Z Machine Makes Progress Toward Nuclear Fusion

sciencehabit writes Scientists are reporting a significant advance in the quest to develop an alternative approach to nuclear fusion. Researchers at Sandia National Laboratories in Albuquerque, New Mexico, using the lab's Z machine, a colossal electric pulse generator capable of producing currents of tens of millions of amperes, say they have detected significant numbers of neutrons — byproducts of fusion reactions — coming from the experiment. This, they say, demonstrates the viability of their approach and marks progress toward the ultimate goal of producing more energy than the fusion device takes in.

Comments

Gotta be a downside somewhere

[RogueWarrior65]

Wouldn't it suck (literally and figuratively) if we discovered that the waste product of a fusion reaction are gravitons?

Re:Gotta be a downside somewhere

[ihtoit]

uh... there's actually no minimum size for a star to collapse from to form a black hole. The only real requirements are that the star reaches the Fe phase at which point nuclear reactions become endothermic and the core collapses, rebounds at the neutron threshold, collides with the plasma outer shell sending that out and imploding with enough force to collapse again - this time beyond the neutron threshold. For a star with a start mass of ~1.4Msol, this would mean the core containing at least 50% of the stellar mass (0.7Msol) collapsing to a neutron sphere no more than 11 miles in diameter. The average mass of a Milky Way black hole is estimated to be 10Msol (or a start mass of 20Msol or thereabouts). The Fe+He phase (also known as the neutrino phase) of stellar evolution is estimated to last somewhere in the region of twenty millionths of a second and produces all the heavier elements in the universe in a supernova explosion. Less massive stars will die less violently, shedding outer layers over time and/or simply cooling. Few if any with masses less than about 0.75Msol will even reach the Fe phase before simply expiring. I do subscribe to the notion that Jupiter is a failed star, particularly given that it does radiate more than it receives from Sol.

Meanwhile in a suburban garage...

[MrKevvy]

... A high school student working on a Farnsworth-Hirsch Fusor for their science fair project, capable of accelerating tenths of amperes, detects significant numbers of neutrons-byproducts of fusion reactions-coming from the experiment. This, they say, demonstrates the viability of their approach and marks progress toward the ultimate goal of producing more energy than the fusion device takes in.

Or not.

Breakeven != economical

[PeterM from Berkeley]

What the Z machine does is zap a little metal box of wires that may contain fusionables with a high voltage/current pulse that is stored in a really enormous bank of capacitors. Naturally that destroys their target and makes kind of a mess in the process.

I think they manage 8 shots/day if they're lucky.
8 shots/day is a far cry from a reasonable power flux. I'm not sure current pulsed power technology (not to mention other engineering) could stand doing this at some reasonable frequency like 1Hz without breaking down in a few minutes.

But at least they put a good fraction of the power input into the target, NOT like laser fusion--the lasers are horribly inefficient. (1%?)

-PM

Re:Just a cry for funding

[Anonymous Coward]

I don't have any reason to believe this specific direction for fusion power is any good, but, yes, fusion power needs more funding if it's ever going to work.

Pulse generation - why?

[Animats]

The whole pulsed laser fusion effort turned out to be a cover for nuclear weapons research. It lets Lawerence Livermore study H-bomb like fusion reactions on a convenient scale. With a gym-sized bank of lasers aimed at a single point, they can pump enough energy into a tiny space to force fusion. That's a research tool.

So is the Z-machine, for much the same reason. It's yet another pulsed-fusion machine relying on inertial containment.

The tokamak crowd has at least been able to hold a fusion reaction together for 400ms or so. But plasma instability is the curse of all tokamak designs, including ITER. There's much doubt that ITER will work. It's conjectured that a bigger plasma will be more stable, but many physicists question this. ITER has become a pork program, though, and it's hard to stop. Cost is about $15 billion. If there was real confidence it would work, the private sector would fund it.

Right now, the new generation of stellerators looks more promising than the tokamaks.

But that's not what they are saying.

[pupsocket]

The article implies a steep logarithmic gain on energy invested into the initial pulses. If Sandia are right, holding the experiment together for a single-digit multiple of the input energy should break even.

Busard's Polywell is more interesting

[msevior]

My submission of a couple of days ago.

"The EM2 corportation has submitted a paper to axiv.org http://arxiv.org/abs/1406.0133 describing their $10 million US Navy project to investigate Bussards Polywell fusion device. NBC has a report on the development http://www.nbcnews.com/science... . Quoting Nicholas Krall, a plasma physicist who has been working in the fusion field for more than a half-century and has been an adviser to EMC2 Fusion, "I think this is the most exciting experimental advance that I've been involved in," he told NBC News. 'I'm stoked.""

Plus there are 2-3 other concepts that gave got Venture Capital funding. Fusion is looking more interesting.