18.12 Lyn Evans MH AY

NEWSMAKER OF THE YEAR NATURE|Vol 456|18/25 December 2008 THE MACHINE MAKER He did more than anyone to build the Large Hadron Collider. This year he saw it finished — and then break down. Geoff Brumfiel profiles the LHC’s project leader, Nature’s newsmaker of the year. YNDON REES EVANS gets up from a little later on. He was entirely focused on the experiment. his desk and crosses his sparsely furnished office At the CERN campus, which sits on the Swiss border about to a shelf filled with notebooks. He pauses before ten kilometres away, the car park by the main entrance was Lchoosing one and bringing it to the table. He opens crammed with broadcast trucks and satellite dishes. Soon, it as fondly as if it were a family scrapbook, flipping through the LHC’s normally hushed control room was packed with pages crowded with diagrams, budgets and the business news anchors, past laboratory directors and distinguished cards of mid-level government bureaucrats. Finally he gets scientists. It was ‘beam day’ — the day on which protons to what he was looking for: a photocopied drawing of a would circulate around the LHC for the first time. “I have conference table. Most of the writing on the diagram is in rarely been in such a stressful situation,” Evans says later; he Japanese, but around the table’s edge someone has written has a lilting Welsh accent that he has kept during four dec- names, including Evans’s, in English. The date at the top is ades of living in France and Switzerland, and a stutter that also in English: 2 March 1995. “This was it, this was the key becomes more pronounced when he is nervous. meeting,” he says. He points to a Japanese character written The machine’s eight sectors turn on one by one. There’s a in a corner. “They even showed where the flowers were.” cheer each time the beam first passes through a sector; but Most laboratory notebooks — like most family scrap- it is the last sector — the one that completes the loop — that books — don’t record the place settings at meetings with really counts. The cameras focus in on Evans’s round face as Japanese parliamentarians. But this is the laboratory note- he stares at a wall of flat-screen monitors. “So it will be on book, or rather one of many notebooks, of the largest sci- the next cycle — in about one minute,” he says haltingly to entific experiment ever constructed: the Large Hadron the crowd. He completes the countdown in French: “Trois Collider (LHC), a particle accelerator at CERN, the Euro- … deux … un … et zéro.” Suddenly, two bright dots appear pean high-energy physics laboratory near Geneva, Switzer- on a screen, a sign that protons have made it all the way land. The LHC represents a level of ambition never before round. The control room bursts into applause. Evans’s face seen in physics, an ambition so monumental that its reali- slackens into a broad smile. He moves around the consoles, zation required it to become the first truly global experi- shaking hands with the individual members of his team. mental undertaking. It consists of hundreds of thousands “Merci,” he tells them all. “Well done.” of tonnes of extremely powerful machinery looped round a “There were The circulation of that beam puts the LHC on to more tunnel 27 kilometres long. Much of this hardware is chilled several clever front pages the next day than any scientific event since to within two degrees of absolute zero by a liquid helium people, but the sequencing of the human genome. Just circulating the system much larger than any seen before. beam, though, is not enough. A second, counter-rotating For most physicists, the LHC story — a new chapter in Lyn was really beam has to be put through the machine. Then the cur- their discipline’s history — has yet to begin. For Lyn Evans exceptional.” rent has to be upped, the acceleration increased, the beams it is almost over. After a decade and a half of daily devotion — Walter focused to the point at which, when they cross inside vast to getting the machine built, he is due to retire at roughly buried detectors, the head-on collisions between protons the same time that the LHC will start to generate data. At Scandale are frequent enough to offer up a wealth of data. All that 63, he is still never more than a quick recap away from being will take weeks, maybe months. up to speed on every detail of its design and engineering. At Then, nine days into the process, disaster strikes. On an one point he more or less redesigned it single-handedly on otherwise quiet Friday morning, physicists in the LHC’s his kitchen table. Since he joined the project in 1993 he has control room were slowly pumping up the current in the built relationships with the world’s physicists, politicians magnets in the region called sector 3–4 to see whether the and industrialists to ensure its support; he has travelled magnets would work as designed. Suddenly, their screens to factories in Europe, North America and Japan to see its lit up with alarms. According to the computer, more than components forged; and he has tackled enormous technical 100 magnets inside the machine had ‘quenched’ or lost challenges — the most recent and dramatic being a galling their superconductivity. Uncontrolled quenches can be accident just weeks after the machine was first turned on. disastrous. Currents of many thousands of amperes can “He’s the guy who made the LHC,” says Chris Llewellyn be handled quite safely by superconductors, but they will Smith, a friend and former director-general of CERN. “That turn magnets to slag if they encounter even a little electrical is what’s going to be on his tombstone.” resistance. Those in the control room knew that what had happened in sector 3–4 was serious even before a second set Rise and fall of alarms warned of falling oxygen levels along a subsection When Evans left his house in Versonnex, France, on of the tunnel. Then, the entire sector’s power cut out. The 10 September 2008, he was heading for the biggest scientific operators were literally in the dark about what was happen- media event of the year. But that sort of slipped his mind. He ing five kilometres away, more than a hundred metres below didn’t even mention to his wife that he would be on television the French countryside. 862 NATURE|Vol 456|18/25 December 2008 NEWSMAKER OF THE YEAR “I was over in the personnel department haggling about tubing. A handful of technicians move between them. some recruitment problem when I got a call,” Evans says. From afar, the magnets look like 15-metre sections of He rushed across the lab to the control room. At first, he what might be a Franco–Swiss oil pipeline. Their long steel says, he couldn’t understand how so many magnets would tubing is painted an evening-sky blue, and some have “LHC M. BRICE/CERN quench simultaneously. But he and others soon realized dipole” in white lettering on their side. Running through that the quench was by design. The LHC had automatically each dipole are the two pipes that carry the colliding proton brought the magnets out of their superconducting state to beams in opposite directions around the machine. protect them. At the same time — and probably for the same “This is the famous busbar that burned,” says Evans, reason — it had sprung a leak. The oxygen alarms had been pointing at a small ribbon of niobium–titanium alloy, no triggered by helium escaping onto the tunnel. wider than his own thick index finger, sticking out of the Two months later, sporting jeans and a red Geneva end of a dipole magnet. To an untrained eye, it is almost Squash Club sweatshirt, Evans introduces me to the culprit indistinguishable from the dozens of other superconduct- behind both quench and leak. The tops of the Jura moun- ing wires that supply the magnets with current. The busbar, tains to the west are obscured by cloud, the Alps to the south however, is the mainstay of the machine’s electrical system. nowhere to be seen. We are in a blocky industrial building It distributes the primary current between all the magnets in on the edge of the campus, where four of the LHC’s super- a given sector. During installation, the busbar ribbon lead- conducting magnets are scattered about in various stages ing from each magnet must be connected manually to the of disassembly amid shelves of vacuum flanges and copper next by brazing. Evans and his team now think a bad braze 863 NEWSMAKER OF THE YEAR NATURE|Vol 456|18/25 December 2008 Synchrotron (SPS) at CERN — were designed to shine their protons on to fixed targets. In fixed-target physics, only a small fraction of M. BRICE/CERN the energy in any of those protons is used to make new particles, and neither the Main Ring nor the SPS had any chance of making the new bosons. In machines that contained two counter- rotating beams it would be possible to arrange head-on collisions between particles — collisions in which a large fraction of the energy released went into producing new stuff. They could make Ws and Zs. The problem was that proton collid- ers were hard to build; there had only ever been one, a CERN machine called the Intersecting Storage Rings, or ISR, and it operated at much too low an energy to make Ws and Zs.

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