As the question of how to make a laser fusion reactor practical rises, scientists at the University of Rochester’s Laboratory for Laser Energetics (LLE) have come up with a way for fusion lasers to essentially manufacture their own fuel pellets.
In December 2022, scientists at the National Ignition Facility at the Lawrence Livermore National Laboratory in California made a breakthrough that was six decades in the making as an experimental reactor using a bank of 192 high-energy lasers focused on a single point struck a pellet of deuterium and tritium and set off an inertial fusion ignition reaction for the first time.
Though this had scientists and engineers popping metaphorical and a few real Champagne corks, a practical fusion power reactor is still a long way away. However, that didn't prevent a Rochester team led by Igor Igumenshchev, a senior scientist at LLE, and Valeri Goncharov, theory division director at LLE, from looking at the logistical problems of how to take laser fusion out of the laboratory and into the real world.
One of the bigger hurdles is how to manufacture the fuel pellets needed to run the reactor. Currently, such pellets are made by a complex and expensive process involving using liquid helium to freeze deuterium and tritium (radioactive isotopes of hydrogen) to a temperature only 11 degrees Kelvin above absolute zero and putting them down in layers to form the pellets.
That may be fine for a laboratory experiment that doesn't have to worry about balancing the books, but an up-and-running fusion reactor will need about a million of these fuel pellets every single day. So, the Rochester team is developing an idea first proposed in 2020 to create a technique where the lasers in the reactor create their own fuel tablets in the laser blast before implosion and ignition.
Instead of using solid pellets, the scientists injected deuterium and tritium into foam capsules. The clever bit is that when the laser array shoots at a capsule, the beams cause the capsule to collapse into a sphere with the same density as deuterium-tritium liquid fuel that then implodes.
At the moment, the process is only a scaled-down proof of concept using LLE’s OMEGA laser. However, the team claims that future lasers with longer and more energetic pulses should be able to take the new capsules to ignition.
"Combining this target concept with a highly efficient laser system that is currently under development at LLE will provide a very attractive path to fusion energy," said Igumenshchev.
The research was published in Physical Review Letters.
Source: University of Rochester
