Ion recombination in liquid ionization chambers: development of an experimental method to quantify general recombination
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
An experimental method (the two-dose-rate method) for the correction of general recombination losses in liquid ionization chambers has been developed and employed in experiments with different liquids and radiation qualities. The method is based on a disassociation of initial and general recombination, since an ionized liquid is simultaneously affected by both of these processes.
The two-dose-rate method has been compared to an existing method for general recombination correction for liquid ionization chambers, and has been found to be the most robust method presently available.
The soundness of modelling general recombination in liquids on existing theory for gases has been evaluated, and experiments indicate that the process of general recombination is similar in a gas and a liquid. It is thus reasonable to employ theory for gases in the two-dose-rate method to achieve experimental corrections for general recombination in liquids. There are uncertainties in the disassociation of initial and general recombination in the two-dose-rate method for low applied voltages, where initial recombination has been found to cause deviating results for different liquids and radiation qualities.
Sensitivity to ambient electric fields has been identified in the microLion liquid ionization chamber (PTW, Germany). Experimental data may thus be perturbed if measurements are conducted in the presence of ambient electric fields, and the sensitivity has been found to increase with an increase in the applied voltage. This can prove to be experimentally limiting since general recombination may be too severe for accurate corrections if the applied voltage is low.
Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2013. , 76 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1567
General recombination, initial recombination, liquid ionization chamber, radiation dosimetry
Other Physics Topics Radiology, Nuclear Medicine and Medical Imaging
Research subject radiofysik
IdentifiersURN: urn:nbn:se:umu:diva-68942ISBN: 978-91-7459-607-6 (Print)ISBN: 978-91-7459-608-3 (PDF)OAI: oai:DiVA.org:umu-68942DiVA: diva2:618929
2013-05-31, Sal 260, by 3A, Norrlands universitetssjukhus, Umeå, 13:00 (English)
Ahnesjö, Anders, Professor
Tölli, Heikki, Filosofie doktorJohansson, Lennart, Filosofie doktor
List of papers