![](http://ImgLib.lbl.gov/ImgLib/COLLECTIONS/BERKELEY-LAB/images/pg59_diagram.thumb2.jpeg) | Schematic of the experiment of Bjorkland et al., showing observation through
a port in the concrete shielding of disintegration photons proceeding against the proton
beam; photons moving in the direction of the protons were observed through the same port
with the beam reversed, 1950. |