Spallatsioon

Spallatsioon, also known as spallation, is a nuclear reaction in which a high-energy incident particle collides with a target nucleus, ejecting a large number of nucleons and light fragments and leaving a residual nucleus with much reduced mass. The outgoing products include neutrons, protons, and light nuclei such as deuterons and alpha particles. The reaction often yields a broad distribution of isotopes, with yields depending on the target and projectile energy.

Mechanism: At high energy, the interaction proceeds through an intra-nuclear cascade, where the projectile and secondary particles strike nucleons inside the nucleus. The excited remnant then de-excites by evaporating nucleons and light clusters; for heavy targets, fission or multifragmentation can occur. The overall cross sections and neutron multiplicities rise with energy.

Energies: Spallation reactions typically involve projectiles in the tens of MeV to several GeV range. Neutron production is a hallmark, generating many neutrons per incident particle, enabling dedicated neutron sources.

Applications: Spallation is exploited to produce intense neutron beams for materials research and industry (spallation neutron sources). It also enables production of medical and research isotopes and is used in accelerator-driven systems for transmutation of nuclear waste. In astrophysics, cosmic-ray spallation explains the origin of light elements such as lithium, beryllium, and boron.

Facilities: Major spallation neutron sources include the Spallation Neutron Source at Oak Ridge National Laboratory (USA), ISIS in the United Kingdom, and the European Spallation Source in Sweden.