Abstracts Brochure - CERN

TUPCH177
TUPCH178
TUPCH179
27-Jun-06 16:00 - 18:00 TUPCH — Poster Session
Measurement of the Sorption Characteristics of NEG Coated Pipes: The Transmission Factor
Method
ZrTiV Non Evaporable Getter (NEG) coat-
A. Bonucci, A. Conte, P. Manini, S. Raimondi (SAES Getters S.p.A.) ings 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.
Deposition of Non Evaporable Getter (NEG) Films on Vacuum Chambers for High Energy
Machines and Synchrotron Radiation Sources
Non Evaporable Getter (NEG) films, sputter
P. Manini, A. Bonucci, A. Conte, S. Raimondi (SAES Getters S.p.A.) 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.
R&D on Copper Beam Ducts with Antechambers and Related Vacuum Components
A beam duct with antechambers is able to
Y. Suetsugu, H. Hisamatsu, K.-I. Kanazawa, K. Shibata (KEK) reduce the effect of photoelectrons and, as a
result, to suppress the electron cloud effect of
positron or proton beam. It will be adopted for a future high current positron/proton rings and also a damping ring
of a linear collider. Copper beam ducts with one or two antechambers were manufactured for test and the feasibility
was studied. The test chambers were then installed into the KEK B-factory positron ring and the performance was
investigated with a beam current up to 2000 mA. The temperature, the pressure and the electron density in the beam
channel were measured during the beam operation. The photoelectron, for example, was found to be well suppressed
as expected compared to that of a simple circular beam duct. The related vacuum components, such as a connection
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