Outgassing properties of vacuum materials for particle accelerators

Gas load and pumping determine the quality of vacuum systems. In particle accelerators, once leaks are excluded, outgassing of materials is an important source of gas together with degassing induced by particle beams. Understanding, predicting, and measuring gas release from materials in vacuum are among the fundamental tasks of ultrahigh-vacuum experts. The knowledge of outgassing phenomena is essential for the choice of materials and their treatments so that the required gas density is achieved in such demanding and expensive scientific instruments. This note provides the background to understand outgassing in vacuum and gives references for further study.