Progress in octahedral spherical hohlraum study

In this paper,we give a review of our theoretical and experimental progress in octahedral spherical hohlraum study.From our theoretical study,the octahedral spherical hohlraums with 6 Laser Entrance Holes(LEHs)of octahedral symmetry have robust high symmetry during the capsule implosion at hohlraum-to-capsule radius ratio larger than 3.7.In addition,the octahedral spherical hohlraums also have potential superiority on low backscattering without supplementary technology.We studied the laser arrangement and constraints of the octahedral spherical hohlraums,and gave a design on the laser arrangement for ignition octahedral hohlraums.As a result,the injection angle of laser beams of 50°-60°was proposed as the optimum candidate range for the octahedral spherical hohlraums.We proposed a novel octahedral spherical hohlraum with cylindrical LEHs and LEH shields,in order to increase the laser coupling efficiency and improve the capsule symmetry and to mitigate the influence of the wall blowoff on laser transport.We studied on the sensitivity of the octahedral spherical hohlraums to random errors and compared the sensitivity among the octahedral spherical hohlraums,the rugby hohlraums and the cylindrical hohlraums,and the results show that the octahedral spherical hohlraums are robust to these random errors while the cylindrical hohlraums are the most sensitive.Up till to now,we have carried out three experiments on the spherical hohlraum with 2 LEHs on Shenguang(SG)laser facilities,including demonstration of improving laser transport by using the cylindrical LEHs in the spherical hohlraums,spherical hohlraum energetics on the SGIII prototype laser facility,and comparisons of laser plasma instabilities between the spherical hohlraums and the cylindrical hohlraums on the SGIII laser facility.

First experimental comparisons of laser-plasma interactions between spherical and cylindrical hohlraums at SGⅢ laser facility

We present our recent laser-plasmas instability(LPI)comparison experiment at the SGIII laser facility between the spherical and cylindrical hohlraums.Three kinds of filling are considered:vacuum,gas-filling with or without a capsule inside.A spherical hohlraum of 3.6 mm in diameter,and a cylindrical hohlraum of 2.4 mm?4.3 mm are used.The capsule diameter is 0.96 mm.A flat-top laser pulse with 3 ns duration and up to 92.73 kJ energy is used.The experiment has shown that the LPI level in the spherical hohlraum is close to that of the outer beam in the cylindrical hohlraum,while much lower than that of the inner beam.The experiment is further simulated by using our 2-dimensional radiation hydrodynamic code LARED-Integration,and the laser back-scattering fraction and the stimulated Raman scatter(SRS)spectrum are post-processed by the high efficiency code of laser interaction with plasmas HLIP.According to the simulation,the plasma waves are strongly damped and the SRS is mainly developed at the plasma conditions of electron density from 0.08 n_(c) to 0.1 n_(c) and electron temperature from 1.5 keV to 2.0 keV inside the hohlraums.However,obvious differences between the simulation and experiment are found,such as that the SRS back-scattering is underestimated,and the numerical SRS spectrum peaks at a larger wavelength and at a later time than the data.These dif-ferences indicate that the development of a 3D radiation hydrodynamic code,with more accurate physics models,is mandatory for spherical hohlraum study.

Progress in optical Thomson scattering diagnostics for ICF gas-filled hohlraums

Optical Thomson scattering(OTS)diagnostics have been continuously developed on a series of large laser facilities for inertial confinement fusion(ICF)research in China.We review recent progress in the use of OTS diagnostics to study the internal plasma conditions of ICF gas-filled hohlraums.We establish the predictive capability for experiments by calculating the time-resolved Thomson scattering spectra based on the 2D radiation-hydrodynamic code LARED,and we explore the fitting method for the measured spectra.A typical experiment with a simplified cylindrical hohlraum is conducted on a 10 kJ-level laser facility,and the plasma evolution around the laser entrance hole is analyzed.The dynamic effects of the blast wave from the covering membrane and the convergence of shocks on the hohlraum axis are observed,and the experimental results agree well with those of simulations.Another typical experiment with an octahedral spherical hohlraum is conducted on a 100 kJ-level laser facility,and the plasma evolution at the hohlraum center is analyzed.A discrepancy appears between experiment and simulation as the electron temperature rises,indicating the occurrence of nonlocal thermal conduction.

无创呼吸机联合药物治疗对重症哮喘患者疗效及肺功能的影响

目的探讨无创呼吸机联合药物治疗对重症哮喘患者疗效及肺功能的影响。方法选择2016年8月~2017年10月我院收治的重症哮喘患者102例,将其随机分为对照组和观察组,各51例。对照组给予常规药物治疗,观察组在对照组基础上给予无创呼吸机机械通气治疗。比较两组血气分析指标、肺功能指标。结果治疗后,两组血气分析指标及肺功能指标均优于治疗前,且观察组优于对照组,差异有统计学意义(P<0.05)。结论无创呼吸机联合物经治疗重症哮喘,能有效改善患者肺功能,降低CO_(2)潴留,值得临床推广。