selenium or iridium

[Ndtmetal]

Regarding film screen radiography in welds, which one of this isotopes do you believe gives the best image quality?
Most references I found support the use of selenium, but I would like to know why and in which way is it better?

 

[JR97]

Ndtmetal,

The answer to your question is it depends!

Image quality depends on a number of factors; pertinent to the isotope are energy level and source size.

Selenium is lower energy then Iridium, therefore the sensitivity would be better but the thickness of material which can be effectively radiographed is decreased.

The source size is dependent on the individual isotope with smaller sources producing better resolution.

You need to match the isotope to the application to produce the best radiograph possible.

JR97