Laser Fusion produced excess energy.

[Skipjack]

IIRC the types of lasers used at NIF can not be more than 5% efficient due their UV wavelength requirements for the lasers.
Laser fusion is not completely unrealistic. E.g. there was this article in nature about a much smaller device in france that uses a very different principle from NIF (and does PB11).
http://www.nature.com/news/two-laser-bo ... gy-1.13914

[ladajo]

The problem with NIF is that it will never lead to an economic fusion reactor.

Why is this a problem? NIF was never meant to be a economic fusion reactor. It was meant to be a weapons test & research tool. The idea is that you can (and they are) using NIF to explore the dynamics of ICF to see if it would be a viable means as a path for economical fusion. This is basic research only, and not NIF's primary purpose.

First of all, the hohlraum is plated with gold

Why yes, yes it is. So what? My child's jewelry is plated with gold as well. You can buy it at Walmart.

it has to be very precise and be placed at the exact center for every shot and you have to do that several times a second.

And NIF never will do that several times a second, because it was not meant nor built to do that. You can not buy that at Walmart.

So essentially you are evaporating several grams of gold a second there.

And this is an issue why? But your estimate of several grams would be off in any event.

These numbers are for a 300eV Hohlraum design:

Fuel Capsule radius is 1 mm, hohlraum half length is 4.6 mm and hohlraum radius is 2.55 mm.

The walls are 75% U and 25% Au. The inner wall has a .5 micron layer of Au.

[ladajo]

And in any event, you don't need to use gold.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3596797/

[Skipjack]

Why is this a problem?

Because they are promoting it as if it was an energy project to the general public, while it is really a more or less hidden defense spending that does not show up in the statistics as such. Also the money could be better spent on fusion projects that have a chance of ever resulting in an economic reactor.

First of all, the hohlraum is plated with gold

Why yes, yes it is. So what? My child's jewelry is plated with gold as well. You can buy it at Walmart.

Yes, but you will have several shots a second and many reactors. That adds up to a lot of gold. We don't just want fusion, we want economic fusion for power generation! Whats the point if you cant compete with coal?

it has to be very precise and be placed at the exact center for every shot and you have to do that several times a second.

And NIF never will do that several times a second, because it was not meant nor built to do that.

And there is no clear path to that either.

So essentially you are evaporating several grams of gold a second there.

And this is an issue why? But your estimate of several grams would be off in any event.

These numbers are for a 300eV Hohlraum design:

Fuel Capsule radius is 1 mm, hohlraum half length is 4.6 mm and hohlraum radius is 2.55 mm.

The walls are 75% U and 25% Au. The inner wall has a .5 micron layer of Au.

Several grams because there will be several shots a second. I did not do the exact math, but it seemed a reasonable estimate.
I might be overestimating it, though, seeing your numbers.
Either way, even if we assume .1 gram a second, we get to 360 grams an hour, that is more than 8.6 kg a day or 3.1 metric tons of gold a year. Add that to the manufacturing cost for the hohlraum and the other issues I mentioned and it just does not add up to something that looks even remotely economical.

[ladajo]

See above post on lead.

[Skipjack]

And in any event, you don't need to use gold.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3596797/

Great if lead works. That still does not fix any of the other problems. The cost of the hohlraum is not just that of the materials. Still no answers regarding the power conversion, the tritium breeding and management and size of the facility and initial capital investment cost. Why would I choose that over a much further developed tokamak?

[Diogenes]

IIRC the types of lasers used at NIF can not be more than 5% efficient due their UV wavelength requirements for the lasers.
Laser fusion is not completely unrealistic. E.g. there was this article in nature about a much smaller device in france that uses a very different principle from NIF (and does PB11).
http://www.nature.com/news/two-laser-bo ... gy-1.13914

FELs can be made for any frequency.

[Skipjack]

IIRC the types of lasers used at NIF can not be more than 5% efficient due their UV wavelength requirements for the lasers.
Laser fusion is not completely unrealistic. E.g. there was this article in nature about a much smaller device in france that uses a very different principle from NIF (and does PB11).
http://www.nature.com/news/two-laser-bo ... gy-1.13914

FELs can be made for any frequency.

Uhmm, not for this purpose and at an efficiency above 5%?

[ladajo]

Why not, and yes much more efficient.

They are the primary goal for ship lasers due to tunability and efficiency.

[Skipjack]

Why not, and yes much more efficient.

They are the primary goal for ship lasers due to tunability and efficiency.

I understand that they meet the requirements for weapons, which are quite different from this. I would like to see some information that states that they can bring the efficiency at the power levels and wavelength required for something like NIF.

[ladajo]

Great if lead works. That still does not fix any of the other problems. The cost of the hohlraum is not just that of the materials. Still no answers regarding the power conversion, the tritium breeding and management and size of the facility and initial capital investment cost. Why would I choose that over a much further developed tokamak?

Of course lead will work. And mass production of hohlraums will further reduce costs (significantly I would say).

As for choosing Tokamak over Laser. Well, let's see. Hmmm. For one Tokamak will NEVER be cost efficient and everyone knows it.
Laser can be much more cost efficient. You are basing all your thinking on NIF. NIF was never meant to represent what an active power plant might look like.
If you think that NIF was commissioned in 2009, and have met a major goal (on the fusion theme) by igniting a pellet, after only 4 years of work. And it took about 5 years to build as I recall. Well let's see again, how long will it take to build ITER? How much will it cost in the end? And will that be a viable power plant?

I would back NIF long before I would back ITER. NIFs only real problem is that the media jacks up reporting on it all the time and misuses terminology and intent.

Outside of the secondary effort fusion research, they have been doing some wonderful weapons work. But you wouldn't know about that would you?

[ladajo]

I understand that they meet the requirements for weapons, which are quite different from this. I would like to see some information that states that they can bring the efficiency at the power levels and wavelength required for something like NIF.

Not yet, but probably within 5 years.

FEL is a fantastic way to lase. And there is no reason they can not be set up for NIF style purposes. The NIF went with the best laser tech available at the time the construction commit was made. If they were building it again today, they would pick a different lasing rig.

[ladajo]

Here is how they would build the NIF laser package today if they did it:

LIFE Laser System Proposal

[ladajo]

Recent work on High Power UV FEL:

High Power UV FEL

[Diogenes]

Uhmm, not for this purpose and at an efficiency above 5%?

Do you have any knowledge of how a FEL works? It's a freakin electron gun with a wiggler.


I'm actually surprised the efficiency mentioned is only 50%.