After reading this answer, I wondered the title question. It seems part of our difficulty in harnessing fusion power is controlling the hydrogen and helium (plasma?) while fusion is taking place, i.e. using electromagnetic fields.

So I wondered, might it be easier, from an engineering standpoint, to control and harness the power of fusion of heavier elements?

  • $\begingroup$ Fusion above Fe does not yield net energy. Nuclei with higher Z numbers have a higher Coulomb barrier to overcome. $\endgroup$ – Jon Custer Jan 30 '19 at 20:14
  • $\begingroup$ @JonCuster, understood, I was referring to elements heavier than hydrogen that yield energy, i.e. Li, Be, B, C, O, Al, Si, P, etc. Does stripping off, or pushing a hydrogen atom past, the electron shell present a significant effort? $\endgroup$ – CramerTV Jan 30 '19 at 20:19
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    $\begingroup$ The Coulomb barrier is between the nuclei - forget the electrons. $\endgroup$ – Jon Custer Jan 30 '19 at 20:25

The more protons the target nucleus contains, the stronger becomes the electrostatic repulsion between the target and the fusion "projectile" (typically a helium nucleus, 2 protons stuck together with 2 neutrons).

This means it takes more work to crush them close enough together to stick. This can be thought of as an "activation energy" barrier which must be overcome before the fusion reaction can occur. The net energy release gets smaller as this barrier gets bigger. Once you have built yourself an iron-56 nucleus this way, the barrier is just as big as the energy released, and the reaction will no longer proceed on its own.

  • $\begingroup$ Thanks. Obviously fusion of the heavier elements is possible and energy is released, so I'm still wondering, even though more energy is required to initiate the reaction of heavier atoms, might it be easier to engineer a way to initiate and sustain fusion of say, lithium/hydrogen or lithium/helium or even lithium/lithium than it has been for hydrogen/hydrogen? $\endgroup$ – CramerTV Jan 30 '19 at 23:21
  • $\begingroup$ Nope, because of the electrostatic issue. in a bomb, some of the pathways involving isotopes of lithium are important, but not in a reactor. $\endgroup$ – niels nielsen Jan 31 '19 at 2:39
  • $\begingroup$ Ok. Hopefully it's clear that I'm asking about all the elements between 1 - hydrogen and 26 - iron and not just lithium. That leaves 23 more... If the answer is the same, that hydrogen/hydrogen is the easiest way (engineering-wise) to create stable fusion, I'm good. I just thought perhaps an element that was easier to handle would help parts of the problem be simpler. $\endgroup$ – CramerTV Jan 31 '19 at 2:49

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