反射宇宙中子法的应用研究

摘要：反射宇宙中子法是一种工程物探新方法。本文论述了宇宙中子、反射宇宙中子的形成过程和反射宇宙中子测量装置的研制及其初步应用。由于反射宇宙中子法不受工业电、磁的干扰和不对民用建筑产生破坏,因而该方法在工业和民用建筑密集区进行工程地质填图,可显示其优越性。     

地—空界面天然中子辐射场的扰动及其环境意义

介绍了地-空界面天然中子流的来源和轻便型天然中子流测量仪器。论述了地-空界面天然中子辐射场的扰动。理论与长期观测表明，在地-空界面上天然中子流注量率随高程的增加而呈指数规律增加，而在近地表（20m内）却随距地面高度的增加而呈指数规律减少；天然中子流注量率与大气压力呈负相关关系，气压系数为（－0．060～－ 0．064）中子计数／30min／kPa；地-空界面天然中子流的纬度效应与高空中更显著；天然中子流注量率异常与气象的变化密切相关；地表介质的含水率增高，则地-空界面上升快中子流明显降低。通过对地-空界面天然中子流测量，可以揭示气象的瞬态变化、确定地表介质的含水率的关系，以及在地震预报与环境电离辐射评价方面具有重要的科学意义与实用价值。     

地—空界面天然中子辐射场的扰动及其环境意义

介绍了地—空界面天然中子流的来源和轻便型天然中子流测量仪器。论述了地—空界面天然中子辐射场的扰动。理论与长期观测表明,在地—空界面上天然中子流注量率随高程的增加而呈指数规律增加,而在近地表(20m内)却随距地面高度的增加而呈指数规律减少;天然中子流注量率与大气压力呈负相关关系,气压系数为(-0.060～-0.064)中子计数/30min/kPa;地—空界面天然中子流的纬度效应与高空中更显著;天然中子流注量率异常与气象的变化密切相关;地表介质的含水率增高,则地—空界面上升快中子流明显降低。通过对地一空界面天然中子流测量,可以揭示气象的瞬态变化、确定地表介质的含水率的关系,以及在地震预报与环境电离辐射评价方面具有重要的科学意义与实用价值。     

核地球物理勘查技术发展概况

本文简要叙述了80年代以来,国内外发展较快的几种主要核地球物理勘查技术的概况。这些方法有：中微子在地球科学中的应用;应用核技术探测纳米级微粒和气体;航空伽马能谱测量;应用核技术原位测品位并计算线储量(包括X射线荧光辐射取样;中子活化辐射取样和伽马射线辐射取样);地面伽马能谱测量;互射线荧光测井;水底和海底天然放射性方法测量;水底和海底中子活化方法测量;水下X射线荧光测量;核磁共振方法;在工程中应用核技术;反射宇宙中子法;以及在环境科学中应用核技术等。     

吉林双辽断陷深层地层特征研究

依据地震、钻井、测井资料,详细分析了双辽断陷内火石岭组、沙河子组和营城组的岩性、电性及地震反射特征.双辽断陷从岩性上看火石岭组由凝灰岩、火山角砾岩、砂砾岩组成;沙河子组主要由灰色泥岩与细砂岩、砂砾岩组成;营城组主要由泥岩与粉细砂岩、砂砾岩组成.从电性上看火石岭组为电阻中到高值,声差低值;沙河子组以一套较连续的弱反射或空白反射为特征;营城组与岩性组合特征一致.从地震剖面上看火石岭组构造高部位为强反射,其下可见削截,其上可见上超现象;沙河子组为由杂乱反射变为空白反射或较连续平行反射;营城组上下为低频、强振幅较连续反射,中部体现弱振幅、空白反射中低频特征.     

基于循环采样统计的敦煌辐射校正场表面反射比空间变异特征研究

利用地学统计中的变差函数,采用循环采样法对敦煌辐射校正场表面反射比的空间分布特征进行了测量和分析,结果表明,其可见光光谱区表面反射比的空间变程约为20～50 m。目前使用的同步测量采样范围（〈5 m）明显小于光谱数据的空间变程,使得测量数据的随机性误差较大,不能准确地代表大尺度的平均反射比。为了减少测量尺度差异造成的偏差,地表同步反射比测量的空间采样范围应该不小于卫星光谱测量数据的空间变程。     

光学浅水遥感水底反射校正研究进展

在水色遥感中,光学浅水底部反射的贡献显著地改变了水体反射信号的强度与光谱分布,成为制约二类水体遥感反演精度的瓶颈问题之一.在分析光学浅水概念和内涵的基础上,从水底反射特性测量、水底二向反射特性(BRDF)与水底反射效应校正模型3个方面论述了国内外在水底反射校正研究方面的进展;指出了发展光学浅水区的提取算法、建立典型底质...     

确定断裂带特征的钻孔雷达

国际Stripa机构开发了一种新的短脉冲钻孔雷达系统(RAMAC)。RAMAC系统目前已应用了3年,在这段期间内完成的测量相当于测量了长度100km以上的钻孔。这些测量大部分是在花岗岩和片麻岩地层中进行的。RAMAC系统使用三种不同的测量排列形式:单孔反射模型、孔间反射模型、孔间层面模型。三种测量模型的数据解释技术也已得到了发展。如果同时分析三种形式的资料,正常情况下可勾绘出断裂带的连续三维模型和其它构造。     

地震资料在徐家围子断陷沙河子组潜在烃源岩预测中的应用

徐家围子勘探实践表明,沙河子组烃源岩的分布控制着烃类气藏的分布。通过比较各种勘探方法及在研究区的具体适用情况,以及在徐家围子断陷勘探程度和各种资料综合分析的基础上,确定以地震相法为主要预测方法。根据钻遇沙河子组地层的单井沉积相并结合井点地震反射特征,总结出4 类沙河子组潜在烃源岩的地震反射特征,并在全断陷对沙河子组的烃源岩品质进行整体评价。结合沙河子组地层厚度、有机碳指标、Ｒo 值、泥地比值和地震相特征等烃源岩品质评价的依据,将沙河子组烃源岩有利区划分为I 类区、II1 类区和II2 类区以及III 类区。     

时间域有限差分法在钻孔雷达探测金属矿中的应用

钻孔雷达相比传统的地球物理方法具有更大的探测范围,可得到更多的地层信息。在地质雷达正演模拟的方法中,时域有限差分法能提高探测的效果和解释的准确性。将两者相结合,通过单孔反射测量对金属矿进行数值模拟及对结果进行分析,说明了单孔反射测量不仅可以确定矿体的位置,而且对矿体形态也具有很好的识别性。     

Research and Application of Cosmic-ray Fast Neutron Method to Measure Soil Moisture in the Field

It is very difficult to measure large region soil moisture. In recent years, measurement of surface soil moisture by the cosmic ray fast neutron probe has gradually attracted more attention. By this passive, non-invasive and intermediate scale measurement, soil moisture at a horizontal scale of around 300 m can be observed, which makes this method available to fill the gap between little scale of traditional point measurement and large scale of remote sensing in the measurement of soil moisture. In this paper, Cosmic-ray Soil Moisture Observing System (COSMOS) and Wireless Sensor Network (WSN) were used to observe field soil moisture in Zhangye Oasis. The results of the COSMOS soil moisture well reflected the variation trend of soil moisture at the field scale. There were some regular changes with the cosmic ray soil moisture during the irrigation period. Combined with irrigation data in cosmic-ray probe footprint, a bimodal change was showed in the cosmic-ray soil moisture figure during irrigation period. This was because that the order of irrigation of the three communities was different in cosmic-ray probe footprint. WSN data were used to validate this result and we found that root-mean-square error between cosmic-ray soil moisture and SoilNET average soil moisture was very large during irrigation periods because of the impact of cosmic-ray measurement theory. While root-mean-square error would decrease from 0.037 m³/m³ to 0.028 m³/m³ after we eliminated the data in irrigation period. So COSMOS can be used to measure field soil moisture under high heterogeneity condition and provide truly ground data for the validation of remote sensing     

The generation of low-energy cosmic rays in molecular clouds

Arguments are presented in support of the idea that the total energy losses of cosmic rays passing through molecular clouds can exceed the energy production due to the action of shocks in supernovae. Galactic cosmic rays interacting with the surface layers of molecular clouds can be efficiently reflected, so that they do not penetrate into the depths of the clouds. Low-energy cosmic rays (E < 1 GeV) that can produce the primary ionization of the molecular-cloud gas can be generated inside such clouds by numerous shocks arising due to supersonic turbulence.     

Radio synchrotron emission by protons and electrons in pulsars and the nuclei of quasars

Relations enabling estimation of the limiting brightness temperature of synchrotron radiation subject to self-absorption and inverse Compton scattering are presented for the case of relativistic electrons (positrons) and protons. Analogous expressions are presented for relativistic particles moving along curved magnetic lines of force (curvature radiation) and coherent radiation by relativistic particles. These relations can be used to determine the brightness temperatures expected for the central regions of active galactic nuclei, neutron stars, and other objects that produce relativistic particles. Radiation by relativistic protons yields higher intensities, and could be a source of the highest-energy cosmic rays.     

Dependence of the neutron and gamma-ray emission of Mercury on its surface composition and temperature

Results of computations of the energy spectrum of neutrons radiated by the planet Mercury, generated by the action of cosmic rays, are presented. The dependence of the neutron radiation on both the temperature and composition of the subsurface layers of the planetary regolith are investigated. The fluxes of γ-rays in lines of aluminum (²⁷Al, 7.7240 MeV), silicon (²⁸Si, 3.5390 MeV), calcium (⁴⁰Ca, 1.9427 MeV), and iron (⁵⁶Fe, 7.6312 and 7.6456 MeV) generated during neutron capture by these nuclei are also calculated. The intensity of the radiation in these lines depends on both the composition and temperature of the surface. This must be taken into account when interpreting measurements of γ-ray radiation from nuclear lines produced in neutron capture reactions on the substance of Mercury.     

The spectrum of solar cosmic rays: Data of observations and numerical simulation

Analysis of the relativistic proton spectra of solar flares occurring in the 23rd solar activity cycle derived from data of a worldwide neutron monitor network and numerical modeling both provide evidence for the acceleration of charged particles by an electric field that arises in coronal current sheets during reconnection. The method used to obtain the spectra is based on simulating the response of a neutron monitor to an anisotropic flux of relativistic solar protons with specified parameters and determining the characteristics of the primary relativistic solar protons by fitting model responses to the observations. Studies of the dynamics of the energy spectra distinguish two populations of relativistic protons in solar cosmic-ray events: the so-called fast component, which arrives at the flux front of the solar cosmic rays, followed by the delayed slow component. The fast component is characterized by strong anisotropy and an exponential energy spectrum, in agreement with the spectrum yielded by mathematical modeling of particle acceleration by an electric field directed along the X line of the magnetic field. The slow component, whose propagation is probably diffusive, has a power-law spectrum.     

Mechanical transport of metallogenic materials in endogenic hydrothermal solutions: evidence from the microspherules in micro-disseminated gold deposits,northwestern Sichuan,China

Numerous steel-gray microspherules were recently unexpectedly discovered in ore and rock samples from several disseminated gold deposits hosted in Middle–Upper Triassic turbidites in northwestern Sichuan Province, China. Both nature surfaces and part sections of 227 microspherules have been observed by reflected light microscope, scanning electron microscope (SEM), electron microprobe analyses, X-ray energy spectra, X-ray powder patterns, the results reveal them to be cosmic dust. It is the first discovery of cosmic dust in this kind of deposits in China.The size of the microspherules ranges from 25 to 185 μm and generally is less than 100 μm. According to their composition, they belong to chromium-rich iron cosmic dust. The microspherules have complex, diverse and diagnostic microscope structures and textures, and such as very distinct airprint structure that are compatible with extraterrestrial material. Variation of geochemical content of the microspherules in the gold deposits in generally positively correlates with both the Ir content of the enclosing strata and the intensity of mineralization and hydrothermal alteration. The abnormally high content of Ir is important evidence for an extraterrestrial source for the microspherules. The fact that a geological body with strong alteration and mineralization is rich in microspherules may raise a new concept: Under endogenic conditions, it is not only possible but also realistic for mineralized material to be transported mechanically, in addition to the generally accepted chemical transport of ore constituents in hydrothermal solution because it is obviously impossible for cosmic spherules to fall directly from space into cemented hydrothermal ore veins more than 1 km deep in the earth.     

Dating of syngenetic ice wedges in permafrost with 36Cl

A new method of permafrost dating with the cosmogenic radionuclide ³⁶Cl is presented. In the first application, syngenetic ice wedges are dated using the ratio of ³⁶Cl and Cl concentrations in ice as the signal. ³⁶Cl is produced in the atmosphere by nuclear reactions of cosmic rays on argon. Stable chlorine enters the atmosphere from the oceans. Their ratio does not depend on chloride concentration in precipitations and on sublimation of snow. In situ production of ³⁶Cl in permafrost ice via cosmic ray-induced reactions and neutron capture are calculated and the dating age limit is estimated as 3 million years. ³⁶Cl/Cl ratios in permafrost samples from cape Svyatoy Nos (Laptev Sea coast), North-Eastern Siberia, are measured by accelerator mass spectrometry. Analysis of the first results and the calculated dates support the feasibility of the ³⁶Cl permafrost dating method     

Radionuclide depth profiles in Dhajala chondrite

Spallation produced radionuclides¹⁰Be,²²Na and²⁶Al and low energy neutron capture radionuclide⁶⁰Co have been measured in several fragments of the Dhajala chondrite, their shielding depth in space having been established by measurement of cosmic ray track density. These data enable us to obtain depth profiles of production rates of these nuclides within the meteoroid body. These profiles are discussed in terms of their dependence on size of the meteoroid and variations of galactic cosmic ray fluxes in time and space. The slowing down density of neutrons of 0.1 neutrons/cm³ sec is determined near the centre of the Dhajala meteoroid based on⁶⁰Co.