ISO 7004:2002 pdf download – Photography – Industrial radiographicfilms – Determination of lso speed, Isoaverage gradient and lso gradients G2and G4 when exposed to x-and gamma-radiation.
5.3.3.2 X-rays from a low potential source
The him/screen combination under test shaM be exposed to X-rays from tungsten target tubes. inherent filtration of the tube, plus an additional copper filter located as close to the target as possible shall provide a filtration equivalent to 2.0 mm ± 0,1 mm of copper. All copper filters specified in this International Standard shall be made of 99,9 % pure copper.
The potential across the X-ray tube shall be adjusted until the halt-value absorption is obtained with 1.0 mm ± 0,1 mm of copper (i.e. the intensity of the X-ray beam with a filtration equivalent to 3,0 mm shall be one- half the value obtained with the total filtration equivalent to 2,0 mm of copper).
A potential of approximately 120 kV generally meets this requirement. No lead screens shall be used.
This Is designated source (1).
5.3.3.3 X-rays from a high potential source
The film/screen combination under test shaM be exposed to X-rays from tungsten target tubes. Inherent filtration of the tube, plus an additional copper filter located as close to the target as possible shall provide a filtration equivalent to 8,00 mm ± 0.05 mm of copper. The potential across the X-ray tube shall be adjusted until the half- value absorption is obtained with 3.5 mm – 0.2 mm of copper.
A potential of approximately 220 kV generally meets this requirement.
Film/screen combinations shall be exposed without interleaving paper and shall be between lead-toil screens. A trial exposure should be made to make sure that the lead-foil screens do not produce streaks or other obvious defects.
The front and back lead-foil screens shall be between 0,020mm and 0,150 mm thick.
II should be noted that changes In screen thickness may result In changes In the sensltometnc charactenstics, Therefore, screen thickness shall be reported when quoting ISO speeds.
Single-coated films shall be exposed with the emulsion-coated surface facing the X-ray tube To obtain sufficient contact, vacuum cassettes or pressixe shall be used.
This Is designated source (2).
5.3.3.4 Gamma rays from an lrldlum-192 (1921r) source
A fdtration of 8.0 mm of copper near the source is required. Film thickness shall be between lead-foil screens with a thickness between 0.02 mm and 0,2 mm.
A trial exposure should be made to make sure that the lead-foil screens do not produce streaks or other obvious defects. It should be noted that changes in screen thickness may result in changes in the film speed. Therefore, screen thickness shaM be reported when quoting ISO speeds.
This is designated source (3).
5.3.3.5 Gamma rays from a cobalt-60 (60Co) source
Lead-toil screens shall be between 0,10mm and 0,50mm thick.
A trial exposure should be made to make sure that the lead-toll screens do not produce streaks or other obvious defects.
It should be noted that changes in screen thickness may result in changes in tim speed. Therefore, screen thickness shall be reported when quoting ISO speeds.
This Is designated source (4).
53.4 Scattered radiation
To minimize scattered radiation when exposing test film/screen combinations, X-ray and y-ray beams shall be diaphragrned and collimated to as small a size as will permit a uniform exposure field for the films (and the measuring device. if included). The amount of scattered radiation reaching the film and measuring device shall be no greater than 6 % of the primary radiation. Constructing the supports for the film system, filters and ion chamber from materials of low atomic number and making such structures as light in mass as possible will minimize scattered radiation (see informative annex B).
5.3.5 Modulation
To determine speed and gradient values, it is necessary to provide exposures that will result in a minimum of 12 data points distributed between the densities of 1,0 and 5.0 above mm.mum density. In practice, this is carried out by changing the exposure time, step by step, combined with a gradual change in radiation dose. The exposure over the useful area of each exposure step shaM be uniform to within 3%.
For each exposure, the air karma. In grays, shall be measured by using an Ionization chamber calibrated for the radiant energy quality and Intensity used for exposing the film. (See annexes C and D for additional information.) A separate sample of the flint shall be left unexposed for measuring Inherent minimum density.
5.4 Processing
5.4.1 Conditioning of samples
In the time Interval between exposure and processing, the samples shall be kept at 23 °C s 5 ‘C and in equilibrium with air at a relative humidity of 50 % ± 20 %.
The processing shall be started between 30 mm and 8 h after exposure.
5.4.2 ProcessIng sp.clfkatlons
No processing specifications are described in this International Standard in recognition of the wide range of chemicals and equipment used ISO speed and ISO gradient data provided by the film manufacturer generally apply to the film when it is processed in accordance with the manufacturer’s recommendations to produce the photographic characteristics specified for the process.