Skyshine - hdbk11080109

DOE-HDBK-1108-97

Radiological Training for Accelerator Facilities

Student's Guide

N Electromagnetic radiation.

N Charged particles.

Skyshine

EO-14

DISCUSS special radiological surveys and techniques.

Skyshine is the radiation scattered from air molecules. Accelerator-produced skyshine is

usually neutron radiation, scattered after emerging more or less vertically from the shielded

enclosure. It can cause elevated radiation fields at ground level considerable distance from

the source.

Due to typical facility design, photon skyshine is usually less of a problem but is a

consideration, particularly where radioactive materials are stored.

Electromagnetic radiation

Electromagnetic radiation (photons) may be classified into several categories.

High-energy photons (X- rays and gamma rays) may be produced by several mechanisms.

When electrons are decelerated, they emit bremsstrahlung "braking" radiation. These are

classified as X- rays. Also, the decay of subatomic particles may produce photons.

Electromagnetic cascades can develop when an electron (or positron) emits a photon that

has sufficient energy to produce an electron-positron pair. These particles produce more

photons, etc. The chain of interactions continues until the photons no longer have

sufficient energy for pair production (about 1 MeV).

Synchrotron radiation is a by-product of the acceleration process. When a charged particle

is bent in a magnetic field, it emits photons. The process depends greatly on the mass of the

accelerated particle; electrons produce much more synchrotron radiation at a given energy