Design And Development Of The Theta-pinch Power System For HFRC

Field-reversed Configuration(FRC)has the advantages of complete axis symmetry,relatively simple structure,β～1 and so on.Therefore,it is of great significance for the research of new fusion configuration,and the future exploration of miniaturization and economicization of the fusion reactors.With the support of the National Key R&D Program and supporting funds from Hubei Province,the research team is developing a pre-research platform for field-reversed configuration research device based on plasma’s colliding and merging,named Hust FieldReversed Configuration(HFRC).The device is mainly divided in plasma formation area and collision fusion and compression area.In HFRC,the theta-pinch power system,which is used to provide current for the theta-pinch coils,is an important part for the plasma formation area.The paper mainly introduces the development of the theta-pinch power system for HFRC.Currently,the diameter of the HFRC formation chamber is designed to be 0.6m.To achieve higher initial plasma parameters,which is expected to achieve a magnetic field with a oscillating frequency of 150 k Hz and a peak value of 0.5 T in the Main period,the requied peak parameters of the theta-pinch power is close to 80 k V/k A.In addition,the formation of the FRC plasma is a high-speed dynamic process.In order to have a better controlling of the plasma’s formation and injection,the discharge adjustment of the power needs to be controlled within 1μs.Therefore,the power requires capabilities of high voltage,large current,and high precision discharging control at the same time.And this brings great challenges to the development of the theta-pinch power system.In the main design part of the theta-pinch power system,according to the physical background and experimental requirements of the field-reversed configuration,the conceptual topology of the theta-pinch power is determined.18 theta-pinch coils are used to reduce the output current of each set of the power to the order of 70 k A.And by the means of theoretical derivation and Simulink simulation,the feasibility of the power design is verified.According to the high-voltage operation characteristics of the power supply,the topology is optimized,and two optimization solutions are analyzed and compared with the help of simulation.Finally,the power supply is decided that two power modules connected in series and their connection point is grounded,which effectively reduces both the withstand voltage of the power module and the power system voltage to ground(<50k V),improving the reliability of the power supply.The 40 k V/70 k A prototype design of the theta-pinch power supply is completed,including high voltage pulse capacitor selection,capacitor charging design,high voltage coxial cable selection,and the power supply frame design.In the design part of power supply control,combined with the high-voltage and highcurrent operating environment and high-precision discharge control requirements of the power supply,TDI series hydrogen thyratrons are adopted as the high-voltage switches.And a corresponding trigger circuit for thyratrons with submicrosecond control accuracy is designed according to the switching characteristics.The trigger circuit of the hydrogen thyratron,including the main trigger circuit based on IGBT and the heating circuit based on TRIAC,is able to achieve a heating voltage of 4～11 V and a trigger voltage of up to 8 k V.Simultaneously,the key components seletion of the trigger circuit and the integration design are completed.In the end of the paper,the research on the trigger experiment of high voltage pulse switch is explored.First,the key component tests of the main trigger circuit is carried out,including IGBT current sharing test and the withstand voltage test of the pulse transformer.The test results show that the parallel IGBTs can be well triggered simultaneously with good current sharing effect,and the withstand voltage of the pulse transformer can reach more than 18 k V.Secondly,an experimental platform for hydrogen thyratron trigger test is developed.The architecture of the platform and the experimental test related processes are designed.And finally,the experimental data of the high-voltage pulse switch tigger test is analyzed.It is found that the designed trigger circuit can successfully and continuously implement the hydrogen thyratron trigger.The breakdown delay time is proved less than 1 μs,with a jitter time within 300 ns,which achieves a well-controlled precise switching.