Are We a Step Closer to Nuclear Fusion?

http://www.xprize.org/news/are-we-step-closer-nuclear-fusion

by Sami_Lehtinen • 11 years ago

31 18 11 years ago

bostik5• 11 years ago

Hidden in the middle of the article there is an interesting tidbit: "When cooled to liquid nitrogen temperature, the superconducting tape can carry as much current as the larger copper conductor."

Material science and superconductivity have come a long way, and they benefit from the feedback loop with fusion research.

All of which reminds me of what a friend told me quite a few years back. At the time, she was doing her PhD in superconductivity at Cern, and while there, her instructor had a very nice project result. The instructor and team discovered an alloy composition that happened to keep superconductivity at temperatures nearly 20 Kelvin higher than other state-of-the-art compounds. At the time most promising superconductors required temperatures in the range of -210°C.

The discovery sounded neat, and a temperature bump like that certainly was cool but it didn't sink in until a bit further just what they had achieved. Superconductivity at temperatures in "low -190's" Celcius meant that suddenly it was possible to use liquid nitrogen (boiling point ~-196°C).

The availability and cost of coolant improved quite a bit.

There have been huge improvements since - the state-of-the art high temperature superconductors now keep up at temperatures around -135°C.[0] Cheaper and more abundant coolant, along with lower delta-T, means that research into applying superconductivity is much more accessible.

Small-scale fusion is likely going to be just a start; I expect to see major improvements in energy transfer, particularly on power loss, over the next 20-30 years.

0: https://en.wikipedia.org/wiki/High-temperature_superconducti...

moreati• 11 years ago

The Breakthrough: The Race for the Superconductor http://www.amazon.com/The-Breakthrough-Race-Superconductor/d... is a nice account of the initial discovery and characterisation of HTSs in the 1980.

bostik5• 11 years ago

Oh, thank you. That went to my read queue.

rsp19842• 11 years ago

Maybe that's an entirely stupid question and please overlook my complete ignorance in this matter, but it certainly sounds quite challenging to keep a superconductor at around -190 deg C while just some feet away there is confined hot plasma at millions deg C. Would this be a problem?

bostik5• 11 years ago

Not a stupid question at all. One could say the foundations of the entire ITER programme circle around need to answer that one. :) [0]

But on a more practical note: the containment for the plasma is a vacuum. All the matter inside the magnetic container is held within the plasma, and in simplified terms, between the "surface" of the plasma and the wall of the container there is _nothing_. Vacuum is a very good insulator, and the magnetic fields that control the plasma serve a dual purpose. Always, to prevent plasma from getting into contact with the walls of the container - but both to keep the energies within the ring, and to make sure any contact with the vessel can't cool the plasma down.

The reason why vacuum is such a great insulator is easy to explain. Heat is transferred by conduction (contact), convection (heat exchangers), and radiation (ejected particles). When surrounded by vacuum, matter isn't in contact with anything and heat transfer by conduction is 0. Because there is nothing for heat to flow to, also convection is effectively 0. Heat loss by radiation is far, far less than by conduction - and since plasma is a cloud of charged particles, even that is subject to the strong magnetic fields pushing the matter back.

0: https://en.wikipedia.org/wiki/ITER#Vacuum_vessel

dghughes2• 11 years ago

I wonder if safety is also a factor seeing that liquid nitrogen to gas expansion ratio is 1:696 and liquid hydrogen is a whopping 1:851.

MichaelMoser123• 11 years ago

wasn't some form of graphene superconductive at room temperatures? Is it possible to turn that into a coil - superconductive at room temperatures?

dghughes2• 11 years ago

I think I read a few days ago when lithium is added to graphene it does something like that, only discovered recently.

I don't think graphene was superconductive until this lithium method was discovered or maybe this allows it to be super conductive a a higher temperature.

smoyer• 11 years ago

An ARC reactor? (Affordable, Robust, Compact) - I can't believe they went there. What percentage of the royalties for this design will go to Marvel Comics?

DrBazza• 11 years ago

Someone posted this the other day (apologies, I can't remember who). http://i.imgur.com/sjH5r.jpg

The image appears to be from 2012. The current funding is 'fusion never'. I hope that's not true.

giarc• 11 years ago

That was first published in 1976 and perhaps updated when re-published in 1986 so perhaps the curves have changed a bit due to technology changes.

ehuna• 11 years ago

Interesting! For an active Nuclear Fusion project in the US (San Francisco Bay Area), check out the 'National Ignition Facility' -

https://en.wikipedia.org/wiki/National_Ignition_Facility

For more links and my modes overview of the project see http://blog.ehuna.org/2009/05/national_ignition_facility_192...

Are We a Step Closer to Nuclear Fusion?

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