【作者】 王同利；

【导师】 陈杰；

【作者基本信息】 中国地震局地质研究所 ， 地球化学， 2006， 硕士

【摘要】 年剂量是影响释光测年的关键因素之一。本论文在前人研究的基础上，首先对本实验室现有厚源ZnSA1pha计数仪和NaI(T1)Gamma谱仪(LEDL)进行了校核与标定，对影响测量的因素进行研究，并建立相应的测试流程。在此基础上，分别选择一岩性均匀和不均匀剖面，通过野外就地Gamma谱仪测量和室内不同测量方法的对比实验，初步获得的认识如下： 一、利用不同标定源对美国Daybreak 582、583型低本底厚源ZnSA1pha计数仪光电倍增管高压(HV)和积分甄别器阈值电压(DISC)进行了标定，并与示波器标定结果进行了对比。用8个标准参考土样对标定结果进行了检验，确定了最终标定值。并对影响厚源ZnSA1pha计数仪测量的因素如氡逃逸、含水量、色度、粒径、测量时间等开展了初步的实验研究，主要获得以下认识： 1)经标定后的美国Daybreak公司582、583型低本底厚源ZnSA1pha计数仪可用于测量U含量在1.5至6.7 ppm范围、Th含量在6.3至27.3 ppm范围的不同颜色(颜色为Hue5YR7／4和Hue5YR4／4除外)样品的α-计数率，583型厚源ZnSA1pha计数仪的测量精度可达3％-5％，582型低本底厚源ZnSA1pha计数仪的测量精度可达3％-10％。 2)建议本实验室今后在用Daybreak582、583型低本底厚源ZnSA1pha计数仪进行测量时，采取以下措施以提高测量精度和可靠性：被测样品必须完全烘干后方可进行测量，样品量2-3克，样品粒径小于63微米；使用美国Daybreak公司生产的新批次ZnS闪烁屏，测量本底计数率要小于0.3计数／千秒；被测样品经研磨封入计数环后，为重建放射性平衡，建议至少放置8天后再进行测量。 3)对被测样品进行密封测量后，再进行不密封测量，根据其比值来判断该样品是否存在氡逃逸现象。 4)建议在实际测量中只测量样品的α计数率，由此计算其α年剂量准确可靠、简便。测量时间视样品α计数率而定，测量时间越长，测量精度越高。对于α计数率为十几个计数／千秒的沉积物样品，当其α粒子总计数大于1000个计数时，其测量精度可达3％左右。 二、高效率低分辨率NaI(T1)Gamma谱仪野外就地测量能够较真实获取样品及采样点周围半径30厘米范围内的放射性γ射线的贡献，尤其是对于岩性不均匀剖面。NaI(T1)Gamma谱仪野外测量的是钾、铀和钍衰变链中能谱峰域的计数更多还原

【Abstract】 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更多还原