Particle-emitting radiation sources ionizing

Particles of radiation from nuclear processes can be counted by Geiger counters or scintillation counters. In a Geiger counter, the particle ionizes a gas, which then conducts a pulse of electricity between two electrodes. In a scintillation counter, the particle hits a phosphor, and this emits a flash of light that is detected by a photomultiplier tube. The activity of a radioactive source, or the number of nuclear disintegrations per unit time, is measured in units of curies (3.700 X 10 ° disintegrations per second). 

Alpha particles are relatively large particles and are emitted with a limited number of energy levels. They carry a double positive charge and as a result attract electrons from the atoms of the material through which they pass, causing ionization effects. They have an extremely short range, even in air, and as a result present very little hazard as an external source of radiation but their effects within living cells or tissues can be serious. 

The second type of detection system uses the delay wire technique (61), and a schematic diagram of this detector is shown in Figure 2. The beta radiation (fast electrons) emitted from the radioactivity source on the plate ionizes the counting gas, which has been specifically chosen so that this process can freely take place. This is the primary mode of ionization and the resultant charged particles, free electrons and positive ions, are then accelerated towards the anode wire and cathode, respectively. In this primary mode of ionization, the free electrons are accelerated to such an extent that they themselves cause ionization of the counting gas, producing further free electrons and ions. This is the secondary ionization mode. This continues causing an avalanche of ionization from the primary point of ionization towards the anode wire. 

ALPHA PARTICLE. An electrically charged particle of ionizing radiation emitted by radioactive materials. An alpha particle is identical to the nucleus of a helium-4 atom, consisting of two protons and two neutrons and acting as a single particle. When an alpha particle is emitted from an unstable radioactive nucleus of an atom, that atom is transmuted into a different element. For instance, plutonium-238 is a well-known alpha emitter when an alpha particle escapes, plutonium-238 is transmuted into uranium-234. Alpha particles have a short range and cannot penetrate the outer, dead layer of human skin. Therefore, external sources of alpha particles pose little threat to human health. However, if radioactive materials emitting alpha particles are... 

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