Which source provides the most penetrating radiation?

The choice indicating that a 15 MeV x-ray betatron provides the most penetrating radiation is based on several key factors regarding the nature of the radiation produced and the energy levels involved.

A betatron is a type of particle accelerator specifically designed to produce high-energy x-rays, with a capability of generating energies around 15 MeV. The energy level of the radiation is crucial for penetration; higher energy x-rays can penetrate materials more effectively than lower energy gamma rays or x-rays. In the context of radiographic testing, this higher energy means that the radiation can pass through denser materials with less attenuation, making it particularly useful for inspecting thick items or detecting flaws in heavy welded structures.

In comparison, while sources like Cobalt-60 and Iridium-192 are indeed commonly used in industrial radiography and have their own penetration qualities, they emit lower energy gamma radiation. For instance, Cobalt-60 emits gamma rays of approximately 1.17 MeV and 1.33 MeV, and Iridium-192 emits gamma rays of about 0.373 MeV. Although they still provide significant penetration for many applications, they do not reach the energy levels necessary for the same level of penetration achieved by the betatron at 15