Getter

Consumable reactive substance used to fix another one such as for oxygen removal in vacuum tubes

A getter is a deposit of reactive material that is placed inside a vacuum system to complete and maintain the vacuum. When gas molecules strike the getter material, they combine with it chemically or by absorption. Thus the getter removes small amounts of gas from the evacuated space. The getter is usually a coating applied to a surface within the evacuated chamber.

This keyword could refer to multiple things. Here are some suggestions: