1930s Geiger Muller tubes for the detection of ionising radiation
commercially produced
c. 1935 Radium 226 gamma ray sources used for the radiography of steel up
to 300 mm thick.
1939 Van der Graaf generator used to produce short burst of very high
energy (1 to 2 MeV) x-rays.
1939 GEC manufactures a 1 MeV ‘resonant transformer’ (an early type of
high voltage x-ray machine).
c. 1940 The first betatron is produced; x-ray energies of up to 25 MeV
become possible.
1941 GEC markets a 2 MeV resonant transformer, the “Resotron”.
c. 1941 Caesium 137, a by-product of nuclear fission becomes available.
Caesium 137 becomes the isotope of choice for industrial
radiography & remains in common use until the mid-1960s.
1946 Man-made isotopes including Cobalt 60 and Iridium 192 become
available.
1960s Linear accelerator high-energy x-ray sources become available.
c. 1970 Advances in radioactive source handling equipment, the first massproduced
cable operated source delivery systems become
commercially available.
1980s Metal ceramic tubes gradually replace glass walled x-ray tubes. High
tube current can be used in micro-focus tubes. The science of x-ray
tomography develops.
1990s Advances in filmless radiography.
Timeline of Industrial Radiography (continued)
1.1 PROPERTIES OF PENETRATING RADIATION
Penetrating radiation can be used in non-destructive examination because:
(1) Penetrating radiation travels in a straight line.
(2) Penetrating radiation is absorbed as it passes through matter. The extent to
which it is absorbed depends upon three factors:
The thickness of the absorber.
The physical characteristics of the absorber (in particular its density and atomic
number).
The wavelength or “photon energy” of the radiation itself.
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