Editing Getter (section)

===Activation===
The typical flashed getter used in small vacuum tubes ''(seen in 12AX7 tube, top)'' consists of a ring-shaped structure made from a long strip of nickel, which is folded into a long, narrow trough, filled with a mixture of [[barium azide]] and powdered glass, and then folded into the closed ring shape. The getter is attached with its trough opening facing upward toward the glass, in the specific case depicted above.

During activation, while the bulb is still connected to the pump, an RF [[induction heating]] coil connected to a powerful [[electronic oscillator|RF oscillator]] operating in the 27&nbsp;MHz or 40.68&nbsp;MHz [[ISM band]] is positioned around the bulb in the plane of the ring. The coil acts as the primary of a transformer and the ring as a single shorted turn. Large RF currents flow in the ring, heating it. The coil is moved along the axis of the bulb so as not to overheat and melt the ring. As the ring is heated, the barium azide decomposes into barium vapor and nitrogen. The nitrogen is pumped out and the barium condenses on the bulb above the plane of the ring forming a mirror-like deposit with a large surface area. The powdered glass in the ring melts and entraps any particles which could otherwise escape loose inside the bulb causing later problems. The barium combines with any free gas when activated and continues to act after the bulb is sealed off from the pump. During use, the internal electrodes and other parts of the tube get hot. This can cause adsorbed gases to be released from metallic parts, such as anodes (plates), grids, or non-metallic porous parts, such as sintered ceramic parts. The gas is trapped on the large area of reactive barium on the bulb wall and removed from the tube.