Study On The Ion Beam Extraction And Transport In Residual Gases

Ion beam extraction and transport are important branches in the field of ion beam technologies.In order to meet some practical requirements of research and solve the problems encountered in the applications,we have carried out a number of experiments and simulation studies on ion beam extraction and transport in residual gases.In this thesis,We make a systematic description of these studies,mainly including the following contents:(1)Expanding the use of 358 dual-plasmatron ion source.In the early stage of a tandem accelerator,we first carried out a systematic research on the ion source to provide a good foundation for the follow-up research work.On the basis of a large number of practical operations,the standard operation method of ion source is summarized,especially the preparation of cathode filament coating and the switch of positive and negative ion extraction mode are described in detail.In addition,to expand ion species the ion source can provide,satisfying demands of more scientific research,we tested five kinds of working gas,namely,H2/D2/He/N2/Ar,successfully extracting beams for all gas.The relationship of beam currents and anode voltages with gas type,gas pressure,arc current,magnetic field intensity and cathode filament are summarized,obtaining the optimal parameters for different working gas.(2)PIC(particle in cell)simulation study on ion filtering by side extraction method.A simple and efficient beam extraction method for ion filtering in vacuum arc ion source is presented.In this method,ions are extracted from the direction perpendicular to the direction plasma jets,and the deviation of longitudinal displacement of different kinds of ions in the extraction path is used to achieve ion filtering.The simulation results show that the side extraction method can filter ions with different masses,charge states and initial energies.In addition,it is also found that the filtering effect can be adjusted by changing the aspect ratio of the extracting hole or changing the extracting distance to obtain the required ion beam.(3)Based on the advanced usage of SRIM(Stopping range of Ions in Matter)software,the quantitative evaluation of the influence of background gas on beam transport is realized.The method can customize beam parameters and target gas parameters,and Monte Carlo simulation of elastic collision and inelastic collision can obtain the energy distribution,beam distribution and beam phase diagram after the beam passes through the background gas,so as to evaluate the influence of background gas on beam quality intuitively and accurately.Using this method,the transport characteristics of protons and heavy ions in different background gases(H2/N2)were studied,the influence of residual gases on beam's energies spectra,profile,phase space distribution and transporting efficiency were analyzed quantificationally.(4)Charge-exchange reactions of H+,H2+and H3+at energies of 1-30 keV in sodium vapor were studied using the charge-exchange canal of a 2×1 MV tandem accelerator.Total attenuation cross sections of all the three species were acquired,among which,the data for H+agree well with the existing data and those for H2+,H3+were first measured.Besides,the yields of negative ions were also obtained.It appears that H+is most efficient to produce H-compared with H2+and H3+.(5)Primary research on ion beam analysis.Au films on Si substrate and Ar cluster implanted Si sample were analyzed with RBS.