LEBT Design Of Molecular Ion Research Facility

Heavy ion accelerator storage ring is a powerful tool for researching the molecular ion dissociative recombination, some laboratories have carried out the related research work. Due to the limitations of the magnetic rigidity, they merely carried on the study of the molecular ion that mass is less than70amu. The storage ring CSRe at the Institute of Modern Physics, can provide enough magnetic rigidity to carry out research on heavy ion of high mass charge ratio. A Molecular Ion Dissociative Recombination Research Facility (MIRF) program for higher-mass molecular ion research is proposing in Institute of Modern Physics, Chinese Academy of Sciences. The main work of this thesis is the design of The low energy beam transport system (LEBT) for MIRF.Based on the original structure of CSRe Lattice, the project require to design a separate molecular ion injection line to accelerate, transmit and inject into CSRe. The MIRF injection line is composed of the Low Energy Transport System (LEBT) and Middle Energy Transport System (MEBT) according to different energy. The MIRF-LEBT is mainly composed of150kV high-voltage accelerators, focusing elements and magnetic analysis system. Its auxiliary equipments include beam diagnosis components, vacuum system, cooling system and control system.The electric field distribution of the150kV voltage high-voltage accelerator is calculated by the Poisson/Superfish code.The simulation results indicates that the values of electric field of acceleration space were far lower than the value of breakdown electric field. The beam transmission process is simulated using Beampath code. The beam envelope reveals that the acceleration field has a strong focusing effect for the molecular ion beam which means beam spot size at accelerating tube exit is small.The simulation from Trace-3D shows that with the focus of the triplet, the molecular ion whose mass range between50～150amu can match to the entrance of the analysis magnets. In order to check the resolving power of the analysis system, we simulated the beam transport of different mass by the Beampath code. The simulation result shows that with the adjustable triplet in front of the analysis magnet, molecular ions of different mass-to-charge ratio will separate apparently.A second triplet is design to focus on beam and to transform phase space, because the Twiss parameters difference that the distinctive mass-to-charge ratio beam through the analysis system. The simulation shows that all kinds of beam can located within the acceptance of the RFQ. Finally, the thesis gives the detailed parameters of each component of MIRF-LEBT. which means the physical design of the low energy transmission system for CSRe Molecular Ion Research Facility has finished.