Intensifying Screens
The STRUCTURIX range offers two intensifying screens. The STRUCTURIX RCF fluorometallic screen and the high speed STRUCTURIX NDT 1200 fluorescent screen.
STRUCTURIX intensifying screens: Advantages
The STRUCTURIX fluorometallic (RCF) and fluorescent screens (NDT 1200) based on the conventional phosphor material calcium tungsten (CaWO4) reduce radiation exposure, and/or the necessary level of radiation energy. They detect the radiographic penetration of thick objects.
Being a more productive and effective testing method the use of the STRUCTURIX RCF and NDT 1200 screens reduces the exposure equipment load.
The flexible screen enables radiography of curved objects.
STRUCTURIX intensifying screens: features
When excited by X-rays or gamma-rays the STRUCTURIX RCF fluorometallic screen becomes blue emitting. The screen has an incorporated filter of lead oxide for scattered radiation. The emission spectrum is matched to the spectral sensitivity of the STRUCTURIX F type films. The strong fluorescent STRUCTURIX RCF screen offers the ideal compromise between detail perceptibility and working efficiency. The extra strong Electron-Beam-Cured (EBC) protective coating and the polyester support make the screen particularly durable.
One of the most important applications of the STRUCTURIX RCF screens lies in the inspection of offshore pipelines. Combining the screen sensitivity and rapid processing of the STRUCTURIX F8 film provides an ideal film-screen system. In the in line as well, the use of the STRUCTURIX RCF-screen in combination with the STRUCTURIX F8 film means a considerable amount of time-saving.
The blue emitting STRUCTURIX NDT 1200 fluorescent screen has an extremely high absorption and conversion efficiency together with acceptable detail perceptibility. The combination with a STRUCTURIX F8 film makes this film-screen system convenient for high-energy applications like the non-destructive testing of heavy specimens, the examination of large concrete structures (bridges and buildings).
The STRUCTURIX NDT 1200 screen can also be a solution for flash radiography by which exposure times are extremely short and for microfocus-enlargment techniques by which radiation doses are very low.
Treatment of STRUCTURIX intensifying screens
The STRUCTURIX screens should be protected from moisture, heat and ultra-violet radiation. Dust and marks should be removed from the screen immediately using an approved Screen Cleaner. The Agfa Screen Cleaner obviously cleans the screen but also contains an antistatic element which provides dirt and dust on the screen caused by static electricity.
Relative Exposure Factor When making exposures with fluorescent screens it is important to understand the potential impact of variables such as temperature, exposure energy and exposure time:
- Intensifying screens fluoresce more brilliantly at low temperature. Therefore the screen efficiency will drop with increasing temperature.
- With increasing energy, the absorption of fluorescent screens is reduced and, as a result, the intensifying effect is diminished.
- Due to the “reciprocity effect” with fluorescent screen systems, the gain in exposure time compared to lead screen systems, diminishes with increasing exposure length.
Relative Exposure | ||||||
---|---|---|---|---|---|---|
F8 | F6 | D7 | ||||
100 kB | NDT 1200 | 0.010 | 0.049 | |||
RCF | 0.030 | 0.174 | ||||
No screen | 1.000 | |||||
300 kB | NDT 1200 + Pb | 0.008 | 0.042 | |||
RCF | 0.022 | 0.132 | ||||
Pb | 1.000 | |||||
Ir 192 | NDT 1200 + Pb | 0.007 | 0.063 | |||
RCF | 0.035 | 0.389 | ||||
Pb | 1.000 | |||||
Co 192 | NDT 1200 + Pb | 0.006 | 0.096 | |||
RCF | 0.040 | 0.562 | ||||
Pb | 1.000 |