University of Groningen Superfluid helium and cryogenic noble gases as stopping media for ion catchers Purushothaman, Sivaji IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2008 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Purushothaman, S. (2008). Superfluid helium and cryogenic noble gases as stopping media for ion catchers s.n. Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date: 11-02-2018
Superfluid Helium and Cryogenic Noble Gases as Stopping Media for Ion Catchers
RIJKSUNIVERSITEIT GRONINGEN Superfluid Helium and Cryogenic Noble Gases as Stopping Media for Ion Catchers Proefschrift ter verkrijging van het doctoraat in de Wiskunde en Natuurwetenschappen aan de Rijksuniversiteit Groningen op gezag van de Rector Magnificus, dr. F. Zwarts, in het openbaar te verdedigen op vrijdag 28 november 2008 om 13:15 uur door Sivaji Purushothaman geboren op 21 december 1978 te Kozhikode Kerala, India
Promotor: Copromotor: Prof. Dr. K. P. Jungmann Dr. P. G. Dendooven Beoordelingscommissie: Prof. Dr. J. Äystö Prof. Dr. Ir. R. A. Hoekstra Prof. Dr. C. Scheidenberger ISBN: 978-90-367-3651-0 Printed version ISBN: 978-90-367-3652-7 Electronic version
This work has been performed as part of the research program of the Stichting voor Fundamenteel Onderzoek der Materie (FOM), which is financially supported by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek ; (NWO). This work has been supported by the EU 6th Framework programme Integrating Infrastructure Initiative - Transnational Access, Contract Number: 506065 (EURONS) and by the Academy of Finland under the Finnish Centre of Excellence Programme 2006-2011 (Nuclear and Accelerator Based Physics Programme at JYFL). Printed by: Ponsen & Looijen B.V., Wageningen, November 2008.
An experiment is a question which science poses to nature, and a measurement is the recording of nature s answer Max Planck Scientific Autobiography and Other Papers, 1949
Contents 1 Introduction 1 2 Physics processes in cryogenic noble gas ion catchers 5 2.1 Electrons in low temperature helium gas................. 5 2.2 Positive ions in low temperature helium gas............... 11 2.3 Charge recombination............................ 13 2.4 Recombination loss factor.......................... 13 2.5 Helium ion species.............................. 14 2.6 Recombination coefficient of helium ions................. 16 2.7 Recombination of noble gas ions in helium................ 19 2.8 Conclusion................................... 19 3 Physics processes in superfluid helium ion catchers 21 3.1 Positive ions in superfluid helium..................... 24 3.2 Electrons in superfluid helium....................... 26 3.3 Snowball and bubble mobility........................ 27 3.4 Charge recombination factor in superfluid helium............ 30 3.5 Positive ions at the superfluid-vapor interface.............. 31 3.6 Ion extraction across the superfluid-vapor interface........... 34 3.7 Conclusion................................... 36 4 Experimental techniques 37 4.1 Cryostat.................................... 37 4.2 Experimental cell............................... 41 4.3 Gas density in the experimental cell at low temperature........ 50 4.4 Conclusion................................... 54 ix
x 5 Cryogenic noble gas ion catchers 55 5.1 Off-line measurements............................ 56 5.2 On-line measurements............................ 62 5.3 Mobility measurements of 219 Rn ions in cryogenic noble gases.... 69 5.4 Conclusion................................... 74 6 Superfluid helium ion catcher 77 6.1 Extraction of 219 Rn ions across the superfluid-vapor interface..... 77 6.2 Second sound assisted superfluid surface evaporation......... 88 6.3 Conclusion................................... 93 7 Conclusion and outlook 95 Summary 101 Samenvatting 103 Acknowledgment 105 List of Figures 109 List of Tables 113 List of Publications 115 References 117