British scientists are to build the world’s most powerful laser, an £85 million device that they hope will accelerate efforts to harness nuclear fusion as a source of near-limitless clean energy.
The Vulcan 20-20 laser, which will be at Harwell in Oxfordshire, will produce a beam a million, billion, billion times brighter than the most intense sunlight.
A single laser pulse will be capable of delivering more power than the entire National Grid but will last for less than a trillionth of a second and be focused on a target just a few micrometres wide. Due to be complete by 2029, the laser will be used for, among other things, testing methods of generating energy through nuclear fusion, a longstanding grail for physicists.
Scientists at other facilities, most notably the Lawrence Livermore National Laboratory in California, are already using powerful lasers to fuse hydrogen atoms together. This can produce helium and energy, mirroring the reactions that occur inside the sun. Recent results from Lawrence Livermore suggest that it is possible to gain more energy from the process than you put in. However, it will have to be made far more efficient to become commercially viable.
Vulcan 20-20 will investigate the underlying physics. In particular, researchers will use it to explore what is known as “shock ignition”.
Roughly speaking, a peppercorn-sized fuel pellet — made up of deuterium and tritium, two isotopes of hydrogen — is placed inside a plastic capsule. Laser beams transform the capsule into a plasma, which rapidly expands. This crushes the fuel pellet to a thirtieth of its original size in a billionth of a second. Pressures are achieved six times greater than those inside the sun. All going well, the fuel “ignites” at a temperature of about 100 million Celsius, giving rise to a controlled, energy-generating fusion reaction.
Using Vulcan 20-20, physicists will seek to observe different parts of the process in isolation. The aim, according to Dr Robbie Scott, a plasma physicist at the Science and Technology Facilities Council (STFC), is to test ideas that might then be used to build experimental power plants.
One challenge is working out how to use a barrage of laser beams to crush a fuel pellet uniformly from all directions at once, a feat that may have to be achieved ten times a second in a full-scale power station.
The Vulcan 20-20 laser will also be used for “laboratory astrophysics”, in which scientists mimic the conditions seen in phenomena such as supernovas, the explosions that accompany the deaths of certain types of stars.
It may also be used to produce matter from light. This could be done by colliding photons, which can be thought of as “packets” of light, to create pairs of electrons and positrons. These particles of matter and antimatter are thought to be produced around neutron stars in the distant reaches of space, but we have little grasp of how they spring into being.
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“If you can produce these pairs using very strong laser beams, you might be able to gain some insights into how this occurs, and there isn’t really any other scientific bit of equipment that would allow you to do this,” Dr Alex Robinson, also of the STFC, said.
Vulcan 20-20 will be built at the STFC Central Laser Facility, which is part of the Rutherford Appleton Laboratory. The first stage of the work — disassembling what used to be the UK’s most powerful laser, called Vulcan, to make space for its successor — has just begun. The facility has received £85 million from UK Research and Innovation, the government-backed science funder.
Vulcan 20-20 will produce a main laser beam with a power of 20 petawatts, alongside an additional eight high-energy beams. This amounts to a twentyfold increase in power on Vulcan, which is expected to make it the most powerful laser in the world.
Professor Mark Thomson, of the STFC, said: “The Vulcan 20-20 programme will keep the Central Laser Facility at the cutting edge of the highest-power laser science and enable entirely new experiments in crucial areas such as renewable energy research.”
Professor John Collier, director of the facility, said: “Vulcan has been the flagship laser at CLF for many years and widely recognised internationally as a pioneering facility.
“Over the past 40 years it has made important contributions to plasma physics research, and hundreds of PhD students have been trained at the facility. It is timely for Vulcan to undergo its next major upgrade, making it ready to serve a new generation of scientists, ensuring the UK retains its leadership role in this field.”
George Freeman, the science minister, said: “Re-establishing Britain as home to the world’s most powerful laser is an exciting opportunity to explore the unexplored in astronomy and physics, stride towards new clean energy sources for the good of our planet and much more.
“By investing £85 million to give our research community the edge in leading crucial scientific discoveries, we are also delivering hundreds of highly skilled jobs in science and engineering that boost the UK science sector and grow our economy.”
