With small size and charge, they penetrate matter more easily than alpha particles but are far more easily deflected. Their high velocity, normally approaching that of light, makes them lightly ionizing. Neutrons - A neutron has the same mass as a proton but has no charge. Neutrons are very difficult to stop. Neutrons can be slowed by hydrogenous material.
Water is an especially effective shield for neutrons.
The capture of a neutron results in the emission of a gamma ray. Protons have a typical range of several centimeters in air and tens of micrometers in aluminum at energies in the MeV range. Cosmic Rays - Energetic heavy ions extending in energies beyond TeV and including all ions in the periodic table. In addition to producing an intense burst of both UV and X-rays, solar flares accelerate solar material to high velocities. These solar particles are similar to galactic cosmic rays, but owing to their different origin, are not identical in composition.