Research On On-line Videometrics Measurement System For Thermal Deformation Of Ion Thruster Optics

The LIPS-300 ion thruster is a new high-power gridded ion thruster in China.Its accelerator device adopts a 30 cm diameter tri-grid ion optics.The test results show that the tri-grid ion optics can meet the performance requirements of the thruster.However,there are problems such as uncontrollable grid hot gap change in the operation,grid deformation,etc.,which increases the risk of thruster failure.Controlling the thermal deformation of the grid and maintaining the stability of the grid hot gap are the key issues to ensure the long-term operation of the ion thruster.To solve this problem,it is first necessary to make a precise measurement of the grid thermal deformation.Therefore,this paper has carried out research on the gird thermal deformation and hot gap measurement system of ion thruster,which is also the key direction in the research of optimization of ion thruster in China.The main work and innovations are as follows:1.Based on the principle of videometrics measurement,a non-contact thermal deformation measurement method suitable for double-grid and tri-grid ion optics is proposed.The two-dimensional videometrics measurement calibration algorithm is used to calibrate the image.The clear edge of multiple circular cooperation logos is obtained by interactive partitioning method,and the least square fitting is used to complete the subpixel level measurement.2.An on-line videometrics measurement system for thermal deformation of grid ion optics is established.The system hardware meets the requirements of stable operation under vacuum,high temperature and plasma environment.The software is developed by Matlab2017 b.Based on the measurement algorithm,the functions of image calibration,real-time measurement,offline measurement,measurement data display and output are integrated to meet the requirements of real-time measurement of grid thermal deformation.3.The maximum error of the system is derived from the thermal deformation of the probe itself.The system measurement accuracy calculated by the accuracy verification experiment is 6.0μm.Considering the influence of the thermal deformation of the probe and other error factors,the system measurement accuracy is corrected to 12.0μm.4.Four experiments of grid heating in atmospheric environment,and two under vacuum environment were carried out with the measurement system.The measurement results of the thermal deformation of the grids are compared with the similar experiments abroad.The characteristics and laws of the thermal deformation of the grids and the hot gap under different conditions are obtained.The feasibility of simulating the thermal deformation of the grids in vaccum by measuring in atmosphere is proposed.