High fluence charged-particle beams are generated in a vacuum or near vacuum environment. To use these beams in an atmospheric pressure environment, they must pass through some form of transmission window between the two environments. To date, thin single metal foils have been used for these transmission...http://www.google.fr/patents/US5898261?utm_source=gb-gplus-shareBrevet US5898261 - Fluid-cooled particle-beam transmission window
