NIF: no ignition this year

KitemanSA · Post by **KitemanSA** » Fri Jul 01, 2011 5:33 pm

Joseph Chikva wrote:
hanelyp wrote:NIIF should produce some interesting physics if it ever runs. Anything beyond that is doubtful.
The efficiency of lasers is very low (~5%) requiring very high target’s amplifying factor. The target turns out complicated and therefore expensive.
And consequently if inertial confinement will ever capable to produce net power, that will be expensive.

UNLESS someone invents a cheap, high efficiency laser OR someone invents a cheap target, OR...

Joseph Chikva · Post by **Joseph Chikva** » Fri Jul 01, 2011 5:59 pm

KitemanSA wrote:UNLESS someone invents a cheap, high efficiency laser OR someone invents a cheap target, OR...

Doubt on high efficiency lasers. Think that impossible to increase efficiency dramatically.

Targets for experiments as I know now produces only one company having know how in this branch. If breakeven will be achieved that company will become monopolist. Price on produced kW*h will be highly dependent on price of targets.

pfrit · Post by **pfrit** » Sat Jul 02, 2011 8:08 am

Actually, a really targeted (non tunable) FEL can get over 40% efficiency. And they are high power as well.

Joseph Chikva · Post by **Joseph Chikva** » Sat Jul 02, 2011 8:58 am

pfrit wrote:Actually, a really targeted (non tunable) FEL can get over 40% efficiency. And they are high power as well.

Now I have in my hands the book: James J. Duderstadt, Gregory A. Moss, INERTIAL CONFINEMENT FUSION, John Wiley and Sons, NY, 1982
So, about 5%. Even less really achieved till 1982.
I admit that during 29 years many improvements could be done. But have not any information about something dramatically improvement of laser's efficiency.
May you please send me a link?

D Tibbets · Post by **D Tibbets** » Sat Jul 02, 2011 8:36 pm

I know little detail, but I believe there is a EU/ Italian, laser fusion experiment. I think the lasers are much weaker than those a the LIF, but possibly can deliver their energy is a shorter pulse, This may have benefits aside from the reduced costs.

Dan Tibbets

Joseph Chikva · Post by **Joseph Chikva** » Sun Jul 03, 2011 3:36 am

D Tibbets wrote:I know little detail, but I believe there is a EU/ Italian, laser fusion experiment. I think the lasers are much weaker than those a the LIF, but possibly can deliver their energy is a shorter pulse, This may have benefits aside from the reduced costs.

Dan Tibbets

If LIF is Light Ions Fusion also unsuccessful program having big problems with focusing of beams.
Heavy Ions Fusion may be will work. As needs less complicated target, provides better energy transfer effect from beam to target, as I know solvable focusing issue, reachable currents by induction linacs with real efficiency 35%.

pfrit · Post by **pfrit** » Sun Jul 03, 2011 4:36 am

Joseph Chikva wrote:
pfrit wrote:Actually, a really targeted (non tunable) FEL can get over 40% efficiency. And they are high power as well.
Now I have in my hands the book: James J. Duderstadt, Gregory A. Moss, INERTIAL CONFINEMENT FUSION, John Wiley and Sons, NY, 1982
So, about 5%. Even less really achieved till 1982.
I admit that during 29 years many improvements could be done. But have not any information about something dramatically improvement of laser's efficiency.
May you please send me a link?

A quick link from a google search.
http://www.nap.edu/openbook.php?record_id=9182&page=18

Please note that you lose a lot of the advantages of a free electron laser when you go for efficiency. But you can make a very efficient high power laser with them if you need one.

Joseph Chikva · Post by **Joseph Chikva** » Sun Jul 03, 2011 5:19 am

My English is very bad. So, please explain me what does it mean?

The efficiency of FELs has been demonstrated to be greater than 40% at long wavelengths, but most will operate at a lower efficiency of a few percent.

As between a few percents and forty percents is a very big gap.
I am only an engineer and not a dreamer.
Also recall that as I know nobody uses FEL for fusion applications.
What do you think why?
May be the key words here "long wavelengths"? How long?
Pulse duration? For note: nanoseconds are required.

pfrit · Post by **pfrit** » Sun Jul 03, 2011 5:15 pm

Joseph Chikva wrote:My English is very bad. So, please explain me what does it mean?
The efficiency of FELs has been demonstrated to be greater than 40% at long wavelengths, but most will operate at a lower efficiency of a few percent.
As between a few percents and forty percents is a very big gap.
I am only an engineer and not a dreamer.
Also recall that as I know nobody uses FEL for fusion applications.
What do you think why?
May be the key words here "long wavelengths"? How long?
Pulse duration? For note: nanoseconds are required.

The longer the wavelength, the less loss the laser experiences. Most people building FELs are looking for soft xrays, not IR. Considering the cost of an FEL, efficiency is just not a concern.
FELs are continous beam as a rule.
Remember than there are only about 20 FELs in the world right now. They are really expensive to build. There really are no practical uses other than research and weapons that can justify the expense right now for them. Fusion may be justified if you could ignite a target with wavelengths at or below IR. I dont know if that is an issue.

Joseph Chikva · Post by **Joseph Chikva** » Sun Jul 03, 2011 6:32 pm

pfrit wrote:FELs are continous beam as a rule.

For inertial fusion pulse's duration should be of nanoseconds order. Or useless for that application. Also the shape of pulse has a matter.

Considering the cost of an FEL, efficiency is just not a concern.

Wrong. Energy pumped in pulse vs. energy gained from that pulse.
If efficiency is 5% and pulse energy on target 2MJ you should spend 2MJ/0.05=40MJ for pumping from a plug.
So, target should provide high - as a rule unreachable amplifying factor: product of fusion energy and efficiency of energy conversion into electricity should exceed 40MJ.
And in case if laser's efficiency will be equal to 40%, only 5MJ should be exceeded.

pfrit · Post by **pfrit** » Sun Jul 03, 2011 7:58 pm

Joseph Chikva wrote:
pfrit wrote:FELs are continous beam as a rule.
For inertial fusion pulse's duration should be of nanoseconds order. Or useless for that application. Also the shape of pulse has a matter.
Considering the cost of an FEL, efficiency is just not a concern.
Wrong. Energy pumped in pulse vs. energy gained from that pulse.
If efficiency is 5% and pulse energy on target 2MJ you should spend 2MJ/0.05=40MJ for pumping from a plug.
So, target should provide high - as a rule unreachable amplifying factor: product of fusion energy and efficiency of energy conversion into electricity should exceed 40MJ.
And in case if laser's efficiency will be equal to 40%, only 5MJ should be exceeded.

The reason I said that efficiency is not a concern is because FELs cost in the billions of dollar each. They are using them to do lasing in realms not acheivable by any other lasers. If they choose to make FEL laser to do fusion, then maybe. I would expect them to be more concerned about making a reasonablly priced facility rather than a facility that would cost several trillion dollars. The price of particle accelerators needs to come down by a couple orders of magnitude before we get common FELs that you could use in a fusion project.

Joseph Chikva · Post by **Joseph Chikva** » Sun Jul 03, 2011 8:20 pm

pfrit wrote:The price of particle accelerators needs to come down by a couple orders of magnitude before we get common FELs that you could use in a fusion project.

That would not be a big problem if all other problems will be solved.
Today particle accelerators are very high value added products because their demand is low and very few manufacturers produce them. There is not a big secret how to produce them in reasonable cost in case of steady demand.