Abstract: A molecular beam epitaxy (MBE) growth chamber which provides separate longitudinally oriented isolation chambers for each effusion cell thereof. Wall structures bounding each isolation chamber are hollow to receive cryogenic material and are in fluid communication with each other. Each isolation chamber has an interior and exterior portal which provide fluid communication between the isolation chambers and the space inside the MBE chamber. An effusion cell is mounted in the interior portal to direct a portion of effusion material through the interior portal in a beam toward a substrate in the MBE chamber. Another portion of the effusion material is directed along the inside of the isolation chamber toward a sensor which controls the effusion cell. The isolation chambers facilitate measurement and control of individual materials effused from separate cells even when those cells are operated simultaneously.