Fundamental Research On Preparation Technology Of Quick - Firing Cone Shell Target

Fast ignition (FI), proposed by M. Tabak at1994, is a potential ignition concept in inertial confinement fusion (ICF). Unlike the conventional approach (central hot spot ignition) where the same laser is used for compression and ignition, in fast ignition separate laser beams are used. Fusion fuel is precompressed by a ns laser, and then the ignition hot spot is created by a ultra-intense source. The FI have substantial advantage over conventional central hot spot ignition:lower ignition threshold, higher energy gain, and lower susceptibility to compress symmetric. To reduce the physical risks caused by the laser-plasmas interaction, cone-shell target is common used in FI experiments. The precision of cone-shell target is dependent on the quality of core on the polymer shell. The different core-drilling methods: ferro-second laser maching and single point diamond maching, are introduced in the paper. We want to solve some fundamental problems to influence the quality of cores drilled on the polymer shells. The research content reads as follows:Interaction between fs laser with polystyrene (PS), deuterated polystyrene (DPS) and gas discharge polymer (GDP) are investigated. The ablation of fs laser on PS and DPS are consistent with the threshold model. The ablation threshold and accumulation time of DPS are higher than those of PS. The ablation of fs laser on GDP is different to the threshold model. The area and morphology of ablation region are influenced by the energy and number of laser pulse. The cone shell mounting holes could be machined utilizing circularly polarized femtosecond laser and combining with the online visual sighting system. The holes own good circular degree, and its positional deviation is less than10μm. However, the spatial distribution of the focused beam will result in the subulate section of cone shell mounting holes. Therefore, a method to reduce obliquity through multiple scan was proposed, and its validity was confirmed.Different with traditional metal material, the polymer exhibit totally different processing characteristics in diamond turning process. Therefore, it’s difficult to directly obtain desired surface quality (i.e. surface roughness) when processing the polymer with the parameters for metal material machining. The technological parameters in diamond turning polymer (taking polystyrene for example) is optimized in the paper. The quadratic regression orthogonal rotation method is adopted for orthogonal experiment design, in which the spindle speed, feeding velocity and cutting depth are parameters, and the machined surface roughness is evaluating criterion. The machining experiments are carried out on ultra-precision machine to obtain the optimal technological parameters in diamond turning polystyrene. Then, the diamond turning technique of polymer materials is studied. In the diamond turning of micro hole on fast ignition capsule, the key technologies are analyzed in details, such as diamond tool trajectory optimization, special diamond tool design and high precision clamping etc. The diamond turning process of polymer material is established initially.Taking deuterated polystyrene (DPS) material as the research object, which is commonly used in laser fusion target, the molecular dynamics simulation method is adopted for the nano-machining process study based on microprobe. First of all, the molecular dynamics models of DPS material and DPS machining process are established. Secondly, the deformation of DPS material in nano-machining is studied. The deformations of DPS material both in indentation stage and cutting stage are revealed. Ultimately, the impact of different factors on the nano-machining process of DPS material is studied, in which the cutting speed, phenyl arrangement and chain length are selected for research. Theresults help to reveal the deformation and movement of DPS samples under different influencing factors.Based on the investigation, the methods of pore-drilling on polymer shells are established. The dependence of pore quality on the parameters and mechanism of nano-machining on polymer are discussed. The polymer shells with high-quality pore are produced.