Hydrogen retention in damaged tungsten at high surface temperatures - The great escape (Dance your PhD 2012)

The sun creates a lot of energy by hydrogen fusion. Scientists are investigating fusion, building our own ‘sun on earth’, as a sustainable energy source on earth. A lot of energy is released when hydrogen isotopes fuse together into helium and neutrons. One of the key problems is that these high energy neutrons can damage the crystal structure of the surrounding tungsten wall. This can create vacancies in the metal lattice, which trap hydrogen atoms. Trapped hydrogen cannot fuse to release energy.

Material temperature turns out to be an important factor in managing hydrogen capture. We investigated how hydrogen can escape if the tungsten material is hot. On the one hand, hot tungsten atoms are more mobile and can move back into vacancies in the crystal, so that the metal effectively heals itself. Additionally, the hydrogen atoms themselves have a higher mobility at a high temperature. They can now escape from their captivity and take part in the fusion process within the heart of the machine; one step closer to creating a sun on earth.

My PhD dance is performed around and on the experiment I’m using for my research, Magnum-PSI (FOM Institute DIFFER, the Netherlands). Magnum-PSI is capable of reproducing the conditions that we expect in the wall of a fusion reactor. We can therefore test materials on their capabilities of withstanding such a harsh environment.

I would like to thank all people that helped me create this dance. We had an incredible amount of fun using the experimental hall in the weekend for a completely different purpose than the usual experiments. Special thanks to FOM Institute DIFFER (www.differ.nl).

Explanation of my PhD dance in detail:
The two dancers at the platform on top of the machine illustrate the fusion of two hydrogen atoms (yellow dresses) into helium within the sun. An abundance of energy is released in this way. Looking down from the machine, we see a single hydrogen atom ‘on earth’. Her movements are the same as in the duet, however much smaller. She dances alone to show that when too much hydrogen is captured in the surrounding wall of a fusion reactor, there is not enough hydrogen to keep the fusion process going.
In the following scene, we see the regular structure of a tungsten material, depicted by the disks on the ground and the three dancers (black dresses). Smoke rings illustrate the high energy neutrons that, released in the fusion reaction, continuously bombard the material. An interaction between neutrons and the tungsten materials will not happen often, but when it does it will cause a chain reaction of displacements in the material; the frisbees move in all directions.
At low surface temperature (blue light), the hydrogen atoms are more easily trapped and hence can no longer take part in a fusion reaction. The yellow dancers are captured in the material, they join in on the movements of the black dancers.
At high surface temperatures (red light) the hydrogen atoms have a higher mobility, which prevents them from getting trapped within the material. Their movements are wider and more energetic. Additionally, the material itself regenerates. The disks return to a regular structure, limiting the number of vacancies in which hydrogen can be captured. Now liberated, the yellow hydrogen atoms escape and dance away from the material.
The dance continues with a duet of hydrogen atoms entangled in a fusion reaction. We end back in the original scene, but this time with two fusion duets; one in the sun (on top of the machine), the other within a fusion reactor (on the floor).