Fusion simulations show high-gain output

Using simulations, scientists believe they may have found a way to make nuclear fusion a practical proposition.

Experts at Sandia National Laboratories say their results show that high-gain nuclear fusion could be achieved in a preheated cylindrical container immersed in strong magnetic fields.

The simulations show that the output of energy could be many times greater than the energy fed into the container’s liner. Indeed, the method appears to be 50 times more efficient than using X-rays — currently Sandia’s preferred method — to drive implosions of targeted materials and create fusion conditions.

“People didn’t think there was a high-gain option for magnetized inertial fusion (MIF) but these numerical simulations show there is,” says Sandia researcher Steve Slutz, the paper’s lead author.

“Now we have to see if nature will let us do it. In principle, we don’t know why we can’t.”

Such fusion, says the team, could eventually produce reliable electricity from seawater – the most plentiful material on Earth.

In the simulations, the output demonstrated was 100 times that of a 60 million amperes (MA) input current. And output rose steeply as the current increased: 1,000 times input was achieved from an incoming pulse of 70 MA.

Since Sandia’s Z machine can only reach 26 MA, the researchers say they’d be happy with scientific break-even – which has never before been achieved – as a proof of principle.

The magnetic inertial fusion (MIF) technique heats the fusion fuel, deuterium-tritium, by compression as in normal inertial fusion. However, it uses a magnetic field to suppress heat loss during implosion, with the magnetic field preventing charged particles like electrons and alpha particles from draining energy from the reaction.

Tests of physical equipment necessary to validate the computer simulations are already under way, and a laboratory result is expected by late 2013, says the team.

Parts of the design are slated to receive their first tests in March and continue into early winter. Sandia has performed preliminary tests of the coils.

There are many potential problems, including controlling instabilities in the liner and in the magnetic field that might prevent the fuel from constricting evenly.

“Whatever the difficulties, we still want to find the answer to what Slutz and co-author Roger Vesey propose: Can magnetically driven inertial fusion work?” says Sandia manager Daniel Sinars. “We owe it to the country to understand how realistic this possibility is.”