https://aip.scitation.org/doi/pdf/10.1016/j.mre.2017.05.002

Conceptual design of a 15-TW pulsed-power accelerator for high-energy-density–physics experiments

A multigaps gas switch (MGS) with corona discharge for voltage balance is developed. The self-breakdown characteristics of the switch under different gas pressures and the volt-ampere characteristics of corona discharge are studied. The experiment results show that to increase the shot times can improve the self-breakdown voltage stability of the switch. After conditioning the switch self-breakdown voltage relative standard deviation is less than 2%, the voltage balance has a good effect; the volt-ampere characteristics of multigaps corona discharge is similar to single gap. The delay time and jitter of the MGS with corona discharge for voltage balance in different conditions have been tested. The trigger stability is fine when switch charging at ±100 kV.

Characteristics Study of Multigaps Gas Switch With Corona Discharge for Voltage Balance

A whole circuit model of a linear transformer drivers (LTD) module composed of 60 cavities in series was developed in the software PSPICE to study the influence of switching jitter on the operational performances of LTDs. In the model, each brick in each cavity is capable of operating with jitter in its switch. Additionally, the manner of triggering cables entering into cavities was considered. The performances of the LTD module operating with three typical cavity-triggering sequences were simulated and the simulation results indicate that switching jitter affects slightly the peak and starting time of the output current pulse. However, the enhancement in switching jitter would significantly lengthen the rise time of the output current pulse. Without considering other factors, a jitter lower than 10 ns may be necessary for the switches in the LTD module to provide output current parameters with an acceptable deviation.

https://iopscience.iop.org/article/10.1088/1009-0630/14/4/15/pdf

Influences of Switching Jitter on the Operational Performances of Linear Transformer Drivers-Based Drivers

As one of the critical elements of fast linear transformer driver (FLTD), gas switch directly influences the output parameters, stability, and reliability of generators based on FLTD technology. In this paper, a multigap gas switch with six gaps in series has been investigated to study the proper firing conditions to get better performance for FLTD. The self-breakdown voltage with different gas pressure has been studied to derive the working ratio of the switch. The triggered breakdown delay and jitter with different charge voltage, gas pressure, and working ratio have been studied. The results indicate that when the switch is triggered by a 100-kV trigger voltage pulse under 180-kV charge voltage and 0.325-MPa pure nitrogen (70% working ratio), the delay time and the jitter are 34 and 1 ns, respectively.

Study on Firing Conditions of Multigap Gas Switch for Fast Linear Transformer Driver

This paper explores the feasibility of improving the load current parameters by optimizing the cavity-triggering sequences for a linear transformer driver (LTD) module with 60 cavities connected in series. The mechanism behind this was analyzed. The results demonstrate that it is necessary for the improvement in the output parameters of the LTD to postpone the closure of the switches in the cavities later than the arrival of the electromagnetic pulse propagating downstream. However, this requires the switches to withstand pulsed voltages higher than their charge voltage before closing. When the LTD switches withstood a pulsed voltage peak of about 400 kV for several tens of nanoseconds before closing, the LTD module could generate a current pulse with a rise time of 12.5 ns and a peak of 1340 kA on the matched load.

Effect of Cavity-Triggering Sequences on Output Parameters of LTD-Based Drivers

Sandia National Laboratories is investigating linear transformer driver (LTD) architecture as a potential replacement of conventional Marx generator based pulsed power systems. Such systems have traditionally been utilized as the primary driver for z-pinch wire-array experiments, radiography, inertial fusion energy (IFE) concepts, and dynamic materials experiments (i.e. ICE).

A 1-MV, 1-MA, 0.1-Hz linear transformer driver utilizing an internal water transmission line

Experiments have demonstrated high-power amplification (100 MW class) from a traveling wave amplifier driven by a modulated electron beam. The modulated electron beam is generated by applying a modulated voltage pulse from a nonlinear transmission line (NLTL) to the cathode of the electron gun. The system showed that over the designed operating range of the disk-on-rod (DoR) TWT amplifier (1.2–1.4 GHz), the peak frequency of the amplifier output tracked the peak frequency of the NLTL to within ±2%; however, the output was not phase stable. Measured RF energy gain for this frequency regime ranged from 1.5 at 1.2 GHz up to 5.0 at 1.4 GHz).

T. Montoya

Papers

A 1-MV, 1-MA, 0.1-Hz linear transformer driver utilizing an internal water transmission line

Experiments on a Disk-on-Rod Traveling Wave Tube Amplifier Driven by a Nonlinear Transmission Line Modulated Electron Beam