A delta ray is a secondary electron with enough energy to escape a significant distance away from the primary radiation beam and produce further ionization, and is sometimes used to describe any recoil particle caused by secondary

ionization Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecul ...

. The term was coined by J. J. Thomson.

Characteristics

Nuclear particle in a diffusion cloud chamber

A delta ray is characterized by very fast

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have n ...

s produced in quantity by

alpha particles Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be prod ...

or other fast energetic charged particles knocking orbiting electrons out of

atoms Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas ...

. Collectively, these electrons are defined as delta radiation when they have sufficient energy to ionize further atoms through subsequent interactions on their own. Delta rays appear as branches in the main track of a

cloud chamber A cloud chamber, also known as a Wilson cloud chamber, is a particle detector used for visualizing the passage of ionizing radiation. A cloud chamber consists of a sealed environment containing a supersaturated vapour of water or alcohol. An ...

(See Figs. 1,2). These branches will appear nearer the start of the track of a heavy charged particle, where more energy is imparted to the ionized electrons.

Delta rays in particle accelerators

Otherwise called a knock-on electron, the term "delta ray" is also used in high energy physics to describe single electrons in particle accelerators that are exhibiting characteristic deceleration. In a bubble chamber, electrons will lose their energy more quickly than other particles through

Bremsstrahlung ''Bremsstrahlung'' (), from "to brake" and "radiation"; i.e., "braking radiation" or "deceleration radiation", is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typical ...

and will create a spiral track due to their small mass and the magnetic field. The Bremsstrahlung rate is proportional to the square of the acceleration of the electron.

Epsilon ray

An Epsilon ray or Epsilon radiation is a type of tertiary radiation. Epsilon rays are a form of particle radiation and are composed of

s. The term was coined by J. J. Thomson, but is very rarely used as of 2019.

References

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"Delta ray"
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Britannica Online

"Delta electrons"
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McGraw-Hill Encyclopedia of Science & Technology Online
Radiation Radioactivity Electron

Characteristics

Delta rays in particle accelerators

Epsilon ray

See also

References