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A new test stand for heavy ion induced gas desorption measurements at TSL
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Nuclear and Particle Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
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2008 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 586, no 3, 377-381 p.Article in journal (Refereed) Published
Abstract [en]

In several experiments at CERN, GSI and BNL it has been found that the lifetime of highly energetic heavy ions in synchrotrons decreases with increasing number of injected ions. This phenomenon occurs due to the collisions of beam ions and residual gas molecules leading to the change of charge of the ions and their loss on the vacuum chamber walls, which in turn cause ion-induced gas desorption and further pressure increase. To gain a deeper understanding of the ion-induced desorption process in the energy range 5-45 MeV/u, a dedicated test stand was built at the end of the K beamline at The Svedberg Laboratory (TSL) in Uppsala, Sweden. The energy range was chosen due to the fact that the injection energy of the heavy ion synchrotron SIS18 at GSI will be 10 MeV/u, and that there are insufficient data in this energy range. A Test Particle Monte-Carlo model of the experimental set-up was build-up, run and analysed for different sample configurations. An important result is that for the same sample material the desorption yield from a flat sample causes a 1.58 times larger pressure increase than that of a tubular sample. A detailed explanation of the set-up is presented.

Place, publisher, year, edition, pages
2008. Vol. 586, no 3, 377-381 p.
Keyword [en]
ultrahigh vacuum, heavy-ion-induced desorption, test particles Monte-Carlo
National Category
Physical Sciences Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-97074DOI: 10.1016/j.nima.2007.12.020ISI: 000253960800001OAI: oai:DiVA.org:uu-97074DiVA: diva2:171860
Available from: 2008-04-18 Created: 2008-04-18 Last updated: 2016-04-12Bibliographically 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.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 425
Keyword
Physics, Heavy Ion Induced Desorption, Ultra High Vacuum, NEG Coating, Heavy Ion Accelerators, Test Particle Monte-Carlo, Gas Flow, Throughput, Laser Refractometry, Metrology, Fysik
Identifiers
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
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Available from: 2008-04-18 Created: 2008-04-18Bibliographically approved

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Edqvist, E.

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Department of Nuclear and Particle PhysicsDepartment of PhysicsThe Svedberg LaboratoryMicrosystems Technology
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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
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