Chemical pumping in vacuum technology

Chemical pumping in vacuum technology has gained an ever increasing importance during the last two decades. It is based on the capability of metals, such as Zr, Ti, Ba and others, in pure or (more usually) alloy forms, to chemisorb the active residual gases present in vacuum devices or systems. These metals, used in powder form or in many different configurations, are known as getters; their role is to improve and maintain the required vacuum in many kinds of vacuum devices working in the range of 1-10(-11) Pa. They are often used, particularly in sealed-off devices, as in situ pumps to speed up the manufacturing process and make if more cost effective. Their application is performed in an evaporated or non-evaporated mode and spans from CRTs to big particle accelerators and even to gas purifiers used in the semiconductor industry. This broad range of applications has required a continuous enhancement in the study of getters from both the technical and the scientific point of view. The most relevant achievements in this field will be here reviewed and discussed.