Transcript Oct 2008

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.
Edit Content

GM: Given all that then, such an important part of the science, where does that lead then? What does it mean in terms of real world applications?

JH: Well, people are interested in how the polymers organise themselves. We’re particularly interested in how they move because that controls how you process them, how you make them into a shape. If you want to squash a polymer material into a shape you’ve got to push it through dies and tubes and stretch it and so forth. And the way the polymer behaves is a consequence of its organisation and its flow. I’ve not been involved in these particular experiments but there were people at the meeting last Monday describing how they labelled the polymer molecules and setup a mini version of the processing equipment in the neutron beam and they were able to confirm the theoretical models of what the polymer molecules were doing as they were pushed through these dies and into the tubes and into the shapes. And it has huge importance for industry because until recently nobody had an idea of exactly how if you changed the molecular weight of the polymer you were going to change all the way it behaved when you processed it. And of course you don’t really want to build all the process equipment again just because you’ve changed some small factor of the polymer like its molecular weight.

GM: So you’re talking about real applications in terms of how polymers are manufactured. So obviously this is to do with materials. Are they materials that people like me might come into contact with in everyday life?

JH: Quite a lot of the work, because it’s the simplest molecule, has been done on polythene and you certainly come into contact with polythene in wrapping, in sheeting, in covering and in all sorts of ways. And it has to be pushed and pulled and generally stretched into the shapes that you need to use it. The polythene bag, which is a cheap and simple thing actually involves the polymer molecules having been pushed into that shape of the polythene bag.

GM: And yet we’ve just seen quite recently the 57th anniversary of polythene so you think we know everything about it already. How does this kind of science allow us to advance our understanding of a material that in many ways I suppose we’ve taken for granted for quite some time?

JH: Well, when they first made polythene they made knew that they’d made long molecules but there would have been a distribution of sizes of the molecules and probably not a very well characterised distribution of the sizes and they would have found out how to process it by trial and error. Now, what people have been trying to do more recently is to design the way it’s going to be processed and design-in the properties. If you make polyethylene in different ways you can have it with more branches or less branches. It doesn’t always make a linear material. If it has more branches that stops it crystallising. It makes it a softer material. Now, you can design your process equipment by trial and error, and historically that’s what happened, but the people who are nowadays in the industry would prefer to be able to design the material to be processed in the way such that they have the properties at the other end.

GM: I suppose there must be an environmental point to all this as well because there’s a lot of research now going into making materials recyclable. And I’m thinking especially of polythene bags as well.

JH: Yes, 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 round so you’ll probably have to use it for a garden gnome or something if you wanted to recycle it. And so people are making materials which are molecularly structured to be able to break them up, which your standard polyethylene probably wouldn’t be. On the other hand what we tend to forget is polyethylene is effectively oil. It came from oil. It’s carbon and hydrogen. It combusts very well so one of the things one should be thinking about using polyethylene for or some polymers is for energy. They should be part of combusting waste.

Dr Varnavas Serghides shows Imperial's flight simulator

GM: Professor Dame Julia Higgins there. Well, currently I’m flying over the Sussex countryside at about 3,500 feet in a Boeing 737. In the captain’s seat is Dr Varnavas Serghides with the Department of Aeronautics. And I think at this point we should come clean, shouldn’t we Dr Serghides, and point out that we’re actually in a flight simulator. We’re very much on the ground here in the department. Tell us a bit about this simulator.

Dr Varnavas Serghides: The simulator is a full motion simulator which we acquired in January 2005 and is used for teaching and research. So on both sides. We have many applications of the simulator, and the one we are flying is a Boeing 737, but in many cases we do fly aeroplanes we do design within the department.

GM: So there are so many different things you can do with this. At the moment, as you say, we are in a Boeing 737. You’re flying along at the moment and you’re doing many of the manoeuvres that a commercial pilot would do aided and abetted by the technology you have on this simulator. For instance, we’re not talking about you just sitting at a desk somewhere in the department with a computer mouse and a monitor. You’ve got full vision for a start. Looking in front of us we have four monitors and the appearance they take on is as if we were looking out of the different sections of the cockpit window. So the whole thing is incredibly realistic isn’t it?

VS: It is very realistic. It’s very close to reality. We try to programme the displays to simulate the environment as closely as possible. It gives the impression when you’re sitting inside the simulator that you are in a real aircraft. You feel the motion. You have the external view. You have the feeling of the aircraft in flight. You have the instrumentation in front of you which closely resembles the one which you will find on a real aircraft with a glass pocket like that. And at the same time you have the sound surrounding you together with all the warnings that you would get from a real live aircraft.

GM: And it’s full motion. The fact is we’re sitting on a platform here and it is moving around. You’re going into a left turn at the moment and we can really feel ourselves leaning to the left and occasionally we just get little judders, little bumps, as we go through what I guess are pockets of turbulence. Can I have a little go? Is that all right to let me have a little go?

VS: Yes. Right, you have control.

GM: Right, I have control in a manner of speaking. I don’t feel very in control but I have one of my hands on the control column here and I’m going to try a few things out. So if I pull back on the control column the nose is going to go up so we lose a bit of the horizon. At the moment I’m looking at blue sky. You’re reducing the power here. So you can hear in the background the sound effects which are so realistic. You can hear the engines have throttled right back. And as any pilot knows if you pull back too much and the nose goes too high we stall. Shall I try stalling it?

VS: Yeah. Pull back on the controls and the speed drops very quickly. You can see here. So first we’ll be getting the first warning. So you can hear the stick shaker. The aircraft goes into a stall and it rapidly descends down now. You are recove ring well by pushing the nose down, maximum power on the throttles and you can hear the engines are revving up and the aircraft begins its recovery. So pull back on the stick and the aircraft has just recovered at this point.

GM: Now, do you trust me enough to have a go at landing this speed bird? Can I try that?

VS: You have control now. You’re about three miles from the runway so short finals.

GM: Okay, short finals. I can see the runways ahead of me. There are two runways, left and right obviously. Shall I come in on the right runway then?

VS: Yes, come in on the right please and I will actually help you with the throttles and I will select for you an undercarriage. That will help things. So you have control now.

GM: And that rumbling sound is the landing gear coming down. So the landing gear is down and locked and I’m pointing the nose down trying to get down to the ground. I suspect that this is a slightly fast final approach. Faster than it should be. This is not what you call a gentle glide slope.

VS: You’re at 300 feet now.

GM: Over the apron of the runway. I’m over the runway now and now I have to bring the nose up. I kind of landed and then the plane bounced right back up again. Oh my goodness. I’ve completely crashed it.

VS: Really this happens very easily. It takes some time to familiarise with correcting your speeds.

GM: It really gives you a sense of the juggling act that every pilot performs when you’re coming into landing. My excuse obviously is I was trying to do an interview and hold the microphone at the same time. I’m going to stick to that excuse. But it is all about having that crucial combination of exactly the right speed, the pitch of the aircraft has to be right. A load of things have to come together. It’s almost like a dance to successfully kiss it down onto the runway.

VS: Very much like so. It takes a little practice and landing an aeroplane is one of the most difficult things for pilots. It takes a long time to get to do it very precisely. It’s not just doing it but doing it precisely. A good landing, pilots say, starts with a very nice approach. So once you have established your aircraft in a nice approach of about 80 miles away then an aircraft will come in. Remember this is a fast aeroplane and also it’s a big airliner. In that sense it will have much higher approach than a light aircraft. People need to get accustomed to those bits.

GM: So now that we are on the ground. Imperial College is a university. It’s not a flying school. You’re training engineers and not pilots here so why the flight simulator here in the Department of Aeronautics?

VS: Very good question. The flight simulator is very important for us because it is providing us with the ability to demonstrate to the students how an aircraft flies without having to take them to an airport and put them on an aircraft in a very expensive way. It is also a very, very safe way of demonstrating very difficult manoeuvres, system failures which are very important in our technology engineering training environment. So for us really the flight simulator is a virtual flight test laboratory.

GM: And it’s largely I suppose about being able to design your own plane. I mean here we’ve been playing around with a Boeing 737 but the fact is you can design your own aircraft, load that design onto the flight simulator and see how it flies can’t you?

VS: What we do is we fly the aircraft using the normal procedures for flight testing aeroplanes in order to establish the data that we require for a particular phase of flight depending on what we are looking for. And eventually after we do a complete flight for an hour or two with various manoeuvres we come back here and we find all the data recorded and we analyse and compare it to our predictions. See how close they are to our calculations, which makes it very attractive for our own engineering work and we can use this for developing our aircraft further.

Because our design will go through various development stages and eventually, as in real industry, the flight development testing will lead to a more optimised aeroplane together with all the calculations behind it. On the other hand the students get a great satisfaction in actually seeing their results working. Because it’s a different thing from doing calculations and knowing perhaps that they are correct but when you actually put all the calculations from a group of students, about 20 people, together who are doing separate calculations and see this working in harmony to a proper flight as expected by an aircraft of its class it’s really very satisfactory.

GM: I suppose it’s a great teaching aid. If you’re lecturing the students over some really complicated principle in flight you can show them all the equations in the world on the whiteboard but then you can actually demonstrate those principles right here in, I say real flight, but as close to real flight as you can get without actually leaving the ground.

VS: It is one of the fundamental applications to demonstrate asymmetric attributes and dynamic instability modes to the students. Because in several occasions we discussed this in the classroom. We describe them as best we can with diagrams and any other aids that we have available in class but it’s very different. It’s here you can actually demonstrate what you can demonstrate in the air. This luxury is not available to the students directly. The simulator is an excellent replacement of that. It shows them how this will happen and how the aircraft attitude and speeds will change during a manoeuvre and they can actually link this to the actual equations. It’s very important to be able to link the physical phenomena to the equations and that will produce better models for design of the aircraft.

GM: How unique is it that here at Imperial College we have a full motion flight simulator like this?

VS: I think we are lucky to have one of the best simulators available to universities. It was manufactured for us to our specification. It’s a customised model by a US company in Pittsburgh. We know this is the only example in Europe outside the US. Although this is very much a customised design which probably makes it unique in the world.

GM: You’re actually a qualified pilot yourself aren’t you?

VS: Yes, I am a fully qualified pilot for more than 25 years now. I’m flying quite often with many different types of light aircraft around the UK. I really love aeroplanes. I was very enthusiastic from a young age about aeroplanes and that led me to this profession which I love. Definitely it is a very interesting profession to be able to design aeroplanes and at the same time to be able to convey this knowledge to students at Imperial College.

GM: Well, Dr Varnavas Serghides thank you so much for showing us the flight simulator. I’m sorry about your Boeing 737 that I managed to trash but it seems as if we can refigure it and get it back again.

Well that’s it for this edition. We’ll have another podcast for you in November of course so do join us for that. This theme music has been written by Ozgur Buldum and the Imperial College podcast is a co-production of our Press Office and the Science Communication Group here at Imperial. The producer is Helen Morant and I’m Gareth Mitchell. Have a great October and I’ll see you in November. Bye for now.