Shielding of Positrons

Shielding of ionizing radiation simply means having some material between the source of radiation and you (or some device) that will absorb the radiation. A multi-layered radiation shield is appropriate to shield positrons. The first layer of such a shield may be a thin aluminium plate (to shield positrons), while the second layer of such a shield may be a dense material such as lead.

positron annihilationThe coulomb forces that constitute the major mechanism of energy loss for electrons are present for either positive or negative charge on the particle and constitute the major mechanism of energy loss also for positrons. Whatever the interaction involves a repulsive or attractive force between the incident particle and orbital electron (or atomic nucleus), the impulse and energy transfer for particles of equal mass are about the same. Therefore positrons interact similarly with the matter when they are energetic. The track of positrons in a material is similar to the track of electrons. Even their specific energy loss and range are about the same for equal initial energies.

At the end of their path, positrons differ significantly from electrons. When a positron (antimatter particle) comes to rest, it interacts with an electron (matter particle), resulting in the annihilation of both particles and the complete conversion of their rest mass to pure energy (according to the E=mc2 formula) in the form of two oppositely directed 0.511 MeV gamma rays (photons).

Therefore any positron shield has to include also a gamma-ray shield. A multi-layered radiation shield is appropriate to minimize the bremsstrahlung. Material for the first layer must fulfill the requirements for negative beta radiation shielding. The first layer of such shield may be a thin aluminium plate (to shield positrons), while the second layer of such shield may be a dense material such as lead or depleted uranium.

See also: Shielding of Gamma Radiation

See first: Shielding of Beta Radiation – Electrons

When a positron (antimatter particle) comes to rest, it interacts with an electron, resulting in the annihilation of both particles and the complete conversion of their rest mass to pure energy in the form of two oppositely directed 0.511 MeV photons.

See previous:

Shielding of Beta Radiation

See above:

Shielding of Ionizing Radiation

See next:

Shielding of Gamma Radiation