A Comparison Of Methods For The Annual Radiation Dose Determination In Luminescence Dating

Determination of annual radiation dose is one of important factor in luminescence dating. First this thesis calibrates thick source ZnS alpha counter (TSAC) and NaI(Tl) in-situ gamma-ray spectrometry in the OSL dating lab based on previous studies. Then it analyzes many influence factors of alpha counting. On basis of this, two different profiles (one is homogeneous profile and the other is inhomogeneous profile, respectively)were selected in Luochuan loess profile and Qieliekeqi terrace profile in the West Kunlun. Through different annual radiation dose methods, including neutron activation analysis, flame photometry , thick source ZnS alpha-counting and NaI(Tl) field (in-situ) gamma-ray spectrometry, the contents of uranium, thorium and potassium in the samples from the profiles are obtained and compared.First, this study compares thick source ZnS alpha-counting calibration results of the photomultiplier tube(PMT) high voltages and thresholds calibrated by the oscillograph with those by different sources. The calibration results are also tested by eight standard reference samples. The best calibration programme applicable to the equipments is chosen. And many influence factors of alpha counting are analysis, such as escape of the radon, sample size, moisture content , colour of sample, density of ZnS scintillator, and measurement time. The main conclusions from this part of the study can be summarized as follows:1. After calibration, the Daybreak 582 and 583 low background thick source ZnS alpha-counting can be used to measure the alpha-rate of different-color samples with U content in the range of 1.5 to 6.7 ppm and Th content in the range of 6.3 to 27.3 ppm. The measurement precision is also improved. Thereby the precision of Daybreak 583 thick source ZnS alpha-counting rises to 3%-5%, 582 thick source ZnS alpha-counting rises to 3%-10% now.2. Before measurement, the samples must be completely dried. The samples are 2～3 gram and the size of them is less than 63 μm. The ZnS scintillator is the new products of the US Daybreak company. Its background rate is less than 0.3 counts/ ksec. In order to reconstruct the radioactive balance, it is proposed that the ground samples should be enclosed in the counting ring and placed at least eight days before measurment.3. After sealed measurements, the sealing cap should be open at once for unsealed...