May 30,Lawrence Berkeley National Laboratory Almost as clearly as a textbook diagram, this image made by a noncontact atomic force microscope reveals the positions of individual atoms and bonds, in a molecule having 26 carbon atoms and 14 hydrogen atoms structured as three connected benzene rings.
Process[ edit ] Fusion of deuterium with tritium creating helium-4freeing Lab report of reaction on beam neutronand releasing Protons are positively charged and repel each other by the Coulomb force, but they can nonetheless stick together, demonstrating the existence of another, short-range, force referred to as nuclear attraction.
This is because the nucleus is sufficiently small that all nucleons feel the short-range attractive force at least as strongly as they feel the infinite-range Coulomb repulsion.
Building up nuclei from lighter nuclei by fusion releases the extra energy from the net attraction of particles. For larger nucleihowever, no energy is released, since the nuclear force is short-range and cannot continue to act across longer atomic length scales. Thus, energy is not released with the fusion of such nuclei; instead, energy is required as input for such processes.
Fusion powers stars and produces virtually all elements in a process called nucleosynthesis.
The Sun is a main-sequence star, and, as such, generates its energy by nuclear fusion of hydrogen nuclei into helium. In its core, the Sun fuses million metric tons of hydrogen and makes million metric tons of helium each second.
The fusion of lighter elements in stars releases energy and the mass that always accompanies it. For example, in the fusion of two hydrogen nuclei to form helium, 0. When accelerated to high enough speeds, nuclei can overcome this electrostatic repulsion and brought close enough such that the attractive nuclear force is greater than the repulsive Coulomb force.
The strong force grows rapidly once the nuclei are close enough, and the fusing nucleons can essentially "fall" into each other and the result is fusion and net energy produced. The fusion of lighter nuclei, which creates a heavier nucleus and often a free neutron or proton, generally releases more energy than it takes to force the nuclei together; this is an exothermic process that can produce self-sustaining reactions.
Energy released in most nuclear reactions is much larger than in chemical reactionsbecause the binding energy that holds a nucleus together is greater than the energy that holds electrons to a nucleus.
Fusion reactions have an energy density many times greater than nuclear fission ; the reactions produce far greater energy per unit of mass even though individual fission reactions are generally much more energetic than individual fusion ones, which are themselves millions of times more energetic than chemical reactions.
Only direct conversion of mass into energysuch as that caused by the annihilatory collision of matter and antimatteris more energetic per unit of mass than nuclear fusion. Research into using fusion for the production of electricity has been pursued for over 60 years.
Successful accomplishment of controlled fusion has been stymied by scientific and technological difficulties; nonetheless, important progress has been made. At present, controlled fusion reactions have been unable to produce break-even self-sustaining controlled fusion.
Workable designs for a toroidal reactor that theoretically will deliver ten times more fusion energy than the amount needed to heat plasma to the required temperatures are in development see ITER. The ITER facility is expected to finish its construction phase in It will start commissioning the reactor that same year and initiate plasma experiments inbut is not expected to begin full deuterium-tritium fusion until The CNO cycle dominates in stars heavier than the Sun.
An important fusion process is the stellar nucleosynthesis that powers stars and the Sun. In the 20th century, it was recognized that the energy released from nuclear fusion reactions accounted for the longevity of stellar heat and light. The fusion of nuclei in a star, starting from its initial hydrogen and helium abundance, provides that energy and synthesizes new nuclei as a byproduct of the fusion process.
Different reaction chains are involved, depending on the mass of the star and therefore the pressure and temperature in its core. AroundArthur Eddington anticipated the discovery and mechanism of nuclear fusion processes in starsin his paper The Internal Constitution of the Stars. This was a particularly remarkable development since at that time fusion and thermonuclear energy, and even that stars are largely composed of hydrogen see metallicityhad not yet been discovered.
Eddington's paper, based on knowledge at the time, reasoned that: The leading theory of stellar energy, the contraction hypothesisshould cause stars' rotation to visibly speed up due to conservation of angular momentum.
But observations of Cepheid variable stars showed this was not happening. The only other known plausible source of energy was conversion of matter to energy; Einstein had shown some years earlier that a small amount of matter was equivalent to a large amount of energy. Francis Aston had also recently shown that the mass of a helium atom was about 0.
All of these speculations were proven correct in the following decades.
The primary source of solar energy, and similar size stars, is the fusion of hydrogen to form helium the proton-proton chain reactionwhich occurs at a solar-core temperature of 14 million kelvin. The net result is the fusion of four protons into one alpha particlewith the release of two positrons and two neutrinos which changes two of the protons into neutronsand energy.
In heavier stars, the CNO cycle and other processes are more important.All information posted on this web site is the opinion of the author and is provided for educational purposes only.
It is not to be construed as medical advice. Photon Torpedo from original Star Trek (). This is basically an antimatter warhead. It was named "photon" because at the time it was believed that an antimatter explosion would be .
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