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Studies on the alpha-recoil implantation of 214Pb and 210Pb in glass surfaces,Implications for retrospective radon measurements

Roos, Birgitta LU (2002)
Abstract (Swedish)
Popular Abstract in Swedish

Glas kan användas för retrospektiva radon mätningar på grund av radondöttrars förmåga att implantera i glasets översta skikt. Mängden implanterad aktivitet blir lätt påverkad av en rad olika faktorer i den omgivande luften. Experimentella metoder har därför utvecklats för att bestämma djupfördelningen av alfarekyl-implanterat 210Po i glas. Detta göres genom gradvis etsning av glasytan. Två etsvätskor har härför används, utspädd HF/HNO3 och NaOH vilka påverkar ytan i olika snabb takt och med olika kemisk upplösning. De erhållna djupprofilkurvorna har jämförts med resultaten från simuleringsprogrammet SRIM. De teoretiskt erhållna värdena visar god överenstämmelse med de experimentella data för... (More)
Popular Abstract in Swedish

Glas kan användas för retrospektiva radon mätningar på grund av radondöttrars förmåga att implantera i glasets översta skikt. Mängden implanterad aktivitet blir lätt påverkad av en rad olika faktorer i den omgivande luften. Experimentella metoder har därför utvecklats för att bestämma djupfördelningen av alfarekyl-implanterat 210Po i glas. Detta göres genom gradvis etsning av glasytan. Två etsvätskor har härför används, utspädd HF/HNO3 och NaOH vilka påverkar ytan i olika snabb takt och med olika kemisk upplösning. De erhållna djupprofilkurvorna har jämförts med resultaten från simuleringsprogrammet SRIM. De teoretiskt erhållna värdena visar god överenstämmelse med de experimentella data för 210Pb eller (210Po) från glasetsningen. Det maximala djupet för implanterad aktivitet erhölls till 100 ± 20 nm. Aktivitet i positioner djupare än 70 nm är associerat med alfasönderfall från 214Po som redan har implanterats vid ett tidigare sönderfall. Inget djup kan helt kopplas till enbart ett alfasönderfall i glasmatrisen. Andra frågeställningar har varit inflytandet av olika partiklar (paraffin/stearin, salt och polystyren) och dess storleksfördelning på implantations sannolikheten från ytan in i glas. Deponerad aktivitet på glasytan har antingen möjlighet att rekylera in i partikeln den är vidhäftad vid, eller att rekylera till viss del direkt in i glaset. Två undersökningsmetoder har tillämpats: den ena undersökningen har genomförts i en vindtunnel med avsikten att minimera inflytandet av icke implanterbara radondöttrar, den andra undersökningen har genomförts i ett stort exponeringsrum för radon. Den implanterade andelen för (214Pb) 214Po varierade från 45% for obunden aktivitet till c:a 10 % för bunden aktivitet till partiklar. Deponeringshastigheter varierade med en faktor 10 till 100 mellan obundna (0.17 –0.09 cm s-1) och bundna (0.001-0.0009 cm s-1) radon döttrar. (Less)
Abstract
Glass sheets are often used in radon surveys to estimate retrospective radon concentrations, as radon progenies are embedded in the upper surface layer. The implanted activity is influenced by a variety of different environmental conditions. In this work, experimental methods based on etching to determine the depth distribution of recoil-implanted 210Po in glass from radon decay in air were developed. By carefully controlling chemical concentrations and the exposure time during which the glass was etched, stepwise removal of the surface material was possible. Two different etching agents, diluted HF/HNO3 and NaOH were utilised, with very similar results. The depth profiles were compared with results from simulations using the SRIM computer... (More)
Glass sheets are often used in radon surveys to estimate retrospective radon concentrations, as radon progenies are embedded in the upper surface layer. The implanted activity is influenced by a variety of different environmental conditions. In this work, experimental methods based on etching to determine the depth distribution of recoil-implanted 210Po in glass from radon decay in air were developed. By carefully controlling chemical concentrations and the exposure time during which the glass was etched, stepwise removal of the surface material was possible. Two different etching agents, diluted HF/HNO3 and NaOH were utilised, with very similar results. The depth profiles were compared with results from simulations using the SRIM computer program. Theoretically estimated distributions showed good agreement with experimental 210Pb (or 210Po) activity depth profiles obtained by sequential etching. The maximum depth of implanted activity was about 100 ± 20 nm, and activity located deeper than about 70 nm was associated with the second alpha decay from 214Po activity previously implanted in the glass matrix. However, there was no depth interval where the activity was solely due to a single decay from the surface. Furthermore, the influence of different types of particles (paraffin/stearin, salt and polystyrene) and different particle size distributions was investigated, in order to estimate the deposition velocity onto surfaces and the implantation probability in glass. Once at the glass surface, the recoil nucleus produced in the radioactive decay may, to a certain extent, implant either into the particle (deposited on the glass) or into the glass matrix. Two approaches were utilised: One investigation of the probability of implantation was performed in a wind tunnel in order to decrease influences from non-implanting radon progeny and the other was performed in a walk-in radon exposure chamber. The measured implantation fractions of (214Pb) 214Po in glass varied from 45% for activity unattached to aerosols to about 10% for aerosol attached activity. The deposition velocity varied by a factor of 10 to 100 between unattached (0.17-0.09 cm s-1) and attached (0.001-0.0009 cm s-1) radon progeny. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Professor McLaughlin, J.P., Physics Department,University College Dublin, Ireland
organization
publishing date
type
Thesis
publication status
published
subject
keywords
unattached activity, attached activity, retrospective radon measurement, long-lived radon progenies, short-lived radon progenies, deposition velocity, implantation, 222Rn, glass surface, etching, simulation, Nuclear physics, Kärnfysik
pages
90 pages
publisher
Department of Radiation Physics, Lund university
defense location
Onkologiska Klinikens Föreläsnigssal, Universitetssjukhuset, Lund.
defense date
2002-09-13 10:15
ISBN
91-628-5315-5
language
English
LU publication?
yes
id
b8ab4b12-d9a1-4ce5-a6cf-bf3049219f5c (old id 464795)
date added to LUP
2007-10-08 10:27:54
date last changed
2016-09-19 08:45:13
@misc{b8ab4b12-d9a1-4ce5-a6cf-bf3049219f5c,
  abstract     = {Glass sheets are often used in radon surveys to estimate retrospective radon concentrations, as radon progenies are embedded in the upper surface layer. The implanted activity is influenced by a variety of different environmental conditions. In this work, experimental methods based on etching to determine the depth distribution of recoil-implanted 210Po in glass from radon decay in air were developed. By carefully controlling chemical concentrations and the exposure time during which the glass was etched, stepwise removal of the surface material was possible. Two different etching agents, diluted HF/HNO3 and NaOH were utilised, with very similar results. The depth profiles were compared with results from simulations using the SRIM computer program. Theoretically estimated distributions showed good agreement with experimental 210Pb (or 210Po) activity depth profiles obtained by sequential etching. The maximum depth of implanted activity was about 100 ± 20 nm, and activity located deeper than about 70 nm was associated with the second alpha decay from 214Po activity previously implanted in the glass matrix. However, there was no depth interval where the activity was solely due to a single decay from the surface. Furthermore, the influence of different types of particles (paraffin/stearin, salt and polystyrene) and different particle size distributions was investigated, in order to estimate the deposition velocity onto surfaces and the implantation probability in glass. Once at the glass surface, the recoil nucleus produced in the radioactive decay may, to a certain extent, implant either into the particle (deposited on the glass) or into the glass matrix. Two approaches were utilised: One investigation of the probability of implantation was performed in a wind tunnel in order to decrease influences from non-implanting radon progeny and the other was performed in a walk-in radon exposure chamber. The measured implantation fractions of (214Pb) 214Po in glass varied from 45% for activity unattached to aerosols to about 10% for aerosol attached activity. The deposition velocity varied by a factor of 10 to 100 between unattached (0.17-0.09 cm s-1) and attached (0.001-0.0009 cm s-1) radon progeny.},
  author       = {Roos, Birgitta},
  isbn         = {91-628-5315-5},
  keyword      = {unattached activity,attached activity,retrospective radon measurement,long-lived radon progenies,short-lived radon progenies,deposition velocity,implantation,222Rn,glass surface,etching,simulation,Nuclear physics,Kärnfysik},
  language     = {eng},
  pages        = {90},
  publisher    = {ARRAY(0xbb5cd48)},
  title        = {Studies on the alpha-recoil implantation of 214Pb and 210Pb in glass surfaces,Implications for retrospective radon measurements},
  year         = {2002},
}