Efficient Simulation Of Three Dimensional Response For Marine Controlled Source Electromagnetic Measurement And Positronium Formation For Positron Scattering From Metastable Hydrogen

The research content of this thesis mainly involves two aspects,the first part is how to efficiently solve the three-dimensional response of the marine controlled source electromagnetic method(MCSEM)in the Marine environment with the axisymmetric conductivity distribution;the other part isaboutthe application of continuous distorted wave method to investigate the positronium formation process in positron scattering from metastable hydrogen atom.These two parts were briefly introduced as follows.The first part: the efficient numerical simulation of three-dimensional MCSEM rseponsesMCSEM is an effective method for reservoir evaluation before drilling.Itis mainly used to identify underwater structure,and storage/the aquifer characteristics in order to reduce blind drilling rate and exploration cost.Therefore,it has become a very important research subject in current geophysics.Its data processing and interpretation,however,is often involved with three dimensional numerical simulation and inversion imaging problems of electromagnetic fields.The practical calculation workload is usually very large,and severely limits the wide MCSEM application.During process of MCSEM data processing and inversion imaging,complex geological bodies such as basalt rock,oil and gas trap structure and the bedrock uplift etc.are usually simplified as abnormal bodies with the axisymmetric electrical conductivity distributionin order to attempt increase of the efficiency of data process and reduction of the nonuniqueness.In order to realize genuinely efficient numerical modeling of MCSEM responses in the case of the axisymmetric electrical conductivity distribution,in this paper,the the scatters are approximated by one or several horizontal concentric disks with different sizes of radius and thickness,based on the axially symmetrical spatial distribution of conductivity.Then,a combination of these concentric disks with air,sea water and surrounding beds will construct a horizontally stratified inhomogeneous formation with common axi-center,whose conductivity spatial distribution is layered in vertical direction and axisymmetric in horizontal direction.Based on the approximations mentioned above,thecomputation of marine controlled source electromagnetic(MCSEM)response excited by horizontal electrical dipole(HED)located at the z-axis in the formationis entirely transformed into two axially symmetrical problems on the Fourier harmonic components of the EM fields.The differential operators about the horizontal magnetic components and transformation of horizontal electrical components and EM other components from horizontal magnetic components are derived.Then,the numerical mode matching(NMM)approach is extended to simulate the electromagnetic(EM)field and 3D MCSEM responses excited by the HED in the formation.The procedure for solving the EM field is offered.The semianalytic solution of EM field in the whole space is obtained to efficiently numerically model MCSEM response in the complex formation.Finally,Numerical results have demonstrated the efficiency and accuracy of this method.Thecharacteristics of 3D MCSEM responses in three different cases are further investigated.The second part: continuous distorted wave method for positronium formation in positronscattering from metastable hydrogen atomPositronium(Ps)formation in positron scattering from atom is one of the most important charge transfer process in atomic scattering researches.The incident positron capturesone of the target electron in scattering reactions and forms a hydrogen-like Ps atom in the exit channel.In this work,we applied the continuum distorted wave method to investigate the Ps formation process in positron scattering from hydrogen in metastable 2s state.We fundamentally present the derivation of the two-channel,two-center eikonal final state-continuum initial distorted wave(EFS-CDW)method in detail and then apply it to calculate the differential,integrated,and total Ps formation cross sections from each channel opening thresholds to high energy region.Our results are compared with other theoretical calculations available in the literature.For Ps formation in s-state at intermediate and high energies,our results are in good agreement with the prediction of distorted wave theory.Those for p-states and the total Ps formation cross sections obtained by using the scaling law are reported for the first time.It is shown that the total Ps formation cross sections for positron scattering from H(2s)state are significantly larger at relatively low energies,while smaller at high energies,compared with those obtained for hydrogen in ground state.