| AVS 57th International Symposium & Exhibition | |
| Vacuum Technology | Monday Sessions |
| Session VT+MN-MoM |
| Session: | MEMS Sensors, Vacuum Gauges, Measurements and Pumps |
| Presenter: | A. Bonucci, SAES Getters S.p.A., Italy |
| Authors: | A. Bonucci, SAES Getters S.p.A., Italy A. Conte, SAES Getters S.p.A., Italy L. Caruso, SAES Getters S.p.A., Italy L. Viale, SAES Getters S.p.A., Italy P. Manini, SAES Getters S.p.A., Italy |
| Correspondent: | Click to Email |
A variety of vacuum systems, such as particle accelerators, synchrotrons, surface science chambers or laboratory equipments, do require the achievement of very high or even extremely high vacuum conditions(UHV-XHV). To this purpose, Ion pumps and Non Evaporable Getter (NEG) technologies are widely applied, since they complement each other effectively. Ion pumps remove ungetterable species like noble gases and methane, while the NEG provides a constant and large pumping speed for all the other gases, in a very compact volume.
So far ion and NEG pumps have been mostly used as separate units mounted in separate part of the vacuum system. In this paper, we investigate how overall pumping performances are influenced by the mounting geometry of the two pumps. In particular we will show that a remarkable synergic effect arises when the two pumps are integrated into one unit having optimized design, known as NEG+.
This configuration allows to minimize the detrimental effect given by outgassed species released by the SIP [1,2]This increases the real pumping speed of the SIP, generally masked in the UHV range by gas desorption from SIP internal surfaces. This effect is particularly noticeable for ungetterable gases like Argon and Methane.
The resulting pumping speed of the NEG+ is therefore larger than the sum of the pumping speed of the two separated pumps.
Reducing the degassing effect also increases the overall pumping efficiency at the lower pressure.
In fact, the presence of oxides and nitride compounds onto the cathode surface are known to slow down the diffusion of hydrogen and helium into the cathode[3], which is mainly an ion implantation driven process.
In the present paper we discuss some of these effects as well as the synergies arising from the NEG+ integrated design. A specific focus will be given to argon [4] and methane, which are important gases to consider in a variety of application including electron microscopy and electron/ion optics.
[[1]] K.M.Welch, D.J.Pate and J.Todd, “Pumping of helium and hydrogen by sputter-ion pumps. II. Hydrogen pumping”, J.Vac.Sci.Technol.A 12(3), May/Jun 1994
[ 2]A Calcatelli et als. “Study of outgassing of sputter-ion pump materials treated with three different cleaning procedures”, Vacuum vol. 47 n. 6-8, 1996
[ 3]M. Audi and M. De Simon, “The influence of heavier gases in pumping helium and hydrogen in a an ion pump”, J. Vac. Sci. Technol. A 6 (3), May/Jun 1988
[ 4]D. Andrew, D.R. Sethna and G.F. Weston, “Inert-Gas pumping in a magnetron pump”, proc. 4th AVS, (1968)