ORIGIN OF MATTER

Quarks and electrons appear to have originated at the end of the Inflationary Epoch when the universe was about 10-32 seconds old. Protons and neutrons formed from a quark-gluon plasma when the universe was about 10-6 seconds old. In the next 3 minutes, fusion formed 4He nuclei. There was not time to make anything heavier. All the atoms heavier than helium have formed by various nuclear processes, mainly in stars, in the remaining 13.8 billion year history of our universe.

FISSION AND FUSION



FISSION!
Enrico Fermi created the first man-made chain reaction in December of 1942 under the football stadium of the University of Chicago, but a natural chain reaction was produced in Gabon, West Africa about 1.7 billion years ago, and ran for several hundred thousand years, producing an average of 0.1 million Watts of thermal power!
Currently there are 100 nuclear power plants operating in the USA, in 31 different states, and 435 operating in the world, in 31 different nations. Despite overwhelming publicity concerning rare accidents, the safety record of these plants is extremely impressive.
What radiation exposure is there from nuclear power in the US? In terms of mSv, the average US citizen gets about 5 x 10-5 of his 1 mSv per year from nuclear power!!


FUSION!
Estimates for the critical temperature required to achieve fusion come in at 400 million Kelvin for D-D fusion, and 45 million K for the D-T variety. But these temperature thresholds depend slightly on the density of the plasma involved.  And of course, a much higher temperature is needed to do more than break even.


Magnetic Confinement (Tokamak)!
Laser Compression!

Neither one of these schemes has worked. In the tokamak you need to hold a plasma at around 100 million K, at a density of about a millionth of the density of air, for several seconds. Instabilities and turbulence have so far made this impossible. In the laser fusion approach, you start with a liquid already but you have only 10-8 seconds to heat it to fusion temperature. Again, instabilities have doomed the laser fusion efforts as well. Two little-appreciated disadvantages to fusion power, even if it worked: it uses a radioactive fuel, tritium, which has to be made nucleus by nucleus by neutron capture on deuterium in fission power plants, and essentially all the kinetic energy in the final state is carried by neutrons, which are not going to boil water, to say the least, since matter is transparent to them!

ITER
National Ignition Facility

Nuclear and Thermonuclear Weapons


Do stars operate by fusion? Well, consider that a typical star, like our sun, consists almost entirely of protons and 4He nuclei. But protons can't be fused, there is no bound state of two protons. 4He can't be fused, since the nucleus 8Be does not exist. Protons can't be fused with 4He since 5Li does not exist. It was a mystery for a while as to how stars work... until the weak interaction was better understood!

Enrico Fermi (1901 - 1954)

George Gamow (1904 - 1968)

Hans Bethe (1906 - 2005)


Since 1950, physicists have been able to trace the origin of each type of atom in our universe. Almost all were orginally thought to have been produced by fusion in old, massive stars, or in the supernova explosions which end a massive star's life cycle.  The first step in the process is a weak decay of a free proton, a process that  has never been seen on earth, but which can be calculated accurately.  This process has such a low probability that Main Sequence stars typically live for 10 billion years, instead of the few minutes they would survive if they contained nuclei that could fuse directly!!  Since the various nuclear reactions involved in the creation of all atoms heavier than helium can be studied in detail in the laboratory, it has been realized that neutron star collisions have played a huge role in the creation of atoms with A of 44 or more.  Such terrifying and violent collisions can now also be observed and studied directly.








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