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Article: Long-term measurements of radon progeny concentrations with solid-state nuclear track detectors

TitleLong-term measurements of radon progeny concentrations with solid-state nuclear track detectors
Authors
KeywordsEquilibrium factor
LR 115 detector
Radon progeny concentration
Issue Date2005
PublisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/radmeas
Citation
Radiation Measurements, 2005, v. 40 n. 2-6, p. 560-568 How to Cite?
AbstractIn this paper, we review existing methods for long-term measurements of radon decay products with solid-state nuclear track detectors. We then propose a method to determine the equilibrium factor using the bare LR 115 detector. The partial sensitivities pi of the LR 115 detector to Rn222 and its α-emitting short-lived progeny, Po218 and Po214, were investigated. We determined the distributions of lengths of major and minor axes of the perforated α-tracks in the LR 115 detector produced by Rn222, Po218 and Po214 through Monte Carlo simulations. The track parameters were first calculated using a track development model with a published V function, and by assuming a removed active layer of 6.54μm. The distributions determined for different α-emitters were found to be completely overlapping with one another. This implied equality of partial sensitivities for radon and its progeny. Equality of partial sensitivities makes convenient measurements of a proxy equilibrium factor Fp possible which is defined in the present work as (f1+f3) and is equal to the ratio between the sum of concentrations of the two α-emitting radon progeny (Po218+Po214) to the concentration of radon gas (Rn222). In particular, we have found Fp=(ρ/ρitC0)-1, where ρ (track/m2) is the total track density on the detector, ρi=0.288×10-2m (for the V function mentioned above and for a removed active layer of 6.54μm), t is the exposure time and C0 (Bq/m3) is the concentration of Rn222. If C0 is known (e.g., from a separate measurement), we can obtain Fp. The proxy equilibrium factor Fp is also found to be well correlated with the equilibrium factor between radon gas and its progeny through the Jacobi room model. This leads to a novel method for long-term determination of the equilibrium factor. Experimental irradiation of LR 115 detectors to known Rn222 concentrations as well as known equilibrium factors were carried out to verify the present method. The relationship between ρi and the removed layer was then derived for the V function specifically determined for the LR 115 detectors we were using for the experiments. The actual removed layers for individual detectors after etching were measured accurately using surface profilometry. A curve showing the relationship between the removed layer and the track diameter of normally incident 3 MeV α-particles is also provided for other researchers, who do not have access to surface profilometry, to use the present technique conveniently. © 2005 Elsevier Ltd. All rights reserved.
Persistent Identifierhttp://hdl.handle.net/10722/80645
ISSN
2015 Impact Factor: 1.071
2015 SCImago Journal Rankings: 0.592
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorYu, KNen_HK
dc.contributor.authorNikezic, Den_HK
dc.contributor.authorNg, FMFen_HK
dc.contributor.authorLeung, JKCen_HK
dc.date.accessioned2010-09-06T08:08:44Z-
dc.date.available2010-09-06T08:08:44Z-
dc.date.issued2005en_HK
dc.identifier.citationRadiation Measurements, 2005, v. 40 n. 2-6, p. 560-568en_HK
dc.identifier.issn1350-4487en_HK
dc.identifier.urihttp://hdl.handle.net/10722/80645-
dc.description.abstractIn this paper, we review existing methods for long-term measurements of radon decay products with solid-state nuclear track detectors. We then propose a method to determine the equilibrium factor using the bare LR 115 detector. The partial sensitivities pi of the LR 115 detector to Rn222 and its α-emitting short-lived progeny, Po218 and Po214, were investigated. We determined the distributions of lengths of major and minor axes of the perforated α-tracks in the LR 115 detector produced by Rn222, Po218 and Po214 through Monte Carlo simulations. The track parameters were first calculated using a track development model with a published V function, and by assuming a removed active layer of 6.54μm. The distributions determined for different α-emitters were found to be completely overlapping with one another. This implied equality of partial sensitivities for radon and its progeny. Equality of partial sensitivities makes convenient measurements of a proxy equilibrium factor Fp possible which is defined in the present work as (f1+f3) and is equal to the ratio between the sum of concentrations of the two α-emitting radon progeny (Po218+Po214) to the concentration of radon gas (Rn222). In particular, we have found Fp=(ρ/ρitC0)-1, where ρ (track/m2) is the total track density on the detector, ρi=0.288×10-2m (for the V function mentioned above and for a removed active layer of 6.54μm), t is the exposure time and C0 (Bq/m3) is the concentration of Rn222. If C0 is known (e.g., from a separate measurement), we can obtain Fp. The proxy equilibrium factor Fp is also found to be well correlated with the equilibrium factor between radon gas and its progeny through the Jacobi room model. This leads to a novel method for long-term determination of the equilibrium factor. Experimental irradiation of LR 115 detectors to known Rn222 concentrations as well as known equilibrium factors were carried out to verify the present method. The relationship between ρi and the removed layer was then derived for the V function specifically determined for the LR 115 detectors we were using for the experiments. The actual removed layers for individual detectors after etching were measured accurately using surface profilometry. A curve showing the relationship between the removed layer and the track diameter of normally incident 3 MeV α-particles is also provided for other researchers, who do not have access to surface profilometry, to use the present technique conveniently. © 2005 Elsevier Ltd. All rights reserved.en_HK
dc.languageengen_HK
dc.publisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/radmeasen_HK
dc.relation.ispartofRadiation Measurementsen_HK
dc.subjectEquilibrium factoren_HK
dc.subjectLR 115 detectoren_HK
dc.subjectRadon progeny concentrationen_HK
dc.titleLong-term measurements of radon progeny concentrations with solid-state nuclear track detectorsen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=1350-4487&volume=40&spage=560&epage=568&date=2005&atitle=Long-term+measurements+of+radon+progeny+concentrations+with+solid-state+nuclear+track+detectorsen_HK
dc.identifier.emailLeung, JKC: jkcleung@hku.hken_HK
dc.identifier.authorityLeung, JKC=rp00732en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1016/j.radmeas.2005.03.007en_HK
dc.identifier.scopuseid_2-s2.0-27744552825en_HK
dc.identifier.hkuros111202en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-27744552825&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume40en_HK
dc.identifier.issue2-6en_HK
dc.identifier.spage560en_HK
dc.identifier.epage568en_HK
dc.identifier.isiWOS:000233487500079-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.scopusauthoridYu, KN=7403385896en_HK
dc.identifier.scopusauthoridNikezic, D=35614145500en_HK
dc.identifier.scopusauthoridNg, FMF=7103125284en_HK
dc.identifier.scopusauthoridLeung, JKC=24080627200en_HK

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