Uniformity: The secret of better fusion ignition

Oct 11, 2013

One of the ways to achieve thermonuclear fusion is through a controlled reaction between two light variants of hydrogen, called deuterium and tritium. Mauro Temporal, from the École Normale Supérieure Cachan, in France, and colleagues have made theoretical calculations indicating how best to improve the ignition stage of fusion reaction. Their approach, described in a paper published in European Physical Journal D, involves increasing the uniformity of irradiation using high-power laser beams on the external shell of a spherical capsule containing a mix of deuterium and tritium.

Reaching uniformity of matters. Indeed, if it can be achieved, it rapidly heats up the capsule and makes it implode, compressing the fuel inside to very high density. This, in turn, induces the compression and heating of a small amount of fuel in a hot spot, which is a sine qua non for reaching the ignition conditions of to produce large energy quantities.

Temporal and colleagues analyse the possibility of using the UK-based Orion facility's high-power laser beams to study uniformity. Orion has a few nanosecond-long pulse -5 kiloJoules in energy -which cannot achieve , but can help to test ways to produce uniform irradiation from non-uniformly distributed beams: a technique called Polar Direct Drive.

Specifically, the authors use numerical simulations to analyse the uniformity of the illumination of a spherical target both in the case of circular or elliptical laser intensity profiles. Their work also takes into account other potentially disruptive factors. These include beam-to-beam power imbalance, laser-beam pointing error and target positioning error.

They demonstrate that this approach reduces considerably the non-uniformity of the capsule irradiation-by 50 percent and 35 percent, for elliptical and circular intensity profiles respectively.

Explore further: New microscope collects dynamic images of the molecules that animate life

More information: Temporal, M. et al. (2013), Polar Direct Drive Illumination Uniformity Provided by the Orion Facility, European Physical Journal D. DOI: 10.1140/epjd/e2013-40362-4

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El_Nose
3.7 / 5 (3) Oct 11, 2013
I am sure NIF scientists are thinking ---
"Hmmph, We could have told you that. You really got a paper out of this?"
antialias_physorg
2.5 / 5 (8) Oct 11, 2013
Just another paywaled journal about research, which is payed from taxes completely.

You really don't get it, do you? The paywall is NOT put up by the scientists (not by their institutions, nor by the government that financed it). The paywalls are put up by profit-oriented publishing companies THAT HAVE NOTHING TO DO WITH THE SCIENCE WHATSOEVER.

Now if you were actually smart (I know you aren't, but let's just ignore observed facts for a sec): you'd simply email the authors directly and ask for a copy of the paper. If you ask nicely then they will send you one, I guarantee it.

Get a friggin' clue.
Eikka
1.9 / 5 (9) Oct 11, 2013
I still don't understand how anyone is proposing to make useful amounts of energy by exploding tiny pellets one by one.

If they scale up the pellets, they're going to be producing explosions so violent that it shakes the whole thing apart, and if they're going to increase the number of explosions per second, they'll be using ridiculous amounts of material and energy just to manufacture enough of them. The pellets are made of gold and platinum and so on! The whole contraption seems just an exercise in futility.

It's like the combustion engine designed by Edison, which was built to run on a spool of guncotton string - at least until the blade that cut the cotton string accidentally ignited the whole spool.
antialias_physorg
2 / 5 (4) Oct 11, 2013
I still don't understand how anyone is proposing to make useful amounts of energy by exploding tiny pellets.

The system I've seen proposed would inject pellets at a rapid rate to be detonated by a fast succession of laser pulses. But somehow I have the feeling that the homogeneity of the pellets would need to be enormously good (and also that the field of implosion would soon be contaminated with residue that would lead to scatter effects.)

Then again I'm not sure the pellet thing is intended to produce useful energy. That approach is more useful in aiding thermonuclear bomb research.
NoTennisNow
1 / 5 (7) Oct 11, 2013
This is old history, but the folks at the Manhattan Project at the LANL had the same issues developing the implosion mechanism for the Little Boy plutonium bomb. Seems like someone forgot to do their homework. In the current problem, how round are the pellets? End result would be the same.
NoTennisNow
1 / 5 (10) Oct 11, 2013
Sent my first comment too soon.

Credit to antialias_physorg for raising the issue of homogeniety.

The folks at the Manhattan Project at the LANL had the same issues developing the implosion mechanism for the Little Boy plutonium bomb. Seems like someone forgot to do their homework. If the NIF folks did their homework, then they should have known from the outset that there needed to be tight control on the shape of the pellets as well as their overall construction and conducted the numerical simulations early on (the guys at the LANL didn't have the luxury of the computers and hydrodynamic codes now available).
Eikka
1 / 5 (7) Oct 12, 2013
The system I've seen proposed would inject pellets at a rapid rate to be detonated by a fast succession of laser pulses.


Each pellet recieves on the order of 100 MJ of energy to compress it sufficiently, and supposing a 1:10 yield in fusion which is considered to make it commercially viable, would produce 1100 MJ of energy or the equivalent of detonating 500 pounds of TNT. Repeating this once per second would yield you an average thermal power of 1.1 Gigawatts, out of which you can extract roughly 400 MW of electric power, or the equivalent of a mid-size powerplant.

Now, if you can build a machine that is capable of withstanding that blast and repeating it in quick succession without pounding itself to rubble, I will tip my hat to you sir.
Eikka
1 / 5 (7) Oct 12, 2013
Correction, the NIF laser system delivers 2 MJ of energy and not 100 MJ as I falsely remembered.

Still, the energy involved is comparable to 10 pounds of TNT which would be like making an engine that works by blowing up anti-tank landmines.
TheGhostofOtto1923
1 / 5 (4) Oct 12, 2013

"Congress Affirms NIF's Mission is Centered on Fusion Energy
I want to affirm with you that the mission of NIF has not changed and that inertial fusion energy and basic science research, as well as stockpile stewardship, will continue to be vigorously pursued at NIF."
http://www.youtub...VhnWFyw8

"An inertial fusion energy (IFE) power plant consists of a target production facility (or target factory), target injection and tracking systems, the laser, a fusion chamber, and a power conversion system... In the plant, many pulses of fusion energy per second (typically 10 to 20) would heat a low-activation coolant, such as lithium-bearing liquid metals or molten salts, surrounding the fusion targets. The coolant in turn would transfer the fusion heat to a turbine and generator to produce electricity... The target factory must produce a continuous supply of high-quality targets at an acceptable cost—typically about one million targets per day at about 25 cents per target."
TheGhostofOtto1923
1.8 / 5 (5) Oct 12, 2013
hen again I'm not sure the pellet thing is intended to produce useful energy.
The 2nd excerpt above is from the NIF website which explains their design goals for a working power plant.

The thing will fire at 10 to 20 pulses per second. How fast does an internal combustion engine cycle? Pulsed fusion is typical of the majority of hot fusion configurations.

You keep professing ignorance on this and other issues AA and I will continue to attempt to inform you.
TheGhostofOtto1923
2.6 / 5 (7) Oct 12, 2013
whereas the cold fusion experiments routinely achieve gain over 1400 percent - and their costs is lower in six orders of magnitude!
-You forgot 'purportedly'. Maybe celani would like to do a reality show (with english subtitles)? That would be a nice way of showing the world a working reactor. Then people could say "No its real! I saw it on tv!"

Time to put up or shut up. They all have had more than enough time.
Eikka
1 / 5 (7) Oct 12, 2013
The thing will fire at 10 to 20 pulses per second. How fast does an internal combustion engine cycle?


Assuming a 6 cylinder four-stroke engine running at 2000 RPM, about 50 times a second.

Although the comparison is not valid because combustion happens gradually, while the fusion is nearly instantaneous. If an engine were to operate similiarily, you're talking about a condition called knocking where the fuel-air mixture is detonating inside the cylinder instead of combusting, which will quickly lead to engine failure.

A common misconception is that diesel engines work by detonating the fuel, but that's false. Even diesel engines can't withstand the shock caused by having all the fuel burn up in an instant.

Well, this perfectly applies to NIF too - or not?


That is the point. If you don't have anything to show, how can you demand them to?
Eikka
1.6 / 5 (7) Oct 13, 2013
Fortunately the http://lenr-canr....Only.htm to show...


Thousands of "studies" showing an effect, yet nothing real has materialized out of them.

Where's the cold fusion reactors? Or is the "man" keeping them down again?
TheGhostofOtto1923
1 / 5 (5) Oct 13, 2013
Even diesel engines can't withstand the shock
You underestimate the extraordinary powers of engineers. Diesels are designed to function with the imposed stresses. Apparently the people at NIF and many other fusion labs around the world are comfortable that working pulsed reactors can be similarly designed, because their configurations all depend on it.

And so if you are truly curious you could do a little research and find out why they think this way, and then you could perhaps be critical of THAT, but it would entail a little more work I suppose. You can imagine that a great deal of work has been done on the concept, investigating present and future materials, radiation levels, service and repair, etc. A million shots a day is what they think they can design for.

General Fusion for instance is one with a similar lithium bath.
TheGhostofOtto1923
1 / 5 (4) Oct 13, 2013
Fortunately the http://lenr-canr....Only.htm

-Pretty dramatic eh? It looks portable. It LOOKS like something Rossi could cart around in a road show to labs, science fairs, energy expos, and comicons around the world. This would be bigger than X-men. Why wouldn't rich entrepreneurs be wanting to pay for a demonstration such as this? They could MAKE money on a show alone.

Rossi apparently has a big-deal US corporate partner. Wouldn't a traveling demo with this thing be great publicity for them?

Let's see it.

TheGhostofOtto1923
1 / 5 (3) Oct 13, 2013
When you edit a post with 2 links in it you lose one link and a lot of text. WHY is that physorg??

A Rossi hotcat roadshow.
http://www.forbes...ter-all/
Eikka
2 / 5 (8) Oct 13, 2013
Apparently the people at NIF and many other fusion labs around the world are comfortable that working pulsed reactors can be similarly designed, because their configurations all depend on it.


Many an engineer has come up with a solution that is actually impossible to build, but it won't become apparent until they get that far in actually building it.

And you're simply begging the question by insisting that it works because someone has made plans for it. Remember that every single Tokamak reactor works on paper according to its designers, yet none of them have actually broken even because of issues like plasma instability and contamination etc. etc.

Similiarily, people have made plans for a space elevator, or magnetically suspended supersonically looping cables that would pull payloads into space, which are all plausible on paper but probably will never be built because they are so ridiculous in scope and depend on all sorts of "unobtainium" for materials.
Eikka
1.5 / 5 (8) Oct 13, 2013
A pulse ignited fusion reaction would make sense if they were designing it with space propulsion in mind, similiar to the Orion drive, where the fusion blast would happen in space and the energy were captured by a dampened reaction plate.

But like AA points out, it's more likely that they're just studying the stuff with the purpose in mind to manufacture fusion bombs that can be imploded into action with less explosives, because currently they require conventional fission driven atom bombs to get going and they'd probably like to have one that's a bit less dirty.

If you had a pure fusion bomb, you could drop it and not leave a permanently radioactive toxic mess. It would be the cleanest nuclear weapon possible, and it wouldn't necessarily even damage any infrastructure because it would be deadly at a distance due to the neutron radiation.
TheGhostofOtto1923
1 / 5 (4) Oct 13, 2013
Many an engineer
-So you stil haven't researched it yet? Why are you wasting tie speculating? This is the Internet.

I can tell you that this is not just one group of engineers involved in one concept, but hundreds of them across a few gens and involved with many different configurations, working at labs all around the world, ALL pursuing the idea that pulsed fusion reactors can be designed to function reliably. They are receiving billions of dollars, euros, rubles, yen etc to pursue this goal.

Encouraged yet? Dont you want to know WHY they think this way? Dozens of sources online. Have a go.
TheGhostofOtto1923
1 / 5 (4) Oct 13, 2013
manufacture fusion bombs
-And you didn't even watch the YouTube vid I posted of the congressional mandate, or visit the NIF site showing the power plant configuration. The 2 of you would rather sit back and pretend to know rather than just LEARN.

I was gonna pm lite/toot and tell him that you're one of the good guys but now I'm not so sure.
so ridiculous in scope
-And 30 years ago you guys were saying similar things about NIF-scale laser arrays and LHC-scale accelerators. And before that space travel and airplanes. Do you know how many airplanes are in the sky this very moment? Picture the guy who was sure the wright bros would never get off the ground.

ROBOTICS will make space elevators possible.
Eikka
1 / 5 (5) Oct 14, 2013
ROBOTICS will make space elevators possible.


First you got to make the cable, so don't step ahead of yourself. THAT is the whole point.
Eikka
1.7 / 5 (6) Oct 14, 2013
or visit the NIF site showing the power plant configuration


Yes I have, and it is downright ridiculous. They want to make 350-500 MW of fusion power out of a fusion blast every 1/10th second, which is 35-50 MJ per blast, which is roughly equivalent to blowing up 17-24 pounds of TNT inside the 15 foot metal sphere.

First I want to see them make that sphere that handles the sort of shock involved in releasing the energy, because they're going to get roughly 10,000 stress cycles a day, and a million in three months, and that's going to be one tough nut with neutron embrittlement and other radiation damage going on inside the thing.

The neutron flux from the blast is supposed to be powerful enough to cause forced fission in spent nuclear fuel pellets outside of the containment sphere with an additional 4-10 times gain in power, but somehow not affect the structure of the sphere itself too much.

Eikka
1.7 / 5 (6) Oct 14, 2013
ALL pursuing the idea that pulsed fusion reactors can be designed to function reliably.


And how much money is being thrown into Tokamak designs, and how many of them actually work reliably? Simply because people are throwing money on a problem doesn't mean it will be solved.

Pulsed fusion is a worthwhile research subject regardless of whether the proposed powerplant configuration actually works, so I can understand the interest.

And 30 years ago you guys were saying similar things about...


30 years ago you couldn't object to the LHC/NIF because they were technically implausible, but because they were too expensive, which is a whole other argument.

brt
1 / 5 (1) Oct 14, 2013
I still don't understand how anyone is proposing to make useful amounts of energy by exploding tiny pellets one by one.

If they scale up the pellets, they're going to be producing explosions so violent that it shakes the whole thing apart, and if they're going to increase the number of explosions per second, they'll be using ridiculous amounts of material and energy just to manufacture enough of them. The pellets are made of gold and platinum and so on! The whole contraption seems just an exercise in futility.

It's like the combustion engine designed by Edison, which was built to run on a spool of guncotton string - at least until the blade that cut the cotton string accidentally ignited the whole spool.


And as a result of Edison's flawed design, we came up with a design that works quite well now. Why would anyone invest in a fusion power plant when we can't even achieve ignition yet? What idiot would do that? You have to take steps 1 & 2 before you take steps 3 & 4.
brt
1 / 5 (1) Oct 14, 2013


But like AA points out, it's more likely that they're just studying the stuff with the purpose in mind to manufacture fusion bombs that can be imploded into action with less explosives, because currently they require conventional fission driven atom bombs to get going and they'd probably like to have one that's a bit less dirty.

If you had a pure fusion bomb, you could drop it and not leave a permanently radioactive toxic mess. It would be the cleanest nuclear weapon possible, and it wouldn't necessarily even damage any infrastructure because it would be deadly at a distance due to the neutron radiation.


I don't think that's correct...http://en.wikiped...ron_bomb
This idea is about 55 years out of date.
What would be more valuable given the increased ease of building a nuclear weapon and international vitriol: knowing how to build one or knowing how to protect against one that has recently detonated? NIF is for the sole purpose of knowledge.
TheGhostofOtto1923
1 / 5 (3) Oct 14, 2013
downright ridiculous
Ahaahaaa let's see we have on the one hand groups of scientists and engrs working for decades on a concept presented on a govt research website, vs someone in a science thread who likes to offer opinions on their work without actually having looked at it. And how do we know he hasn't looked at it? Because he says
metal embrittlement
... Sorry eikka I guess you missed the 'low activation coolent' of molten metal or salts meant to convert the neutron flux and protect the chamber.

All fusion reactors not using aneutronic processes have to contend with fast neutron effects on materials. It's an old problem which you can imagine is central to their design. You totally missed the NIFs proposed solution to it. Many papers out there offer other solutions which are being explored.

What else have you missed which might force you to change your opinions?
TheGhostofOtto1923
1 / 5 (3) Oct 14, 2013
Here's more discussion on the issue, and indications of the effort being applied:

"Developing materials for fusion reactors has long been recognized as a problem nearly as difficult and important as that of plasma confinement, but it has received only a fraction of the attention."
http://en.wikiped...Facility

-This facility hasn't even been built yet. I am assuming this is because researchers felt that this was the proper time to begin investigating.
http://en.wikiped...material

-General Fusion plans to use their capture medium as a the primary source of energy for fusion:
http://en.wikiped...l_Fusion
TheGhostofOtto1923
1.7 / 5 (3) Oct 15, 2013
not utility-driven society
Utility in this instance is pursuing the research which best benefits future civilization. Learning how to create, store, manipulate, and transport materias in plasma form is vital to the future.

The promise of cheap power is something the public understands. The promise of reaction chambers which can withstand the rigors of plasma and controlled fusion, is something which the scientific community understands. One enables the other.

Why do you not understand this simple equation jigga? Is it because you have an aversion to equations of any sort?
Eikka
not rated yet Oct 16, 2013
And where are the hot fusion reactors?


Look up at the sun. There's one mighty big one there. There's also a number of sub-unity reactors that show the theory is correct, like the Farnsworth-Hirsch fusor that is usually built for a neutron source.

And as a result of Edison's flawed design, we came up with a design that works quite well now. Why would anyone invest in a fusion power plant when we can't even achieve ignition yet?


Edison's flawed design didn't lead to anything and he never took it further. It was a dead end along with every other attempt to make an internal combustion engine that ran on solid fuel like gunpowder or coal dust etc.

Sorry eikka I guess you missed the 'low activation coolent' of molten metal or salts meant to convert the neutron flux and protect the chamber.


Oh, and you suppose the molten metal just hangs around floating in air in the form of a sphere without a support from, let's say, a solid metal sphere??

Eikka
not rated yet Oct 16, 2013
Here's more discussion on the issue, and indications of the effort being applied:


Yet in your very quote it says:

but it has received only a fraction of the attention.


Which is my entire point. Everyone is stepping ahead of themselves, designing a space elevator before they even know how to build the cable to pull it up.

Lots of money and manpower is being spent simply on "what-ifs".

Ahaahaaa let's see we have on the one hand groups of scientists and engrs working for decades on a concept presented on a govt research website, vs someone in a science thread


Yes, and the emperor really has clothes on.

Lots of engineers have done lots of work that has never lead to anything, because not all ideas always work in the end. Assuming that they do just because you spend lots of money on it just makes you the fool.
Eikka
not rated yet Oct 16, 2013
With the same approach I could say easily, I wouldn't belive in ITER or NIF, until they will be available at the commercial basis (which is the apparent nonsense).


It is the nonsense you put in.

There is no solid evidence for cold fusion happening anywhere, and everyone who's claiming they have simply don't measure up to the standards of "evidence". Because as you say cold fusion doesn't require billions of dollars to pull off, so everyone should be able to replicate it, given that someone would simply publish the information about how to do it.

Yet nobody has published anything that actually works in independent review under public scrutiny. You'd think that if it actually works, they'd build one in friggin North Korea and then gloat about how they got fusion and the west doesn't.

All you have is cranks like Rossi.
TheGhostofOtto1923
1 / 5 (2) Oct 16, 2013
hangs around floating in the air
Naw this would only happen in microgravity. Many configurations propose a curtain of free-falling medium around the reaction. The general fusion machine spins it up and uses it to transport sonic energy to the reaction. You don't know enough about what's going on to speculate.

But contained or not it is usually separate from the vessel and is used to protect it. And they are working on promising materials. The shuttle devt proceeded with the necessary tech not yet created such as the tiles.

Fusion scientists obviously have sufficient confidence that neutron-resistant materials can be found as they have waited to build the test facility until now.
lots of naked engrs
Not to this scale with 1000s of them across a few gens at dozens of labs with billions of dollars to play with. As I say the science and the tech are absolutely critical to the future of this species.
TheGhostofOtto1923
1 / 5 (2) Oct 16, 2013
before they even know how to build the cable
There are think tanks around the world full of very intelligent people who sit around all day analyzing the course of science and technology and make learned predictions about what to expect. Most big-ticket science and defense projects are planned and begum based on the confidence that these people generate. We can look at projects like iter and NIF with the understanding that this confidence is guiding planning and effort.

And then instead of speculating and poo-pooing like an old woman, we can do some research to try to understand the source of this confidence.

Unless we are an old woman in which case we can try to contain ourselves.
crank like Rossi
'Alleged' crank. Evidence says we ought to withold judgment. Put the hotcat on mythbusters. Have the amazing randi and bill nye and neil degrassi tyson on as guest stars. That should settle it.
TheGhostofOtto1923
1 / 5 (2) Oct 17, 2013
neutron embrittlement and other radiation damage going on inside the thing... molten metal just hangs around floating in air in the form of a sphere


Here is the transfer medium in ITER. Note the form-fitting config:

"The blanket covers the interior surfaces of the vacuum vessel, providing shielding to the vessel and the superconducting magnets from the heat and neutron fluxes of the fusion reaction. The neutrons are slowed down in the blanket where their kinetic energy is transformed into heat energy and collected by the coolants. In a fusion power plant, this energy will be used for electrical power production.

"The ITER blanket is one of the most critical and technically challenging components in ITER: together with the divertor it directly faces the hot plasma. Because of its unique physical properties, beryllium has been chosen as the element to cover the first wall."
http://www.iter.o.../Blanket