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Improved determination of the gas flow rate for UHV and leak metrology with laser refractometry
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Nuclear and Particle Physics.
2006 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 17, no 10, 2767-2772 p.Article in journal (Refereed) Published
Abstract [en]

A system often used for vacuum metrology purposes in order to calibrate vacuum gauges in the UHV region and to calibrate gas leak rates is the throughput system, employing the continuous ( or dynamic) expansion method. An important component in such systems is the flowmeter, which has to deliver a pure and well-determined gas flow into the system. To determine the generated gas flow, a number of factors including the pressure inside the flowmeter have to be determined. However, it has turned out that the calibration uncertainty when measuring the pressure in the flowmeter gives a main contribution to the total uncertainty (of typically about 0.1%) for the generated flow, thereby limiting the accuracies of the generated vacuum pressure as well as gas leak rates in UHV metrology. A feasibility study is reported in this paper about the possibility of using laser refractometry to monitor dynamic gas density in situ in the flowmeter, as an alternative and possibly more accurate means of determining the generated gas flow, thereby potentially improving the calibration gas leak rates in the range 10(-8) - 10(-4) Pa m(3) s(-1).

Place, publisher, year, edition, pages
2006. Vol. 17, no 10, 2767-2772 p.
Keyword [en]
laser refractometry, gas flow, metrology, throughput, UHV
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-97078DOI: 10.1088/0957-0233/17/10/031ISI: 000241989700033OAI: oai:DiVA.org:uu-97078DiVA: diva2:171864
Available from: 2008-04-18 Created: 2008-04-18 Last updated: 2011-05-12Bibliographically 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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