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The Atomic Nucleus
Published in Alan Cottrell, An Introduction to Metallurgy, 2019
Usually in such work β and γ emitter isotopes are used because these radiations, if of fairly high energy (e.g. 0.1 to 4 MeV), can penetrate thick pieces of metal and other solids. The range of α-particles is generally much shorter and few will penetrate even an 0.05 mm thick aluminium sheet. The radiations can be detected and measured by various instruments, e.g. ionization chambers, Geiger counters and scintillation counters. In autoradiography a polished flat surface of the specimen to be examined is held against a photographic plate. The radiations emitted by the radioisotopic atoms in the surface layers of the specimen blacken the photographic plate locally and so produce an image of the distribution of the element in the specimen. This technique is useful for studying the fine-scale distribution of substances in metals and also for determining the migrations of atoms in solids (diffusion).
Ionizing Radiation
Published in David M. Scott, Industrial Process Sensors, 2018
The detection of X-rays and gamma rays is based on their ability to ionize matter. Counters are detectors that use ionization events to record the passage or energy of radiation. A well-known radiation counter is the Geiger counter, which detects radiation that passes through its thin-walled metal tube (Figure 6.4a). The Geiger counter uses a high voltage source to maintain a potential difference of several thousand volts between a center electrode and the wall of the tube, which is filled with an inert gas. When a gamma ray or X-ray passes through the tube, it partially ionizes the gas; the resulting ions accelerate due to the strong electric field in the tube and create additional ions by colliding with other gas atoms. Within a very short time, secondary and tertiary collisions lead to an avalanche of ions and electrons racing toward the electrodes (Figure 6.4b). This avalanche is a current pulse that, when fed to a speaker, produces the familiar clicking sound of a Geiger counter. Versions of the Geiger counter can also detect high-energy particles, such as alpha rays.
Protecting Humans from the Harmful Effects of Radiation
Published in Robert E. Masterson, Nuclear Engineering Fundamentals, 2017
All Geiger–Muller counters are operated in region IV of the gas curve. Here their sensitivity to alpha particles and beta particles is essentially the same. One interesting characteristic of a Geiger counter is that all the events that occur in region IV of the gas curve are treated identically. This means that all of the output signals from the circuits in a Geiger–Muller counter have the same magnitude regardless of the type of radiation that is causing the pulse. In other words, a Geiger counter cannot distinguish between an alpha particle, a beta particle, or a gamma ray. Indeed, it cannot even distinguish between the energies carried by each of these individual types of radiation. A modern Geiger counter is shown in Figure 19.21, and the picture also shows an example of a portable ion chamber. Both types of devices are relatively small, cheap, and easy to carry today. Most radiation technicians have at least one of these radiation measurement tools in their offices.
Thin film thickness measurement with triple gas electron multiplier detector by 55Fe radiation transmission and background detection using energy distribution analysis
Published in Instrumentation Science & Technology, 2020
Freddy Fuentes, Rafael M. Gutiérrez
Current instrumentation primarily uses gas detectors (Geiger counters) and the intensity method (radiation counting) for thickness measurements due to the simplicity and low cost.[3,4] The radiation rate transmitted through the absorber is determine by the following equation: where Io is the incident intensity, I is the intensity that passes through the absorber, µ/ρ is the mass attenuation coefficient, and x is the thickness of the absorber.