Chambre à émission secondaire (CES)

An assembly of 40 foils for a secondary emission chamber (SEC). The foils are separated by glass insulators and the connections on alternate foils which are taken to positive voltage can be seen on the left. The top twenty foils have a central aperture and serve to help beam control by giving signals only when the beam is not well collimated. The lower foils cover the whole aperture and give signals proportional to beam intensity.