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This question already has an answer here:

Just looking at the beam energy and peak power for the LHC, 360 MJ and petawatts, respectively, dumped in about 100 µs, would this be sufficient to do useful fusion experiments?

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marked as duplicate by John Rennie, ACuriousMind, Qmechanic Apr 10 '15 at 22:55

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    $\begingroup$ possible duplicate of Could we use particle colliders as fusion generators? $\endgroup$ – craq Apr 10 '15 at 14:46
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    $\begingroup$ actually the answers in the link above do not address the point that fusion means a nuclear bound state. In order to have a crossection large enough for the fusion state the ions hitting each other should have low enough energies for capture. Lhc is way above those energies . en.wikipedia.org/wiki/… $\endgroup$ – anna v Apr 10 '15 at 15:33
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The simple answer is No.

Fusion happens at nuclear energies between particles to be fused, i.e. MeVs, because it is at the framework of nuclear bound states.

LHC particles start with energies of TeV, so particle particle interactions are way over any nuclear bound state levels. Even if one accelerates deuterium nuclei the phase space is way over the fusion levels.

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  • $\begingroup$ not quite MeVs, more like 10-100keV. See this graph for the fusion cross section vs. particle energy. You'll see it dropping off at high energies... Of course, I don't know of any reason why the LHC couldn't be run at lower energies, and then (inefficient) fusion would be possible $\endgroup$ – craq Apr 10 '15 at 14:30
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    $\begingroup$ @craq there are many low energy machines for nuclear experiments . Not to forget the tokamaks and ITER $\endgroup$ – anna v Apr 10 '15 at 15:00
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    $\begingroup$ Indeed - we use a fairly ordinary ion implanter to accelerate deuterium for either D-D or D-T fusion neutron production. The peak of D-T is around 100keV. D-D doesn't peak until several MeV, but is still reasonable at a few hundred keV. The graph referenced by @craq frankly looks a little off compared with the real nuclear cross section data that can be found at the ENDF site at Brookhaven. $\endgroup$ – Jon Custer Apr 10 '15 at 15:11
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    $\begingroup$ @JonCuster the value is in electron volts for temperature, this means average temperature, or black body temperature, and it is the the high end of the distribution that will have enough energy for the crossection. $\endgroup$ – anna v Apr 10 '15 at 15:36
  • $\begingroup$ @annav - Ahhh - I'm used to the nuclear cross section literature where the cross sections are measured at specific center of mass energies. Got it. $\endgroup$ – Jon Custer Apr 10 '15 at 17:26
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No, because the LHC puts too much energy into its particles for them to fuse. While we need enough energy to fuse particles, too much will stop it from happening.

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  • $\begingroup$ I was thinking something like inertial fusion using a high density hohlraum $\endgroup$ – user56903 Apr 10 '15 at 13:24
  • $\begingroup$ @DirkBruere Even so, the beams would likely give off too much energy for it to work. $\endgroup$ – Jimmy360 Apr 10 '15 at 13:26
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Nuclear-fusion experiments have been extensively performed with accelerators in the last decades of the 20th century reaching the proton drip-line. Today they are still object of interest allowing the study of superheavy elements.

However the energy of the LHC is way too high. At that energy scale you go in the regime of quark-gluon plasmas and the nuclear structure is completely destroyed. It is impossible to run the LHC down at some MeVs: the field quality of its magnets would be terrible, moreover an effect called space charge would destroy the beams in probably less than a single turn.

If you are interested in energy-production-oriented nuclear fusion, then you need a lot of particles at quite low energy which is the opposite of the LHC. There exist very specific magnetic designs to obtain that characteristics, the most promising being the Tokamak, the Stellarator and the Reversed Field Pinch.

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  • $\begingroup$ I think Polywell and Plasma Focus are more likely to result in a useful powerplant. Tokamaks are engineering nightmares $\endgroup$ – user56903 Apr 10 '15 at 17:35
  • $\begingroup$ @DirkBruere Stellarators and RFPs are even worse than Tokamaks, but to my knowledge these are the only designs that could possibly become self-sustained by the fusion process. $\endgroup$ – DarioP Apr 10 '15 at 17:42