A distributed parameter model of transmission line transformer for high voltage nanosecond pulse generation

Abstract

A transmission line transformer has potential advantages for nanosecond pulse generation including excellent frequency response and no leakage inductance. The wave propagation process in a secondary mode line is indispensable due to an obvious inside transient electromagnetic transition in this scenario. The equivalent model of the transmission line transformer is crucial for predicting the output waveform and evaluating the effects of magnetic cores on output performance. However, traditional lumped parameter models are not sufficient for nanosecond pulse generation due to the natural neglect of wave propagations in secondary mode lines based on a lumped parameter assumption. In this paper, a distributed parameter model of transmission line transformer was established to investigate wave propagation in the secondary mode line and its influential factors through theoretical analysis and experimental verification. The wave propagation discontinuity in the secondary mode line induced by magnetic cores is emphasized. Characteristics of the magnetic core under a nanosecond pulse were obtained by experiments. Distribution and formation of the secondary mode current were determined for revealing essential wave propagation processes in secondary mode lines. The output waveform and efficiency were found to be affected dramatically by wave propagation discontinuity in secondary mode lines induced by magnetic cores. The proposed distributed parameter model was proved more suitable for nanosecond pulse generation in aspects of secondary mode current, output efficiency, and output waveform. In depth, comprehension of underlying mechanisms and a broader view of the working principle of the transmission line transformer for nanosecond pulse generation can be obtained through this research.

Dependence of nonlinear coupling among turbulence, geodesic acoustic modes and tearing modes on magnetic island width in the HL-2A edge plasmas

“…The typical discharge waveforms and magnetic configurations are shown in figure 2 for two different MI widths of W ≈ 6.2 cm and W ≈ 2.8 cm. The flux surfaces and safety factor (q) profiles are calculated by the equilibrium and reconstruction fitting code while the density profiles are reconstructed from the hydrogen cyanide formic acid (HCOOH) laser interferometer [38] measurements through Abel inversion method. It is clearly shown in figures 2(c) and (d) that the electron density profiles and the magnetic flux surfaces have rather small difference for the two discharges, whereas the difference in q profiles are suggested to be resulted from the changes in the plasma current, i.e., the lower plasma current the higher safety factor.…”

Repetitively pulsed gas discharges: memory effect and discharge mode transition

“…In contrast to the traditional scenario where a spark is ultimately maintained in the high‐frequency repetitive pulsed discharge, we have provisionally discovered a periodical discharge mode transition sustained by long‐term repetitive 20 kV 15 ns voltage pulses (0.1 MPa nitrogen and no gas flow). The repetitive nanosecond pulses were produced based on a hybrid pulse combined topology [85, 86]. In 5 mm cone–cone and cone–plate configurations, the discharge mode experienced a periodical transition at 5–10 kHz excitation rate, i.e.…”

Evolution of streamer dynamics and discharge mode transition in high-pressure nitrogen under long-term repetitive nanosecond pulses with different timescales

“…The amplitude deviation in a pulse train was approximately 2%. The type-II short-width RNP generator (15 ns in pulse width) was based on a unique hybrid pulse combining topology [37,38], consisting of the avalanche transistor Marx circuit bank, transmission line transformer, and high-frequency magnetic cores. The output negative voltage of the type-II RNP generator was of the maximum amplitude of 25 kV, the rise time of 10 ns, the pulse width of 15 ns.…”