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[en] Of the 36 levels of 214Po populated in the β decay of 214Bi which have been proved by γ-γ coincidences, 34 are observed as lines of a ''summing coincidence'' spectrum counted only in some hours
[fr]Sur les 36 niveaux excites de 214Po formes dans la desintegration β- de 214Bi dont l'existence parait justifiee par des mesures de coincidence, 34 ont pu etre observes directement comme raies d'un spectre de coincidence et addition au terme d'une mesure de quelques heures
[en] A level scheme of 214Po formed in the beta decay of 214Bi is proposed. It is based on the analysis of the γ spectrum above 1 MeV of a 226Ra source in equilibrium, on the γ-γ coincidences with the gammas of 609,4 and 665,6 keV of 214 Po, and on sum rules
[fr]Un schema de desexcitation partiel de 214Po est propose, qui est base sur l'analyse du rayonnement γ d'energie superieure a 1 MeV d'une source de 226Ra en equilibre, sur l'observation des coincidences γ-γ avec les gammas de 609,4 et 665,6 keV de 214Po, et sur les regles de somme
[en] Any confined air volume holding radon (222Rn) gas bears a memory of past radon concentrations due to 210Pb (T1/2 = 22 y) and its progenies entrapped in all solid objects in the volume. The efforts of quantifying past radon exposures by means of the left-behind long-lived radon progenies started in 1987 with this author's unsuccessful trials of removing 214Po from radon exposed glass objects. In this contribution the history and different techniques of assessing radon exposure to man in retrospect will be overviewed. The main focus will be on the implantation of alpha recoils into glass surfaces, but also potential traps in radon dwellings will be discussed. It is concluded that for a successful retrospective application, three crucial imperatives must be met, i.e. firstly, the object must persistently store a certain fraction of the created 210Pb atoms, secondly, be resistant over decades towards disturbances from the outside and thirdly, all 210Pb atoms analysed must originate from airborne radon only. For large-scale radon epidemiological studies, non-destructive and inexpensive measurement techniques are essential. Large-scale studies cannot be based on objects rarely found in dwellings or not available for measurements
[en] Results: of the analysis of a time series of values of the half-life (τ) of the 214Po nucleus with a different time step obtained from the TAU-1 (354 days) and TAU-2 (973 days) installations are presented. The annual variation with an amplitude of (9.8 ± 0.6) × 10−4 and daily variations in the solar, lunar, and sidereal times with amplitudes of (5.3 ± 0.3) × 10−4, (6.9 ± 2.0) × 10−4, and (7.2 ± 1.2) × 10−4, respectively, are found in the series of τ values. It is shown that variations in microclimatic parameters cannot be a cause of τ variations.
[en] We have studied the α-decays of 214Po into 210Pb and of 212Po into 208Pb tagged by the coincidence with the preceding β-decays from 214Bi and 212Bi, respectively. The 222Rn, 232Th, and 220Rn sources used were sealed inside quartz vials and inserted in the Counting Test Facility at the underground Gran Sasso National Laboratory in Italy. We find that the mean lifetime of 214Po is (236.00 ± 0.42(stat) ± 0.15(syst)) μs and that of 212Po is (425.1 ± 0.9(stat) ± 1.2(syst)) ns. Our results, obtained from data with signal-to-background ratio larger than 1000, reduce the overall uncertainties and are compatible with previous measurements. (orig.)
[en] The brief description of installation TAU-2 intended for long-term monitoring of the half-life value τ(T1/2) of the 214Po is presented. The methods of measurement and processing of collected data are reported. The results of analysis of time series values of τ with different time step are presented. Total measurement time was equal to 590 days. Averaged value of the 214Po half-life was obtained τ = 163.46 ± 0.04 μs. The annual variation with an amplitude A = (8.9 ± 2.3) × 10−4, solar-daily variation with an amplitude ASo = (7.5 ± 1.2) × 10−4, lunar-daily variation with an amplitude AL = (6.9 ± 2.0) × 10−4 sidereal-daily variation with an amplitude AS = (7.2 ± 1.2) × 10−4 were found in a series of τ values. The maximal values of amplitude are observed at the moments when the projections of the installation Earth location velocity vectors toward the source of possible variation achieve its maximal magnitudes.
[en] Measurement of the 214Po half-life with the DEVIS track setup at the Institute of Theoretical and Experimental Physics (ITEP, Moscow) by means of a procedure based on determining lifetimes of individual nuclei is described. The value obtained for the 214Po half-life is 163.8 ± 3.0 µs. The possibility of reaching the accuracy of the measurements that is required for testing the statement that the decay of some nuclei has a nonexponential character and the source intensity necessary for this are discussed.
[en] Polonium isotopes 214Po and 212Po are part of the 238U and 232Th decay chains, respectively. There exist only a few measurements of these two mean lifetimes with precision better than one or two percent. Since we have been studying decay spectra of 214Bi and 212Bi with the purpose of experimentally constraining anti-neutrino spectral shape important for geoneutrino studies, we have a large statistics of decays of 214Po and 212Po collected with the Counting Test Facility (CTF), which was operational in the underground I.N.F.N. Gran Sasso National Laboratory. The apparatus consisted of an external cylindrical water tank (diameter ∼ 11 m, high ∼ 10 m; ∼ 1000 tons of water) serving as passive shielding for 4.8 m3 of liquid organic scintillator contained in an inner spherical vessel with a diameter of ∼ 2 m. The inner vessel was realized with a nylon membrane (∼ 500 ?m thick), with excellent optical clarity, which allowed the effective transmission of the scintillation light to the 100 phototubes (PMTs) forming the optical read-out, anchored on a 7 m diameter support structure inside the water tank. The high purity and low background in CTF allows a favourable signal to background ratio for these measurements. More specifically the ratio of signal to background of the present measurements is more than three orders of magnitude larger than the best existing measurements. We have studied the decays of 214Po into 210Pb and of 212Po into 208Pb tagged by the coincidence with the previously decays from 214Bi and 212Bi by using 222Rn, 232Th and 220Rn sources sealed inside quartz vials and inserted in the CTF
[en] Radon (222Rn) is a radioactive noble gas that is the decay product of 238U. Radon has a half life of 3.8 d that allows it to travel easily from its place of origin (the ground or the building materials) to the open air. Radon accumulates in closed spaces like underground mines or inside buildings. It can reach relatively high concentrations in areas where high concentrations of 238U and especially of its decay product, 226Ra, exist in the ground. Radon is known as the main contributor to the exposure of the population to natural sources of ionizing radiation. The exposure occurs as a result of the inhalation of the radon decay products which are attached to the aerosols in the air. Most of the dose comes from the alpha and beta particles emitted from the 4 short-lived decay products of radon: 218Po, 214Pb, 214Bi and 214Po. The results of a radon survey in single-family houses in Israel were published in 2006 (1). The survey included almost 2,000 dwellings and its goal was to determine the average radon concentration in single-family houses and to identify radon prone areas around Israel based on long-term measurements using Solid State Nuclear Track Detectors (SSNTD) commercially known as CR-39. It was found that the average radon concentration inside single-family houses is equal to 47.3 Bq/m3 and that a correlation between indoor radon concentration and the geological group on which the dwelling is built exists. In the present study a radon survey of apartments in multistory buildings was conducted. The results of the two surveys were combined in order to assess the average radon concentration in Israeli dwellings and the annual dose to the Israeli population due to radon inhalation