Researchers at the National Ignition Facility (NIF) say they have met many of the demanding challenges leading up achieving the highly stable, precisely directed implosion required for fusion ignition.  The NIF, engaged in a collaborative project led by the Department of Energy’s Lawrence Livermore National Laboratory, reports that there is at least one significant obstacle to overcome.

It’s the same matter that bedevils every one else, crushing the fuel is like squeezing a balloon in one’s fist, a lot of the fuel or balloon squishes out of the lower and less restrained areas.

National Ignition Facility Laser Reamplifier.  Click image for more info.

National Ignition Facility Laser Reamplifier. Click image for more info.

The dream of igniting (another way to say ‘breakeven’) a self-sustained fusion reaction with high yields of energy is a feat likened to creating a miniature star on Earth.  The NIF project is a multi-institutional effort including partners from the University of Rochester’s Laboratory for Laser Energetics, General Atomics, Los Alamos National Laboratory, Sandia National Laboratory, and the Massachusetts Institute of Technology.

In what must be a dreadful sense of confusion the group was scooped by the mass media a few weeks ago with a less than stellar report that cast much doubt on their success.  Oddly the groups research report, received back in March was accepted in June after the peer review and was published back at the end of July in the journal Physics of Plasma.  The press release only came out this past Monday.  Wow, that’s months late.  Anyway, the progress is much better than the wire service writer and the assorted mass media stories made the progress out to be.

To reach ignition (defined as the point at which the fusion reaction produces more energy than is needed to initiate it), the NIF focuses 192 laser beams simultaneously in billionth-of-a-second pulses inside a cryogenically cooled hohlraum (from the German word for “hollow room”), a hollow cylinder the size of a pencil eraser. Within the hohlraum is a ball-bearing-size capsule containing two hydrogen isotopes, deuterium and tritium (D-T). The unified lasers deliver 1.8 megajoules of energy and 500 terawatts of power – 1,000 times more than the United States uses at any one moment – to the hohlraum creating an “X-ray oven” which implodes the D-T capsule to temperatures and pressures similar to those found at the center of the sun.

John Edwards, NIF associate director for inertial confinement fusion and high-energy-density science explains, “What we want to do is use the X-rays to blast away the outer layer of the capsule in a very controlled manner, so that the D-T pellet is compressed to just the right conditions to initiate the fusion reaction. In our new review article, we report that the NIF has met many of the requirements believed necessary to achieve ignition – sufficient X-ray intensity in the hohlraum, accurate energy delivery to the target and desired levels of compression – but that at least one major hurdle remains to be overcome, the premature breaking apart of the capsule.”

In the article, Edwards and his colleagues discuss how they are using diagnostic tools developed at NIF to determine likely causes for the problem. “In some ignition tests, we measured the scattering of neutrons released and found different strength signals at different spots around the D-T capsule,” Edwards said. “This indicates that the shell’s surface is not uniformly smooth and that in some places, it’s thinner and weaker than in others. In other tests, the spectrum of X-rays emitted indicated that the D-T fuel and capsule were mixing too much – the results of hydrodynamic instability – and that can quench the ignition process.”

There’s quite a lot to examine and improve.  The lasers have to go off exactly at the right time, focused precisely correctly on a target so uniformly built that the fuel inside gets compressed and heated properly.  That’s the simplest explanation of something that involves a huge amount of energy on a wee bit of material in a tiny moment.

Edwards said that the team is concentrating its efforts on NIF to define the exact nature of the instability and use the knowledge gained to design an improved, sturdier capsule. Achieving that milestone, he said, should clear the path for further advances toward laboratory ignition.

That may be the last step to a breakeven event.  So far humans have only managed fusion breakeven inside explosions.  Whoever gets it done first will prove lots of ideas might be possible ways to burn fusion fuel beyond breakeven.  Then the engineering race will get underway.

It’s going to happen.  Somewhere and maybe soon.


5 Comments so far

  1. Matt Musson on September 25, 2013 6:15 AM

    “I need a nuclear reaction to generate the 1.21 gigawatts of electricity…”

    Dr. Emmett Brown

  2. Alex on September 25, 2013 8:27 AM

    It may be close to break-even at laser energy in to heat energy out but nowhere close at the total energy needed to drive the lasers (only a few % efficient) or converting the heat back. Also, the expense and effort required to create the pellets and breed the tritium is immense. Billions spent with no hope ever of making this into a commercial reality and even if it’s classed as basic research it’s not clear the last few billion $ have greatly enhanced our understanding. Instead it feels more like a pointless engineering proof at this stage and we should stop throwing good money after bad. 10% of that money would have been far better spent to fund other, more commercially minded approaches like LPP, TriAlpha, General Fusion, Lockheed Martin or EMC2 as they have a shot of delivering real, cheap, usable power within 10-15 years.

  3. Bård Havre on September 26, 2013 5:46 AM

    With A COP of 2 (optimistic), laser to output energy, it looks like they have to repeat this process at a rate of at least one implosion every second to deliver one MW of usable power. And that is without all the conversion losses at either end. I can not see this fit into a 40 foot container anytime soon.

  4. Pierre René on October 10, 2013 12:08 PM

    I believe miniaturization will come quickly once the fundamentals are mastered. The pressure to succeed is enormous and any sign of progress in the fusion arena is a clear sign of hope for any viable future of humanity on this over-stressed planet.

    Given the recent realization that humans are at the root cause of climate change, it would be insane to cut funding of projects that could offer solutions that have the potential of reversing the damage done by fossil fuels.

    Many ‘Manhattan project’-scale initiatives should be the order of the day if we want to progress to a type-1 civilization 😉

  5. Sean Sloan on October 14, 2013 12:31 PM

    This is awesome, as long as someone else is paying for it. Think of all the other research we could do with this money like welding Aluminum to Titanium. While I scratch for pennies to research real solutions, these guys are wasting money on something my children’s children will never see. This is just another tower of Babel with no feasible outcome forseen. We can do it but why? Think of the moon shots. We got so many useful things from that…but each one could have been researched individually for much less. Other than these, what useful thing did we get by actually going to the moon besides satisfying curiousity. Let us instead focus on helping people with applied research.

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