Joliot Curie at the Collège de France, where he specialized in particle detection. A detailed account follows of all the steps in the invention of the multiwire chamber, from Curie’s lab through Charpak’s career at CERN to applications in medicine. This is all complete with images, anecdotes and original documents. “One of the ambitions of the book,” Charpak writes on the back cover, “is to show the extraordinary construction of particle physics in the space of one century”. For this reason he asked Vannucci to write an in-depth but accessible explanation of the meaning of the Standard Model, which is included in this section.
Another objective of the book is to “throw light on the imminent threat to all the treasures accumulated by civilizations over thousands of years, if we do not change radically the way that mankind manages its material and spiritual richness, its creativity and the education we give to children”. The last part, “Citoyen du monde” (Citizen of the world), written with Richard Garwin, details another chapter of Charpak’s life, devoted to the teaching of science to the young and towards the cause of total nuclear disarmament – “le danger toujours plus pressant … non seulement pour la paix mais pour la survie même de l’humanité” (the most pressing danger, not only for peace but for the survival of mankind).
Personal anecdotes provide another enjoyable feature of the book. As Charpak says, he “did not hesitate to describe … his short-term dreams”, such as his research on fossil sound in ancient objects and his attempts to sell a comedy scenario inspired by Dr Strangelove to Hollywood.
by Leonard Susskind, Little Brown and Company. Hardback ISBN 9780316016407, $27.99.
Despite appearances, you will not encounter Stephen Hawking in an armoured wheel chair, Lenny Susskind wearing a short spade and a net, or Gerard ’t Hooft with a spear and a shield; all three in the gladiator’s arena. This book contains a lot of drama, but most of it happens in the heads of these physicists and in their discussions. All three, the main characters of the book, are good friends and respect each other profoundly.
In the 1970s Hawking studied quantum mechanics near black holes and made the remarkable discovery that they are not black after all. They radiate energy with an apparently thermal spectrum, the temperature of which is inversely proportional to the mass of the hole. For the black holes that occur in nature at the centre of galaxies, or as the final products of the deaths of supermassive stars, this radiation is completely negligible. So, what was the point? Elaborating on his computations, Hawking concluded that in this process, if some information is gobbled up by the hole once it passes its event horizon, it will be forever lost. There is no way to retrieve it.
This was the starting shot in the war, and what a shot it was. As Susskind explains in great detail, it rocked the boat of physics so badly that it almost caused it to sink.
The claim was made in the late 1970s but ’t Hooft and Susskind learnt about it in a special meeting in 1981, in the attic of Werner Erhard (of “est” fame). Many physicists at the time dismissed the problem, but our two heroes recognized the mortal blow that it represented to the heart of quantum mechanics. A basic feature in the quantum description of nature is the conservation of information. In more technical terms, we believe that no matter how complex a process, it will never violate the unitarity of quantum evolution in time. The formation of a black hole out of ordinary stuff – and its subsequent evaporation – should not represent an exception despite its complexity. Hawking put his finger on a fundamental issue that hindered the possible unification of general relativity and quantum mechanics, which was a major preoccupation of Albert Einstein and many after him.
Hawking had clearly won, by surprise, the first battle. This we learn at the beginning of the book. The rest describes Susskind’s strategy of attrition until he could claim victory a quarter of a century later.
In sharing the author’s path to victory you will learn a lot of deep physics: the basis of quantum mechanics; the fundamental characteristics of black holes; the need to use string theory and some of its tools developed in the 1990s – arcane notions such as the principles of black-hole complementarity, the discovery of D-branes by Joe Polchinski and, above all, the holographic principle that appeared first in the study of the problem by Susskind and ’t Hooft, but that was masterfully formulated in string theory by Juan Maldacena. There are many other heroes in this story: Strominger, Vafa, Sen, Witten, Callan, Horowitz, Giddings, Harvey, Thorlacius and Russo etc. – who all provided the ammunition necessary to demolish Hawking’s edifice, to the point that he surrendered by around 2003.
In parts three and four of the book, the going gets necessarily rough. The ideas are deeply unfamiliar and one may from time to time feel some form of mental saturation. Being a consummate storyteller, the author punctuates the more difficult passages with a good deal of irreverent and iconoclastic humour. Read the chapter “Ahab in Cambridge”. His description of life and academia in Cambridge, England, is hilarious. Indeed, throughout the book you will get a good number of laughs.
In all, the book presents a fascinating and intellectual adventure in accessible terms where you can learn some of the more challenging ideas in modern theoretical physics. The author follows to the letter Einstein’s mandate of making things as simple as possible, but not simpler. It is original, honest, profound and fun. You could hardly ask for more.
The US Department of Energy (DOE) has selected Michigan State University (MSU) to design and establish the Facility for Rare Isotope Beams (FRIB), a new research facility to advance the understanding of rare nuclear isotopes and nuclear astrophysics. It should take about a decade to design and build at an estimated cost of $550 million. FRIB will serve an international community of around 1000 researchers. MSU currently hosts the National Superconducting Cyclotron Laboratory (NSCL). Its director, Konrad Gelbke, will lead the team to establish the FRIB on the MSU campus.
The joint DOE–National Science Foundation Nuclear Science Advisory Committee (NSAC) first recommended as a high priority the development of a next-generation nuclear structure and astrophysics facility in its 1996 Long Range Plan. Since then, the FRIB concept has undergone numerous studies and assessments within DOE and by independent parties such as the National Research Council of the National Academy of Sciences. These studies – in addition to NSAC’s 2007 Long Range Plan – concluded that such a facility is a vital part of the US nuclear-science portfolio. It complements existing and planned international efforts, providing capabilities unmatched elsewhere.
The DOE issued a Funding Opportunity Announcement (FOA) on 20 May 2008 to solicit applications for the conceptual design and establishment of the FRIB, to enable fair and open competition between universities and national laboratories. The proposals received were subject to a merit-review process conducted by a panel of experts from universities, national laboratories and federal agencies. The appraisal included rigorous evaluation of the proposals based on the merit review criteria described in the FOA, presentations by the applicants and visits by the merit review-panel to each applicant’s proposed site.
Rolf-Dieter Heuer is no stranger to CERN. He first joined the laboratory’s staff in 1984 to work on the OPAL experiment at LEP. Nor is he a stranger to top-level management in particle physics. Having been spokesman of the 330-strong OPAL collaboration from 1994, he took up a professorship at the University of Hamburg in 1998 and became research director for particle physics and astrophysics at DESY in 2004. For the past 10 years he has steered DESY’s participation in projects such as the LHC and a future international linear collider. He has also fostered the restructuring of German particle physics at the high-energy frontier. Now he faces new challenges and new opportunities as he takes over the reins at one of the world’s largest scientific research centres.
As Heuer begins his five-year mandate as CERN’s director-general the first goal is clear: to see LHC physics in 2009. The immediate priority is to repair the machine following the damaging incident that occurred soon after the successful start-up last September. Heuer recalls how smoothly the machine operators established beam on 10 September, with the experiments timing in on the same day (CERN Courier November 2008 p26). “This was a big success,” he asserts. “When you look back to LEP, it’s amazing how fast it went.” For Heuer, the start up demonstrated not only that the LHC works, but that it works well. “The LHC as a project is now completed,” he adds. In his view, the repairs underway are part of the continuing commissioning process and he has full confidence in the team to have the LHC operating again as expected later this year.
A machine for the world
Longer term, Heuer’s vision for CERN stretches to horizons beyond the LHC, not just in time but also in terms of the broader particle-physics arena. This wider view includes several aspects with a common underlying theme of communication, from external relations with other high-energy physics laboratories to the transfer of technology and knowledge to society. One of his first acts as director-designate was to propose a management structure that includes a highly visible external relations office. This is to be a conduit for communication with laboratories and institutes not only in CERN’s 20 member states but also in the other nations with which the organization has relations at one level or another.
Another way in which CERN reaches beyond its boundaries as a centre for particle physics is through knowledge and technology transfer (KTT). Here Heuer believes that there should be more emphasis on knowledge, which he feels has not been sufficiently exploited in the past. He stresses that the goal should not primarily be potential funding, but to make a big impact on global society. “It’s great to have additional funding, but that should be secondary. It’s not funding that should drive KTT” he says.
The LHC will be the world machine for many years
Rolf Heuer
However, Heuer’s most ambitious – and perhaps contentious – goals are arguably his aspirations for CERN positioned as a laboratory for the world. In some respects that process has already begun. “We are about to enter the terascale in particle physics,” he says. “The LHC will be the world machine for many years.”
A first priority will be to strengthen CERN’s intellectual contribution, so that it has a role beyond that of a service laboratory. “CERN has to provide a service,” Heuer explains. “But to provide the best results we need the best people and therefore there needs to be an intellectual challenge.” A first step will be to create a new centre at CERN for the analysis and interpretation of LHC data. The idea is to create close contact between staff and users, between experiment and theory. “It should be a focal point in addition to other centres,” says Heuer. In particular, he envisages “a centre that fosters open discussion between theorists and experimenters, where people can discuss and perhaps develop common tools”. He acknowledges that it will be a challenge, but as he says: “I want to challenge people.”
A global view
Out on the broader world stage, Heuer hopes to influence the current panorama in particle physics. He believes that it is important to combine the strengths of the particle-physics laboratories around the world and to co-ordinate the various programmes. In general, “we need breadth with coherence”, he says. Starting at home, there are plans for a workshop on “New Opportunities in the Physics Landscape at CERN” in May to look at the future for fixed-target experiments at the CERN.
In this context, breadth also means to venture beyond the conventional boundaries of particle physics, particularly to overlaps with astroparticle physics and nuclear physics, where there are common aspects of experimental methods and theoretical ideas. “We need a closer dialogue with other communities,” he explains. “We should not separate fields too much. There are differences but we should emphasize the commonalities and aim for a ‘win–win’ scenario.”
Co-operation and collaboration are key words in Heuer’s view. “High-energy physics facilities are becoming larger and more expensive,” he points out, “and, to state it positively, funding is not increasing.” However, long-term stability in funding is going to be a necessary condition for the future survival of the field. “We need new approaches from funding agencies,” he says, “which look beyond national and regional boundaries.” One step could be for funding agencies to meet on a more global basis. Here the CERN Council provides a model that these agencies are already studying for, as Heuer notes, “it seems to work”.
More generally, keeping particle physics and CERN on track for a fulfilling future will no doubt require an organizational form that has yet to be defined. “We need to be open and inventive,” says Heuer. “A key word is partnership.” He argues that it will be crucial to retain excellent national and regional projects in addition to global initiatives to maintain expertise world wide; for example, he believes that it is essential to have accelerator laboratories in all regions.
“May you live in interesting times” is a supposedly a curse, but taken at face value it could also be a blessing. CERN, and Heuer as director-general, are certainly experiencing interesting times. The hope at CERN and in the wider particle-physics community must be that the future is not only interesting but global and bright.
Physicist Georges Charpak joined CERN 50 years ago on 1 May 1959. He retired from the organization in 1991 and now lives in Paris, where he studied and worked for the CNRS before coming to CERN. In August 2008 I visited him (with a cameraman and photographer) at his apartment in rue Pierre et Marie Curie. There is perhaps no better address for a physicist who developed detection techniques that have not only allowed a deeper study of the structure of matter but also found important applications in medicine and other fields. This work led to his Nobel Prize in 1992.
The photo session was to complete CERN’s Accelerating Nobels exhibition with photographs by Volker Steger, which was one of the features of the LHC inauguration. As we entered Charpak’s chaotic but charming office, he made jokes about his Nobel Prize: “Ca devait être une année creuse” (“It must have been a slack year”) for the Nobel Committee. Then he patiently accepted Steger’s request to make a drawing of his discovery with coloured pens on a big sheet of white paper, and finally to sit for the photo session.
The caption that he added to his drawing of a wire chamber is a good summary of the value that his contribution made to particle physics: “D’un fil isolé à des centaines de milliers de fils independents” (“From an isolated wire to hundreds of thousands of independent wires”). As Charpak explains in his latest book (Mémoires d’un Déraciné, Physicien, Citoyen du Monde), in 1968 his first 10 × 10 cm2 proportional multiwire chamber “was perfectly capable of detecting in an independent way, and on each of the wires, separated by a millimetre, the pulses produced by the nearby passage of an ionizing particle. In this way we could fill the space with thousands or hundreds of thousands of wires to visualize the trajectory of charged particles”.
This was an experimental technique that many others had attempted but had until then produced catastrophic results, ending in the destruction of “a thousand dollars’ worth of amplifiers”. What was missing was an understanding of the formation of pulses in a proportional multiwire chamber. Charpak realized that they were produced by the movement of positive ions, which induced pulses of opposite polarity near the wires. This approach to solving experimental problems, through an in-depth study of the phenomena involved, reveals the theoretical physicist’s spirit in Charpak. His secret dream, as he confesses in his book, has always been to be a theoretician.
You had a long career in experimental physics. Which result are you most proud of?
It was my first experiment, with Richard Garwin and Leon Lederman (five scientists signed the paper), and CERN’s first large experiment at the time: g-2. That was an extraordinarily elegant experiment. At last, we had contributed to measuring the magnetic moment of the muon to some 10 decimal places, and that was a real tour de force.
Then, of course, came our research on wire chambers, which were very small and became huge – with large groups making all sorts of experiments, also with cosmic rays. They were incredibly successful. The teams using wire chambers in medical applications are very small – I like teams where I can keep human contact with people and where I can minimize bureaucracy.
The wire chambers led to the Nobel Prize in Physics. What did this bring to you?
Free coffee whenever I entered a bar, a lot of visibility in the streets of Paris because of the television – people still stop me to express their admiration – a lot of travelling and even a dozen pairs of shoes that were offered by fans.
What would your advice be to a young physicist who would like to receive the Nobel prize?
If I were a young experimentalist, I would do experimental physics with cosmic rays because they enable you to reach much higher energies than at the LHC, even if you have to build a 1 × 1 km2 or 10 × 10 km2 detector, and even if there’s only one good event per year – that one event will bring something extraordinary. Then I think that sooner or later physics will need very good thinkers – theoreticians who are able to imagine new things. Theoretical physicists have an important role to play, provided that they do not become dictators. I understand the excitement that they get from the prospects in high-energy physics today. I think physics is experiencing a rejuvenation.
After your research work at CERN, you devoted your time to the industrial applications of detectors. Tell us about that.
I do not have the gifts to be a department – or even group – leader. I’ve never been anything like that outside my own group. I’m very unorganized and I hate hierarchies. Very quickly my small detectors were used inside big detectors, but when I saw groups with more than 1000 physicists I became scared. So I decided to switch to the application of my detectors to medicine and biology. I have had some success in radiology for children – the best instrument available is still the one that I proposed.
Another question is to see whether it will sell, or flood hospitals because it is the best, but this unfortunately is a commercial question. Physicists are not necessarily businessmen. You can have as many Nobel Prizes as you want, but once you go out to industry it’s a completely different story. I go to many conferences on children’s diseases, I make presentations about the instruments I make, but the difficulty is in introducing these new instruments to hospitals. You need the approval of the US Food and Drug Administration and the agreement of insurers to reimburse, and this is not my competence. But I am not ruined yet and I’ll go on.
I am annoyed because I lost part of my autonomy after a small accident. I survive. I continue doing some physics – that’s the easiest – and I am working on a book to teach nuclear physics to children. I took out a patent three months ago, and built a detector 50 times less expensive than a standard one. I hope to be able to offer cultivated people the possibility of buying a book for their children that is written by very good physicists (I did not do it all by myself). I have proposed building instruments that make measuring radioactivity a very trivial thing. So I am working in education.
For the last 12 years I have been involved with a huge educational project, La Main à la Pâte, which certainly is my most important contribution to society – schools in the Amazon basin practise La Main à la Pâte. This new educational method based on learning science through direct experiment is becoming more and more popular. We need a revolution in science education because we live in a world where obscurantism has too big a role, for my taste, and this is my personal fight against obscurantism in collaboration with people from around the world. I received a prize for it in Mexico together with Leon Lederman, which was a very pleasant surprise for me. It indicated that what we do in France with children has reached such a level, that even in a place as monopolized by the US as Mexico is, our work is recognized.
CERN’s immediate future lies with the LHC. What discoveries do you expect?
We expect the unknown – to see things that are not necessarily foreseen by theory. Because there are still mysteries in physics – dark matter, for example – there are answers from theoreticians and there are many questions from experimentalists like myself. If theory were completely accurate we would not need to build an accelerator.
The LHC might bring unexpected results, and the fact that we have a suspicion about the existence of a form of matter that is not the same as the one that makes up the known universe is very exciting. Personally, I find it very amusing to expect new matter. Is it true or false? If it’s false it’s a myth, and maybe some people will have to give back their Nobel medals because they will have foreseen false entities. But if it is true, it is very exciting because there are still extraordinary things to discover in the universe. Young people who enter the field now are lucky that this physics is not completed.
At its meeting on 12 December, CERN Council thanked the organization’s outgoing management and welcomed in the new. It was an occasion to take stock of the achievements of the past five years and to look forward to the next. Robert Aymar, the departing director-general, looked back on his five years at the helm, while his successor, Rolf Heuer, presented his vision for the future.
Aymar’s five-year mandate encompassed both CERN’s 50th anniversary and the first beams in the LHC. “It has been a privilege to lead this great organization for the last five years,” Aymar told Council. “My mandate started on a high note – the celebration of 50 years at the cutting edge of science and innovation – and it is also finishing on a positive. After a year of highs and lows, I am leaving CERN with a clear route to physics at the LHC in 2009.”
Council was also informed of the actions taken following the incident that brought LHC commissioning to a halt on 19 September (Mobilizing for the LHC). The scientific policy committee, an advisory body for Council, had an extensive session on this matter and reported its findings, endorsing the robust manner in which CERN is addressing the issue. “We have been impressed by the rapid and professional manner in which this situation has been mastered,” said Torsten Åkesson, president of Council, “and look forward to the LHC experiments collecting their first colliding-beam data in 2009.” Council’s confidence was underlined by its endorsement of the existing LHC project-management team until the machine is handed over for routine operation.
Presenting his ambition for the future, Heuer stressed that physics at the LHC would be the top priority in 2009. Looking farther ahead, he outlined his vision of a key role for CERN in an increasingly global basic-research environment. “CERN is a European lab hosting a global project,” he said. “The LHC project has evolved this way. In the future, however, we need to go further, working together with our partners around the world on the basic programme, with national projects, regional projects and global projects all serving a common goal. Now is the time for us to lay the foundations for such future programmes, which will be built on strong national and regional pillars in the Americas, Europe and Asia. In my view, CERN is Europe’s pillar.”
Following a period of study, Romania was formally accepted as a candidate for accession to membership of CERN. Its membership will be phased in over a five-year period during which the country’s contributions will ramp up to normal member-state levels in parallel with Romanian participation in CERN projects.
Setting a marker for the future, Council approved the creation of a study group to examine the geographical and scientific enlargement of CERN. This group will hold its first meetings in early 2009.
In its European strategy session, Council decided on the procedure to recognize and follow projects that are relevant to the European strategy for particle physics, including projects that are not necessarily based at CERN’s Geneva laboratory. Council followed these new procedures in recognizing four projects in the EU’s Seventh Framework Programme that are related to accelerator R&D and future facilities.
DESY has commissioned two consortia of renowned building contractors to construct the underground buildings (tunnels, shafts and halls) for the 3.4 km long X-ray laser facility, European XFEL.
The contracts for the sites at Schenefeld, in the Pinneberg district (Schleswig-Holstein), and Osdorfer Born, in Hamburg – which add up to nearly €206 million – were awarded to the consortium Hochtief/Bilfinger Berger. The commission for the civil-engineering works at the Hamburg site of DESY-Bahrenfeld amounts to €36 million and goes to the consortium Züblin/Aug. Prien. The contracts were awarded on 12 December and construction started officially on 8 January. DESY is at present acting for the future not-for-profit company European XFEL GmbH, which is to be founded in spring 2009 and will be in charge of the construction and operation of the new research facility.
The 3.4 km long research facility will be located between the DESY site at Bahrenfeld and the neighbouring town of Schenefeld. It will begin at DESY, where the central supply stations will be situated. In the last kilometre, the tunnel will fan out into several separate tunnels in which the X-ray laser flashes will be generated and transferred to the experiment stations. The site at Osdorfer Born, which will comprise another access and supply building, will be established at the beginning of this tunnel fan. The underground experiment hall at the end of the facility will be located on the future 15 ha research campus in Schenefeld and provide space for 10 experiment stations. It will be 14 m deep, with a surface area of 4500 m2. The contracts that were awarded in December cover all civil-engineering works. These comprise eight shafts leading into underground halls, the experiment hall and all of the tunnels. The total length of tunnel system will be 5.8 km and will be constructed using tunnel-boring machines.
The investment costs for the European X-ray laser facility amount to €986 million (at 2005 price levels). As the host country, Germany will cover as much as 60% of the investment costs and at least 40% will be borne by the international partner countries. Alongside the German federal ministry of education and research, the City of Hamburg and the German federal state of Schleswig-Holstein, 13 countries are participating: China, Denmark, France, Greece, Hungary, Italy, Poland, Russia, Slovakia, Spain, Sweden, Switzerland and the UK.
The European Particle Accelerator Conference (EPAC) has been a regular feature on the conference calendar since the first meeting in Rome 20 years ago. It brings together accelerator specialists working in areas ranging from fundamental physics through applications in material science, biology and medicine to commercialization in industry. EPAC ’08, the 11th in the series, took place in Genoa, the Italian port city with links to Christopher Columbus and Marco Polo – explorers who established some of the first routes from Europe to the Americas and the Far East. It was a fitting location, because this was the final conference in the series. EPAC will merge with the related American and Asian conferences into the International Particle Accelerator Conference (IPAC), which will roam between America, Asia and Europe on a three-yearly basis.
High energies and high intensities continue to be the major goals in the field, with a common thread of superconducting technology. The drive for high energies comes principally from high-energy particle physics, where CERN’s LHC is poised to lead the field. The machine was entering the final stages of hardware commissioning at the time of the conference. It is often pointed out that the LHC is its own prototype, breaking new ground in many ways in terms of scale and complexity – from the world’s largest vacuum system to the quench-protection systems and interlocks. Problems have been inevitable; the latest (Mobilizing for the LHC) will surely be overcome as previous ones were. One lesson that can be learned for future projects of this scale is not to forget the infrastructure while focusing on the more challenging aspects.
High aspirations
For now, the Tevatron at Fermilab and RHIC at Brookhaven continue to provide the high-energy frontier in hadron collisions. Thanks to a number of improvements, the Tevatron reached a peak luminosity of 3.15 × 1032 cm–2s–1 in 2008, exceeding the goals of the upgrade for Run II. Beam–beam interactions remain a major limitation, but work on compensation using two electron lenses installed in the ring is providing promising results in increasing the lifetime of the proton beam. Similarly RHIC has exceeded its design parameters, not only with gold–gold collisions but also in operating as a high-luminosity polarized-proton collider. Runs have reached a peak luminosity of about 35 × 1030 cm–2s–1 and a polarization of around 60% for a 100 GeV proton beam. To reach higher luminosities, electron cooling of the heavy-ion beams is being investigated, and a 20 MeV energy-recovery linac (ERL) is under construction for tests. This could also be used to study the new idea of coherent electron cooling in which density variations induced in the electron beam by the hadron beam are amplified by a free-electron laser (FEL) and fed back to correct the hadron beam – a variation on stochastic cooling. In addition, the ERL can test design ideas for the proposed electron–ion collider, e-RHIC.
For some years the international particle-physics community has been pursuing options for a future linear electron–positron collider to complement the high-energy hadron collisions at the LHC. In 2004 the International Technology Recommendation Panel decided that a future International Linear Collider operating in the 0.5 TeV centre-of-mass region should be based on 1.3 GHz superconducting RF technology. The Reference Design Report released in 2007 specified two 11 km linacs with an accelerating gradient of 31.5 MV/m and a peak luminosity of 2 × 1034 cm–2s–1.
A major goal of the first stage of the technical-design phase is to demonstrate by mid-2010 the feasibility of an accelerating gradient of 35 MV/m in 9-cell cavities, thereby allowing an operating margin of 10%. Global R&D on cavity shapes, fabrication and surface preparation is under way to meet this challenge. While tests have achieved field gradients as high as 41 MV/m, average results worldwide are still 15–20% short of reliably meeting the design requirement. A further challenge is the beam-delivery system, and particularly the issue of chromaticity, which is being investigated by a large international collaboration, with dedicated test facilities existing and under construction at SLAC and at KEK. The positron source is another challenging area because the design luminosity demands a source that delivers 1000 times as many particles per pulse than previous sources, together with the added complication of a possible upgrade to high (60%) polarization. Tests at SLAC have shown that a superconducting-undulator solution is feasible and development work is now in progress in the UK.
In parallel, an increasing international effort in the Compact Linear Collider (CLIC) study is investigating an innovative two-beam accelerator concept, which aims at a centre-of-mass energy of 3 TeV and a luminosity of 2 × 1034 cm–2s–1. Tests are under way at CERN in the CLIC Test Facility with a view to the production of a conceptual design report by 2010. Accelerating structures have already been tested to the required field gradient of 100 MV/m.
More futuristic is the attempt to harness electric fields in plasmas to accelerate particles (e.g. in the plasma-wakefield approach). Studies at the Accelerator Test Facility at Brookhaven are using multiple electron bunches only 5.5 ps long to generate the wakefields in a potentially more efficient manner. New results demonstrate a maximum wakefield of around 22 MV/m near the tail of the bunched beam. At Lawrence Berkeley National Laboratory, tests with laser wakefields reached 1 GeV in a distance of only 3 m in 2006. The goal now is to develop this principle into a laser accelerator to drive a short-wavelength FEL.
Current plans for the LHC foresee a series of luminosity upgrades by 2017, with a new injection system that could easily be upgraded to provide a multimegawatt beam. Another future option, which is still in the embryonic stage, would be to build an electron ring in the LHC tunnel to allow electron–proton collisions. The aim is for a luminosity of 1.1 × 1033 cm–2s–1, some 10 times as high as at DESY’s HERA collider, which ceased operations in 2007. Another option would be for a 140 GeV linac to supply the electrons. In either case, ERL technology should prove useful.
Intense and brilliant
In other areas of particle physics, the emphasis is on high intensities, because physics beyond the Standard Model may well lie in processes that are rare and/or difficult to observe. By the time it ceased operations in April 2008, the PEP-II B factory at SLAC had surpassed its design luminosity by a factor of four, reaching 1.2 × 1034 cm–2s–1, thanks to successive improvements, including continuous injection. The machine also provided valuable lessons to be learned for the design of future machines, such as in feedback. Elsewhere, commissioning is in full swing on the upgrade of the Beijing Electron–Positron Collider, BEPCII, to increase the collision rate by a factor of 100. At the Budker Institute of Nuclear Physics in Novosibirsk the aim is to achieve higher luminosity in the VEPP-2000 collider by means of innovative ideas, using existing injectors in a restricted area.
KEKB, the asymmetric e+e– collider for the study of B mesons at KEK, has operated with crab cavities for more than a year, the first installation to do so, following 13 years of R&D. The scheme using a single cavity per ring gives somewhat lower luminosity than without, but also at a lower beam current. The system needs further study to understand the effects limiting the luminosity at higher currents. A similar R&D programme at the DAΦNE e+e– collider at Frascati is investigating the use of a “crab waist” scheme, with sextupoles that give a factor of three shrinkage in the vertical plane as well as a narrower crossing. Put into operation in early 2008, they reached a peak luminosity 50% higher than the previous record, but at lower currents and two-thirds power.
Elsewhere, high-intensity facilities offer the possibility of a range of research. At the Japan Proton Accelerator Complex (J-PARC), the main ring is a 50 GeV synchrotron designed to deliver a 0.75 MW beam. This will serve kaon-rare decay studies, for example, and provide the first-ever megawatt-class fast-extracted beam to create neutrinos for the Tokai to Kamioka experiment. It will be fed by a 3 GeV 1 MW rapid-cycling synchrotron (RCS), which will also serve muon and neutron production targets in the Materials and Life Science Facility. The RCS already operates at design energy in conditions corresponding to a beam power of about 130 kW.
The Facility for Antiproton and Ion Research (FAIR), which is planned for Darmstadt, is set to be the largest science project funded in Europe in the next decade. It will provide beams of antiprotons and heavy ions at intensities 100 times as great as present, with additional capabilities for fragment-separation and plasma physics using ion bunches and petawatt lasers. Technical challenges surround the high-current beams, control of the dynamic-vacuum pressure and the design of rapid-cycling superconducting magnets. With two linacs and eight rings (including four storage rings), the FAIR complex will involve interesting beam manipulations with implications for RF synchronization. Experiments are expected in 2013.
The techniques of in-flight separation and isotope separation online (ISOL) are currently providing a turning point for research using radioactive beams. Superconducting linacs are the key in providing beams of heavy ions, while cyclotrons and synchrotrons are needed to reach high energies at in-flight facilities such as FAIR and the Radioisotope Beam Factory at the RIKEN institute in Japan. Studies in Europe, meanwhile, are leading towards the European ISOL facility, EURISOL, with a planned beam power of 5 MW. In the US both the National Superconducting Cyclotron Laboratory at Michigan State University and the Argonne National Laboratory have proposals for facilities that include the possibility of reaccelerating rare isotopes. TRIUMF has a slightly different proposal to use a megawatt-class electron linac for the photofission of a uranium target to produce neutron-rich rare isotopes (MW linacs could supply medical isotopes).
Design ideas for the necessary low-energy deuteron accelerator are already being pursued in the context of an international agreement between Euratom and Japan
Neutron sources also demand high-incident beam intensities for neutron production. The Spallation Neutron Source at Oak Ridge National Laboratory has a design-beam power of 1.4 MW, which is to be achieved after three years of operation. Since start-up in October 2006 the facility has reached 0.52 MW, making it the world’s most powerful spallation neutron source. There have been problems, however, with the low-energy beam transport and the superconducting 1 GeV proton linac. An intense neutron source is also a key element of the International Fusion Materials Irradiation Facility, which will study the responses of materials to the high flux of neutrons (1018 n/m2s) that would be emitted in a future fusion reactor. Design ideas for the necessary low-energy deuteron accelerator are already being pursued in the context of an international agreement between Euratom and Japan.
For facilities using FELs to provide short-wavelength photon beams for a variety of science, the key word is “brilliance”. While synchrotron sources can provide high energies (and hence short wavelengths), FELs offer the route to increased brilliance. The Free-electron Laser in Hamburg (FLASH) at DESY has been operating successfully for more than a year, delivering pulses at 6.5 nm. For the future, there is ongoing accelerator R&D for an X-ray FEL (XFEL) based on a 17.5 GeV electron linac, compared with the 1 GeV linac in FLASH. At SLAC, meanwhile, the Linac Coherent Light Source is under construction to operate at X-ray wavelengths (0.15–1.5 nm). This will use a new 135 MeV injector and the downstream third of the famous 3 km linac to reach a final energy of 14 GeV. It is on course to provide X-rays for the first experiments in summer 2009.
Beyond the laboratory
The main use of particle accelerators is outside research, particularly in X-ray machines in medicine. Now an increasing number of machines are being designed and built explicitly for hadron therapy using protons and carbon ions. In April 2007, PSI started the treatment of patients with a proton-scanning system based on a commercially supplied 250 MeV superconducting cyclotron. The Heidelberg Ion Therapy Facility is set to be Europe’s first dedicated proton- and carbon-therapy facility, with a synchrotron to provide the particles. Commissioning for three fixed beams was finished in April 2008, and commissioning of the gantry for scanning has begun. In Italy, the Centro Nazionale di Adroterapia Oncologica in Pavia is under construction, and commissioning the sources and the low-energy beam transfer is also under way.
As hadron therapy moves out of research laboratories and into hospitals, there is a growing market that industry can serve by providing not only the basic accelerators but also other items and services related to the treatment of patients. In this area, as well as in others, collaborations between industry and researchers provide an important means of transferring from a project to a product.
Indeed, working closely with industry is an increasingly important part of the accelerator scene. The LHC has led the way for “mega projects”, with industrialization of the magnet construction. One problem, however, is that the duration of such big projects can be longer than the lifetime of some companies. Nevertheless, co-operation with industry is essential from an early stage. The European XFEL project has already begun to work with industry in the production of the 100 cryomodules – each with eight 9-cell superconducting RF cavities and superconducting magnets. At the same time, research institutes that require linacs can benefit from being able to acquire customized systems direct from industry, particularly from the company ACCEL Instruments. There are many other specialized areas where partnerships between research and industry have proved mutually beneficial.
The accelerator scene continues to evolve and grow, not only in underlying technology, but also in its relations with other areas of science and industry. It is therefore fitting that the conference scene should reflect this evolution. The last EPAC provided a worthy ending to a successful series and the community now looks forward to the first IPAC, in 2010 in Kyoto, following the last in the Particle Accelerator Conference series, in Vancouver in May this year.
• The organizing committee for EPAC ’08, chaired by Caterina Biscari of INFN, and the scientific programme committee, chaired by Oliver Bruning of CERN, were formed by the board elected by the European Physical Society Accelerator Group, plus representatives of APAC and PAC, while the local organizing committee, chaired by Paolo Pierini of INFN, included a dozen members from INFN (Genoa, LASA, LNF), SINCROTRONE Trieste and CERN.
EPAC ’08: a hard act to follow
EPAC ’08 was a resounding success: the fruit of 20 years of experience in organizing these events with exciting scientific programmes reflecting the state of the art. More than 1000 delegates from 38 countries converged on EPAC ’08, the last in the biennial series as the conference joins Asia and North America to propose an International Particle Accelerator Conference on a three-year cycle.
As is customary for EPAC, the four-and-a-half-day programme consisted of plenary sessions at the opening, closing and prize sessions (with no more than two oral sessions in parallel), followed each afternoon by plenary poster sessions, allowing delegates to derive maximum benefit from the scientific programme. The meeting was augmented by the regular industrial exhibition, which for EPAC ’08 was the largest ever, with 90 companies participating. Many conference delegates also attended the traditional session for industry.
The 2008 prizes for the European Physical Society Accelerator Group were awarded during the prize ceremony, with the Rolf Wideröe prize going to Alex Chao of SLAC; the Gersh Budker prize to Norbert Holtkamp now at ITER and formerly of the Oak Ridge National Laboratory (ORNL) and Spallation Neutron Source (SNS); and the Frank Sacherer prize to Viatcheslav Danilov, also of ORNL/SNS.
With the continuing financial support of European laboratories, 66 students from around the world attended the conference. They had an extra opportunity to present their work in a special student-poster session. A prize was awarded in two categories: for a young physicist or engineer for quality of work and promise for the future; and for best posters. The prize for the best student poster went to Rocco Paparella of INFN–LASA.
Thanks to the team effort of the Joint Accelerator Conferences website (JACoW) collaboration editors, the proceedings were published “prepress” on the last day of the conference, and in record time at the JACoW open-access site three weeks later.
by Takashi Nakamura, Mamoru Baba, Eishi Ibe, Yasuo Yahagi and Hideaki Kameyama, World Scientific. Hardback ISBN 9789812778819 £56 ($98).
Terrestrial neutron-induced soft errors in semiconductor memory devices are currently a major concern in reliability issues. Understanding the mechanism and quantifying soft-error rates are primarily crucial for the design and quality assurance of semiconductor memory devices. This book covers relevant up-to-date topics in terrestrial neutron-induced soft errors and aims to provide succinct knowledge on these soft errors by presenting several valuable and unique features. It should be of interest to students and researchers in radiation effects, nuclear and accelerator physics and cosmic-ray physics; and to engineers involved in reliability, the design/quality assurance of semiconductor devices and IT systems.
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