Polonium contains especially alpha rays and a few gamma rays. In the case of uranium, the alpha rays have extremely slight penetrating power, and cannot even impress photographic plates.
That was the dangerous kind, because both beta particles and gamma rays could penetrate clothing and skin.
Natural phenomena such as mass extinctions, supernovae and gamma ray bursters are more problematic for civilization.
Recent investigations of cosmological gamma ray bursts suggest that these too could cause ozone depletion.
The exact form of the source modulation and the nuclear-resonant thickness of the resonant absorber determines the shape of the time-differential resonant gamma ray transmission spectrum.
To my knowledge, gamma ray irradiation has been known to scientists for over 30 years.
We know all that there is to be known about gamma ray irradiation at the present time.
The chamber would manipulate the gamma ray into a way that it could be recorded.