Radioactivity backgrounds in ZEPLIN-III     

H.M. Araújo  D.Yu. AkimovE.J. Barnes  V.A. BelovA. Bewick  A.A. BurenkovV. Chepel  A. CurrieL. DeViveiros  B. EdwardsC. Ghag  A. HollingsworthM. Horn  G.E. KalmusA.S. Kobyakin  A.G. KovalenkoV.N. Lebedenko  A. Lindote  M.I. LopesR. Lüscher  P. MajewskiA. St. J. Murphy  F. Neves  S.M. PalingJ. Pinto da Cunha  R. PreeceJ.J. Quenby  L. ReichhartP.R. Scovell  C. SilvaV.N. Solovov  N.J.T. SmithP.F. Smith  V.N. StekhanovT.J. Sumner  C. ThorneR.J. Walker 《Astroparticle Physics》2012,35(8):495-502

We examine electron and nuclear recoil backgrounds from radioactivity in the ZEPLIN-III dark matter experiment at Boulby. The rate of low-energy electron recoils in the liquid xenon WIMP target is 0.75 ± 0.05 events/kg/day/keV, which represents a 20-fold improvement over the rate observed during the first science run. Energy and spatial distributions agree with those predicted by component-level Monte Carlo simulations propagating the effects of the radiological contamination measured for materials employed in the experiment. Neutron elastic scattering is predicted to yield 3.05 ± 0.5 nuclear recoils with energy 5-50 keV per year, which translates to an expectation of 0.4 events in a 1 yr dataset in anti-coincidence with the veto detector for realistic signal acceptance. Less obvious background sources are discussed, especially in the context of future experiments. These include contamination of scintillation pulses with Cherenkov light from Compton electrons and from β activity internal to photomultipliers, which can increase the size and lower the apparent time constant of the scintillation response. Another challenge is posed by multiple-scatter γ-rays with one or more vertices in regions that yield no ionisation. If the discrimination power achieved in the first run can be replicated, ZEPLIN-III should reach a sensitivity of ∼1 × 10⁻⁸pb · yr to the scalar WIMP-nucleon elastic cross-section, as originally conceived.  相似文献   

Geochemical Atlas of Slovakia and examples of its applications to environmental problems   总被引：2，自引：0，他引：2  

S. Rapant  D. Bodiš  K. Vrana  V. Cvečková  J. Kordík  K. Krčmová  I. Slaninka 《Environmental Geology》2009,57(1):99-110

Results of comprehensive geochemical mapping and thematic studies of the Slovak territory (rocks, soils, stream sediments, groundwaters, biomass, and radioactivity) in the first half of the 1990s led to several new research programmes in Slovakia, within the frame of which new methodologies for geochemical data evaluation and map visualization were elaborated. This study describes the application and elaboration of data from the Geochemical Atlas of the Slovak Republic at national and regional levels. Based on the index of environmental risk (I_ER = ΣPEC/PNEC), the level of contamination for the geological component of the environment in Slovakia was evaluated. Approximately 10.5% of Slovakia’s territory was characterized as being environmentally disturbed to highly disturbed. In the areas where environmental loadings have accumulated, 14 regions where environmental risks existed due to high element concentrations were defined. The model calculations of health risk estimates based on the databases of the Geochemical Atlas for groundwater and soils indicate that the possible risk occurrence of carcinogenic diseases from groundwater arsenic contents is high in more than 10% of Slovakia, whereas the chronic risk is negligible. To determinate the background and threshold levels a combined statistical–geochemical approach was developed and applied as an example for groundwater at the national level as well as for single groundwater bodies. The results of statistical method application for the whole groundwater body (GBW) were compared with the background values for anthropogenically non-influenced areas in GBW. Final background value took into account time variations and spatial distribution of the element in GBW. Furthermore, based on the database from the Geochemical Atlas for groundwater, groundwater bodies potentially at qualitative risk were delineated for the whole of Slovakia. From a total of 101 groundwater bodies 17 were characterized as being at risk and 22 as being at possible risk.  相似文献   

关于成都地震台测震资料中2～4 Hz干扰频率范围的研究     

何思源  李贵元 《内陆地震》2019,(1):80-90

通过提出3个思考,研究了2～4 Hz干扰的性质以及演变的过程,结合仪器响应以及背景噪声分析干扰产生的原因。分析结果表明:2～4 Hz干扰已成为成都地震台测震资料中的固有干扰,2011年开始出现且现今广泛存在于成都地震台5.5级及以下且震中距大于20°的远震波形、4.5级及以下的近震波形内。成都地震台的背景噪声水平于2011～2012年陡增,2012年达到峰值。干扰的演变规律与台基背景噪声变化走势有着良好的对应关系,与仪器响应并无直接的关联性。  相似文献   

江淮地区地震动区划的研究     

翟洪涛  姚大全 《内陆地震》2005,19(2):170-174

尝试性地提出了基于地震动参数背景值的确定性方法,将概率性地震危险性分析和确定性地震危险性分析相结合,对江淮地区这一中强震过渡区的地震动参数特征进行了研究,并把地震动参数背景值的计算结果绘制成平面等值线图和立体等高线图。为中强震过渡地区的地震动区划研究提供了一个实例。  相似文献   

新疆西天山金、铜矿地球化学背景探讨及其找矿方向   总被引：4，自引：0，他引：4  

廖启林  戴塔根  刘悟辉  胡云锋 《矿产与地质》1999,13(4):235-240

对西天山金、铜矿成矿地球化学背景的分析,认为浅成低温热液型金矿是其最主要的成矿类型,浅成变质碎屑岩型金矿、铜镍硫化物矿床、块状硫化物铜矿床为其重要的矿化类型,指出了Ｃ１－１次火山岩地层等有利成矿部位,并就本区金、铜矿找矿方向问题提出了具体意见。  相似文献   

Mosaic方法在非均匀下垫面上的适用性研究   总被引：1，自引：1，他引：0  

姜金华  胡非  李磊 《高原气象》2007,26(1):83-91

在非均匀下垫面情况下, Mosaic方法是目前国际上广泛运用于模式中计算地表通量的方法.大量的研究表明, 下垫面的非均匀分布会引发局地环流, 非均匀分布的空间尺度较大时, 所引起的环流甚至可以达到海陆风的强度.这种环流的存在直接影响到次网格地表通量的计算.次网格地表非均匀分布, 尤其是大尺度模式中的次网格非均匀分布, 必将影响地表通量的计算.本文针对次网格地表非均匀问题, 设计了高分辨率的Mosaic试验和非均匀试验, 开展了不同背景风情况下的一系列数值试验, 以探讨这种影响的程度.结果表明, 在土壤湿度空间分布不均匀的情况下, 运用Mosaic方法计算得到的地表潜热通量偏小, 背景风较小的时候偏差较大, 背景风增强时偏差减小.  相似文献   

吉林省地下水环境质量分区及特征     

滕继硅 《吉林地质》1991,10(3):74-78

本文在获得大量的地下水环境背景值资料的基础上,依据“地下水质量标准”和“生活饮用水卫生标准”,运用地下水环境背景值,对吉林省具有供水意义的各类地下水进行了环境质量分区,共划分了五个水质区。论述了各类水质区的分布特点及地下水环境质量与背景特征。  相似文献   

机载激光扫描测距仪的性能分析   总被引：4，自引：0，他引：4  

江月松  李树楷 《遥感学报》1998,2(3):161-165

本文对机载激光扫描测距系统的探测信号功率、背景噪声、信噪比等性能以及它们之间的关系等进行了定量化的评估和定性的分析,探讨了探测信噪比与测量距离、恒虚警概率探测时阈值／噪声比等问题,为机载激光扫描测距系统在遥感和测绘中的使用及系统性能的改进提供了科学的参考依据,其分析方法具有普遍意义,可用于不同的机载或星载激光扫描测距系统的分析。  相似文献   

^14C年龄测定中有关问题的探讨     

阮成雯 《内陆地震》1998,12(2):126-132

新疆地震局＾１４Ｃ实验室为提供准确可靠＾１４Ｃ年代 数据,在选择,制备、测量本底苯,制备、测量糖碳苯,分析产品的淬灭对＾１４Ｃ年代的影响等方面进行了有效的试验与探讨。  相似文献   

Stratigraphic sequence, elemental concentrations and heavy metal pollution in Holocene sediments from the Tinto-Odiel Estuary, southwestern Spain   总被引：1，自引：0，他引：1  

F. Ruiz  M. L. González-Regalado  J. Borrego  J. A. Morales  J. G. Pendón  J. M. Muñoz 《Environmental Geology》1998,34(4):270-278

 The Holocene filling of the Tinto-Odiel Estuary comprises seven lithofacies over a Mio-Pliocene substrate. The sequence includes three system tracts: lowstand system (10 000 to 8700 years BP), transgressive system (8700 to 7000 years BP), and regressive system (7000 to Recent). Twenty sediment samples from the 50-m borehole were analyzed for their major components and minor element concentrations. Two multivariate analysis methods, principal component analysis and cluster analysis, were performed in the analytical data set to help visualize the sample clusters and the element associations. Samples corresponding to unpolluted, pre-mining sediments are clearly separated by cluster analysis, mainly as a result of the low content in sulphide-associated heavy metals such as Cu, Zn, As, Ag, and Pb. So, these sediments may be utilized as a background for geochemical analysis (bulk sample) in other adjacent estuaries, both in sandy and silty-clayey sediments. As a consequence of large-scale mining and smelting operations occurred since prehistoric times on the river banks, a rapid rise in the metal pollution was found in the upper 2.5 m of the natural filling, with values exceeding up to ten times the natural background levels. In addition, since the mid-1960s, large amounts of waste and pollutant effluents have been discharged from industries located around the estuary, increasing the heavy metal content in the last 0.3 m of the natural sedimentation. Received: 18 August 1997 · Accepted: 19 January 1998  相似文献