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    $\begingroup$ Wow. This is a great answer! I was missing a lot of factors that go into it like you've pointed out. However, I didn't know that the collisions of the protons are smaller than a joule per pair. This seems confusing. $\endgroup$ – QEntanglement Nov 2 '12 at 19:37
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    $\begingroup$ BTW the LHC consumes about 1,000 GWh per year, see lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/faq/… - that's $10^{12}$ times 3600 joules, i.e. $3.6\times 10^{15}$ joules per year. The total energy in the protons that have collided, see the previous comment, is roughly millions of times smaller: 99.9999% of the energy was "lost". This hapless efficiency can't be improved too much. $\endgroup$ – Luboš Motl Nov 2 '12 at 19:56
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    $\begingroup$ This answer replies to the question asked, of course. the link @AlanSE provided in his now deleted answer offers an alternative to laser ignition by particle accelerator ignition, and is an interesting concept by itself , (the balance of energy in /energy out is different than in this answer) so I am giving the link for completion . fusionpowercorporation.com $\endgroup$ – anna v Nov 3 '12 at 5:38
  • $\begingroup$ So basically, they can't hit the broad side of a barn? $\endgroup$ – Gene Feb 4 '16 at 15:16








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    $\begingroup$ The LHC is an abhorrent example as it accelerates ions to energies dramatically greater than what a fusion reaction produces. Fusion cross-sections have an optimal energy, increasing it further can only hurt. These mechanisms by which the ions lose energy depends on the design and is unclear here. $\endgroup$ – Alan Rominger Nov 2 '12 at 19:53
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    $\begingroup$ The LHC was identified in the question, plus it was the easiest accelerator to find information on. And it's only meant to demonstrate how the power produced would only be a small fraction of the required energy input, which is something that one could expect to hold for any accelerator. If someone asked a question about a specific lower-energy accelerator, then I suppose we could dig up some numbers for that case as well. $\endgroup$ – David Z Nov 2 '12 at 20:16
  • $\begingroup$ The question has the LHC tag. $\endgroup$ – David Z Nov 2 '12 at 20:28

The problem is that the power demsity of fusion is in the range of 10^20 watts per kilogram. To achieve this requires a magnetic field of > 12 tesala to compress the plasma and increase the fusion rate to a self sustaining reaction.

This is the goal of the ITER fusion project. To achieve this a new tube of power vacuum is being developed to drive the currents into the superconducting magnets.

The power density of the fusion I driver must be higher fusion. Many scheme fail be attempting to parallel multiple low power density devices. This was the issue with the NIF Laser system---the 'noise' adds up faster then the power.

The Sun uses gravity to compress the plasma in the Stars--of course a fission device is used to compress the fusion in an H-bomb; which has a power density much higher than fusion.

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    $\begingroup$ "The power density of the fusion I driver must be higher fusion." <- This sentence it is unclear a little bit. $\endgroup$ – peterh Aug 14 '16 at 10:14

A typical fusion reaction liberates about $10~$MeV of energy, therefore in order to obtain a moderate (thermal) power of $1~$GW we need about $6\times10^{20}$ reactions per second. The number of particles required in each of the two beams we be few order of magnitudes larger as we will manage to fuse only a fraction of them, say $1/100$. Assuming that these particles have a charge of $1~e$, we get an average beam current of $10~$kA.

We have no clue of how to provide that.

To give you an idea, to my knowledge, a proton injector never went above $100~$mA. We are several order of magnitudes away from even just a concept.


protected by Qmechanic Aug 14 '16 at 11:00


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