Science Interviews


Sun, 19th Oct 2008

Fusion Power with Lasers

Kate Lancaster, STFC Rutherford Appleton Laboratory

Listen Now    Download as mp3 from the show Fusion - The Power of the Sun

Helen - Now we have Kate Lancaster in the studio with us. Sheís from the Rutherford Appleton Laboratory. Sheís 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 Iíll describe the current most popular way of doing it. Essentially itís 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 Iím 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 - Youíve 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 Newtonís 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 itís like a sphere and itís 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 - Thatís enough to heat up this sphere of matter?

Kate - The heat part comes next. Basically, as I said itís like a petrol engine so youíve 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 Iíve said, this has been around since the 1960s. Itís the spark plug bit which is the unknown thing. What I spend most of my time trying to investigate how these particles are generated Ė 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 (Iím 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 weíre trying to get a laser facility built in Europe called HiPER laser. Itís not the same scale as ITER but itís a huge facility which will try to test this technique and try to get gain out of it Ė actually get energy out. It wonít generate electricity but again itís going to be one of those things where we can actually try to prove the principle. If youíre interested in the details of the website itís There youíll find all the details of this project. Weíre currently in the preparatory phase at the moment. Weíve got money from Europe to try and design this laser. Itís very exciting.

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

Kate - The time scales are Ė Hyper is going to take 8 years to de-risk and design and should be operational by the early 2020s. After that itís going to be at least 20 years after that. Itís a long term thing but the fact is that itís 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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