Research On Retarding Field Analyzer In KMAX Device And Design Of Dust Accelerator System

KMAX is a new tandem magnetic mirror device located at the University of Science and Technology of China(USTC),on which the dissertation was performed.The studies include:(1)fabrication and operation of optical diagnosis and retarding field analyzer,(2)Development of a high voltage DC power supply used for dust accelerator,and(3)design,processing and testing of low-energy dust source system.As a versatile plasma research platform,KMAX is carrying out different experiments,among which ion cyclotron resonance heating(ICRH)and field-reversed configuration(FRC)are two major topics.To measure the plasma parameters,electrostatic probes,Mach probes,APD optical diagnostic system,retarding field analyzers and interferometer system have been successively installed.Among them,the retarding field analyzer(RFA)is mainly used for Ti measurement.In this dissertation we found that the greater the total transmission of the grids is,the higher the accuracy of parameters obtained by the RFA,and the total transmission is closely related to the grids structure.A three-dimensional model based on the physical environment of KMAX device was established for the RFA based on the finite element software COMSOL,and the relationship between the total transmittance and lens effect of the grids structure,the grids shape,the grids distribution,and the ion incidence angle was studied.Lens effects have different effect on different energy ion beams.The grid shape,the optical transmission rate of the single grid,and the distribution of grids entirely affect the total transmittance.The effective incident angle range is 00-100.These simulation results are valuable for the RFA design.In the application of RFA,the capacitance effect becomes severe at fast sweep,and it is found that a shot-by-shot voltage scan is more practical.As for the dust accelerator,the purpose is to inject a high speed dust into a magnetized plasma and acquire the magnetic pitch angle by measuring the direction of the dust tail.Its essential component is high voltage power supply.The cascade voltage multiplier DC power supply has the advantages of compact structure,small size and strong portability.For the Cockcroft-Walton voltage multiplier circuit,the feasibility and optimization of the circuit scheme were firstly verified by theoretical calculation and Simulink simulation.Then a COMSOL simulation is used to verify the design of power structure.Finally a 120kV power supply was successfully built by a new insulating material,and a new type of measurement of voltage above 100kV Was independently proposed.The greatest challenge of the dust accelerator system is how to feed the high voltage into electron inside a vacuum chamber while maintain the chamber in a high vacuum condition.The experiment shows that the optimized dust source has effectively solved this problem.Preliminary experiments show that the dust accelerator system operating at low voltage can achieve dust charging and accelerations.Finally,the principle of electrostatic induction method for charged dust measurement was also reported,which should be instrumental to the next experiment.