Research On Numerical Simulation Method And Application Of Pulse Power Device Based On LTD

The Linear Transformer Driver(LTD),as an innovative pulse power technology,finds extensive application in various fields such as Z-pinch compression,flash photography,and high-power microwaves.With the advancement of technology and the development of key techniques,the pulse output potential of LTD has been further explored,enabling the construction of large-scale devices based on LTD pulse power technology.In recent years,LTD has gained significant attention from researchers in the field of pulse power sources,both domestically and internationally,due to its advantages of compact structure,flexible parameter adjustment,and high energy efficiency.It is poised to become the preferred technical route for the design of future high-current pulse drive devices.Therefore,full three-dimensional(3D)research on the numerical simulation and theoretical analysis of such devices is essential.Currently,the numerical simulation methods for LTD pulse power devices mainly include circuit simulation methods and Particle-In-Cell(PIC)methods.However,neither of these methods can fully simulate the entire device from circuits to electromagnetic fields to particles in 3D.In addition,there has been limited research on the effects of changes in the physical properties of device’s loads on pulse shaping.Dissertation aims to conduct comprehensive and in-depth research on circuits-electromagnetic fieldsparticles collaborative simulation of LTD pulse power devices,as well as related boundary algorithms.The developed algorithms are applied to simulate LTD pulse power devices.Additionally,combined with the Monte Carlo Collision(MCC)method,the impact of gas ionization in device’s loads on pulse shaping is studied.On this basis,the focus shifts towards the optimization simulation study of more complex LTD pulse power devic.The core research content of the dissertation covers the following aspects:1.In response to the absorption boundary model of the Finite-Difference TimeDomain(FDTD)algorithm of central difference is no longer applicable to the simulation of time-biased and high-quality factor FDTD algorithms,the reasons for inapplicability are analyzed firstly.Then Uniaxial-anisotropy Perfectly Matches Layer(UPML)absorption boundary models based on time-biased and high quality factor FDTD algorithms are developed respectively.The algorithm formulas of the two models in cartesian and cylindrical coordinates are derived in detail,and then implemented on the particle simulation software CHIPIC platform,and then the corresponding 3D models are constructed in cartesian and cylindrical coordinate to simulate and verify the two absorption boundary models.The results show that the relative reflection error of these two absorption boundary models is lower than-80 dB.Finally,the two absorption boundary models were loaded into the constructed high-power microwave devices,and the simulation study was carried out.The correctness and effectiveness of the two absorption boundary models were verified by comparing the simulation and experimental results,which laid a foundation for the subsequent simulation research of the LTD pulse power device.2.Developed a full 3D circuit-field-particle collaborative simulation algorithm for the LTD pulse power device.Based on the Modified node analysis method,a circuit simulation module is initially developed,and a 3D visual circuit modeling program was constructed.Subsequently,various circuits were simulated,and the effectiveness of this module was validated by comparing the simulation results with those of the internationally recognized circuit simulation software PSPICE.Based on this,research was conducted on the coupling of circuits,fields and particles,leading to the realization of a fully 3D collaborative simulation method for LTD pulse power devices from circuits to LTD cavities to loads.Subsequent preliminary validation of this method was conducted through simulations of relevant devices.Then,a 10-stage damping wave-type LTD pulse power device was constructed,and the results of circuit-field-particle collaborative simulations were consistent with experimental results when the magnetically insulated transmission line(MITL)operated in a self-limiting flow state.However,discrepancies between simulation and experimental results arose when the MITL operated in a loadlimited flow state,attributed to the influence of plasma diffusion on device measurement parameters.Nevertheless,when plasma was injected into the load at a rate of 0.004ml/ns,the simulation results matched experimental results,demonstrating the universal applicability of the collaborative simulation method.3.To investigate the impact of gas ionization in the load of LTD pulse power devices on pulse shaping,a collaborative simulation module capable of calculating gas ionization,combined with the Monte Carlo Collision(MCC)method,was developed.Using this module,simulations of LTD pulse power devices with gas ionization in the load were conducted.The research findings indicate that the plasma generated by gas ionization in the load can cause load short-circuiting and impedance mismatch,resulting in a reduction of pulse waveform width and changes in peak power.Additionally,the spatial charge effect of plasma disrupting electron beams alleviates the constraint of space charge,thereby resulting in an increase in electron beam current.4.A 6-stage rectangular wave-type LTD pulse power device was constructed,and the circuit-field-particle collaborative simulation was conducted.The results show that when the initial charging voltage of the intermediate capacitor in the Blumlein Pulse Forming Network(BPFN)circuit is 135 kV,the device’s foil-free diode load can achieve a half-height pulse width of 190 ns,a top width of approximately 80 ns,a voltage of about738 kV,a current of approximately 11.73 kA,and an output power of about 8.657 GW when impedance matched.The overall energy transfer efficiency of the device can reach75.81%;When the load is a flat diode,a pulse waveform with a half-height pulse width of 189 ns and a top width of about 80 ns can be obtained.The output voltage is approximately 738.4kV,the current is approximately 11.8kA,and the output power is approximately 8.69 GW,with the overall energy transmission efficiency of the device reaching over 75%.The experimental results are consistent with the simulation results.Additionally,the circuit-field-particle collaborative simulation method was used to simulate the magnetron driven by the pulse power source,and the simulation results were compared with those of the magnetron driven by the ideal fit waveform.The research demonstrate that the circuit-field-particle collaborative simulation can clearly reflect the mutual influence between the load and the pulse power source.5.To meet engineering requirements,a more complex 50-stage rectangular wavetype LTD pulse power device was constructed.Initially,the inherent relationship between additional inductance in the BPFN circuit and pulse waveform was simulated,enhancing understanding of the operating mechanism of the BPFN circuit.Subsequently,the device structure was optimized through separate simulations using the circuit-field and circuitfield-particle collaborative simulation methods,providing a reference for selecting device structure parameters in engineering.By comparing the two simulation results,the advantages of the circuit-field-particle collaborative simulation method in simulating load particle emission were elucidated.