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Heavy-Ion Induced Desorption of a TiZrV Coated Vacuum Chamber Bombarded with 5 MeV/u Ar8+ beam at grazing incidence
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Nuclear and Particle Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
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2009 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 27, no 1, 139-144 p.Article in journal (Refereed) Published
Abstract [en]

TiZrV nonevaporable getter (NEG) coated vacuum chambers is a new vacuum technology which is already used in many particle accelerators worldwide. This coating is also of interest for heavy-ion accelerator vacuum chambers. Heavy-ion desorption yields from an activated as well as a CO saturated NEG coated tube have been measured with 5 MeV/u Ar8+ beam. The sticking probability of the NEG film was obtained by using the partial pressure ratios on two sides of the NEG coated tube. These ratios were compared to results of modeling of the experimental setup with test particle Monte Carlo and angular coefficient methods. The   partial pressures inside the saturated NEG coated tube bombarded with heavy ions were up to 20 times larger than those inside the activated one. However, the partial pressure of methane remained the same. The value of the total desorption yield from the activated NEG coated tube is 2600 molecules/ion. The desorption yields after saturation for CH4, H-2, and CO2 were found to be very close to the yields measured after the activation, while CO increased by up to a factor of 5. The total desorption yield for the saturated tube is up to 7000 molecules/ion. The large value of the desorption yield of the activated NEG coated   tube, an order of magnitude higher than the desorption yield from a stainless steel tube at normal incident angle, could be explained by the grazing incident angle.

Place, publisher, year, edition, pages
2009. Vol. 27, no 1, 139-144 p.
Keyword [en]
carbon compounds, desorption, hydrogen, ion beam effects, metallic thin films, Monte Carlo methods, titanium alloys, vanadium alloys, zirconium alloys
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-97077DOI: 10.1116/1.3032914ISI: 000264017300019OAI: oai:DiVA.org:uu-97077DiVA: diva2:171863
Available from: 2008-04-18 Created: 2008-04-18 Last updated: 2010-08-12Bibliographically approved
In thesis
1. Studies of Heavy Ion Induced Desorption in the Energy Range 5-100 MeV/u
Open this publication in new window or tab >>Studies of Heavy Ion Induced Desorption in the Energy Range 5-100 MeV/u
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

During operation of heavy ion accelerators a significant pressure rise has been observed when the intensity of the high energy beam was increased. The cause for this pressure rise is ion induced desorption, which is the result when beam ions collide with residual gas molecules in the accelerator, whereby they undergo charge exchange. Since the change in charge state will affect the bending radius of the particles after they have passed a bending magnet, they will not follow the required trajectory but instead collide with the vacuum chamber wall and gas are released. For the Future GSI project FAIR (Facility for Antiproton and Ion Research) there is a need to upgrade the SIS18 synchrotron in order to meet the requirements of the increased intensity. The aim of this work was to measure the desorption yields, η, (released molecules per incident ion) from materials commonly used in accelerators: 316LN stainless steel, Cu, Etched Cu, gold coated Cu, Ta and TiZrV coated stainless steel with argon and uranium beams at the energies 5-100 MeV/u. The measurements were performed at GSI and at The Svedberg Laboratory where a new dedicated teststand was built. It was found that the desorption yield scales with the electronic energy loss to the second power, decreasing for increasing impact energy above the Bragg Maximum. A feasibility study on the possibility to use laser refractometry to improve the accuracy of a specific throughput system was performed. The result was an improvement by up to 3 orders of magnitude, depending on pressure range.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 65 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 425
Physics, Heavy Ion Induced Desorption, Ultra High Vacuum, NEG Coating, Heavy Ion Accelerators, Test Particle Monte-Carlo, Gas Flow, Throughput, Laser Refractometry, Metrology, Fysik
urn:nbn:se:uu:diva-8654 (URN)978-91-554-7168-2 (ISBN)
Public defence
2008-05-09, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15
Available from: 2008-04-18 Created: 2008-04-18Bibliographically approved

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