Cosmic ray spallation

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Cosmic ray spallationis a form of naturally occurring nuclear fissionand nucleosynthesis. It refers to the formation of elementsfrom the impact of cosmic rayson an object. Cosmic rays are highly energetic charged particlesfrom outside of Earthranging from stray electronsto alpha particles. These cause spallationwhen a cosmic ray (e.g. a proton) impacts with matter, including other cosmic rays. The result of the collision is the expulsion of large members of nucleons(protons and neutrons) from the object hit. This process goes on not only in deep space, but in our upper atmosphere due to the impact of cosmic rays. Cosmic ray spallation produces some light elements such as lithiumand boron. This process was discovered somewhat by accident during the 1970s. Models of big bang nucleosynthesissuggested that the amount of deuteriumwas too large to be consistent with the expansion rate of the universe and there was therefore great interest in processes that could generate deuteriumafter the big bang. Cosmic ray spallation was investigated as a possible process to generate deuterium. As it turned out, spallation could not generate much deuterium, and the excess deuterium in the universe could be explained by assuming the existence of non-baryonicdark matter. However, studies of spallation showed that it could generate lithium and boron. Isotopesof aluminum, beryllium, carbon(carbon-14), chlorine, iodineand neon, are also formed through cosmic ray spallation.

[edit] See also

• Astrophysics
• Cosmic rays
• Nuclear fission
• Nucleosynthesis
• Spallation

[edit] External links

• Ray Isotope Spectrometer
• University of Leeds paper
• Heavy Cosmic Ray propagation Using New Spallation Cross-Section Expressions
• Evidence for cosmic ray spallation production of helium and neon found in volcanoes

Nucleosynthesis