Suzie Sheehy

Suzanne Lyn Sheehy (born 1984) is an Australian accelerator physicist who runs research groups at the University of Oxford and the University of Melbourne, where she is developing new particle accelerators for applications in medicine.

Quotes

5 things you should never do with a particle accelerator (~2013)

A creative commons YouTube Video from the Institute of Physics channel.

What is a particle accelerator? ...This is the Large Hadron Collider ...the world's biggest particle accelerator. It's 27 kilometers in circumference ...buried about 100 meters underground between the borders of France and Switzerland, near Geneva.

That's only one particle accelerator. There are actually over 26,000 of them in the world.

I'll tell you very briefly how they work. ...The first thing we need is some ...subatomic particles, or even atoms themselves perhaps.

Four different types of particles: electrons, neutrons, protons and gold atoms. ...Can anyone suggest which one you can't put in a particle accelerator? ...A neutron. Yep! Do you know why? Because it isn't charged. Thank you very much. ...[I]t doesn't have an electric charge.

Now there's another one... that might not have an electric charge... The gold atom, yes. Can anyone suggest a way to get that gold atom into a particle accelerator? ...You can ionize it. Thank you. So to ionize a gold atom you can rip the electrons off or add more electrons on... Give it an electric charge, and then we can put it into a particle accelerator. So that's the kind of particles we need.

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 Van de Graaff generator which does that...

Building up charge, actually building up voltage, 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.
- 4:01

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.
- 4:50

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 cryogenics? 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 ultra-high vacuum, or would you die from the radiation 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 Large Hadron Collider. ...It's minus 271 degrees. ...This is a picture of one of the 15m long dipole magnets, 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 ultra-high vacuum? ...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 Large Hadron Collider 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 beam dump, which is a massive long block of very dense graphite, which absorbs the energy. But even then there's so much energy that they can't just dump it directly on it, or the thermal shock 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, Anatoli Bugorski, 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 nuclear physics 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 Nobel prize for work, which doesn't justify it, but there have been people who have stuck their heads in particle accelerators.
- Fluorescent screen Ref: David Nygren, A History of Particle Detectors (2012) Lawrence Berkeley National Laboratory

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 Bragg peak.

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... proton therapy, 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 accelerator-driven subcritical reactor. This is where you take a nuclear reactor, a fission reactor. In the core, instead of having uranium, it has an element called thorium, 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 neutrons... [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 chain reaction, 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.
- Ref: Overhead list of things Mangetout ate: 18 Bicycles, 15 Shopping trollies, 7 Television sets, 6 Chandeliers, 2 Beds, 1 pair of Skis, 1 Sessna aircraft, 1 Coffin, 400m of steel chain.

So what is radiation? 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 ionizing radiation 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 lead.

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 potassium 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 Geiger counter, 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 particle accelerator 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 Salmonella.

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 astronauts' 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 particle accelerator...

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...

[D]on't be afraid to challenge yourself. Don't shy off doing something just because you think that it's hard. It's when we're doing something hard that we really make a difference. So dig deep and don't be afraid to dream.

I will leave you with some photographs of some of the places that my career in physics has taken me so far, and I hope to add many more to this list in the future.

So that's 5 things you should never do with a particle accelerator. Thank you.

The Secrets of Particle Accelerators (~2018)

, Dr Suzie Sheehy (Wuthering Bytes 2017) A creative commons YouTube Video from the Abopen channel.

So my name's Suzie. I'm a physicist... an accelerator physicist, and I work at the University of Oxford. I run a research group there in... high intensity Hadron particle accelerators... I... spend half my time at Harwell campus... I'm also a member of the ISIS Neutron and Muon Source, not the other ISIS, just to be clear.

What I'm going to talk about today is the fascinating world, and I really think it's wonderful, of particle accelerators.

Has anyone heard of a particle accelerator other than the Large Hadron Collider? ...We actually have two at Harwell... If you were pushed, could you give a back of the envelope explanation of how a particle accelerator works?

Most people now, when I say particle accelerator, think of... the bohemoth. This is the Large Hadron Collider. It is almost 27 km in circumference, which is why the tunnel looks almost straight. It's about 100 meters underground, over the border between France and Switzerland. ...Inside these magnets here, these big blue long ones it's one of the coldest places in the universe at 1.9°K above absolute zero. ...[I]t accelerates two beams of protons, from inside the atom, in opposite directions at 99.99999% (that's the exact number) of the speed of light and smashes them into each other... [I]t is what I like to call an impressive shiny huge piece of kit that's bigger than everyone else's!
- 1:16

This... is only one particle accelerator in the world... there are actually about 35,000 of them...

So why was that particular one built? ...I don't have time to give you a crash course in particle physics. Are there any particle physicist in the room..? No, I'm safe. It's fine, okay. No, I used to be one, and then I switched fields.

The reason the Large Hadron Collider was built was... to... investigate the fundamental constituents of matter...

[I]nside the atom there are only... three different types of particles, which are the up and down quarks, they're the constituents of protons and neutrons inside the atom, and the electron. Everything else there plays very little role in our day-to-day lives. But over about the last century we've discovered that all of these particles fit together in a neat theory that describes our universe to something like 9 or 10 decimal places. It is an incredible amount of discovery and work that's gone into it, and I cannot do it justice in... two minutes. But the latest piece that we've discovered using the Large Hadron Collider, and one of the reasons, but not the only reason that it was built, was to discover... the Higgs boson.

2:43

[T]he way that we've learned all of this stuff about the universe is by taking the particles... smashing them into each other, and literally seeing what comes out.

[I]f you take Einstein's equation E=mc², E is energy, m is the mass and c is 299,792,458 meters per second, so that squared, I'd have to get Siri to tell me what that is, but that's a very big number. So it takes an enormous amount of energy to create even a tiny tiny amount of matter. So that's why, over the years, our machines have gotten bigger and bigger and bigger, and reached up to higher and higher energies in order to create particles of higher and higher masses. Now that might seem slightly counterintuitive, but if we look down at the low energy scale, we get our... everyday objects, and in fact up here at sort of 10 MeV, which is like a sort of everyday energy scale, are the up and down quarks where our protons and neutrons are created from. And if we go up in energy scale, we slowly... over time discovered all these other types of quarks and leptons, and all these other things that seem to play no role in our everyday lives.
- 3:45

Standard Model Equations written on the stone outside the CERN Control Centre

And if you go up and up and up and up, we understand how the different forces in the universe work, from electromagnetism to the strong and weak nuclear force, and then finally right at the top we get to this Higgs thing, which is the theory behind why all of the other particles in the Standard Model have a mass.

The amazing thing about this collection of particles, which admittedly looks arbitrary until you learn it in more detail, is that you can take the entire description of every known particle and interaction, other than gravity, in the universe, and write it down on a mug.
- 5:10

[T]his is called the Standard Model Lagrangian, that curly ${\mathcal {L}}$ ${\mathcal {L}}$ at the start is for Lagrangian... and there's lots of different components of that. Now if I write it out in full, I get what is the most egotistical physics teacher in the entire world. So if I wrote it out in full... really you don't need to read it, I promise, all of the different terms in that equation describe an interaction between different types of particles and force carriers...
- 5:29

[Y]ou may have seen... when the LHC was in the news, diagrams that look a little bit like this. These are called Feynman diagrams after the famous physicist, Richard Feynman... [W]hat... most of my colleagues in particle physics do, is they take this [full Standard Model] equation, they figure out which particle's interacting and how: what's coming in, what coming out. They do twenty-one pages of calculations, and they come out with a number that is the probability of that interaction happening... [D]epending on which particles go in, you choose a different term that corresponds to those, and which particle comes out, you choose a different term that corresponds to those. Turn the handle and you get your result out the other end. I just taught you quantum field theory in about 2 seconds.
- 6:05

It's really hard to convey in a few minutes, how amazing it is that we know this about the universe, and the predictive power that it has... [T]hat is the reason why we really built the Large Hadron Collider.

But I'm not, anymore, a particle physicist. I'm a particle accelerator physicist, and so it's my job to understand how to build the machines that we use in this field. And so I briefly want to run down... how these amazing machines actally operate.

I want to go back to about the late 1920s and 1930s when a new type of particle accelerator was invented, called the cyclotron. These are still in operation today, but the original ones... This is a patent from... Ernest Lawrence and this is 2 Ds as we call them... electrical cavities which would sit inside a whopping great magnet... [W]e start in the center with some particles, and they always have to be charged particles. So either electrons, protons... ions, charged atoms. Things like that, and we give them a bit of a kick, because there is a voltage between these two [Ds] halves, and each time the particle moves between those two halves they get a little bit of a kick, a little bit of energy. Now because they're sitting in a whopping great magnetic field, the effect... that has on a charged particle is to actually bend it around a corner. So it bends around a corner and it comes back again crossing this gap, gaining a little bit more energy and... as it continues to gain energy it spirals out... So the limit in the energy in this machine is mostly how big you can build your magnet, and how much iron you're willing to afford. Now this really was the original type of... high energy particle accelerator, and this is a photograph of Ernest Lawrence and his student Milton Stanley Livingston, who I should say, actually built the thing... [T]his machine got up to about 1 million electronvolts.

In physics I use this energy range of electronvolts which means the energy an electron would gain if I put it through a potential of 1 volt. So MeV is million electronvolts. And that's the scale of that... [cyclotron] they're standing next to...

So we still use a few cyclotrons, but most of the machines that people talk about, especially in the media, are a different type of machine which we call a synchrotron, and we have two of these types of machines at the Rutherford lab at Harwell. One is the ISIS Neutron Source that I'm associated with, and there's also the Diamond Light Source...

[S]ynchrotrons are fascinating machines. The original idea was actually from an Aussie... called Marcus Oliphant and the idea here... instead of them having particles that start in the center and spiral outwards... you keep the particles confined to one radius, one torus, and as the particles gain energy you increase the field in the magnets, the magnetic field, in time with the energy gained, in order to keep them going around in the same path.

If you look at a real one... the ISIS synchrotron. There are 10 sections that look almost identical... and you have these big yellow magnets... They're... dipole magnets. They bend the beam around, and then there's two other main components. There are quadrupole magnets... and... a radiofrequency cavity. Now this is basically a big box like your microwave, into which we pump electromagnetic waves, and this sets up a standing wave inside there, and you have to time the voltage of that standing wave with the passage of the particles in order to get them to accelerate.
- 10:12

Now it's not obvious to most people how this acceleration mechanism of using a wave to accelerate particles actually works. So I have a little demonstration... of an everyday example where I can use a wave to accelerate some particles. This is just an ordinary fluorescent tube that you have in the ceiling... Over here I have a plasma ball which has a 30 kHz oscillating AC voltage supply. So there's a voltage, it's a couple of kilovolts that's going up and down, up and down, up and down in the center of that thing, 30,000 times a second. And because of that, out of the plasma ball... comes an electromagnetic wave that's traveling... through space. So move towards the plasma ball and point the fluorescent tube toward the plasma ball. [It lights up] ...So actually if you move it away, notice that it's still on. Now a lot of people show this demonstration with the fluorescent tube touching the plasma ball and say that it's something about plasma completing a circuit... It's not. It's the electromagnetic wave that's coming out... which is traveling through the fluorescent tube, exciting the electrons inside. ...you know how a fluorescent tube works.
- 10:53

Try something for me. ...Hold [the tube] halfway down. [Half of the lamp goes out] ...You're grounding any of the electrons which are... moving inside there...
- 12:54

So that's one example of how a wave can be used to accelerate particles, but... I brought along some scale model protons [large beach balls] and I thought what I'd get you to do is for you guys to be the wave and the scale model protons are going to accelerate across the wave [beach balls moved by audience hand wave]... Eleven-year-olds do this really well, I'm warning you. You've got competition.

I mean you guys are a rubbish accelerator, but we do that very very precisely. ...So what happens in a synchrotron... is that you have to time that wave very very precisely with the increase in the magnetic field in order to get the particles all synchronized, and that's why we call it a synchrotron.

[A]... Large Hadron Collider radiofrequency cavity... is one of the devices, and... operates at... superconducting temperature at 400 MHz... [T]his is one of the devices into which we pump a large amount of RF energy, send the particles through and as they go through, as you demonstrated very nicely, they gain a little bit of energy...

Smallest Radiofrequency Cavity from the Compact Linear Collider project, Dr Suzie Sheehy (Wuthering Bytes 2017)

This is actually a real one. ...This is ...the smallest radiofrequency accelerating cavity in the world... This one is from a project called the Compact Linear Collider which is one idea of the next generation of colliders to reach even more precise measurements in particle physics, and the inside of this thing is machined to a sub-micron precision... [T]here's a hole at the end. ...This one's for electrons, which are a very small beam, so it can be very small hole, and they travel through there. ...These are the RF ports. These are the vacuum ports. ...[T]his thing would give an electron an energy gain of ...probably 10 million electron volts. This is also a very very high gradient cavity so it gives a lot of energy in a very small space. ...The higher the frequency the smaller they get. ...That one operates at 30 GHz. It was actually so small and the machining tolerances were so tight that they've actually decided to go for 12 GHz instead... because it makes the engineering slightly easier.
- 15:59

The Matter of Everything (2023)

: How Curiosity, Physics, and Improbable Experiments Changed the World

I'd just been asked by four particle physics professors... my PhD interview was conducted over an unstable internet connection... "what do you find fascinating about particle physics?" ...I told them of my wonder at the way physics seemed to be able to describe everything: from the smallest subatomic particles to the atoms that make up our bodies, up to the largest scales of the Universe, and how all of this was connected.
Particle physics, I said, was the foundation of it all.

Five years earlier... [a]s my eyes adjusted to the darkness, the true wonder of this designated "dark sky site" revealed itself. ...The stars and planets weren't up there and I wasn't down here: it was all part of one enormous physical system called the Universe. I was a part of it too. ...I'd never really felt my place in it until that moment.

Suddenly, nothing else mattered. I wanted to know... about gravity and particles and dark matter and relativity. About stars and atoms and light and energy. Above all, I wanted to know how it was all connected and how I was connected to it. ...[I]t mattered to me as a human ...if I managed it even a little bit, I'd not have wasted this little blip of time as a conscious being. I decided to become a physicist.

[A]s I studied more physics the question... at the core... was: "What is matter, and how does it interact to create everything around us—including ourselves?"

I suppose I was trying to figure out the meaning of my own existence. ...I went about it in a more indirect way: I set about trying to understand the entire Universe.

Our view of the smallest constituents in nature has changed rapidly in the last 120 years... Some way into the twentieth century this work became known as "high-energy physics,"... Today the study of all the many particles and how they formed, behave and transform is simply called particle physics.

The Standard Model of particle physics classifies all known particles in nature and the forces through which they interact. ...[O]ur current version came about in the 1970s. This theory is an absolute triumph: it is mathematically elegant and unbelievably precise, yet it fits on the side of a mug.

The Standard Model tells us that all the matter that makes up our everyday existence is composed of just three particles. ...[T]wo types of quarks called "up" and "down" which forms our protons and neutrons. These... with the electrons make up atoms, held together by forces: electromagnetism and the strong and weak nuclear forces.

The reason we can say today that we know all this stuff, that we think our theoretical models represent reality, is not because we have pretty mathematics but because we have done experiments.

[E]xperiments take us to that frightening frontier of vulnerability: the real world.

While a theoretical physicist's ideas must take into account the results of experiments, an experimental physicist has a more nuanced job. She is not simply testing out the ideas of theoretical physicists; she is asking her own questions and designing and physically building equipment she can use to test those ideas. ...[H]er practical knowledge ranges from electronics to chemistry, from welding to liquid nitrogen.

Over the last century the experiments... have gone from single-room setups led by one person to the largest machines on Earth. The era of "Big Science," which began in the 1950s... now... involve collaborations of over a hundred countries and tens of thousands of scientists. ...[N]o individual country can achieve these feats alone.

Accelerator physicists constantly discover new ways of creating beams to help learn... about particle physics. ...[T]he nearest hospital almost certainly houses a particle accelerator. ...We build particle accelerators to study viruses, chocolate and ancient scrolls.

In this book, I will take you through twelve key experiments that marked... a discovery... we now see as essential to our understanding of the world... [T]hese experiments embody the spirit of enquiry that stems from human curiosity. ...[T]hey have changed our lives in almost every aspect, from computing to medicine, from energy to communications and from art to archaeology.

Physics will always be, at its core, about understanding our place in the Universe...

Quotes about Sheehy

Beginning with the discovery of x-rays, Sheehy... continues... through a series of experiments that led to the discoveries of the electron (1897), atomic nucleus (1911), and measurement of the electric charge (1923). By the end of the first third of the book the theory that the atom is the smallest piece of matter is in tatters and the remaining chapters of the book describe the fascinating experiments physicists designed to better understand the particles that make up an atom.
- Michael Janezic, The Matter of Everything by Suzie Sheehy (Feb 17, 2023) Open Letters Review

Later sections... describe the gargantuan instruments that enabled scientists to detect... elusive particles at the heart of the standard model... as the neutrino and... Higgs boson. Through each tale, The Matter of Everything explores how the pursuit of basic science has led to unexpected discoveries... These findings now underpin cancer treatments, personal electronics, and... how scientists investigate the way lava flows deep below Earth’s surface. Sheehy carefully considers each of these breakthroughs through the lens of the people who defied the odds to uncover the mysteries of our universe.
- Ariana Remmel, Accelerator physicist Suzie Sheehy discusses how curiosity-driven research can change the world (May 7, 2023) c&en Chemical and Engineering News, American Chemical Society (ACS). A version of the story appeared in Vol. 101, Issue 15.

External links

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Suzie Sheehy

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Suzie Sheehy University of Melbourne Associate Professor In Medical Accelerator Physics‎