Alpha Beta and Gamma Radiation
Alpha, beta, and gamma radiation are types of ionizing radiation. Alpha radiation consists of helium nuclei, beta radiation involves high-energy electrons or positrons, and gamma radiation is a form of electromagnetic radiation. These types of radiation differ in their ability to penetrate materials and their ionizing power, with alpha being the least penetrating and gamma being the most penetrating.
7 Key excerpts on "Alpha Beta and Gamma Radiation"
eBook - ePubPharmaceutical Dosage Forms and Drug Delivery
Revised and Expanded
- Ram I. Mahato, Ajit S. Narang(Authors)
- 2017(Publication Date)
- CRC Press(Publisher)
...In diagnostic applications, radiopharmaceuticals accumulate in specific tissues or cells and emit radiation, which can be collected and processed into images, showing the location of the accumulation in the body, for diagnostic purposes. In therapeutic applications, the high-energy radiation released by radiopharmaceuticals destroys undesired local cells and tissue. 13.1.1 Types of radiation The unstable nuclei of radioisotopes dissipate energy, in the form of specific types of radiation, as they spontaneously convert to the stable parent isotopes. These radiations are commonly known as alpha, beta, or gamma rays. Alpha radiation is a result of excess energy dissipation by unstable nuclei in the form of alpha particles. The alpha particles have two positive charges and a total mass of four units. This is exemplified by polonium 210 Po 84 decaying to 206 Po 82, in a notation where superscript before the element’s symbol represents the atomic mass and the subscript after the element’s symbol represents the atomic number. The alpha particles, being heavy, are ejected at about 1/10th the speed of light and are not very penetrating. They can travel about 1–4 inches in the air. Beta radiation is produced through beta decay of unstable nuclei and can follow either of the three processes: electron emission, positron emission, and electron capture. Negative beta decay involves the emission of an energetic electron and an antineutrino (which does not have a resting mass). In the resulting nucleus, a neutron becomes a proton and stays in the nucleus. Thus, the proton number (atomic number) of the resulting nucleus increases by one, while the mass number (total number of protons and neutrons in the nucleus) does not change. For example, this process occurs for tritium (3 H) decay to radioactive helium (3 He). Positive beta decay involves the emission of a positron, similar to an electron in all aspects but with opposite charge, and a neutrino...
eBook - ePub- Alan Martin, Sam Harbison, Karen Beach, Peter Cole(Authors)
- 2018(Publication Date)
- CRC Press(Publisher)
...This means that β particles have a greater range than α particles in dense media. Gamma radiation loses its energy mainly by interacting with atomic electrons and is able to penetrate large distances even in dense media. Neutrons give up their energy through a variety of interactions, the relative importance of which are dependent on the neutron energy. For this reason, it is common practice to divide neutrons into at least three energy groups: fast, intermediate and thermal. Neutrons are very penetrating and will travel large distances even in dense media. The properties and ranges of the various nuclear radiations are summarized in Table 2.3. The ranges are only approximate since they depend on the energy of the radiation. Table 2.3 Properties of nuclear radiations Radiation Mass (u) Charge Range in air Range in tissue α 4 + 2 ∼ 0.03 m ∼ 0.04 mm β 1/1840 − 1 (positron + 1) ∼ 3 m ∼ 5 mm X and γ radiation 0 0 Very large Through body Fast neutron 1 0 Very large Through body Thermal neutron 1 0 Very large ∼ 0.15 m Summary of key points ■ Radioactive decay: Transformation of an unstable atomic nucleus into a more stable one, usually accompanied by the emission of charged particles and γ rays. ■ Alpha (α) radiation: Helium nuclei, two protons and two neutrons, mass 4 units, charge + 2 units. ■ Beta...
eBook - ePub- William H. Hallenbeck(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...CHAPTER 3 Interaction of Radiation with Matter It is important to understand how various radiations interact with matter in order to predict levels of exposure and required thicknesses of shielding. The mode of interaction is a function of type of radiation, energy of the radiation, and type of media. Some types of radiation can be completely absorbed (alpha, beta, and neutron) and others can only be reduced to safe levels (gamma and x-ray). The interactions of alpha, beta, gamma, x-rays, and neutrons with matter are discussed in Chapter 3. 3.1 ALPHA RADIATION Without artificial acceleration, the kinetic energies of alphas range from 1.8 to 11.6 MeV. Only a few alphas exceed 8 MeV. Velocities range from 9 × 10 8 to 2 × 10 9 cm/sec (speed of light in a vacuum is 3 × 10 10 cm/sec). Due to its large mass and charge, alphas are weakly penetrating and can be stopped by a sheet of paper. Alphas are an external hazard only if kinetic energy exceeds 7.5 MeV. When E α < 7.5 MeV, alphas cannot penetrate the dead outer layer of skin (0.07 mm). Alpha emitters usually emit gamma radiation which is an external hazard. Both alpha and gamma radiation are internal hazards. When alpha particles interact with a medium, they cause ionization and excitation of electrons. Ionization occurs when electrostatic attraction between an alpha particle and an orbital electron causes the electron to be completely removed from an atom. Excitation results when electrostatic attraction between an alpha particle and an orbital electron raises the electron to a higher energy level without ionization. Both mechanisms of interaction cause the partitioning of the kinetic energy of the alpha particle between the alpha particle and an orbital electron. The average energy transferred by a charged particle to create an ion pair is a function of the type of media...
eBook - ePub- Mark E. Byrnes(Author)
- 2000(Publication Date)
- CRC Press(Publisher)
...In fact, interactions between all types of radiation (including alpha and beta particles) indirectly produce X rays in this manner. X rays can travel great distances in the air but have smaller ranges in dense materials like lead. X-ray machines are used to generate high-energy photons for diagnostic, therapeutic, or research activities. However, these X rays are not relevant in an environmental setting. 3.1.4 Gamma Rays Gamma rays, or gamma particles, are identical to X rays with two notable exceptions: gamma particles originate from the nucleus instead of the orbital electrons, and gamma particles are typically more energetic than X rays. A gamma particle is produced when a neutron or proton drops from a high energy level to a lower energy level from inside the nucleus. Gamma particle energies are characteristic of the radionuclide source, similar to X rays and alpha and beta particles. Many radionuclides emit energetic gamma particles well into the kilo- or megaelectronvolt range and at intensities that are a concern to human health. The billiard-ball-like collisions between a gamma particle and an electron are the same as the X-ray collision except the gamma energy and the energy transfer may be larger. These gamma particles may be measured in the field from a significant distance. In fact, gamma radiation surveys have been performed using detectors mounted on the bottom of helicopters flying hundreds of feet above the ground (see Section 4.2.1.1). Needless to say, gamma particles (or any energetic photon) can travel great distances in air, but like X rays have limited range in dense material such as lead...
eBook - ePubRadiation Detection
Concepts, Methods, and Devices
- Douglas McGregor, J. Kenneth Shultis(Authors)
- 2020(Publication Date)
- CRC Press(Publisher)
...Today, we know that gamma rays are high frequency electromagnetic radiation whose energy is carried by particles called photons. The alpha particles, being deflected to the right, had positive charge. They were deflected far less than were the beta rays, an indication that the alpha particles have a charge-to-mass ratio q e / m far less than that of beta particles. Either the positive charge of the alpha particle was far less than the negative charge of beta particles and/or the alpha particle’s mass was far greater than that of a beta particle. Figure 3.7. Deflection of α, β, and γ rays by a magnetic field out of and perpendicular to the page. A quantitative analysis of the deflection of alpha particles showed that their speeds were of the order of 10 7 m/s. The charge-to-mass ratio was found to be 4.82 × 10 7 C kg −1. By contrast, the charge-to-mass ratio for the hydrogen ion is twice as large, namely, 9.59 × 10 7 C kg −1. Thus, if the alpha particle had the same charge as the hydrogen ion, its mass would have to be twice that of the hydrogen ion. If the alpha particle were doubly charged, its mass would be four times as large and would correspond to that of the helium atom. That an alpha particle is an ionized helium atom was demonstrated by Rutherford who used the experimental arrangement of Fig. 3.8. The alpha particles from the radioactive source penetrate the thin-walled glass tube and are collected in the surrounding evacuated chamber. After slowing, the α particles capture ambient electrons to form neutral helium atoms. The accumulated helium gas is then compressed so that an electrical discharge occurs when a high voltage is applied between the electrodes. The emission spectrum from the excited gas atoms was found to have the same wavelengths as that produced by an ordinary helium-filled discharge tube. Therefore, the alpha particle must be a helium ion...
eBook - ePubIllustrated Toxicology
With Study Questions
- P.K. Gupta(Author)
- 2018(Publication Date)
- Academic Press(Publisher)
...Gamma rays are not material particles at all, but a form of pure energy very similar to x-rays, traveling at the speed of light. Q.9 How far can atomic radiation penetrate? Gamma rays penetrate through soft tissue just as light shines through a window. Beta particles have less penetrating power, traveling less than 2 cm in soft tissue. Alpha particles have the least penetrating power, traveling just a few micrometers in soft tissue, equivalent to a few cell diameters. Q.10 Is radioactivity dangerous? Alpha particles, beta particles, and gamma rays can do great harm to a living cell by breaking its chemical bonds at random and disrupting the cell’s genetic instructions. Massive exposure to atomic radiation can cause death within a few days or weeks. Smaller doses can cause burns, loss of hair, nausea, loss of fertility, and pronounced changes in the blood. Still smaller doses, too small to cause any immediate visible damage, can result in cancer or leukemia in the person exposed, congenital abnormalities in his or her children (including physical deformities, diseases, and mental retardation), and possible genetic defects in future generations. Outside the body, alpha emitters are the least harmful, and gamma emitters are more dangerous than beta emitters. Inside the body, however, alpha emitters are the most dangerous. They are about 20 times more damaging than beta emitters or gamma emitters. Thus, although alpha radiation cannot penetrate through a sheet of paper or a dead layer of skin, alpha emitters are extremely hazardous when taken into the body by inhalation or ingestion, or through a cut or open sore. Exercise 2 Q.1 How do radioactive elements produce other radioactive elements? When atoms undergo radioactive decay, they change into new substances, because they have lost something of themselves. These by-products of radioactive decay are called “decay products” or “progeny.” In many cases, the decay products are also radioactive...
eBook - ePubX-Ray Imaging
Fundamentals, Industrial Techniques and Applications
- Harry E. Martz, Clint M. Logan, Daniel J. Schneberk, Peter J. Shull(Authors)
- 2016(Publication Date)
- CRC Press(Publisher)
...For further discussions on these types of sources, see Section 8.4. 4.2.2 T HE N UCLEUS AND γ-R AY AND X-R AY G ENERATION γ-rays, by definition, are high-energy electromagnetic radiation that arise from the decay of a radioactive nucleus. Often people think that x-rays are lower in energy than γ-rays. This is not true. They only differ by definition, i.e., origin of the electromagnetic radiation. It is very important to point out that x-rays can be higher in energy or equal to γ-rays and visa versa. The nucleus of a hydrogen atom (one proton) is stable without a neutron. If we add two neutrons to the stable hydrogen atom, it becomes the unstable radioactive isotope tritium. An isotope is any of two or more atoms of a chemical element with the same atomic number (number of protons) but different mass numbers, i.e., they differ in the number of neutrons. If a nucleus has too many or too few neutrons, it is energetically unstable and will decay to a more stable energy state. The decay process is accompanied by the emission of alpha particle (α), β, neutron, γ, or x radiation in some combination. Some common radioactive isotopes used in industrial imaging are given in Figure 4.9 along with their decay mechanisms (Knoll 2000). A spectrum for 60 Co and 137 Cs is given in Figures 4.10 and Figure 4.11, respectively (Heath 1974). FIGURE 4.9 Decay schemes for some common γ radioactive sources. Only major transitions are shown. The energies and yields per disintegration of x-ray and γ-rays emitted in each decay are listed below each scheme. (Knoll, G.F.: Radiation Detection and Measurement, third edition. 2000. Copyright Wiley-VCH Verlag GmbH & Co. KGaA. Reproduced with permission.) Since we have already defined x-rays as arising from orbiting electrons, an explanation is in order as to how nuclear decay can result in x-rays. There are two basic mechanisms. The nucleus can move toward stability by capturing an electron— electron capture (EC)...
