The ternary alloys NEG (TiVZr)  which has been used extensively in particle accelerators has an activation temperature of 180°C while the quaternary alloy NEG  (TiVZrHf) introduced by ASTeC has an activation temperature of 140°C  due to its even smaller grain size as compared to ternary alloy. NEG morphology plays an important role in its combined properties. A columnar and porous structure will provide an efficient pumping surface, as a dense structure it provides an effective semi-surface barrier, acting as reservoir for hydrogen diffusion from the chamber’s wall into the vacuum system. On the other hand, NEG in nitride form will perform as true barrier for hydrogen diffusion. Hence at ASTeC we devised a triple layer structure starting with a nitride layer followed by a thick dense layer terminated by a highly columnar structure.   

As the new generation of particle accelerators aims to achieve the lowest emittance and highest luminosity possible there is a push to reduce the beam pipe dimension to as low as few mm in diameters. This brings new challenges in term of coating of long narrow tubes, which is needed to be solved in order to achieve the goals set by the new generation of particle accelerator. Surface impedance of vacuum chambers play an important role in accelerator facilities instabilities. It can significantly effect on budget of total impedance of machine and therefore degrade the beam emittance. The surface resistance of traditional ternary NEG is several of magnitude higher than copper, which can be an inhibiting factor in choosing NEG as active surface of the vacuum vessel. To address this problem, a conductive NEG has been proposed and tested to reduce the surface resistance of the NEG comparable to copper but keeping its all other combined properties.  The conductive layer is consist of traditional NEG with added high conductive elements of Au, Ag, Al, or Cu. We report on the activation temperature, activation procedure, pumping speed and sticking probability of CO, CO2, H2, secondary electron yield (SEY), photon electron yield (PEY), photon and electron stimulated desorption (PSD, ESD), surface resistance and film structure, morphology and composition of all different type of NEG thin film.

The bulk composition of the film is determined with Rutherford back scattering (RBS), Secondary Ion Mass Spectroscopy (SIMS) and the surface composition and chemical bonding are determined by X-ray photo-electron spectroscopy (XPS). The surface topography is determined with scanning electron microscope (SEM) and scanning tunnelling microscope (STM) and the film grain size is calculated by X-ray diffraction (XRD) and electron back scattered diffraction (EBSD).