| AVS 64th International Symposium & Exhibition | |
| Vacuum Technology Division | Tuesday Sessions |
| Session VT+MN-TuA |
| Session: | Pumping |
| Presenter: | Marco Urbano, SAES Getters, Italy |
| Authors: | P. Manini, SAES Getters, Italy E. Maccallini, SAES Getters, Italy M. Urbano, SAES Getters, Italy M. Mura, SAES Getters, Italy T. Porcelli, SAES Getters, Italy F. Siviero, SAES Getters, Italy |
| Correspondent: | Click to Email |
Non Evaporable Getter (NEG) pumps are frequently used when large pumping speeds for H2 and active gases (i.e., H2O, O2, CO, CO2) are required in conjunction with very small weight and size, reduced magnetic interference and vibration, or negligible power consumption. Thanks to these qualities NEG pumps are widespread in basic and applied research, such as particle accelerators, storage rings, synchrotrons and physics projects to achieve UHV or XHV conditions. Moreover, their use is becoming familiar in UHV analytical instrumentation such as SEM, TEM, surface science as well as portable mass spectrometry and transportation vacuum boxes.
In spite of the excellent results in terms of pressure (10-11 mbar are currently achieved in many machines and values lower than 10-12 mbar have been measured in various experiments using NEG pumps), application in cryogenic superconductive radio frequency (SRF) cavities and other particle sensitive systems is not common so far. As a matter of fact, the use of NEG pumps is limited as a precaution against potential dust emission, which can be transported inside the vacuum envelope and may interfere with the electromagnetic fields and promote unwanted quenching phenomena.
Nevertheless, these systems could greatly benefit from the high pumping speed and compactness of NEG pumps, so that an assessment of the actual risk of dust release is gradually being undertaken by different players, including potential users in the accelerator community. Here we present and compare experimental data on particle emission collected with several techniques both on compressed and sintered NEG elements, discussing the differences. In particular, a class of sintered getters based on the ZAO® alloy proved to have extremely low particle emission, as shown by tests carried out in actual SRF cavities, where no measurable particle contamination as well as detrimental effect on the cavity efficiency and performances was observed.