Sundome

By Alex Davies

I am part of the Graduate Scheme at CCFE (Culham Centre for Fusion Energy). CCFE operates JET (Joint European torus), which is the largest tokamak, or magnetic ‘star bottle’ in the world, and MAST (Mega Amp Spherical Tokamak), which is like JET but with different geometry.

Figure 1: The Joint European Torus

One of the goals of the Graduate Scheme is to communicate to the outside world about fusion energy and the work that is ongoing at CCFE (hence this blog). Something close to my heart is supporting science lessons in the school in a gender inclusive way. So it wasn’t too much of a leap to know that I wanted to volunteer with a CCFE outreach program called the Sun Dome.

Figure 2: Freeze-frame of footage from the Sun Dome Movie - opening clip

The Sun Dome is essentially a prop. A big, inflatable prop, that is somewhere between pretending to be a star and pretending to be a cinema. Bear with me on this!

In years 5 & 6 at primary school, most students will have learned vaguely about what stars and planets are. A few may have heard the word ‘atoms,’ and a small number might even be able to tell me that atoms are small and make up everything. (Occasional brainboxes go on to talk about electrons, protons and neutrons. Once I even heard the word quark!) But learning this in a classroom is one thing, seeing it in front of you as you float through the Universe is another.

The Sun Dome is a projector inside a big inflatable dome that shows science movies about nuclear fusion. As we lie down watching the movies, we journey into stars and watch Hydrogen atoms fuse into Helium atoms, and then we see the same process happen inside a computer animation of JET. It’s all very exciting!

Figure 3: Sun Dome from the outside

The Sun Dome has a specific format, with 4 parts:
1. Introduction
2. First movie
3. Game
4. Second movie

Introduction

This is where you tell them about atoms, and how atoms make all solid, liquid and gaseous matter in the universe. You ask the pupils to pretend to be atoms in a solid, by sitting as close to their neighbours as possible with their arms around their neighbours. Then they might name solid things such as brick, floor, window etc. Then they are asked to be atoms in a liquid and they spread away from their neighbours, but always within arm’s reach of at least one other person. They can name milk, washing up liquid and water. Then you ask them to be atoms in a gas by standing up and finding a space as far away from anyone else as possible. They can name air, steam and sometimes Oxygen and Carbon Dioxide, with reference to how humans and plants need these to live respectively.

Afterwards you tell them that the Sun is a ‘hot gas’ with a core temperature of 15 million C. Reactions to this vary from absent-mindedly staring at the floor while toying with their shoelaces to gasps of shock and awe.

You talk about how two Hydrogen atoms in the core of the Sun are moving so fast that they can collide and become a Helium atom – in a bit of a hand wavy sort of way. And when this Fusion Reaction happens it gives off an explosion of energy.

I am very aware of how this is an extremely hand wavy description; but honestly, the point isn’t to turn them all into plasma physicists. The point is to make them aware of fusion and enthusiastic about science. 

First Movie

When you tell them that inside the Sun Dome is a projector that is going to show them movies about the Universe the reaction is nearly always one of excitement. Who doesn’t like going to the movies, right? Then you tell them no popcorn is allowed and no whispering and they always groan ‘Nooooo’ with massive grins on their faces.

Inside the Sun Dome they are told to find a space on the floor and look up at the ceiling as a short movie describes how stars live in galaxies, and how the Sun was created, and how Hydrogen atoms in the Sun move and fuse into Helium.

Figure 4: Freeze-frame of footage from the Sun Dome Movie - the Sun

Game

Then it’s time to play a game. It helps keep the students focussed if we break up the movies with a game in the middle. The objective of the game is to get the students moving around the hall as if they were Hydrogen atoms in the Sun. 

On the Surface of the Sun it is cooler, so they walk slowly. As we journey closer to the centre of the Sun it gets hotter and hotter, and the students run faster and faster to replicate this. Then, when you shout ‘FUSION’ they have to find a partner and collide with them to produce a Helium atom.

Often, at this point, I ask them ‘Are you all worn out, now?’ to which the answer is invariably ‘NO!’ Which prompts us to do the whole thing over again, and the chaos continues.

Second Movie

Afterwards we have one more movie to show, so the students all return inside the Sun Dome. This movie focusses on the Science and Engineering that CCFE does, when we use our tokamaks. There are clips of JET and MAST during a pulse, and I narrate that MAST can reach the same temperature as the core of the Sun (15 million C), but JET can reach ten times hotter than that. We talk about how our remote handling system, MASCOT, helps maintain and repair the inside of JET when it isn’t pulsing.

Figure 5: Freeze-frame of footage from the Sun Dome Movie - MASCOT making repairs to JET

Then we talk about the future. The plan is to build ITER (the International Thermonuclear Experimental Reactor) to investigate materials that a tokamak should be made out of amongst other things, and DEMO (Demonstration Power Plant) as a future fusion power plant. By this age, most pupils know about fossil fuels and that they are bad for the environment. Some will have heard about greenhouse gasses, and there is a vague awareness of needing to build a power plant that doesn’t pollute.

Figure 6: Children watching the Movie

At the end there is time for questions. Not all students will have a question to ask, but occasionally they do. Usually they want to know if a tokamak will explode if its goes wrong– the answer is no! All of the engineering for fusion goes into making the reaction happen. In contrast to nuclear fission, where all of the engineering goes into slowing the reaction down. If something were to interrupt the systems that let JET function, then the reaction would just stop – which we call a disruption.

Once I had a pupil ask if we had heard of Adamantium – the material that Wolverine’s skeleton and claws are made from. If we made our tokamaks from that then we wouldn’t have any problems with melting, because it’s the best material in the world. We said that we would let our material scientists know!

I love that I work for a company that lets me communicate science to students! As a female engineer and physicist, I am aware that it is very easy to opt out of science due to peer pressure. Giving all students an enthusiasm for science early in their education is so important.

Figure 7: Letters from children who have seen the Sun Dome.

When you get feedback like this it’s easy to see that you’re making an impact. The Sun Dome is so useful to getting the next generation of scientists and engineers enthusiastic! After all, once JET is being decommissioned, we are going to need people from the next generation to run ITER and DEMO. Big science projects like these last generations, and the knowledge that is learnt creates a legacy for future scientists and engineers to build upon. This is why science communication is so important. This is why I volunteer at the Sun Dome.