Physicists From Australia

"The next thing we want to do with those particles is to give them some energy. That's the basics of how an accelerator works. I've got a machine here called a which does that..."

"Building up charge, actually building up , is the key to giving particles energy in a particle accelerator. ...Now some of the first particle accelerators were actually genuinely using this mechanism of having a belt and some rollers, and building up lots of voltage. They were called Van de Graaff accelerators. They still exist. I've worked on one... If they're the same charge, which get repelled, and there's force there, they're pushed away and they gain some energy... [I]n the case of an accelerator we'll get our particles... going faster and faster and faster toward the speed of light."

"I have a demonstration... which is the simplest particle accelerator I could make.... in a giant salad bowl. ...[W]hen it goes over the charged strip it picks up the same charge and it gets repelled ...then it hits the grounded strip and it dumps all of that charge, but it keeps its momentum, it keeps rolling around ...So every time it goes over one of those four [repelling] strips ....it gets a kick, or gets accelerated and it gains energy again and again. ...In this demonstration, the ball has to change charge, and fundamental particles don't change charge, so in this case my voltage in constant and the ...[ball] changes charge, in a real accelerator we have a constant charged particle, and that means we have to change the voltage."

"Why couldn't you put your pet in a particle accelerator? ...It doesn't have an electric charge. ...He's slightly too big, and the other thing... he's going to be affected by the vacuum in the pipe of the machine..."

"What I'm going to do is suck out all of the air out of this container and see what happens to marshmallow man, or indeed, what might happen to our pet bunny rabbit in a particle accelerator. ...Oh my gosh it's huge! That's amazing! Sorry, we haven't tested this. I didn't realize it was going to be this good. ...That's probably what would happen to your little bunny rabbit, but in a slightly more horrific fashion."

"So my number two thing you probably shouldn't do with a particle accelerator. You probably shouldn't put your head in the beam... On this one I want to have... a vote... What might kill you first? ...Would your head freeze because of the ? It's at minus 271 degrees Celsius] in some accelerators... take the Large Hadron Collider for example. There the magnets are pretty cold, or would the heat from the beam make your head explode, or would your head explode from the , or would you die from the dose? ...I want a show of hands for which one you think would get you first."

"It depends on which accelerator we're talking about, but let's consider the . ...It's minus 271 degrees. ...This is a picture of one of the 15m long s, one of the [beam] bending magnets in the machine... but it's extremely difficult to get your head in there. So... you wouldn't stick your head in the dipole. You'd stick it in somewhere easier... that wasn't cooled down to minus 271."

"What about the ? ...People have done studies in outer space of astronauts and how long they could survive in the vacuum... That information say that you can survive in outer space with your spacesuit open for about ten seconds before you're ripped apart by the vacuum. So I don't think that's going to get you first."

"So what about the heat from the beam? Well this is a challenge... [I]t's actually incredibly difficult to stop the beam, and if you put your head in front of the beam... it would actually go straight through and out the other side. In fact it has enough energy to go through your head and out the other side about 100,000 times before it loses all it's energy... [T]hat's actually one of the issues they had to deal with when designing the machine, is how do you stop the beam... [W]e want to stop it occasionally, intentionally..."

"So they had to put a lot of effort into designing... the , which is a massive long block of very dense , which absorbs the energy. But even then there's so much energy that they can't just dump it directly on it, or the would make the thing explode. So they actually have to paint the beam in... a swirly pattern... to spread out the load of the heat from the beam on this huge graphite block."

"If you just put this beam onto a massive block of copper, you could actually melt 600 tons of copper from solid to liquid, just using the Large Hadron Collider beam."

"So it's interesting, even though it seems like a stupid question to say what would happen if you stuck your head in it. It does actually present some interesting real problems in engineering, in actually designing these machines."

"Radiation effects. ...There's this guy, , who... before the days of such strict health and safety, somehow managed to bypass a safety mechanism on an accelerator, and stick his head in a 76 GeV proton beam. Now that's quite a lot lower than the Large Hadron Collider beam, but the amazing thing is that he just saw a really bright flash, and he didn't feel any pain at all... Most people think, "Well, this beam, it's got lots of energy. It will just destroy you" but actually that's not quite what happened. ...[A]fter it happened his face swelled right up and the skin on that side pealed off, but he didn't die. ...[H]e went on to get his PhD and... he worked as a scientist for many years... [H]e's actally still alive in Russia, living in relative obscurity. ...A journalist interviewed him few years ago and... because the side of his face that the beam irradiated was paralyzed... and he hasn't been able to move the skin on that side of his face for so many years. That side of his face like it was... the day that this accident occurred. When I... read this, I was like, "Miracle cure for aging!" Yea, paralyzed face is probably not a miracle cure..."

"So you can actually put your head in the beam of an accelerator and survive it. And he's not the only one to have done it."

"In the days of Cockroft and Walton, when they were first developing particle accelerators they didn't know about the dangers of radiation, and so one of the ways that they counted the events... what was happening in their experiments, was... to sit... under the beam. The beam would come down, some nuclear reaction would happen, and... his fluorescent screen... would light up every time what they were looking for happened... [T]hey would sit there and count each time it lit up, sitting underneath the beam, being irradiated. ...[T]hese people lived relatively healthy lives, and Cockroft and Walton got a for work, which doesn't justify it, but there have been people who have stuck their heads in particle accelerators."

"Nowadays you wouldn't want to do that voluntarily, and you wouldn't want to do it without understanding the consequences, but there are some situations that you might want to do it in... [T]here's a very good reason for that, because if you take a much lower energy beam that the Large Hadron Collider beam, and you put it into water, or into the human body, or into tissue and you start it with the correct amount of energy, it will actually slow down and stop, and deposit almost all of its dose (or its energy) in one spot... [W]e call this the ."

"Now the radiation dose that the LHC beam could give you could kill you 76,000 times over, but the radiation dose you'd receive from a beam of say 200 MeV, a relatively modest proton beam, is much lower and can... be used to treat cancer... [W]e use this in... , which we're getting in the UK. We actually did pioneer it and... it hasn't quite come back onto the NHS yet..."

"[I]n cancer therapy usually you like to direct a dose of radiation exactly where you'd like it, so in this case... a child with a spine that needs irradiating. They've had a tumor removed from the base of the skull and they need to irradiate the spine in order to stop the cancer spreading down the spine... With... usual X-ray radiotherapy the dose distribution there is the best that we can do using all modern techniques. You can see that underneath the spine in... the stomach area there is quite a lot of radiation dose that we might not want..."

"If you use protons instead you can... get a much better defined distribution of the dose and this is really a fantastic treatment. It is more expensive than x-ray radiotherapy, but based on the basic physics of how a beam reacts inside... the body, or inside tissue... it's a fantastic treatment, and one that we should look forward to using in the future."

"So it sounded like a crazy question, but if you had a brain tumor you might very well want to stick your head in the beam of a particle accelerator."

"Number three. Don't use a particle accelerator as a death ray. When I was putting together this lecture I asked... my very esteemed colleagues, "Has anyone ever tried to develop an accelerator as a weapon?" And they said, "Oh mumble, mumble cold war, space, Star Wars something or other... No" That was their conclusion... They were wrong."

"People in the U.S. did think about building a particle accelerator (a neutral beam accelerator) that they would launch into space... and then they would use it to shoot down satellites and... missiles and destroy anything that they didn't like, because they were going to have this super powerful beam in space."

"Well they quickly realized that this was crazy, and that they were never going to be able to actually make a weapon out of one of these machines. Mostly for the reasons that I explained before. Even if you had the Large Hadron Collider in space, I have no idea how you'd get it up there, but even if you did, it would... be difficult to do damage with it. Mostly because beams would just go through things and out the other side."

"But they did, in fact. One of the interesting things I discovered, they did put a particle accelerator in space, which I think is fantastic."

"They developed this machine which was only about this big [~1 meter] and they used ultra-lightweight materials, and it only weighed about 50 kg. So compare that with a 27 kilometer long ring. ...It was only low energy but they... sent it up in a rocket and they actually tested it in space and brought it back down... and they tested it again on earth, and it still worked, which I think is an incredible feat of engineering... [P]eople really haven't heard of this experiment... It's called the BEAR (Beam Experiments Aboard a Rocket) project in 1989, and I have a contact who worked on it..."

"So we can't use it as a weapon. ...No deployed weapon has ever used this technology."

"What could you do... if you took particle accelerators, and you made them really powerful... [T]his is something that I work on, is taking proton accelerators of relatively low energy, but putting more and more particles in, and getting a really high beam power..."

"[O]ne of the reasons we want to do this is because we want to drive... an . This is where you take a , a fission reactor. In the core, instead of having , it has an element called , which is... much more abundant, and you don't have to refine it. You can use all of it. Hook up to the reactor a particle accelerator, a very high power proton accelerator. So the protons come in and they smash into a heavy metal target and create s... [T]hose neutrons... drive the reaction in the reactor, so without the accelerator there, the reactor is subcritical. It doesn't produce energy. It doesn't sustain a , but once you add in the accelerator you can continue to drive the reaction and generate energy... [I]n fact you could transmute existing nuclear waste into something much shorter lived and much safer."

"So there's some really interesting applications of accelerators, way outside of the realm of particle physics, that we're starting to get a handle on."

"The only problem is [that] the accelerator for this is about 10 times more powerful... than we can currently make. So there's lots of challenges for people like me who design accelerators, to try and come up with ways of making them more and more powerful, for very good reason."

"So we can't use it as a weapon of mass destruction. This is another one... that someone told me that you shouldn't do with a particle accelerator... [Y]ou shouldn't eat it, which is true."

"There's this guy called Monsier Mangetout... a Frenchman who, according to Wikipedia ate all of these crazy things. Even he, though, wouldn't eat a particle accelerator because parts of the machine become radioactive, and while he seems to be fairly stupid, given the things he ate, even he wouldn't go that far."

"So what is ? It's energy in the form of moving particles or waves, emitted by an atom or another body as it changes from one energy state to another. That's the official definition."

"[Y]ou can have two... main types of radiation, which are ionizing, or non-ionizing."

"Now is the stuff that does us damage, and there's three... types... called alpha, beta and gamma radiation. ...Alpha radiation won't go through your hand, beta radiation won't go through a piece of aluminum [a few millimeters thick] and gamma radiation is penetrating and won't go through a big piece of ."

"The interesting thing about radiation is it is naturally present in most of the things around us. ...How many bananas do you think you'd have to eat to get a dose of radiation that would make you sick? ...It's the in the bananas. ...A very small percentage of the potassium is naturally radioactive, but you... have to eat five million... in one sitting to get sick..."

"That thing... is radioactive. They're called thoriated rods, and they're used in welding. You can... just buy them."

"This thing... is a , and it will tell us whether these things are radioactive. ...There is something coming off [clicking noise from the thoriated rods] there. Just to demonstrate that the bananas are really only mildly radioactive, we can't pick them up with a Geiger counter. It's really is very mild."

"So when we're thinking about radiation and radioactivity, it is worth keeping in mind that just the fact that something is radioactive does not means it's harmful..."

"There are foods which are naturally radioactive, but most of us would like to think we've never eaten food that actually been in a particle accelerator. ...That sounds a bit crazy. ...In the UK we don't eat many things that have in a particle accelerator but things like herbs and spices, and some other things occasionally go through a process called cold pasteurization, electronic pasteurization, which uses electrons from a to treat the food. ...It is legal in the UK and in the EU, and it's fully authorized... [T]here's a number of foods... which have been irradiated, or could have been irradiated, and that goes... from bananas, sometimes... to slow down the ripening process... so they have a longer shelf life... [A]s you increase the amount of radiation that these things are treated with... from some grains, seafood to kill bacteria, herbs and spices are a more common one, and then even sometimes higher doses on things like poultry, to kill ."

"In the U.S. if you see this green symbol on your food, that doesn't mean it's organic. It means it's been irradiated, which is a little bit misleading..."

"This is not a dangerous process. In fact it's a really really useful process to kill the bacteria in our food and make it healthy for human consumption, and just because we've irradiated it does not mean that it becomes radioactive. So there's a distinct difference here between a naturally radioactive food, or something [like a thoriated rod] which would be genuinely harmful to me if I ate it, and food which has been irradiated, because it's only gone through that process to treat it to make it fit for human consumption."

"A lot of s' food is irradiated before they send it up so that they... aren't going to get sick from it."

"So yes, you probably have eaten something that's been through a ..."

"So the final thing that you probably shouldn't do with a particle accelerator is: You probably shouldn't destroy the Earth with it. ...People seem to think that when we design new massive particle accelerators that are going to have particles that are huge energies that we've never created before in the lab, that somehow... we just built it for the lulls, and then we're going to destroy the earth with it, and that we haven't quite thought it through, and that we're not quite sure what we're doing... If you're at all concerned, please go to HasTheLargeHadronColliderDestroyedTheWorldYet.com and... you can tell me what you find there."

"In answer to some of the questions that we had a few years ago when the Large Hadron Collider started up... "Could it destroy the world?" ...The most convincing answer to me as to why it couldn't, is because we have particles in outer space from cosmic rays and things like that, at much much higher energies than we could ever dream of creating in the lab. And so far they haven't done anything catastrophic to us and we're perfectly fine. So in terms of just reaching a higher and higher energy... it doesn't really matter what we do in the lab. We should be safe on earth from these high energy particles."

"[I]f we start creating things like mini black holes, which we may or may not, they will pop out of existence so quickly that they wouldn't have time to suck any matter in... [T]he interesting message that I take from this is that these machines are built so infrequently... 25-30 years between these big accelerators. Every time it happens, I'm told by my... retired colleagues... It happens every time, this scare story that we're going to destroy the earth with it, because it's so long between them that people actually forget the media hype that happened the last time around."

"So I'm tasking you with the job. When you're older and one of these machines starts up, and people start going, "It's going to destroy the earth!" That you think uh-huh, I've heard this before. It's not really going to happen."

"[S]ometimes some of our craziest ideas, and I've been through some pretty crazy ideas of things that you could do with a particle accelerator here... [S]ometimes they turn out to be surprisingly good ones if you do them in the right way, and these machines are not just useful for particle physics. They're useful for all sorts of other things like cancer treatment, like killing bacteria in food, and other things I haven't discussed like carbon dating, and imaging down to the atomic scale, and all sorts of other things..."

"I'd just like to leave you with my advice in choosing your career... [F]ind something that makes you sit up and think, "This is really important" or "This is fascinating" or "This is what I'm passionate about" and it can be in any area... Something like space might get you, of climate change... you might really like astronomy, or you might be more passionate about world hunger, injustices in the world, the availability of water, energy, health, aging, anything like that. Think about it, and do something about it. That's all, really, you need to do, and make a career out of doing something about it. Because if you do something that you're passionate about, and you love... You're not even going to feel like you're going to work each day. ...You're just going to feel like you're getting up and you're doing what it is that you're passionate about..."