Abstract: Process and apparatus for providing an imaging gas under pressure to the imaging chamber of an electron radiographic system. After closing the imaging chamber, air is flushed out by introducing a condensable gas such as a Freon. The Freon is then flushed out by a charge of the imaging gas, such as xenon and krypton. The exhausted air-Freon mixture is collected and pressurized to condense and separate out the Freon from the air. The liquid Freon is then expanded into a gas and used for a subsequent flushing step. Similarly, the exhausted Freon-zenon mixture is retained and pressurized to liquify and separate the Freon from the xenon. The liquid Freon is expanded to a gas and used for a subsequent flushing operation and the xenon is used for a subsequent charge into the imaging chamber. After an exposure, the imaging gas is flushed out with Freon and the chamber may then be opened.