| Paper |
Title |
Page |
| TUPCH177 |
Measurement of the Sorption Characteristics of NEG Coated Pipes: The Transmission Factor Method
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1432 |
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- A. Bonucci, A. Conte, P. Manini, S. Raimondi
SAES Getters S.p.A., Lainate
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ZrTiV Non Evaporable Getter (NEG) coatings of vacuum chambers have found application in the particle accelerators to lower the gas pressure, during the operative conditions. For that, the characterization of the actual pumping speed of the NEG coating is a key issue. It is carried out by means of the dynamic sorption method according to ASTM F798-82 standard, conducted "offline" on a sample (coupon), suitably positioned inside the chamber to be coated and recovered after the process. To evaluate in-situ the sorption characteristics of getter coated chambers, a different measurement technique (Trasmission Factor Method) is here described. It is based on the measurement of pressures ratio at the inlet and the outlet of a coated pipe, under a flow of test gas. A calibration curve permits to evaluate sticking probability of the coated surface from the pressure ratio. The use of reference samples to calibrate the method is quite difficult. A better approach is a modellistic one, finding the dependency of pressure ratio on the average sticking probability, the pipe length and the section geometry and dimensions. Preliminary experimental results will be shown.
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| TUPCH178 |
Deposition of Non Evaporable Getter (NEG) Films on Vacuum Chambers for High Energy Machines and Synchrotron Radiation Sources
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1435 |
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- P. Manini, A. Bonucci, A. Conte, S. Raimondi
SAES Getters S.p.A., Lainate
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Non Evaporable Getter (NEG) films, sputter deposited onto the internal surfaces of vacuum chambers reduce thermal out-gassing and provide conductance-free distributed pumping ability, allowing the achievement of very low pressure inside narrow and conductance limited chambers, like Insertion Devices. NEG films do show additional interesting features, like low secondary electron yield and low gas de-sorption rates under ions, electrons and photons bombardment. They seem therefore ideal to reduce electron multi-pacting and dynamic gas de-sorption induced beam instabilities in high energy machines. This paper presents SAES getters experience in the NEG coating of chambers of different geometries and sizes for a variety of projects related to high energy machines and synchrotron radiation facilities. Examples of applications, as well as most common issues related to chambers preparation, film deposition, characterization and quality control, are given. Areas where further work is still necessary to fully take advantage of NEG film properties will be also discussed.
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