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Z Machine Advances Fusion Race
Sandia Labs has announced a new milestone in Linear Transformer Driver technology that aims to solve one of the biggest obstacles to practical fusion reactors. Getting the current needed to "spark" a burst of fusion is doable; getting a constant series of sparks going to create a continuous chain of fusion bursts has never been achieved. The LTD, which allows the Sandia Z machine to fire once every 10.2 seconds, makes it look achievable. The press release (which has been picked up in a few places, but with no further analysis) says that practical fusion power could now be 20 years off.
Weren't we closer 30 years ago?
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> says that practical fusion power could now be 20 years off.
Twenty years off what? And are they light years or dog years?
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Well, since every comment here is about that "20 years off" quote, I'll add mine.
That twenty years (here and decades ago) assumes that governments won't pull funding for fusion research. But they did, and will again. ITER could have been built years ago. It wasn't a lack technology holding it back, it was a lack of money. So don't blame the scientists who give those 20 year estimates, blame your governments.
Actually, measured in light years, practical fusion is only 1.58e-5 light years away.
Even if we had a breakthrough and suddenly we had all the equations and knowledge to build practical fusion reactors, fusion power would still be at least a decade away.
5 years to design it into a power plant, find and obtain a site, necessary permits, etc... Then 5 years to actually build the thing.
I'll believe that it's twenty years away when we have a working plant sustaining a fusion reaction for testing purposes. IE operating the thing for days/weeks, not seconds/minutes.
We had the first nuclear pile in 1942. The first nuclear reactor to produce electricity came online in 1951. It wasn't until 1957 when the first commercial fission plant came online. 15 years from the first pile until a commercial plant. All signs point towards fusion being bigger and more difficult, so I figure one will take even longer to build than a fission plant.
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It is worth noting (and it is also mentioned in TFA) that this development advances the field of Inertial Confinement Fusion, which is an area that has not traditionally been considered the most likely candidate for commercial fusion power generation. ITER and all other experimental tokamak reactors are of the other variety (magnetic confinement fusion), where a magnetic field is used to keep the plasma in place during the reaction. During ICF, each fusion reaction has a duration short enough that it isn't necessary to hold the plasma back against the forces of gravity. Hence the need to produce a "spark" quickly and efficiently, as many consecutive reactions are necessary to produce any significant amount of power. http://en.wikipedia.org/wiki/Inertial_confinement_ fusion
The article lacked a photo of the Z Machine in operation. Amazing!
Bad choice of name. The Z-Machine, which is short for Z-Pinch Machine is a fusion confinement machine that has been around for five and a half decades. http://en.wikipedia.org/wiki/Z-Pinch Numerous experimental devices have been built around the world in government labs and universities.
Contrary to the misconception people keep throwing arround, it wasn't 20 years of 20 years ago. The confusion arises because one was talking about different things. One estimate was when we would reach break-even. That eastimate was for year 2000, and at the time ( 1970) it was 30 years into the future. As it happens, the JET reactor has managed to heat a plasma to the temperatures needed for break-even, but that doesn't mean it is practical as a powerplant. I have a 30 year old book about electricity generation, which estimates the first powerplant for 2050. Furthermore, last time I heard "it was always X years ago", X was 30. Before that X was and had "always" been 50 years ( Tho my Swedish book still says 2050 and was written in the 70ies ). I bet in 2040 we will hear people saying how widescale worldwide deployment of fusion powerplants was "always" 10 more years. When in fact, the estimate of today is that the technology needed to build a practical powerplant ( not necessarily an economically competative one ) is 2027. These "that is what they said back then" quotes usually have no substance in reality. It is just like saying "well they said chernobyl was safe", which of course nobody ever claimed ( in contrast the department of energy stated that no water cooled graphite moderated reactor would be licensed in the US ). However, the claim sounds so damning that people want to believe it. It is the same thing with fusion. The scientists never claimed we would be using fusion plants today. They claimed that IF funding was continued, and IF projects were not cancelled, then we would be able to have a controlled fusion reaction by the year 2000. As it happens we have done better than that. We have managed to initiate fusion reactions that produce more energy than is needed to sustain them. This is however not the same thing as an economically competative powerplant, and it is not the same as ignition ( a fusion plasma that needs no external energy input once it is burning). If you keep changing the goal to be something more difficult, then yes, the goal will always be in the future, that doesn't mean the original estimate was wrong tho. It just mean you were talking about something else.
The original hydrogen bomb was known as the "Super" before it was called a hydrogen bomb, and the idea is what every wide-eyed geek in elementary school imagines the H-bomb to be -- put an A-bomb next to a vat of deuterium, and the A-bomb blasts the deuterium hot enough to make it fuse.
As the dudes as Los Alamos started building computers to do numerical models of fluids and radiation and everything, it became apparent that Teller's Super was a dud. The physics of radiation were such that simply sticking a fission bomb next to a pile of heavy hydrogen was simply not going to do anything. What if you sweetened the deuterium with tritium -- then what? As it turned out, you would need gobs of tritium, so the whole thing was a non-starter.
As it turns out, Stanislaw Ulam came up with the idea of a staged atom bomb -- a small atom bomb would provide the shock to compress a big freepin pile of plutonium to make a big honkin atom bomb, and Teller got ahold of that idea to make the staged H-bomb. The staged H-bomb used to be a very dark secret, but the combination of Richard Rhodes "Dark Sun" and that Progressive Magazine article kind of let out at least the general H-bomb concept. Teller's stamp on the staged bomb was that prompt x-rays from the atom bomb would be the way of getting compression instead of Ulam's original idea of the shock wave, but that the radiation would act first is obvious once anyone with physics knowledge starts working on a staged design, and Teller kind of took all the credit.
But the actual staged H-bomb not only focuses A-bomb radiation to compress a pile of deuterium, it also compresses a plutonium "spark plug" in the middle to make Ulam's staged A-bomb. The combination of heat and pressure from the radiation compression along with the flood of fast neutrons from the plutonium spark plug manage to fuse the deuterium, which produces its yield mainly in the form of yet more neutrons, which provides fission of a U-238 blanket to provide much of the explosive power of the bomb.
Fusion is really, really hard, even with the heat and pressure from an atom bomb, and the real H-bomb is a Rube Goldberg set of multiple effects which use fission-driven neutrons to produce fusion neutrons to produce gobs of explosive power from non-critical fission of U-238. Fusion is really, really hard, even for the Sun, because while the Sun is not using deuterium but straight hydrogen, for all of the intense heat and pressure in the interior of the Sun, the reaction rates are really, really low, which is a good thing, because otherwise the Sun wouldn't have lasted 5 billion years to allow us to be here.
So back to the fusion power reactor. All of the claims of imminent fusion power are based on using lots of tritium for D-T fusion for the same reason that Teller's Classical Super would have needed gobs of tritium and for the same reason that the actual H-bomb that burns D-D needs three stages of fission to get its explosive power. Just as the need for tons of T made Teller's Super a non-starter, the need for tritium means that the current frontier of fusion power is a non-starter. Yes, you breed tritium in the lithium blanket, but you have to compare the breeding doubling time with the half life of tritium and wonder how much seed tritium will you need to get a fusion power economy going and how many decades of breeding tritium will be required to switch the economy over the fusion power before the oil runs out.
I remember seeing a powerpoint lecture given by one of the researchers there, who calculated that to make the Z machine feasible for providing fusion power, they would need to fire one of these off every 0.1 second, so once every 10 seconds is not even close. Plus, the simple fact that there's an enormous explosion going off ten times a second, which destroys the chamber that holds the capsule, makes it seem like there's a definite engineering feat to overcome, otherwise the whole thing is liable to crumble to bits. Right now, they only fire off the Z machine a few hundred times a year... going from that to a few hundred times a minute is a big step.
I also wouldn't want to live anywhere near there; it feels like a moderately strong earthquake in the area everytime they fire that thing; it seems like the ground beneath and around a rapid-fire facility would quickly weaken and collapse.
So yes, the Z machine is an excellent source of x-rays, and those x-rays can definitely be used to collapse a fusion capsule, but how applicable is it for fusion power?
Fuck "in God we Trust," we should just print "don't rock the boat" on our money.
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