Delta ray

Nuclear particle in a diffusion cloud chamber

Delta electron

Delta ray refers to the secondary electrons that are produced as a result of the ionization of a medium by a fast-moving charged particle, such as an alpha particle or a proton. These secondary electrons are ejected from atoms in the medium and can themselves ionize further atoms, creating a cascade of ionization events. Delta rays are significant in the fields of radiation protection, nuclear physics, and medical physics, particularly in the context of understanding the interactions of ionizing radiation with matter and its effects on biological tissues.

Overview

When a charged particle, such as an alpha particle, proton, or any heavy charged particle, moves through a material, it can interact with the electrons of the atoms in the material, causing ionization or excitation. A delta ray is produced when the energy transferred in such an interaction is sufficient to eject an electron from an atom with enough kinetic energy that it can go on to cause further ionizations in the material. The term "delta ray" was originally used to describe the tracks seen in cloud chambers and bubble chambers, which were used in early nuclear physics experiments to visualize the paths of charged particles.

Production and Characteristics

Delta rays can be produced by various types of radiation, including alpha particles, beta particles, and other charged particles. The production of delta rays is a stochastic process, meaning it is random and subject to statistical fluctuations. The range and energy of delta rays depend on the energy of the primary charged particle and the type of material through which it is passing. In general, denser materials will produce more delta rays due to the higher probability of interactions between the charged particles and the atoms in the material.

Biological Significance

In radiobiology, delta rays are of particular interest because they contribute to the linear energy transfer (LET) of radiation, which is a measure of the energy deposited per unit length of tissue. High-LET radiation, such as alpha particles, is more effective at causing biological damage compared to low-LET radiation, such as gamma rays, because it produces a dense trail of ionizations, including delta rays, along its path. This can lead to DNA damage and other cellular effects that are critical in assessing the risks associated with radiation exposure.

Applications

Delta rays have applications in various scientific and medical fields. In radiation therapy, understanding the production and effects of delta rays is important for accurately predicting the dose distribution within the body and minimizing damage to healthy tissues. In nuclear physics and particle physics, delta rays are used to study the properties of charged particles and the interactions of radiation with matter.

Detection and Measurement

Delta rays can be detected and measured using various types of radiation detectors, such as cloud chambers, bubble chambers, and more modern devices like semiconductor detectors. These detectors allow scientists to visualize and analyze the paths of charged particles and the cascades of ionization caused by delta rays.