The future of particle physics

Inside the CERN particle laboratory

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1:39Hello, and welcome to Inside Science, and this week we are on location. That location, we are 100 metres below a French McDonald's. More specifically, we are in one of the massive cathedral-like caverns that constitute a small part of CERN, the particle physics laboratory. The detector is off. They are upgrading CERN. They are looking to bash more particles together, more often, to find out more things about the universe.

2:10But why, and what do they hope to find out? We are here for a special episode to see exactly what's going on in CERN. We are here outside a really big warehouse that's got really big pipes, and I can see a really big metal door. Everything is really big in CERN. You can hear that there's a lot of construction going on. That's because we are above the biggest upgrade they've been up to in quite some time, and I

2:43suspect we're about to go into what will also be a really big lift, because we're going to go down there, and we're going to see what they're doing. So we're in the lift, and we're currently at ground level. This will take us not to the main tunnels of CERN, but to the service tunnels, to the high lumi upgrade. We have an altimeter, minus 32 metres, minus 40 metres, taking us all the way down to minus

3:1570 metres, where we're going to meet the man who is overseeing this upgrade.

3:25My name is Paolo Fessia. I am the deputy project leader of High Luminosity LHC. I am in charge of managing all the installation activities in the different work sites. Let's start at the basics. Somewhere over there, there's a really big tunnel. What happens in it? That tunnel hosts the Large Hadron Collider, that is an accelerator of particles, where we accelerate protons in two separate beams, and inside the experiments, as we call them,

3:58we bring those beams together in order to collide. This collision can create high energy particles. That's why we have this large detector that works like a photographic machine, in order to take photos of the events, and through that, try to understand which type of particle we are looking at. And why do we want to look at interesting high energy particles? What's this telling us about the world? Because we are moving towards the limits of what is called the standard model.

4:35This large theory that tries to put together all the different types of forces that are managing the interactions of the particles. And today, this standard model is perfect, but it doesn't explain all. So here we are pushing it towards the limit in order to try to complement it and make it evolve. So you found the Higgs boson, the particle that gives other particles mass, and you found it here in 2012, and you've been busily, happily smashing particles together all of that

5:10time. Why do you now need to stop the whole thing and give it an upgrade? Because today we are going to study much rarer events, and in order to study these events, you have to collect more of them. So we will collide and we'll create 10 times more events per unit of time. So basically you want more of those protons to hit each other? Exactly. First of all, we are going to put more fuel in the machine, more protons, and the second

5:41thing, we are going to concentrate those protons in much smaller volume in such a way that the density when they cross each other is much higher, and then the probability that one guy meets the other guy is much higher. And in order to do that, we are going to install much more powerful superconducting magnets that create much higher field, and this field will have exactly the same function that an optical lens of a telescope. Instead of putting, collimating light, it will collimate particles in the center in a much

6:17smaller volume, and therefore increasing the probability that we add a collision. We are going to also change the shape of the beam. So today the beam, they cross inside the experiments with an angle, and the beam is a kind of an ellipsoid. That means that the sections that superpose of one ellipsoid over the other is just a small fraction. This ellipse, we are going to take it and turn it in such a way that when they now will

6:51cross, they will cover completely one with the other. And this will allow us to use in much more efficient way the number of protons that we will have put in the machine. And that is the function of the crab cavity. And why are they called crab cavities? Because your beam is going to be twisted and it will move like a crab that is walking on the sand, walking not in the direction of the beam, but is walking transversally to the direction of the beam. So we are just now walking towards the top of the LHC tunnel.

7:28The LHC tunnel is 10 metres in front of us and 10 metres below us. So in a few seconds we will just be standing on the top of it. So the LHC ring is just running below our feet. So these are the service tunnels and these are, I guess, about the size of a London underground tunnel. At the moment you have got a lot of cables, a lot of MDF, a lot of construction. And I saw a bicycle, is that for getting around? Yes. In LHC we move around a lot with bicycle because you have one axis of point every 3.3 kilometres.

8:05So if the issue that you need to solve is in the centre of the arc, you have about 1.7 kilometre to go and that is much better to go with bikes. You must be fit. Of course. OK, so once you've got your cryogenics installed, all of your electricity up here, the thing's running and you've got 10 times as many collisions per second as you normally do, what's the thing that would most excite you if they discovered it? Ah, something that we don't expect.

8:36That will be the most exciting thing, something that will open a new door. Also some of the technology that we are doing here, we are also moving towards, for example, energy recovery. The big superconducting magnets, by definition, they do not use energy. You inject current, but then you don't need to still pump current to make it work. So when we are going to decrease the field, we will have here batteries that will recover the energy that gets out from the magnet and we will use the same energy after to re-energise,

9:10to re-pump up again the magnetic field. What is your electricity bill then? We are about the consumption of a city of about 300,000 inhabitants. OK, so you're about an extra two-thirds of Geneva.

Making clouds to study climate change

9:21OK, so my name is Antti Onnela, I'm a mechanical engineer at CERN, and I'm the mechanical engineer in the cloud experiment. So the building is entered here. So this building, we're in this huge warehouse, and this sits at the end of one of the early accelerators. Yes, yes, on the side. So it's part of the accelerator chain. To get the protons to the LHC, the biggest accelerator in the world, in fact, it's accelerated

9:53by smaller accelerators. You start from first gear, second, third, fourth, et cetera, and this is about the third or fourth gear. When it's not accelerating protons for injection to the bigger accelerators, all the rest of the time it can be used for sending protons to target areas, which is this one over here. The protons are hitting a target upstream over here, and then we get secondary particles over here. And those secondary particles are guided by magnets to these target areas, where we then

10:24have experimental devices, development of instrumentation, and then we have this zone here, which is used by cloud. How does one make a cloud? How does one even define a cloud? Well, clouds we are making with the reduction of pressure inside the aerosol chamber. We have to be able to make condensation on aerosol particles inside the chamber. So you've got a chamber full of little particles of what? What we are studying in cloud, formation of aerosol particles in the atmosphere.

10:56There are two kinds of aerosols in the atmosphere, directly produced aerosols, which are coming from sand, dust, exhaust emissions from cars, industry, et cetera. And then there are aerosols which are indirectly produced, so they are first in gas phase, but which then are converted into particles in the atmosphere. And these mechanisms of how to get into these aerosols is the key thing that cloud is studying. We're looking at a sort of thing which has got pictures of how these are made, and you've

11:27got a cow. How's the cow making aerosols? So the cows are, and agriculture in general, it is emitting ammonia, amines, which are then part of these aerosol formation processes in the atmosphere. So then you've got your aerosols in the chamber. How do you then make the cloud from that? What's the next step? So most of the studies, in fact, until now, have been on the aerosol formation itself, not on the formation of the clouds. The aerosols are needed for forming cloud droplets.

12:02So they have a cloud condensation nuclei, as they are called, on which water molecules are going to condense to form droplets, ice particles in the atmosphere. So in a sense, we are looking at the birth of clouds. This is all fascinating, and you've got a very big chamber beyond us that all this happens. Why is this happening at CERN? Well, the key reason for being at CERN, in the gas-to-particle conversion processes, electric charge is one of the key elements on the formation rates.

12:37And electric charge in the atmosphere is created from a few different origins. One of them is cosmic rays, and cosmic rays ionizing molecules in the atmosphere. And to study how much this ionizing radiation will influence or not aerosol formation rates, the idea was that, okay, why not putting the aerosol chamber to a beam where we can modulate the cosmic ray quantities, which otherwise we can't. In fact, they just come as they come. But here we can. So we have kind of similar particles as the cosmic rays are,

13:12and we are able to modify the ionization rates. Effectively, what we are doing with the particle beam is like elevating the chamber in the atmosphere to higher altitudes, because the cosmic ray levels at higher altitudes is higher. And that's why, so listeners might think that this is called cloud because you make clouds, but it's called cloud because it's Cosmics Leaving Outdoor Droplets, this totally natural acronym. You must have been so surprised when it turned out that spelt out cloud.

13:42Yeah, I think that must have been one of the most important things. How do you invent the acronym? That makes some sense. So you've got the clouds in the chamber. Describe the chamber to me. The chamber itself is inside that thermal housing. So if you want, we can go to the platform to see a bit of the scale.

14:01So we have a 20 centimeter thick layer of insulation, and then we have 15 centimeter thick layer of air, which we circulate when we are running to control the temperature of the chamber. And what you see there behind is the wall of the chamber itself with a couple of ports for putting probes, instruments inside the chamber. So it's like a massive thermos, it's just lots. Yes, yes, yes, exactly. And we are able to go to around minus 70 degrees.

14:32And so presumably you can't go in there and be rained on or experience your cloud or... No, no, absolutely not. So we keep it closed at all times. We are always flushing it with a very clean air to keep the inside of the chamber as clean as we possibly can. These are the things that Eva can be explaining.

14:54Recording here? Yeah, it's recording now. Oh, hello, hello. Hi, Eva. So I am Eva Sommer. I came to CERN as a PhD student, and I also work as the cloud-run coordinator. We are very different from most other experiments at CERN. We are an environmental science experiment. Now, I noticed on the way into and out of the cloud chamber that there were a lot of clouds above my head that didn't need a cloud chamber at CERN. Why are we studying these at all in a cloud chamber? Why don't you just look at the many clouds that are made in the atmosphere without all of this faff? Well, because our atmosphere is extremely complicated.

15:27We have millions and millions of different compounds in our real atmosphere all the time. And the one thing that cloud can do, we can isolate different molecules or different chemical processes and really study only that one thing without being confused by the millions of other things that are going on. So the cloud experiment at CERN is the world's cleanest aerosol chamber, which means that we can control all of the trace gases that we put inside our chamber and down to the part per trillion volume level. And why? Why do we need to study clouds?

15:59So in the end, the overarching goal of the cloud experiment is to improve our uncertainties in climate predictions. We as human beings, we warm our climate by emitting CO2 and other greenhouse gases, but we also produce a certain amount of global cooling. Now, clouds, as we know, they tend to be white, right? So clouds tend to have a cooling effect on our atmosphere. And they do that because as we receive radiation from the sun and sunlight hits the planet, if it hits a cloud or a white surface,

16:29a large fraction of that is being reflected back into space. So overall, if you have more clouds, you have a cooler climate. So for us to actually understand climate change and to make reliable predictions for how the climate will evolve in the future, we need to understand how our clouds and the cloudiness of our atmosphere will behave in the future and has behaved in the past. So if we want to understand what our impact on the cloudiness of our planet is, we need to understand all of the microphysical processes that are involved in making clouds and making aerosol particles

17:00so that we can feed this information into a climate model and then can make accurate predictions. Recently, you've been looking at marine aerosols. What are you injecting differently into your cloud chamber when it's marine versus terrestrial? So at cloud, we can simulate different environments and we distinguish them by, of course, by temperature, by humidity, but also mainly by the trace gases that we inject. In the marine atmosphere, we have this compound called DMS or dimethyl sulfide. And this is emitted naturally by phytoplankton.

17:30The DMS in the real atmosphere is then oxidized and to form two compounds that are important for aerosol particle formation. One of them is sulfuric acid and the other one is called MSA. So we have simulated cold conditions from between minus 50 something, I believe, and like minus and plus 10 degrees. And we've had these two compounds made from DMS in our chamber. And what we found and what was not known before is that MSA, very much like sulfuric acid, is very active in participating in the formation of aerosol particles.

18:00So the big implication that this new publication of ours has is that we have identified a natural source.

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19:41Of aerosol particles, which is not impacted by human activity as much. This is very important for actually estimating this offset that we are causing in addition to the global warming. Do you find it strange that something as basic as a cloud isn't completely understood? Well, if I'm not giving an interview here, I'm sitting here writing my thesis. So I want to say that a cloud is not a very basic thing. It's a very, very complex mechanism to end up with a cloud in our atmosphere. It's actually fascinating that it works at all.

20:12So we have come and grabbed ourselves a coffee.

Planning the Future Circular Collider

20:23We're in the CERN cafeteria. I can see Mont Blanc in front of me. And I have a bunch of physicists, mathematicians, and engineers chattering away behind me. But in front of me, I also have Guy Wilkinson. And we're here to talk about the future. We're at a particle physics laboratory. We're above a really, really big tunnel. But there's a plan to build a really, really, really, really, really big tunnel. Tell us about the Future Circular Collider.

20:55Yeah, the Future Circular Collider is a project that's been gestating for, I think, about 15 years now. So this would be a collider of circumference 91 kilometres to be contrasted with the LHC, which is 27 kilometres. It would go under the lake, but it would collide electrons and positrons. That's different from the LHC, which collides protons and protons. Its purpose would be to make extremely precise measurements of many of the most important subatomic particles we know of, in particular the Higgs boson.

21:25This will for sure tell us an enormous amount. What I don't know, but it will be a very fascinating journey. It sounds like a huge project. Why does the tunnel need to be so big to achieve that? If you accelerate electrons or positrons, they have the characteristic that they emit radiation as you try and turn them round a bend. This is useful for some applications, but for particle physics colliders, this is a bad thing because you're losing an energy. So in this accelerator, we want to go to very high energies,

21:58we want to have many, many collisions, and so we want to minimise this loss of energy through what's called synchrotron radiation. One way you can do that is by making the bend they go around as gentle as possible, and that motivates having a very big circumference tunnel. Why electrons and positrons? Why specifically this? Electrons and positrons, when they collide, the environment is incredibly clean. The advantage of protons and protons is you can go to very high energies without suffering this problem of synchrotron radiation

22:28I said earlier. But environment is very messy. There are backgrounds. So if you're wishing to study the Higgs boson, for example, you can only really spot the appearance of the Higgs boson in a collision if it does something very dramatic, very unusual. From this, the LHC has made some very important measurements. But if you want to characterise everything that the Higgs boson does, you want an environment where you can see every Higgs boson that's produced, this can only be done in an electron-positron collider. And when would it be finished?

22:59We would hope for project approval in 2028. Construction of the tunnel would begin in the early 2030s, so we're talking about the mid-2040s. How much is this going to cost? It's been costed at approximately 15 billion Swiss francs. So that's about 14 billion pounds, 18 billion US dollars. It is a very large amount of money, but let me try and put this in context. So this is something that would be used by an extremely large community of physicists. Moreover, it is for a project which would last

23:31in its first incarnation for 15 or 20 years. And then there is the possibility to reuse the tunnel for a new accelerator which would run for another 30 years. So we do feel that this is a value-for-money investment, one which really does justify the cost. It hasn't been met with universal acclaim in the physics community, has it? There's been some physicists who are quite critical of the proposal and the scale and say that the money could be better spent on smaller projects and more smaller projects.

24:03If we speak about the particle physics community, there has not been unanimity, but that is never the case for any project. But there has been an overwhelming consensus. There was a process which concluded early this year where we examined with great detail what would be the best new collider to build. There were various possibilities on the table. None of these offered the same physics reach, the same precision for the studies of the Higgs boson, nor breadth of physics in other areas.

24:33So when it came to each country casting its vote and each physicist expressing their opinion, I would say that the verdict was overwhelming to a surprising degree. One quote, so Helena Abramovich from Tel Aviv University said, the issue is whether the community is willing to sacrifice the next 50 years to get a toy which may or may not be the way for fixing the standard model. It may or may not fix the standard model, but everyone agrees it will tell us an enormous amount and the journey will be very worthwhile.

Turning tunnel excavation waste into soil

25:11We are 20 minutes outside of Geneva in the countryside. We are still above the CERN beamline, which is why you might hear a bit of construction work in the background. But we are also surrounded by plant life. There are olive trees, there are fruit trees, there are hedgerows. And we are here with someone who can explain what is going on and why this is still very much to do with CERN. My name is Christiana Staudinger. I am a plant biologist and I help CERN with working on the project Open Sky Lab.

25:44That's a project where we develop strategies for how we could use excavation materials to create engineered soils or planting substrates from them. CERN digs a lot of tunnels and is planning to dig a lot more tunnels and when you do that, you've got a lot of stuff you need to use. Yeah, so when CERN constructs, for example, something as big as the Future Circular Collider, most of the excavation materials that surface

26:16are sedimentary rocks that come from the erosion of the Alps. And these rocks, we call them molasses. Here we want to test whether these molasses materials contain minerals with a specific texture and with specific physico-chemical properties that are really positive for constructing soils. Can you define for me what a soil is? For me as a biologist, the soil is a living system and it's the very first crust that we have

26:48on our terrestrial surfaces that allows for our life to unfold. And as someone who has spent quite a large part of his life walking on things that I consider to be soil, it's quite a surprise to me that we might not have enough of it, but we don't. There is a shortage because we, first of all, we destroy so much of it through the process of soil artificialisation. And also soils grow so slowly.

27:19The global annual average is of about 10 micrometres per year. We risk running out of soils if we continue destroying them. And so you think that this waste, waste, which we'd normally call waste, that we're taking from the tunnels underneath CERN, could actually have value and could be something that can be turned into a soil? Yeah. Those mineral waste, they can be used to really specifically target the soil functions that we want to reach

27:50in some years from now. That could be something like the capacity to hold water, the capacity to filter water, or the capacity to build biomass, for example. And that's what we are doing here in the OpenSkyLab. We installed our soils, we developed our soil formulations, and from now on we observe how those soil functions slowly start to emerge and how our soils start to be populated by microbes, plants, microarchipodes, etc., etc.

28:21Take me through the process of, you take the waste from CERN, you take it from the tunnels, and you bring it up here. What happens next? What do you do and what does nature do so that at the end of it you have a soil? We crush the molasses to have a particle size distribution from about 0 to 20 millimetres. And then the molasses will be mixed with varying proportions of organic amendments. In this case we used green waste compost.

28:54Our plant species that we selected and our management practices, in some instances also our microbial amendments, will do the rest. So show us what we've got. So here we're walking by a hedgerow. Yeah, here we have a hedgerow. This hedgerow combines so-called ornamental species, but they're also very useful for pollinators. We also introduced other species that enhance insect biodiversity in its surroundings.

29:24So that's the thought that we had behind the selection of those. And is everything growing as it should? Here it's growing really well. For all of our shrubs and trees that we planted, we only have a mortality rate of 10%. So that's still at the moment very positive. We will see what happens over the coming years. And so then you leave this out and slowly nature colonises it and it becomes what you need. And we observe it. So we have installed lots of soil sensors

29:56and we do regular soil sampling events. And we observe the slow colonisation, we observe the slow emergence of the soil functions. And from this first year, we can already say that the nutrient cycles are starting to be formed. And also we have some first soil structure formation, which is very important because soils need a lot of porosity to be functional. And we also have quite satisfactory biomass production. We're back in CERN cafeteria.

30:34Mont Blanc is shining a little less bright and the physicists are now drinking beers, not coffee. And below us, the tunnels are preparing to smash even more protons, even more often. The glorious thing is, when they do, we genuinely don't know what they will find out. That's it from Inside Science on tour at CERN. Cheers. Cheers.

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