Luo Daling

Measurement of mixed radon and thoron daughter concentrations in air

Abstract The method of measuring mixed radon and thoron daughter concentrations during and after sampling is discussed and a versatile computer program for analyzing observed data of radon and thoron daughters has been written based on a mathematical technique using a matrix and weighted least squares calculation. The program is also suitable for calculating the concentrations of radon daughter from the total alpha spectroscopy data during and after sampling. A set of optimum time intervals is recommended for measuring the concentrations of mixed radon and thoron daughter.

DEFECTS IN SAPPHIRE:MN INDUCED BY NEUTRON IRRADIATION

Abstract After neutron irradiation, some impurity ions changed their valence states, as well as some new defects such as vacancies, interstitials and the clusters were produced. The thermoluminescence (TL) with electron paramagnetic resonance (EPR), positron annihilation technique (PAT) measurements were used to determine the defects in Sapphire: Mn irradiated by fast neutron of 2 MeV average energy and thermal neutron of 0.023 eV. The results of TL show that before irradiation peaks of 171°C, 259°C, 320°C, 350.2°C and 408°C all belong to the intrinsic crystal, the peak of 196°C is induced by impurity ion of Mn. After neutron irradiation, the peaks all moved to higher temperature, but got different shifts and produced a new peak of 154°C. The shift of peak 196°C is about 30°C. It is explained that Mn ion aggregated with a nearest defect and formed a cluster, which corresponding to EPR results might be Mn 2+ –F cluster and the nearest defect might be F type center. The mechanism of other shifts and another peak are also discussed in the paper.

Investigation of ESR, TL and positron annihilation in -ray irradiated magnesium sulphate

The thermoluminescence (TL) glow curves, electron spin resonance (ESR) spectra and positron lifetime spectra in anhydrous magnesium sulphate powder after -irradiation are presented. The ESR isochronal annealing characteristics of -irradiated samples show that the peak f -) attributed to radicals does not decay after annealing at . The TL glow curves obtained at a heating rate of were deconvoluted into four elementary peaks at , , and based on the general-order kinetics equation. The trap parameters, including activation energy E, frequency factor S and kinetics order b, for each peak were obtained by using the initial values estimated from the variable heating rate method before fitting. The TL and ESR dose-responses of in the range from 1 Gy to 20 kGy at room temperature are obtained and fitted with a dose response function to provide nonlinear characteristic parameters, one action factor R and characteristic dose . It is shown that the ESR dose-response for peak f - attributed to radicals is sublinear, while for peak g - attributed to radicals it remains linear. TL dose-responses for the four glow peaks are supralinear. It is therefore assumed that the generation of TL events undergoes a complex, multistage process in which not only anion radicals but also vacancies and impurities might be involved. This argument is supported by the positron lifetime parameters of samples, also obtained in this work.

Gamma-spectrometric measurements of natural-radionuclide contents in soil and gamma dose rates in Yangjiang, PR China

Abstract The average concentration of natural radionuclides in a high-radiation-background area and a control area in Yangjiang and the Enping county of the province Guangdong, PR China, have been measured by in-situ gamma spectrometry and by sampling analysis in our laboratory. Average data on surface and depth distributions in soil have been obtained. The exposure rates to the environmental gamma-radiation field in both areas have been calculated from in-situ gamma spectra with Becks conversion factor and by the method of total spectrum energy. The averaged total absorbed dose rates, including the cosmic-ray contribution obtained from in-situ gamma spectroscopy, are (18.2 ± 5.0) × 10 −8 and (6.6 ± 1.2) × 10 −8 Gy/h in the high-background and control areas, respectively.