All the helium on Earth arose from natural fission of uranium and thorium in the planet’s crust and mantle. We can access it only through certain natural gas deposits – many of them in Texas – which contain enough of the gas to make it possible to isolate. This is the helium of every high-voiced balloon prank, as well as of every MRI scanner and high temperature superconductor. About 1/4 of helium use is in cryogenic applications. Helium is ideal for such purposes, as it has the lowest boiling point of any known element.
What is not commonly appreciated is that, once these particular gas reserves are depleted, we will know of nowhere from which to get helium. Whatever helium is released into the atmosphere gradually rises through it, eventually drifting into interplanetary space. Despite all the helium being released by human beings, atmospheric concentrations have remained constant at around 5.2 parts per million.
We can produce minute quantities of helium through hydrogen fusion, of the kind that will eventually take place in the International Thermonuclear Experimental Reactor, but it will not be even close to the quantity that will be required to cool the superconducting magnets that will keep the plasma inside that device contained.
It would be particularly ironic if a long-hoped-for source of renewable energy (nuclear fusion) proved impractical not because of issues associated with energy levels of plasma containment, but because we had squandered the planet’s accessible supplies of coolant.