This photo is looking upstream. The regenerator consists of a stack of scintillator plates which are read out by photomultiplier tubes attached to the top and bottom of each plate. The electronics associated with the photomultiplier tubes are water-cooled, necessitated by operation in vacuum. During normal operation KTeV uses two parallel neutral beams which consist primarily of K-long mesons and neutrons. The regenerator is used to regenerate a small fraction of the K-long mesons into K-short mesons, both of which are necessary in order to measure epsilon-prime/epsilon. The regenerator moves from one beam to the other once per minute.