title: Determining the charged fractions of 218Po and 214Pb using an environmental gamma-ray and Rn detector.
abstract: The rate of 218Po and 214Pb atoms collected electrostatically inside an environmental gamma-ray and 222Rn detector (EGARD) was measured. These measurements were used to directly infer the charged fraction of 218Po and to calculate the charged fraction of 214Pb. Thirty-two percent of the 218Po was collected electrostatically using approximately -1500 V on a 2.54 cm diameter Mylar covered disc inside a vented A1 EGARD of 1 L volume. About 91% of the 214Pb is collected electrostatically under the same conditions. The measurements were performed in a calibrated 222Rn test chamber at the Environmental Measurements Laboratory (EML) using the Thomas alpha-counting method with 222Rn concentrations averaging about 4300 Bq m-3. The atomic collection rates were used with other measured quantities to calculate the thermoluminescent dosimeter (TLD) signal acquired from EGARD for exposure to 1 Bq m-3 of 222Rn. The calculations account for 222Rn progeny collection using a Teflon electret and alpha and beta detection using TLDs inside EGARD. The measured quantities include the energies of 218Po and 214Po alpha-particles degraded by passage through the 25 microns thick electret. The TLD responses to these alpha- and beta-particles with an average energy approaching that obtained from the combined spectra of 214Pb and 214Bi were also measured. The calculated calibration factor is within 30% of the value obtained by exposing EGARD to a known concentration of 222Rn. This result supports our charged fraction estimates for 218Po and 214Pb.
authors.affiliation: Environmental Measurements Laboratory, U.S. Department of Energy, New York, NY 10014-3621.
authors.forename: M L
authors.initials: ML
authors.lastname: Maiello
authors.forename: N H
authors.initials: NH
authors.lastname: Harley
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000396:Air Pollutants, Radioactive / Q000032:analysis*; D004553:Electric Conductivity; D004583:Electrons; D004735:Energy Transfer; D004867:Equipment Design; D007856:Lead Radioisotopes / Q000032:analysis*; D010795:Phthalic Acids; D011059:Polonium / Q000032:analysis*; D011092:Polyethylene Glycols; D011093:Polyethylene Terephthalates; D011851:Radioactivity; D011874:Radiometry / Q000295:instrumentation; D011886:Radon / Q000032:analysis*; D012588:Scintillation Counting / Q000295:instrumentation
chemical_list: D000393:Air Pollutants; D000396:Air Pollutants, Radioactive; D007856:Lead Radioisotopes; D010795:Phthalic Acids; D011093:Polyethylene Terephthalates; C025539:Lavsan; D011092:Polyethylene Glycols; D011059:Polonium; D011886:Radon