  A high vacuum gate valve for skimmed molecular beam experiments is described.
It is designed with a very short extent of only 10 mm along the molecular beam
axis to minimize the distance between the molecular beam source and the
experiment to provide the maximum molecular flux to the experiment. At the same
time it provides free space on both sides of the skimmer to not disturb the
supersonic expansion in front of the skimmer, to give optical access to the
full distance between beam source and skimmer, and to allow for placing
electrostatic devices very close behind the skimmer. The gate valve allows to
maintain high vacuum conditions (10^{-8} mbar) in the experimental chamber
while the source chamber is brought up to atmospheric pressure for
modifications or maintenance. The valve can be operated from outside the vacuum
chamber while maintaining vacuum conditions in all chambers.
