GFA Accelerator Seminars

NEG Coatings as a complex solution for Particle Accelerators

by Dr Oleg B. Malyshev (STFC Daresbury Laboratory)

WSLA/008 (PSI)




A non-evaporable getter (NEG) coating was invented by C. Benvenuti (CERN) in the nineties.

    A surface of vacuum chamber which is fully coated with a thin layer of NEG has two main properties: (1) it outgasses as little as possible           (‘nil’ ideally), (2) it does pump, however, will not be contaminated due to a very low outgassing rate from the coated surfaces. 

Since 2002, ASTeC Vacuum Solutions Group is running a programme on studying and further developing the NEG coating to meet new demanding specification for different applications. The main highlights are the following:

  • ASTeC NEG activation procedure allowing to minimise the NEG coating poisoning from non-coated parts of vacuum chamber;
  • Inventing quaternary Ti-Zr-Hf-V NEG coating with demonstrated lower activation temperature and higher sorption capacity than widely used Ti-Zr-V film
  • Inventing of alloy deposition targets of Ti-Zr-Hf-V and Ti-Zr-V wich allows to further reduce the activation temperature and increase the sorption capacity than for the NEG films deposited from the twisted single metal wire targets.
  • Developing the deposition and testing facilities for narrow tubes with an inner diameter d ³ 5 mm.
  • Studying the effect of NEG coating composition and morphology on its pumping properties, electron stimulated desorption (ESD) and surface resistance Rs
  • Developing high electric conductivity NEG coating to address the problems related with RF surface resistance in particle accelerators: beam impedance, energy spread increase and vacuum chamber heating by the image current.