Suppressing stimulated Raman side-scattering with vector light

Recent observations of stimulated Raman side-scattering(SRSS)in different laser inertial confinement fusion ignition schemes have revealed that there is an underlying risk of SRSS on ignition.In this paper,we propose a method that uses the nonuniform nature of the polarization of vector light to suppress SRSS,and we give an additional threshold condition determined by the parameters of the vector light.For SRSS at 90°,where the scattered electromagnetic wave travels perpendicular to the density profile,the variation in polarization of the pump will change the wave vector of the scattered light,thereby reducing the growth length and preventing the scattered electromagnetic wave from growing.This suppression scheme is verified through three-dimensional particle-in-cell simulations.Our illustrative simulation results demonstrate that for linearly polarized Gaussian light,there is a strong SRSS signal in the 90°direction,whereas for vector light,there is very little SRSS signal,even when the conditions significantly exceed the threshold for SRSS.We also discuss the impact of vector light on stimulated Raman backscattering,collective stimulated Brillouin scattering and two-plasmon decay.

Critical tectonic events and their geological controls on deep buried coalbed methane accumulation in Daning-Jixian Block, eastern Ordos Basin

Commercial exploration and development of deep buried coalbed methane (CBM) in Daning-Jixian Block, eastern margin of Ordos Basin, have rapidly increased in recent decades. Gas content, saturation and well productivity show significant heterogeneity in this area. To better understand the geological controlling mechanism on gas distribution heterogeneity, the burial history, hydrocarbon generation history and tectonic evolution history were studied by numerical simulation and experimental simulation, which could provide guidance for further development of CBM in this area. The burial history of coal reservoir can be classified into six stages, i.e., shallowly buried stage, deeply burial stage, uplifting stage, short-term tectonic subsidence stage, large-scale uplifting stage, sustaining uplifting and structural inversion stage. The organic matter in coal reservoir experienced twice hydrocarbon generation. Primary and secondary hydrocarbon generation processes were formed by the Early and Middle Triassic plutonic metamorphism and Early Cretaceous regional magmatic thermal metamorphism, respectively. Five critical tectonic events of the Indosinian, Yanshanian and Himalayan orogenies affect different stages of the CBM reservoir accumulation process. The Indosinian orogeny mainly controls the primary CBM generation. The Yanshanian Orogeny dominates the second gas generation and migration processes. The Himalayan orogeny mainly affects the gas dissipation process and current CBM distribution heterogeneity.