English: Early mercury diffusion pump developed by Irving Langmuir at General Electric in 1916. The diffusion pump is the vertical chamber in the foreground, the machine in the background is the "backing pump" required to establish the initial low vacuum. The mercury diffusion pump was invented by German researcher W. Gaede in 1913. Langmuir's innovation was a nozzle that directed the mercury vapor away from the inlet, allowing the inlet to be made larger, greatly increasing the pumping speed. He received a patent on his "mushroom cap" nozzle in 1921. The Langmuir pump, which achieved pressures down to 10^-10 atmosphere, enabled the production of the first "hard vacuum" thermionic valves (vacuum tubes) which dominated radio and electronics technology for 50 years. It also was important for making incandescent light bulbs. Alterations to image: removed unrelated text from accompanying article from white area in upper right corner of image.