Neutron
Neutrons are electrically-neutral hadrons composed of two down s and one up quark. Atomic nuclei consist of protons and neutrons held together by gluons. They have an antiparticle with the same mass but opposite baryon number, the antineutron.

Because of their properties (mass, magnetic moment, etc.), neutrons can be applied for microscopy. In 2152,  had a neutron microscope aboard. ()

Neutrons could also be used as a form of energy. The Xindi-Reptilian Damron utilized a bio-reactor with a neutronic power source when attempting to manufacture a bioweapon with which to destroy Humanity. ()

In 2265, Captain James T. Kirk left orders recommending that the surface of Delta Vega be subjected to a lethal amount of neutron radiation if he did not contact the  in twelve hours, should he be unsuccessful in stopping his old friend Gary Mitchell, who had developed dangerous and god-like psychokinetic abilities. () 

Starships tended to emit quantities of neutron radiation as a property of their warp cores, detectable by any other starships close enough to scan for it. In 2293, Captain Spock noted a large concentration of neutron radiation that resulted from a Klingon Bird-of-Prey commanded by General  moving into position at extremely close quarters to the hull of Spock's ship, the . ()

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Particles
Radiation