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. The term 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 Electric charge, charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged at ...

. 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 in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

s produced in quantity by alpha particles or other fast energetic charged particles knocking orbiting electrons out of

atoms Atoms are the basic particles of the chemical elements. An atom consists of a nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished from each other ...

. 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 chamber, is a particle detector used for visualizing the passage of ionizing radiation. A cloud chamber consists of a sealed environment containing a supersaturated vapor of water or alcohol. An energetic ...

(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 A bubble chamber is a vessel filled with a superheated transparent liquid (most often liquid hydrogen) used to detect electrically charged particles moving through it. It was invented in 1952 by Donald A. Glaser, for which he was awarded th ...

, electrons will lose their energy more quickly than other particles through Bremsstrahlung 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 Particle radiation is the radiation of energy by means of fast-moving subatomic particles. Particle radiation is referred to as a particle beam if the particles are all moving in the same direction, similar to a light beam. Due to the wave–p ...

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