James R. Gibson

The Lifeline of the Oregon Country: The Fraser-Columbia Brigade System, 1811-47

A getter device for releasing an evaporable getter metal such as barium in a vacuum tube comprising a ring and a getter metal releasing material attached to the ring. The getter metal releasing material has a zone of high density adjacent to the ring. It also has a zone of low density adjacent to the zone of high density. In getter devices of the present invention, upon release of the getter metal, the getter metal releasing material remains attached to the ring.