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Stanley514
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Was this technique ever demonstrated experimentally, or it could be regarded as practically failed theory?
https://lasers.llnl.gov/science/ignition/fast-ignition
https://lasers.llnl.gov/science/ignition/fast-ignition
Is there any difficulty to construct a laser set they describe? It should be pretty easy to do?phyzguy said:I am not sure, but I think the answer to your question is "neither". I think it is still considered a promising approach which has not yet been experimentally verified because the necessary laser hardware isn't there yet. Anybody else know more?
Stanley514 said:Is there any difficulty to construct a laser set they describe? It should be pretty easy to do?
EulersForumula,EulersFormula said:Fast ignition is pretty much dead. We can't make the electrons do what we want them to do. There is little funding left for it.
EulersFormula said:Greg,
What you are describing is an x-ray backlighting diagnostic. This is different than trying to ignite the compressed fuel with a beam of hot electrons.
It was concluded in a National Academy of Sciences report last year that fast ignition was not the most promising path to fusion due to complications with controlling the fast electron beams. Many of the scientists who specialized in fast ignition are now changing research directions.
EulersFormula,EulersFormula said:Why are my claims erroneous? The report specifically quotes " Conclusion 4-5: At this time, fast ignition appears to be a less promising approach for IFE than other ignition concepts." Complicated target design and problems with laser-target energy coupling were cited.
You can argue all you want about how we have the technology to create the beams that we want, but it doesn't change the fact that we are unable to achieve good energy coupling between the beam and target. You are delusional if you think fast ignition is a "hot topic" in the ICF community.
Boot-strapping results when alpha particles, helium nuclei produced in the deuterium-tritium (DT) fusion process, deposit their energy in the DT fuel, rather than escaping.
EulersFormula said:You are giving me a link of a fast ignition simulation dating more than a year ago. Can you tell me what useful results have been generated with since then?
I'm also not saying that there is nobody in the US who is studying fast ignition, but I am seeing a trend of researchers moving away from it. If you really do not notice this, then I am guessing that you are not actively involved in the ICF community.
If we cannot understand how normal cryo implosions are performing, then how can we possibly understand what is going on in a fast ignition scheme which has much more complicated targets?
I also don't understand your point about the hight foot campaign. That has nothing to do with fast ignition. They increased the adiabat to stabilize their implosions.
jim hardy said:Fascinating !
from first link:
What discourages the alphas from going their own separate ways ?
Inertia, for the time required, as in the name of this approach to fusion.jim hardy said:Fascinating !
from first link:
What discourages the alphas from going their own separate ways ?
The goal of controlled fusion is to obtain sufficient energy from the alphas to 1) heat a magnetically confined plasma, or 2) release maximum amount of thermal energy.jim hardy said:Fascinating !
from first link:
What discourages the alphas from going their own separate ways ?
Stanley514 said:Initially they proposed to use a picosecond laser as the ignitor in fast fusion. What if instead we use femtosecond or even attosecond laser for this purpose? Could it change conditions of fast fusion drammatically or not too much?
What do you mean as "intensity"? Lasers are characterized by power and energy. As we go to shorter pulses their power automatically increases, but energy requirements (for the fusion) diminish. The very point of fast ignition is to use picosecond laser which has higher power, but much smaller energy demands. I wonder what will happen if they will proceed to even much shorter pulses.the_wolfman said:We can't build a femto or attosecond laser with sufficient intensity to "spark" the fusion reaction. In order to spark fast fusion you need to deliver sufficient energy to your target. As you go to shorter pulses, the necessary intensity of your laser increases.
And let's not ignore all the physics of the laser-plama interactions. These tend to get more detrimental as you go to extreme laser intensities.
Intensity is power dived by the cross sectional area of the laser pulse.Stanley514 said:What do you mean as "intensity"?
No, the energy requirement of fusion does not diminish. Why do you think that it would?Stanley514 said:As we go to shorter pulses their power automatically increases, but energy requirements (for the fusion) diminish.
the_wolfman said:Intensity is power dived by the cross sectional area of the laser pulse.
No, the energy requirement of fusion does not diminish. Why do you think that it would?
To achieve inertial fusion we have to first compress a target, and then heat the target. Success requires you to heat a "hot spot" to a specific temperature. The amount of energy to heat a hot spot of fixed size to a specific energy is fixed! This energy represents a minimum amount of energy you have to deliver to you compressed target to initiate fusion.
Stanley514 said:"If successful, the fast ignition approach could dramatically lower the total amount of energy needed to be delivered to the target; whereas NIF uses UV beams of 2 MJ, HiPER's driver is 200 kJ and heater 70 kJ, yet the predicted fusion gains are nevertheless even higher than on NIF."
But was this principle ever successfully demonstrated in an experiment? I mean successful fast ignition of at least one target with a sole lasers shot? If yes, what was energy release in comparison to energy spent? And if not, does it mean that there were a failed experiments?mfb said:The concept is not dead, but they are far away from any realistic power plant. Both the efficiency (fusion output per energy required for the lasers) and the repetition rate (multiple shots per second instead of a few per day) would have to increase by several orders of magnitude to reach the relevant region.
"the necessary laser hardware isn't there yet" sounds much more promising than it is.
"We cannot fly to other stars with half the speed of light because the antimatter drive hardware isn't there yet".
mfb said:I don't know about the details of their fusion tests. They can get some fusion. A while ago they announced the amount of energy released by fusion exceeded some specific part of the input energy - which was a small amount (something like 1%) of the laser energy, which itself is a tiny amount of the total grid power the facility needs for a shot.
Stanley514 said:But was this principle ever successfully demonstrated in an experiment? I mean successful fast ignition of at least one target with a sole lasers shot? If yes, what was energy release in comparison to energy spent? And if not, does it mean that there were a failed experiments?
The fast ignition fusion approach is a potential method for achieving controlled nuclear fusion reactions. It involves using a high-intensity laser to rapidly heat and compress a small pellet of fuel, which then undergoes fusion reactions and releases energy.
The fast ignition fusion approach differs from other methods, such as magnetic confinement fusion, in that it uses a high-energy laser to directly heat and compress the fuel, rather than relying on external magnetic fields to confine and heat the fuel.
The fast ignition fusion approach has several potential advantages, including the ability to use a smaller and more compact fusion device, the potential for higher fusion yields, and the ability to achieve fusion reactions at lower temperatures and pressures.
One of the main challenges of the fast ignition fusion approach is the development of high-power, ultrafast lasers that can deliver the necessary energy and precision to ignite the fuel. Other challenges include effectively compressing the fuel and controlling the resulting plasma for sustained fusion reactions.
The fast ignition fusion approach is still in the early stages of research and development. While significant progress has been made in demonstrating the basic principles of the approach, more research and development is needed before it can be considered a viable method for commercial fusion energy production.