Beryllium and Boron: More Cosmic Connections with FusionJune 27, 2018
Our new planned experiments will be critically based on two particular elements—beryllium for our electrodes and boron, which, together with hydrogen, will be our aneutronic fuel. These two elements, not coincidentally, are also bound together in their origins, for all beryllium and most boron are produced deep in space by cosmic rays. Only lithium and deuterium, an isotope of hydrogen, share this origin. All other elements that have nuclei lighter than that of iron are produced by fusion reactions in stars. The heavier elements are produced when large stars explode as supernova.
Scientists agree that the light nuclei deuterium, lithium, beryllium and boron can’t be produced in space by stars for a simple reason—they burn up by fusion reactions too quickly after they are formed. This is connected with their small mass and small number of electrical charges in two ways. First, their nuclei have less binding energy than helium, so reactions that produce helium release energy, and a smaller charge means it take less velocity and therefore lower temperature to force the nuclei together to undergo nuclear reactions.
But these characteristics make boron an ideal fusion fuel—it burns fairly readily and produces no neutrons. Beryllium is desirable for us as an electrode material because its few electrons don’t absorb many X-rays and because, as an impurity, it won’t make much difference to the plasma.
The only reason we can use these materials is because they are produced by cosmic rays. Researchers are certain of this observationally because boron and beryllium are almost a million items more abundant in cosmic rays than in the solar system. From accelerator experiments we also know that when high-energy protons (tens of Mev to Gev) in cosmic rays smash into carbon, oxygen and nitrogen nuclei, they produce boron and beryllium. Carbon, oxygen and nitrogen, which are of course key components of all life, are the nuclear ashes left behind by fusion reactions. The energy for cosmic rays also comes from fusion reactions in stars, vastly concentrated by magnetic fields. So boron and beryllium could be viewed as the re-kindled ashes of stars.
In the next LPPFusion report, we’ll explain how the abundance of boron and beryllium in stars can be used to test if the universe ever passed through a hot, dense stage—in other words if there ever was a Big Bang. Stay tuned!