High reliability low jitter 80 kV pulse generator

Abstract

Switching can be considered to be the essence of pulsed power. Time accurate switch/trigger systems with low inductance are useful in many applications. This article describes a unique switch geometry coupled with a low-inductance capacitive energy store. The system provides a fast-rising high voltage pulse into a low impedance load. It can be challenging to generate high voltage (more than 50 kilovolts) into impedances less than $10\text{ }\text{ }\ensuremath{\Omega}$, from a low voltage control signal with a fast rise time and high temporal accuracy. The required power amplification is large, and is usually accomplished with multiple stages. The multiple stages can adversely affect the temporal accuracy and the reliability of the system. In the present application, a highly reliable and low jitter trigger generator was required for the $Z$ pulsed-power facility [M. E. Savage, L. F. Bennett, D. E. Bliss, W. T. Clark, R. S. Coats,J. M. Elizondo, K. R. LeChien, H. C. Harjes, J. M. Lehr, J. E. Maenchen, D. H. McDaniel, M. F. Pasik, T. D. Pointon, A. C. Owen, D. B. Seidel, D. L. Smith, B. S. Stoltzfus, K. W. Struve, W. A. Stygar, L. K. Warne, and J. R. Woodworth, 2007 IEEE Pulsed Power Conference, Albuquerque, NM (IEEE, Piscataway, NJ, 2007), p. 979]. The large investment in each $Z$ experiment demands low prefire probability and low jitter simultaneously. The system described here is based on a 100 kV DC-charged high-pressure spark gap, triggered with an ultraviolet laser. The system uses a single optical path for simultaneously triggering two parallel switches, allowing lower inductance and electrode erosion with a simple optical system. Performance of the system includes 6 ns output rise time into $5.6\text{ }\text{ }\ensuremath{\Omega}$, 550 ps one-sigma jitter measured from the 5 V trigger to the high voltage output, and misfire probability less than ${10}^{\ensuremath{-}4}$. The design of the system and some key measurements will be shown in the paper. We will discuss the design goals related to high reliability and low jitter. While reliability is usually important, and is coupled with jitter, reliability is seldom given more than a qualitative analysis (if any at all). We will show how reliability of the system was calculated, and results of a jitter-reliability tradeoff study. We will describe the behavior of sulfur hexafluoride as the insulating gas in the mildly nonuniform field geometry at pressures of 300 to 500 kPa. We will show the resistance of the arc channels, and show the performance comparisons with normal two-channel operation, and single channel operation.