Tuesday, March 20, 2012

Sandia Labs Fusion Simulation Points to Promising New Approach to Magnetic Inertial Confinement Fusion

Sandia Labs has published results of simulations for a novel approach to fusion which appears promising for high gain fusion energy production, at this early stage.
High-gain nuclear fusion could be achieved in a preheated cylindrical container immersed in strong magnetic fields, according to a series of computer simulations performed at Sandia National Laboratories.

The simulations show the release of output energy that was, remarkably, many times greater than the energy fed into the container's liner. The method appears to be 50 times more efficient than using X-rays—a previous favorite at Sandia—to drive implosions of targeted materials to 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," said 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."

...In the simulations, the output demonstrated was 100 times that of a 60 MA input current. The 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 bring a maximum of only 26 MA to bear upon a target, the researchers would be happy with a proof-of-principle result called scientific break-even, in which the amount of energy leaving the target equals the amount of energy put into the deuterium-tritium fuel.

This has never been achieved in the laboratory and would be a valuable addition to fusion science, said Slutz.

...The MIF technique heats the fusion fuel (deuterium-tritium) by compression as in normal inertial fusion, but uses a magnetic field to suppress heat loss during implosion. The magnetic field acts like a kind of shower curtain to prevent charged particles like electrons and alpha particles from leaving the party early and draining energy from the reaction.

The simulated process relies upon a single, relatively low-powered laser to preheat a deuterium-tritium gas mixture that sits within a small liner.

At the top and bottom of the liner are two slightly larger coils that, when electrically powered, create a joined vertical magnetic field that penetrates into the liner, reducing energy loss from charged particles attempting to escape through the liner's walls.

An extremely strong magnetic field is created on the surface of the liner by a separate, very powerful electrical current, generated by a pulsed power accelerator such as Z. The force of this huge magnetic field pushes the liner inward to a fraction of its original diameter. It also compresses the magnetic field emanating from the coils. The combination is powerful enough to force atoms of gaseous fuel into intimate contact with each other, fusing them.

Heat released from that reaction raised the gaseous fuel’s temperature high enough to ignite a layer of frozen and therefore denser deuterium-tritium fuel coating the inside of the liner. The heat transfer is similar to the way kindling heats a log: when the log ignites, the real heat—here high-yield fusion from ignited frozen fuel—commences. _R&D
This approach to fusion is not likely to provide useful commercial power for many decades yet, if ever. But it opens a window onto the new world of high energy physics, which begins with computer simulations, and progresses step by experimental step toward proof or falsification of the underlying ideas.

This is quite different from the politicised world of climate science, where poorly vetted computer simulations are used to steer public policy on a national and international scale. In the world of climate science, contrary opinions are suppressed, and any research which does not toe the orthodox line is either not funded or not published.

Fortunately, most areas of science have not descended so far into politicised corruption as climate science. We should hope that it never does.



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