Fusion Power with Lasers

19 October 2008

Interview with

Kate Lancaster, STFC Rutherford Appleton Laboratory

Helen - Now we have Kate Lancaster in the studio with us. She's from the Rutherford Appleton Laboratory. She's looking at generating fusion using lasers. Hi, Kate. Thanks for coming on the Naked Scientists.

Kate - No problem.

Helen -   Great to have you here. First of all, why lasers? Where do they fit in to this whole picture of fusion in the laboratory?

Laser experimentsAir Force Research LaboratoryKate - Ever since lasers were invented in the sixties there was an idea that you could use lasers to drive fusion. Essentially, there is more than one way to skin a cat with lasers but I'll describe the current most popular way of doing it. Essentially it's like a petrol engine where you have a compression phase where you use long-pulse lasers to compress a fuel capsule made of deuterium and tritium, the two isotopes of hydrogen that Steve was talking about earlier. Then the second phase is to heat this. The long pulse lasers that I'm describing are a billionth of a second so not particularly long n your field of view but actually acres of time in laser terms. The point of compressing the capsule is basically in order to move the atoms much closer together so you compress the material to hundreds of times solid density.

Helen - How are you doing that compression?

Kate - You've got symmetrically irradiated capsules so you irradiate all around a sphere. The laser hits the surface and heats up some of the surface which flies away. Basically, due to Newton's third law the rest flies forward. If you can do this symmetrically all of the material flies forward and compresses together to high density.

Helen - So it's like a sphere and it's all coming towards the core of the sphere.

Kate - Exactly.

Helen - You said the lasers are very quick and short in duration. Are there lots of them? Is it a continuous stream of them coming on and off?

Kate - No essentially this compression phase takes the duration of the laser pulse. A few nano-seconds which is this billionth of a second.

Helen - That's enough to heat up this sphere of matter?

Kate - The heat part comes next. Basically, as I said it's like a petrol engine so you've done the compression part but now you need the spark plug. What you do is you have an even more intense, more powerful laser beam which is injected in. What happens there is that actually when it interacts with the dense material it produces hot particles like electrons, for example. They stream in and deposit their energy to raise it to the 100,000,000 degrees centigrade that you need for fusion to occur. We know quite a lot about the compression side of things because, as I've said, this has been around since the 1960s. It's the spark plug bit which is the unknown thing. What I spend most of my time trying to investigate how these particles are generated - how they do the heating.

Helen - Have you got this to actually work yet or are you still fiddling around with that ignition part?

Kate - yeah so essentially laser facilities at the moment are only just being built which have any capability of really properly demonstrating such a technique. There were proof of geometry (I'm not even going to say proof of principle experiments) that you could compress and inject some short pulse heating beam in Japan back in 2000, 2001. They were very successful experiments and they sort of spawned this whole field of interest that really helped. You know, essentially we have a lot of work to do in order to demonstrate. But we're trying to get a laser facility built in Europe called HiPER laser. It's not the same scale as ITER but it's a huge facility which will try to test this technique and try to get gain out of it - actually get energy out. It won't generate electricity but again it's going to be one of those things where we can actually try to prove the principle. If you're interested in the details of the website it's
www.hiper-laser.org. There you'll find all the details of this project. We're currently in the preparatory phase at the moment. We've got money from Europe to try and design this laser. It's very exciting.

Helen - I'm quite keen to know what sort of scale this might be on. Also really when is it going to happen if you're going to take a guess? When are we going to see this?

Kate - The time scales are - Hyper is going to take 8 years to de-risk and design and should be operational by the early 2020s. After that it's going to be at least 20 years after that. It's a long term thing but the fact is that it's so attractive you have to continue to work on it.

As well as her work on making fusion power a reality with lasers, Kate is also part of the EPSRC's NOISEmakers campaign.  To find out more, visit the
New Outlooks in Science and Engineering (NOISE) website.

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