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Jimmy Holloway

James ‘Jimmy’ Holloway is a third year PhD student working at University College London (UCL) in the field of plasma accelerator physics. He is a member of the Advanced Wakefield Experiment (AWAKE) being carried out at CERN.

 When I was a teenager I was a very tricky student to have in your science class.

On what plasma accelerator physics is

Accelerator physics is the physics of getting elementary particles, or small particles, to go faster and faster, get them to go as close to the speed of light as we can.  So in the LHC they accelerate protons up to 7TeV, or it will be 7TeV.  So conventional accelerator physics is where you basically get your metal cavity, your metal pipe, evacuate it and use alternating electrical fields to make your particles go faster and faster.  Plasma physics is, broadly speaking, just the instabilities of plasmas…using their kind of quirky instabilities to try a whole host of different things.  You can use them to investigate stars and space and all sorts like that, ah, but where these two come together is there’s a new idea called – well I say new – called Plasma Wakefield Acceleration.  Without going into the full nitty gritty, the idea is to accelerate your particle within a plasma instead of a metal cavity.  The downside to the traditional way is you keep turning up the voltage and eventually this metal cavity will arc, lightning will discharge and it’s very…yeah, you don’t want that.  However, a plasma is basically an ionised gas.  It’s a gas that is already decomposed so it’s resistant to these kinds of further decompositions, so you can achieve these extraordinarily high electric fields within a plasma where you can’t in your traditional metal cavity, so we’re trying to accelerate particles to higher and higher energies in short distances of plasma is the idea.

On becoming interested in science 

So, when I was very young I made a torch out of a jam tart box; I don’t know why I’m telling you this, but the interesting bit was I got a lead pencil – or a graphite pencil – split it down the middle and you could basically put one wire on one end and slide another wire along and what I got was a variable resistor, essentially, and this made the bulb brighter and dimmer and that was, like, fascinating.  A switch is one thing, I’d seen it every day in the kitchen and on the wall and stuff, but when I was physically, hands on, making the brightness of the bulb change I thought, ‘Ah, that’s really cool.  Why’s that happening?’  That’s probably the first thing that got me interested. 

Now, this is going to sound really cheesy but I’m gonna say it anyway.  My dad really pushed me into following what I’m interested in, and that was science as a young boy, I was interested in…just, why.  I’d ask that question a hundred times a day and he would always make sure that I had every opportunity to go into university and all the rest of it, something that he didn’t have the opportunity to do so, yeah, as cheesy as that sounds, it was my father.

So, I went and did my A levels, I did my undergraduate degree in physics with astrophysics, so I had that kind of astrophysics aspect just because I was interested in it, then I applied to do a PhD at UCL and I took a sharp left turn into this plasma physics field because I saw a very interesting presentation by my now current supervisor, Professor Matthew Wing, and he just put that concept in a nutshell – this Plasma Wakefield Acceleration in a nutshell – and I thought, ‘That’s really cool.  That’s a really good idea.’  It’s a young field – it’s one where it hasn’t been completely, you know, dredged, if you will, and had all the ideas already thought of – so I thought there was a field I could make a difference in.

I mentioned that I found astrophysics fascinating and the thing that really started this fascination with astrophysics was the fact that the universe is expanding and it seems like it’s not just all fuzz hanging there in the void but it’s dynamic and it’s changing and it’s evolving and in a billion, five billion years’ time we could be in a contracting phase of the universe and stuff like this and that’d be a very different universe to live in, so, just that whole concept that it’s a lot more complicated up there than some pin pricks of light is something that got me really interested in the whole thing.

On communicating high concept physics

That’s something you learn, right, that’s something you get better at, is how to communicate ideas.  It depends who you’re talking to.  I’ve got some friends who are my age, and are kind of into the stuff I’m into and I know them pretty well and, um, you’ve just got to break it down to them really. Hand waving, I find, is very good.  You know, get expressive…and pen and paper.  When I’m trying to convey…like I just talked about this Plasma Wakefield idea, if I wanted to go any further I’d literally have to draw something for it but that’s probably just how my mind works more than anything.  Visualising it is very key I think.  That is, for me, pivotal.  To have a mental image and conceptualise it right.  I was asked a question by some students recently on how do you prepare for exams, how do you do it: there’s exams coming up, what do we do?  And my first phase, my first technique, was just parrot fashion, you know, writing the lines out and then you remember the equation, fine.  Then I went to mind maps and I found that a bit better but by far the most effective way for me to retain information, in the long term especially, is, you know, conceptualise that core concept, whatever that may be and forget the little fringe details, you can drive that later, or work your way there later but, for me at least, it’s very much you’ve gotta have that mental image of what’s happening, or that concept, that’s the key.

So, talking about going to and from equations to these mental images, so there’s an equation which described a Gaussian distribution, and this applies to my field because when we model a particle beam in an accelerator, we don’t say, ‘Oh, it’s like a cylinder or a bullet’, we say, ‘It’s like a fuzzy ball’, which we describe as bi-gaussian in our two dimensional space or tri-gaussian if it was in 3D.  That means that a few particles around the outside, then denser, denser, denser, denser, so, yeah, it’s like a fuzzy ball, but when you write that out as an equation, you look at the equation and you can’t just leap from one to the other but what you can do is, yeah, I imagine something in my mind and kind of play with this toy that I construct to kind of see new ideas, or new conditions or things I want to try.  You’ve got a beam that’s trying to cut it in half, so discard the front and put that through, what would happen?  So with fundamental physics that’s a lot harder to do because you’ve got these equations called Lagrangians, they’re, yeah, they’re really incomprehensible stuff, you know, you’ve got to be able to imagine multi-dimensional spaces in some situations which I don’t think is possible but, yeah, it’s a big leap to make but I think once you have made a leap from reading an equation, memorising it, to being able to imagine it or conceptualise it then I think you can say you understand it then.

On accepting the incomprehensible 

When I was a teenager I was a very tricky student to have in your science class, Miss Reynolds would tell you, because I’d be refuting the GCSE stuff.  ‘Oh no, atoms, they must be compressible. If you’ve got an atom at the bottom of the ocean and it’s got all this stuff sitting on top of it, you’re telling me that it maintains the same volume?’  I was quite cantankerous.  But then you get to the stage where you go to A level physics, and undergrad physics, and you start to encounter, like, Quantum Mechanics and all of a sudden it’s so far from the everyday world we live in and see that, yeah, you do initially say, ‘What do you mean the particle went through both slits?  It’s got to go through one or the other.’  And all of a sudden you have to, ah…it’s not believe it – experiments are there to prove these things – but you have to take it as, yes, there is this fundamental force called electromagnetism or the weak force or whatever and you can’t ask why it is the way it is, it’s just a fundamental building block of the universe.  So as far from our everyday life as it seems, you have to kind of take that on board and realise we live in a macro world and the very small world is very different.

On getting people interested in physics

I think that you’ve got to get them curious, you’ve got to present them with something that is unintuitive or is interesting or they wouldn’t have expected to be that; like the classic, you know, you get a copper pipe and it’s non magnetic and you get your magnet and you drop it through and it just slows to a crawl and then it falls again, but it’s not magnetic, it’s not interacting, but it is interacting, so what’s happening there and why?  And this is great with kids because there’s wide-eyed disbelief and I think that’s a very good time to expose people to physics when they’re young; it’s when they’re still really curious and imaginative, so get them involved then.

You do have weeks when you’re coding, or sifting through data, or you’ve hit a roadblock or whatever it may be, but it kind of makes that breakthrough much sweeter, makes it much more satisfying, you know?  So when you do get your good results back and you’re thinking, ‘Wow, I’m looking at something that only I’ve seen’, because it’s literally hot off the press, or just come back from the computer, it’s really quite exciting, you get that buzz.  I think that keeps you going, just discovering that next little bit.  It’s that little next step.  When you have a new small result, whatever it may be, and you’ve applied it and it seems to work and you think, ‘Wow, where can I go from this now?’  It’s a dynamic job.  You’re taking new things all the time, you’re taking small steps forward so, yeah, seeing where you end up I guess.

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