排序方式： 共有29条查询结果，搜索用时 15 毫秒
1.
M. J. Carson J. C. Davies E. Daw R. J. Hollingworth V. A. Kudryavtsev T. B. Lawson P. K. Lightfoot J. E. McMillan B. Morgan S. M. Paling M. Robinson N. J. C. Spooner D. R. Tovey 《Astroparticle Physics》2004,21(6):667-687
Simulations of the neutron background for future large-scale particle dark matter detectors are presented. Neutrons were generated in rock and detector elements via spontaneous fission and (α,n) reactions, and by cosmic-ray muons. The simulation techniques and results are discussed in the context of the expected sensitivity of a generic liquid xenon dark matter detector. Methods of neutron background suppression are investigated. A sensitivity of 10−9–10−10 pb to WIMP-nucleon interactions can be achieved by a tonne-scale detector. 相似文献
2.
E. Tóth F. Deak C. S. Gyurkócza Z. S. Kasztovszky R. Kuczi G. Marx B. Nagy S. Oberstedt L. Sajó-Bohus C. S. Sükösd G. Toth N. Vajda 《Environmental Geology》1997,31(1-2):123-127
A steady radon exhalation is assumed in most publications. In a village of North-East Hungary, however, high radon concentrations
have been measured, differing strongly in neighbouring houses and varying in time, due to the interplay of geochemical phenomena.
Received: 20 November 1995 · Accepted: 18 June 1996 相似文献
3.
Gamma activity from the naturally occurring radionuclides namely, 226Ra, 232Th, the primordial radionuclide 40K was measured in the soil of Cuihua Mountain National Geological Park, China using γ-ray spectrometry technique. The mean
activity of 226Ra, 232Th and 40K were found to be 27.2 ± 6.5, 43.9 ± 6.2 and 653.1 ± 127.6 Bq kg−1, respectively. The concentrations of these radionuclides were compared with the typical world values and the average activities
of Chinese soil. The radium equivalent activity, the air absorbed dose rate, the annual effective dose rate, and the external
hazard index were evaluated and compared with the internationally approved values. All the soil samples have Raeq lower than the limit of 370 Bq kg−1 and H
ex less than unity. The overall mean outdoor terrestrial gamma dose rate is 66.3 nGy h−1 and the corresponding outdoor annual effective dose is 0.081 mSv. 相似文献
4.
Twenty-eight samples of groundwater from bedrock boreholes in three distinct Norwegian geological provinces have been taken and analyzed for content of Rn, U, and Th, together with a wide variety of minor and major species. Median values of 290 Bq/1, 7.6 g/1, and 0.02 g/1 were obtained for Rn, U, and Th respectively, while maximum values were 8500 Bq/1, 170 g/1, and 2.2 g/1. Commonly suggested drinking water limits range from 8 to 1000 Bq/1 for radon and 14 to 160 g/1 for uranium. Radioelement content was closely related to lithology, the lowest concentrations being derived from the largely Caledonian rocks of the Trøndelag area, and the highest from the Precambrian Iddefjord Granite of southeast Norway (11 boreholes) where median values of 2500 Bq/1, 15 g/1 and 0.38 g/1, respectively, were obtained. The Iddefjord Granite is not believed to be unique in Norway in yielding high dissolved radionuclide contents in groundwaters, and several other granitic aquifers warrant further investigation in this respect. 相似文献
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7.
J. Ulrych J. Adamovic
K.
k J. Frna Z. &#x;anda A. Langrov R. Skla M. Chvtal 《Chemie der Erde / Geochemistry》2007,67(4):301-312
Barite occurrences related to the Cenozoic (Late Alpine) low-temperature hydrothermal activity are present in the continental Ohře (Eger) Rift area. A specific, Ra-bearing type of barite has been known under the name “radiobarite” from this area since 1904. Revision of 12 localities revealed the presence of alleged radiobarite only in the Teplice (Lahošť–Jeníkov) and Karlovy Vary areas. Barite from other localities is radium-poor. Barite crystals showing concentric oscillation colour zoning totally prevail. Isomorphous substitution of Sr (X×10−1 to X×wt%), Ca (X×10−2 wt%) and Fe (X×10−1 wt%) for Ba was proved. Average SrO contents of 0.4 wt% are markedly exceeded in some samples from Lahošť–Jeníkov (max. 3.2 wt%) and Karlovy Vary (max. 4.9 wt%). Besides inclusions of stoichiometric iron disulphide, the same samples also contain iron disulphides with unusual high contents of Co (max. 12.2 wt%) and Ni (max. to 8.4 wt%). Specific activity of 238U in the studied barites is very low while that of 226Ra reaches 8 Bq/g in several samples. Therefore, 226Ra is not in equilibrium with its parent uranium. These “radiobarites” or their parts must be therefore relatively young, not older than 10–15 ka. Very low uranium contents (<0.4 ppm) were also confirmed by neutron activation analyses of barite samples.
Unit-cell dimensions refined from X-ray powder diffraction data do not show any systematic variation with the measured chemical composition. Their values agree with the data given in the literature. Reflection half-widths, however, seem to correlate with chemistry. Peaks are wider in samples from Lahošť–Jeníkov and Karlovy Vary.
Sulphur and oxygen stable isotope compositions of the Cenozoic barite mineralization of Teplice area are very uniform (δ34S values between 3.9‰ and 7.1‰ CDT, and δ18O values between 6.1‰ and 7.7‰ SMOW), while the barites of Děc˘ín area show more variable sulphur sources. Sulphate derived from sediments of the Tertiary Most Basin seems to dominate for the Teplice area, while Cretaceous sediments are a more probable sulphur source in the Děc˘ín area. Calculation of oxygen isotope composition of hydrothermal fluids based on fluid inclusion homogenization temperatures and barite δ18O data shows δ18Ofluid values in the range of meteoric waters or δ18O – shifted deep circulating meteoric or basinal waters. 相似文献
8.
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
9.
Current predictions as to the impacts of climate change in general and Arctic climate change in particular are such that a wide range of processes relevant to Arctic contaminants are potentially vulnerable. Of these, radioactive contaminants and the processes that govern their transport and fate may be particularly susceptible to the effects of a changing Arctic climate. This paper explores the potential changes in the physical system of the Arctic climate system as they are deducible from present day knowledge and model projections. As a contribution to a better preparedness regarding Arctic marine contamination with radioactivity we present and discuss how a changing marine physical environment may play a role in altering the current understanding pertaining to behavior of contaminant radionuclides in the marine environment of the Arctic region. 相似文献
10.
William Sidle 《Environmental Geology》2009,57(2):377-388
Recent identification of elevated excess 210Pb (≤302.6 mBq L−1) and 137Cs (≤111.3 mBq L−1) activity in drinking water wells up to 20 m depth indicates some transport of airborne radionuclide fallout beyond soils
in the Shaker Village catchment, Maine. Estimated airborne mass loading 210Pbex fluxes of about 0.9 mBq m−3, canvass this headwater catchment and may be sufficient to pose risks to unprotected shallow wells. Inventories of 210Pbex and 137Cs in pond sediments indicate maximum median activities of 943 mBq g−1 and 40.0 mBq g−1, respectively. Calculated 210Pbex fluxes in the catchment soils range from 0.62–0.78 Bq cm−2 year−1 and yield a mean residence time of near 140 years. Measured 137Cs activity up to 51.1 mBq g−1 occurs in sediments at least to 5 m depth. Assumed particle transport in groundwater with apparent 85Kr ages less than 5 years BP (2005) may explain the correlation between these particle-reactive radionuclides and elevated
activity in some drinking water wells. 相似文献