Controller Design And Property Test For Radio Frequency Ion Source Used In Ion Beam Figuring

Ion beam figuring has been gradually developed into the last procedure of optical parts surface super-finishing,and ion source is the core part of the ion beam figuring tool.Today,the frequently-used ion source is the thermionic cathode direct current Kaufman ion source.Kaufman ion source has the problem of cathode consumption,cathode material pollution to the work-piece surface and bad compatibility with the reactive gas.Radio frequency(RF)ion source is a sort of alternating current ion source.Compared with the Kaufman ion source,it is simple and doesn't have the problem caused by cathode consumption mentioned before.Thus,this article will apply RF ion source on ion beam figuring machine,and do some performance tests.The major research efforts include the following points.1)The RF ion source's working principle and structure are discussed,and the RFion beam figuring machine is established.Distributed dispersed control method is used to design the controller for the RF ion source parameters,and the integrated control panel is established.A simple control and operation convenient RF ion beam figuring machine is built for the follow_up work.2)Performance tests are studied on the RF ion source.Firstly,the shape and value of removal function are tested by an experiment.This experiment finds out that the removal function of the RF ion source is Gauss type.Then,more experiments are done to discuss the short-term repeat-ability,long-term stability,material removal linearity and small disturbance robustness for the Gauss type removal function.3)The variation rules that the removal function changes with the major parameters of RF ion source are studied by experiments.The major parameters include beam voltage,RF power,target distance and ion source gas flow.The experiments focus on the peak removal efficiency,volume removal efficiency and full width at half maximum of removal function.According to the removal function's influence rule with each parameter,the optimized parameter selection range is provided for ion beam polishing.4)Optical processing test is performed on the RF ion source.The RF ion source is used in an ion beam polishing machine to process an ?100mm crystallize.The results show that the PV value of surface shape error degrades from 194.9nm to 24.6nm,and the RMS value degrades from 47 nm to 1.25 nm,the total convergence ratio comes to 37.6.It indicates that the RF ion source has the ability to be used in the optical surface nanometer precision polishing process.The results in this paper show that the RF ion source is stable and reliable,and has the ability to be used in the optical surface figuring process.