Suzie Sheehy Quotes

This is actually a real one. ...This is ...the smallest radiofrequency accelerating cavity in the world... This one is from a project called the 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.

[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...

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.

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.

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...

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 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.

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... s. They bend the beam around, and then there's two other main components. There are ... 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 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.

[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 , one , 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.

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 , 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 ...

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

I want to go back to about the late 1920s and 1930s when a new type of was invented, called the . These are still in operation today, but the original ones... This is a patent from... and this is 2 Ds as we call them... electrical cavities which would sit inside a whopping great ... [W]e start in the center with some particles, and they always have to be charged particles. So either electrons, s... s, 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 s.

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.

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.

[Y]ou may have seen... when the LHC was in the news, diagrams that look a little bit like this. These are called s 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.

[T]his is called the Standard Model Lagrangian, that curly <math>\mathcal{L}</math> 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...