Jon Cartwright: September 2008 Archives

By Jon Cartwright

A few years back after a particularly wet spell, Lenny Smith found that his local pub in Oxford had been flooded. This was of course bad news for Smith’s beer provisions, but for the pub’s owner the more desperate issue was that the flood waters had spilled into the basement and wrecked thousands of pounds worth of new kitchen equipment. So, asks Smith, how much should the owner spend on his kitchen next time? This is the sort of real-world decision related to climate change that he thinks can too easily be forgotten by climate modellers.

I was listening to Smith, a mathematical physicist (and an expert on chaos theory) at the University of Oxford, talk at the international conference on Climate Change Impacts and Adaptation at the University of Exeter, UK, yesterday. He was arguing that it is fruitless to mindlessly improve climate models in all areas. Rather, he said, we should investigate how robust current climate models are by checking for consistencies among them.

By Jon Cartwright

Many of you will be wondering how the Large Hadron Collider (LHC) has been getting on since last Wednesday’s celebrated “switch on”. Well, if you are willing to overlook one 30 tonne hitch, commissioning is still going well.

On the switch-on day itself, if for some reason you left the planet, the operations team managed to get proton bunches all the way around the LHC’s 27 km-long ring in both directions. But even though the media had trickled away by early evening, the LHC team didn’t stop ploughing ahead, as I discovered when I went to the control centre the morning after. By then they had already had an anticlockwise bunch endlessly circulating, albeit spread or “de-bunched” around most of the ring. To correct the de-bunching, the team initiated their radio-frequency systems, which by Friday had been successfully tuned in both frequency and phase.

Friday, unfortunately, also brought difficulties. A transformer weighing some 30 tonnes developed a short circuit, forcing the team to replace it. As I hear from Lyn Evans, the LHC project leader, the new transformer has been lifted into place and the electrical systems, which feed the vital cryogenics systems, should soon be back on line.

The good news, however, is that Evans is planning to try some low-energy collisions next week. Hang on to your hats.

The LHC control room (heavy lever obscured from view).

By Jon Cartwright

Until a few months back I had an excited vision of the moment the great LHC “switch on” would take place. Here’s how it goes: The control room, normally frantic with the workings of scientists, falls under tense silence as a lone technician grips a heavy lever. Just as the quiet becomes unbearable, the director general mutters: “OK, let’s go.” Beads of sweat trickling down his temples, the technician heaves back the lever while averting nervously to a dial that has coloured bars going from green to yellow to red (450 GeV…5 TeV…7 TeV…DANGER) . “Faster!” cries the director general, his eyes glowing with a sort of manic intensity, “Faster!” Then the control room begins to shake and the scientists dive under their workstations to avoid the plaster and tiles falling from the ceiling.

Needless to say, the real event tomorrow will not satisfy onlookers with any cinematic clichés (and nor will the beams break any speed records — they will be strictly cruising at their injection energy of 450 GeV). But that’s not to say the event will be without drama, as I found out today when I went to CERN’s Meyrin site for for lunch with Paul Collier, head of the accelerator operations team.

“It’s not like blasting off from Cape Canaveral,” he said, referring to the fact that there is no definite countdown for performing certain tasks. Rather, the operations team will be learning as it goes, and we will get to watch — milestones, mistakes and all. The current plan is to inject the first beam into the ring at around 9:30 am, but it could happen anytime between 9 and 10 am (keep an eye out on this blog for the decisive moment). From then on, the team will take the beam round the LHC’s 27 km-long ring in a dozen or so sections, each initially fenced-off by a physical barrier.

By Jon Cartwright

In my last blog entry on the Large Hadron Collider (LHC) I asked if CERN could make it to Wednesday without any further difficulties. Well, there’s been one — a thunderstorm-induced power cut that took out the cryogenic systems for the weekend — but other than that it’s all systems go for the eagerly awaited “start up”.

On Friday evening, according to CERN spokesperson James Gillies, the LHC operations team successfully performed a third and final synchronization test. Unlike the previous two tests, which concerned “kicking” proton beams from the Super Proton Synchrotron into the LHC’s ring, the aim on Friday was to make sure the protons could be booted out of the ring at the “beam dump” point located between sectors five and six. The latest test also demonstrated that the team could navigate the protons around two sectors, or about 7 km. That means they’ve already reached 25% of their target for Wednesday, when they plan to get a low-energy beam cruising around the 27 km ring in one direction.

Talking about Wednesday, physicsworld.com is now reporting from CERN to bring you all the news in the run-up to the big day. You can also expect an analysis of the events in the October issue of Physics World.

By Jon Cartwright

Physicists used to be able to show preliminary results at conference presentations, safe in the knowledge that no-one would steal their data. Now, with the advent of the “physics paparazzi”, things have changed.

It started a few weeks back when, at a high-energy physics conference in Philadelphia, a member of the PAMELA team flashed a slide that depicted an excess of high-energy positrons in the ionosphere. Although several conference attendees suggested the positron excess could be evidence for dark matter — the elusive substance thought to make up some five-sixths of all matter in the universe — the team did not make the slide available to journalists or other scientists.

That, however, didn’t stop Marco Cirelli of CNRS in France and Alessandro Strumia of INFN in Italy. Those attendees managed to take a snapshot of the slide during its momentary disclosure and use the picture as the basis for an analysis which they published on the arXiv preprint server.