they didn't think there was technology that could withstand the radiation that would be created in the LHC, so there was basically a lump of lead in the middle of this object with some detectors around the outside, but subsequently we have developed technology.
On pensait qu'aucune technologie ne pourrait supporter les radiations que l'un des grands détecteurs aurait à subir, et on a donc imaginé un gros bloc de plomb entouré de quelques détecteurs, mais la technologie fut ensuite créée.