[PHY] X-rays and gamma rays

-can both of then ionize air?

Yes. both X and gamma rays causes ionization in air, but their ionization power are weaker than alpa and beta particles.
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-can both of them be detected by a diffusion cloud chamber?

Cloud chamber tracks are formed due to formation of ions inside the chamber. Because of the weak ionization power of X and gamma rays in air, their cloud chamber tracks are not easily observable.

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-can both of them be used to detect cracks in metal?

Yes. The use X or gamma rays to detect cracks depends on the depth of the crack present in the metal. Should a very thick metal be tested (e.g. in power plant boilers), the more penetrating gamma rays would be used.
The size of the crack also determines whether X or gamma radiation be used. A crack of very small size could only be detected by the very short avelength gamma radiaiton because of less diffraction effect (higher resolution).

They are both high energy radiation (light).

The ionization power of X-ray is stonger than that of gamma ray.
They are both hardly seen is the cloud chamber.
They could be both used to detect cracks in metal, but it is much better to use X-ray than gamma ray since the penetrating power of gamma is stronger, the image of it will be in a worser constrast.

The source of x-ray is always comes from decelerating of a fast electron (electron beam hit at a metal target and release x-ray.) While daily gamma ray comes from nuclear decay (one of the nuclear raidations).