In LENR fusion, the fusing of two protons which is the first step of the proton-proton cycle created great problems for early theorists because they recognized that the interior temperature of the sun (then 20,000,000C, but now assumed to be some 14 million Kelvins) would not provide nearly enough energy to overcome the coulomb barrier of electric repulsion between two protons.
With the development of quantum mechanics, it was realized that on this scale the protons must be considered to have wave properties and that there was the possibility of tunneling through the coulomb barrier. Arthur Eddington thought that nuclear processes must be involved to account for the radiant energy of the sun, but was criticized because the temperature was seen to be not hot enough when considered by classical physics alone. His tongue-in-cheek reply to his critics: "I am aware that many critics consider the stars are not hot enough. The critics lay themselves open to an obvious retort; we tell them to go and find a hotter place." Even so, it was unclear how proton–proton fusion might proceed, because the most obvious product, helium-2 (proton), is unstable and almost instantly dissociates back into two protons. In 1939, Hans Bethe proposed that one of the protons could decay by beta emission into a neutron via the weak interaction during the brief moment of fusion, making deuterium a vital product in the chain. Most of the time, when two protons collide together, they simply do just that: collide, and bounce off one another. But under just the right conditions, with high enough temperatures and densities, they can fuse together to form a state of helium you’ve probably never heard of: a diproton, made up of two protons and no neutrons. The overwhelming majority of the time, the diproton — an incredibly unstable configuration — simply decays back into two protons. But every rare once-in-a-while, less than 0.01% of the time, this diproton will undergo beta-plus decay, where it emits a positron (the electron’s antiparticle), a neutrino, and where the proton transmutes into a neutron. While it takes on the average 10 billion years for two protons in the core of the Sun to fuse together into deuterium, it takes only about a second for deuterium to fuse with a proton and become helium-3. This diproton idea was part of the body of work in stellar nucleosynthesis for which Bethe won the Nobel Prize in Physics in 1967. In a LENR reactor that uses a 1/10 of a gram of fuel to produce the LENR reaction, how can PP fusion be occurring? If the core of the sun cannot overcome the coulomb barrier, how can hydrogen in a metal lattice produce pp fusion? Solar observational science has improved greatly in just the last few years. So rethinking about solar nuclear reactions are now in order. Recently through analysis of the solar wind, the magnetic ropes that generate mass coronal ejections generate 10,000 times more He3 than the ambient solar concentration of that helium isotope. And that isotope is transmuted in just an hour or two, even through the temperatures produced in the magnetic ropes are just 10,000,000C. Something is wrong with the solar model that has been generally accepted and is now in place.