Putting Big Squeeze Fusion to the Test

A new Sandia National Laboratories-based approach to fusion that’s shown promise in computational simulations has passed its first bricks-and-mortar experimental test.

MagLIF (Magnetized Liner Inertial Fusion) envisions using Sandia’s Z machine as a massive magnetic vise to implode, and thus heat, a tiny cylinder full of deuterium to Sun-like temperatures, igniting a fusion reaction.

“I wanted an experimental platform that we could test and see if it works the way we think it will,” says Sandia fusion physicist Steve Slutz, who led the MagLIF computer simulations. “Now our approach is to put the simulations to the test one step at a time.”

The first experimental step was a successful one. In the first use of the Z machine as a nanosecond-fast magnetic boa constrictor, the pulse machine successfully crushed an empty, cylindrical beryllium fuel liner – one designed to hold deuterium-tritium fusion fuel.

“The experimental result – the degree to which the imploding liner maintained its cylindrical integrity throughout its implosion – were consistent with results from earlier computer simulations,” Sandia’s Ryan McBride, the lead researcher on these MagLIF experiments, said in a Sandia announcement last year when his team’s results had been accepted for publication in Physical Review Letters. The major concern in this experiment was whether the beryllium liner was thick enough to withstand the enormous electrical current passing along its surface – a current that gradually vaporizes the liner’s outer surface. “You might say the race is on,” McBride continued. “The question is, can we start off with a thick enough tube such that we can complete the implosion and burn the fusion fuel before the instability eats its way completely through the liner wall?”

In fact, the simulations appear to have found a liner-width sweet spot – X-ray diagnostic imaging of the implosion revealed that the liner walls maintained their integrity throughout the implosion.

“Our 2D simulations (of the liner walls) were too pessimistic,” Slutz says. “The instabilities didn’t grow as much in the experiments as in the simulations.”

After several more step-wise experiments, the MagLIF team hopes to perform a full-integrated experiment of the concept in late 2013.

Says Slutz, “If the fusion yield results are close to what we’re predicting, then we’ll know we’ve got the physics right in the simulations.”