Gareth Mitchell: Hello and welcome to the Imperial College podcast. I’m recording this little bit at the end of September and as I’m sure you’ll be aware scientific research on the Large Hadron Collider at CERN has been delayed after its massive super cooled magnet effectively overheated releasing large amounts of liquid helium into the tunnel. And I mention all this because, as you’re about to hear in this month’s podcast, we actually have an interview with an Imperial Scientist involved with the LHC. So this little bit is just to point out that that interview was actually recorded shortly before that unfortunate breakdown at CERN. But rest assured it’s still a great interview and it’s still perfectly relevant so I hope you enjoy it. But with that let’s crack on with the podcast.
This is the official podcast of Imperial College London. And I’m Gareth Mitchell in a quantum super position of simultaneously being a lecturer in our Science Communication Group and presenter of Digital Planet on the BBC. Hello. So the large Hadron Collider is up and running at long last and after all the champagne and fanfare of last month when they switched it on now it’s time to press on with the science. A few words with one of the Imperial people involved in just a moment.
Also one of the UK’s top women scientists happens to be here at Imperial and as a meeting is held in her honour she has a few words for us on this podcast.
Professor Dame Julia Higgins: Making things recyclable in the polymer area is quite tricky. Because what you’d really like to do is unzip the molecules back to the individual pieces that make them and then knit them up again into new molecules and then you can have what you want. Actually trying to take that polythene bag and, as it were, melt it and chop it up what you do is you degrade the polymer. You won’t get as good a polythene bag the second go around so you’ll probably have to use it for a garden gnome or something if you wanted to recycle it.
GM: A one-to-one with Professor Dame Julia Higgins. And later on I’m at one with our state of the art flight simulator.
Varnavas Serghides: That rumbling sound is the landing gear coming down. So the landing gear is down and locked and I’m pointing the nose down. This is not what you’d call a gentle glide slope.
GM: And we’ll have some headline news from around the campus. That’s all right here on the official podcast of Imperial College London.
Professor Jordan Nash on the Large Hadron Collider
So at long last, after much anticipation, LHC, the Large Hadron Collider at CERN, is go. Lots of excitement obviously in CERN but also over here at Imperial and in this office as well because I’m with Professor Jordan Nash in the High Energy Physics Group which is part obviously of the Department of Physics. And while we’re speaking literally within a week of the switch on, Jordan, at the time of recording this interview, exciting times I should think over the last couple of weeks.
Professor Jordan Nash: Very exciting times. We’ve been on this project in the group for nearly two decades. And I think it’s something that so many people have worked so hard for to see it finally starting and to go from the time when we were thinking about how we would do something so ambitious to actually thinking about how we’re going to analyse the data that comes out is great.
GM: So where now? Obviously it’s time for some science. You’re with a number of the detectors and perhaps we could speak first of all about the CMS detectors. So what’s the role now? What’s on your work schedule over these coming months?
JN: Well as the machine starts up the amount of data we collect will grow and grow. And what we first have to learn to do is to learn how to operate the CMS detector and extract the science signals out. So really calibrate it. Understand how it reacts to the little collisions we make. And we have quite a big team out at CERN who’s actively involved in taking the first data, looking at it, understanding it and also just running day to day operations on the detector. Because we have to keep it running 24 hours a day. So I think there’s more than 20 members of the Imperial group permanently based out at CERN at this point really keeping things going.
GM: And what science in particular are you going for? Because I know obviously everyone is talking about the hunt for the elusive Higgs boson particle but there’s so much more to it than that so what’s next on the agenda?
JN: We have to understand all the pieces that go into measuring a Higgs boson decay. So it means understanding how our detector responds to particles we’ve already discovered in the past but we’re now creating in large numbers. So I think the Higgs boson is something that our teams are preparing the groundwork to get ready for to do probably in a year and a half to two years’ time to really start to look for that signal. In the meantime there are some very exciting signals that could come out fairly early. For instance, super symmetry which might be a candidate for dark matter is something that can have some quite spectacular signals early on in data taking and we’re also preparing to look for that.
GM: And this is literally happening almost as we speak and probably by the time people hear this podcast you’re going to be colliding particles into each other and the idea of the detectors then is to look out for the signatures of these collisions. So how will they then lead you to hopefully saying this is a clue for dark matter?
JN: Well the way you see dark matter is that when you have a collision you expect a sort of balancing of energy and momentum. You shouldn’t be missing energy and momentum. And we’ll look at the remnants of a collision and if there’s a big amount of missing momentum with one half of our detector full of energy and the other half isn’t it means something invisible carried away energy and momentum. So we don’t expect dark matter candidates or super symmetry particles to be visible in our detectors otherwise we’d see them in nature. So if we spot the remnants of a collision where something invisible has gone away we can study the properties of that invisible particle. It’s a very spectacular looking signal. Imagine you have an explosion and it only goes in one direction and you get things coming out. It really does show up.
GM: It’s almost as unintuitive as that then? It would look like an asymmetric explosion?
JN: Exactly. You would see fragments of particles going one way and nothing in the other direction. So it really stands out. Now, we’re going to need a few things to happen before we see those so I think probably it’s going to be early into next year when we start to collect data at high enough energy and high enough intensity to start really having a chance to see that sort of signal. And the data we’ll be looking at between now and then will be getting us ready to understand whether we’ve seen something in our apparatus that’s mimicking that or we’re really seeing a signal like that. Because you can imagine if half of the apparatus wasn’t working it could pretend to be like that. So we have to be dead sure that what we’re seeing is really the signal we’re looking at. And that’s what we’ll be doing in the next few months as the machine winds up its intensity and energy.
GM: So it’s going to be months, maybe years, before we get those signatures that you can verify and validate and say this is a clue as to what dark matter is. When, and I am going to be optimistic and say when rather than if, but when that happens how significant will that be for physics when you can say this is dark matter?
JN: Well I hope it’s when as well. That is a huge moment for science. Because up till now astronomical measurements have shown us that we don’t know what 95 per cent of the material in the universe is. And if we can establish first off that there is a candidate for dark matter and its properties it will have a huge implication for our understanding of what most of the universe is made of. And it’s quite odd that we have a very good understanding of a few percent of the mass of the universe and don’t know anything about the rest of it.
GM: And you’re working on the CMS detector but we mustn’t forget of course there are other detectors. Atlas is the other big one that people speak about alongside CMS but there are two other detectors running experiments that you’re involved with as well aren’t there?
JN: In this group we’re involved in the LHCB experiment which is looking at the matter and anti-matter imbalance in nature. And one of the real mysteries of course was when the universe was created from energy it should have created equal amounts of matter and anti-matter which should have annihilated each other and there should be no matter. But there’s an imbalance. The room here is full of matter and no anti-matter. And that’s a really important question, understanding what is the mechanism for that imbalance? And that’s the main target of the LHCB experiment. And CMS of course is looking for all of the new types of phenomenon by being a more general apparatus to search for those. So those are the two experiments we work on here in the Imperial group.
GM: Professor Jordan Nash in our High Energy Physics group. And as I mentioned at the start that interview was recorded before those difficulties arose with the magnets in the LHC at the end of September. In a moment why the idea of recyclable plastic bags is actually more complicated that it might seem on first analysis. I’ll be speaking to Imperial’s resident polymer polymath. First though let’s have some headlines.
Headlines from around the College
If you eat salad, especially of the prewashed packaged variety that you find in the supermarkets you might be at risk of salmonella. Now that might come as a surprise especially as you more frequently associate the disease with eggs or meat products. But it turns out that the bacteria responsible for salmonella can cling on to salad leaves and now an Imperial researcher thinks he knows why. Professor Gad Frankel of the Centre for Molecular Microbiology and Infection working with colleagues in Birmingham has been studying structures called flagella that the bacteria use to propel themselves.
But Professor Frankel found that the bacteria have a secondary use for these flagella where they flatten out under the organism forming finger-like structures that grip on to salad leaves. The discovery came from experiments with bacteria that had been genetically modified to grow without these little fingers. So sure enough when these flagella lacking organisms came into contact with salad the leaves remained uninfected. With the infection mechanism now identified the researchers hope it should help in finding methods for keeping salads free of the pathogens they come into contact with.
And also this month meet Gertrude. That’s the name affectionately given to a life-like simulator that mimics an eight month old baby girl. Gertrude has been developed by a team at St Mary’s Hospital, which is part of the Imperial College NHS Trust, to aid paediatric training. The mobile infant simulation system can be transported to various medical centres so it can therefore make training scenarios more authentic as they can be played out in the context of the actual centre involved. Gertrud’s developers are now calling for training on simulated infants to be made compulsory. The simulation technology is advanced enough to accurately mimic real-life situations. And after all, the Mary’s researchers add, airline pilots are required to rack up the hours in flight simulators.
Which is all very appropriate seeing as we’re going to be talking about flight simulators in just a few moments right here on this very podcast. And of course you can catch up with all the latest goings on at Imperial via our press office website and that’s at Imperial.ac.uk/news.
Professor Dame Julia Higgins on polymer science
But now though congratulations are in order to Professor Dame Julia Higgins here in the Department of Chemical Engineering who’s had a long distinguished and ongoing career here at Imperial. She’s been here for over 30 years. And in fact in her honour in the last few weeks we’ve just had a conference devoted to her pet subject which is polymers. Well, congratulations obviously Professor Higgins. First can you just tell me what polymers are? Because I think it’s one of those words that we all think that we know but I’m sure you can probably define polymer better than I can. So what do you mean by that?
Professor Dame Julia Higgins: Well, polymers are generically any of the long molecules but they normally refer to the synthetic ones rather than the biological ones, and indeed they are the materials we call plastics.
GM: You’re studying these polymers literally right down to the molecular level and using a technique, a tool, called neutron scattering. So what’s that exactly?
JH: Well, neutrons are particles you find in nuclei. They’re neutral and because they’re particles they also act like radiation. Just like electrons can be used in electron microscopes. But the neutrons are much heavier, they travel more slowly, and they can be used to look at the structure of materials. They’re very interesting for polymers because a neutron sees a heavy hydrogen atom, deuterium, as though it was completely different from ordinary hydrogen. Now, plastics, polymer materials, are full of hydrogen so if you can change the hydrogen in the plastic material for deuterium, or some of the hydrogens for deuterium, you can label those molecules or bits of molecules. And for the neutron it’s like having painted those bits red. So you can take a material which is a jumble of many, many molecules but because some of them have got hydrogen and some of them have got deuterium for the neutron scattering technique you’ve distinguished some molecules from the others and you can tell how they organise themselves, how they move, all those sorts of things.
GM: So what kind of things are going on in that experimentation when you do these neutron scattering tests?
JH: Well, the UK has one of the most powerful neutron sources in the world called the Isis Facility at the Rutherford Appleton Laboratory. That has apparatus clustered round it. That’s an interesting technique because it does work more like nuclear physics. The earlier neutron scattering was done on reactors but this is done on what’s called a pulse neutron source. And in this case protons are accelerated round a ring but much smaller than the LHC ring and then they’re thrown at a heavy metal target. And this could be uranium but in fact it’s tantalum. And the neutrons are essentially stripped off the nuclei and come out in bursts. We look at the bursts. We guide them on to our samples and look at them as scattering spectra.
GM: Could you think of this of being a kind of microscopy? It just gives you a really detailed high resolution idea of what the material is made of? Not just what it’s made of but also its functional properties as well?
JH: Exactly. That’s precisely it. And the equivalent also is x-ray scattering. People have x-ray scattering in the lab but they also go to central facilities and in fact at the Rutherford there’s also the Diamond Source which is a source for x-rays.
GM: So we have this technology then for taking a really detailed look at polymers and how they behave so how is that advancing the science of polymers?
JH: Well, the particular thing about neutrons is this business of being able to differentiate between hydrogen and its heavy isotope deuterium. It’s not difficult chemically to replace a hydrogen with deuterium and until neutron scattering came along nobody could demonstrate the shape of a molecule in a piece of plastic material relative to all the other molecules. And because they’re very long actually thinking about what shape they might take was quite a theoretical effort. A guy called Paul Florey made a lot of the predictions but until the experiments with neutrons came along nobody had actually seen what the molecules looked like. And then subsequently there have been lots of experiments about how the molecules deform when they’re stretched and when they flow. And all of this could only be done with neutron scattering. It’s an extremely important technique for polymer science. And if I could add just one thing, when I was a postdoc in France, before I came to Imperial, working with one of the distinguished French polymer scientists, Henri, I remember him saying in the very early days, he said in the future there will not be a textbook on polymers that doesn’t have a chapter on neutron scattering. And he was right.