Low jitter, low inductance solid dielectric switches.
It has been shown that the use of graded solid dielectric sandwiches in laser-triggered spark gaps (LTS) can lead to highly desirable multichannel operations while maintaining the low delay and jitter performance characteristics of LTS. As many as ten separate breakdown channels were observed when small circular or hexagonal aluminum inserts were inserted between two Mylar dielectric sheets stressed at 4.1 kV/mil. A reduction in rise time was noted for these multichannel switching events.
Laser-Triggered Solid Dielectric Switching
A Q-switched ruby laser was used to initiate breakdown in solid dielectric switches with a jitter of less than 3 ns. "Lexan" polycarbonate in thickness from 40 to 80 mils withstood applied voltage pulses (less than 1 ?s duration) of up to 400 kV. Laser pulse energy of less than 1 joule was sufficient to initiate breakdown in the solid dielectric. A focusing lens and the switch container were immersed in a grading solution of copper sulfate and water. Command triggering down to 50% of the dielectric's self break voltage was demonstrated. A test system employing a miniature Marx generator, and a high energy system switching 150 kA at 400 kV to form precisely timed relativistic electron beams, are described.
Geomagnetic Polarity Epochs: Sierra Nevada Data, 3
Available paleomagnetic and radiometric results for about 60 igneous rocks 3.6 m.y. old or less are consistent with the following geomagnetic polarity epoch time scale: Brunhes normal polarity epoch, 0.0 to 0.85±0.15 million years; Matuyama reversed polarity epoch, 0.85±0.15 to 2.4±0.1 million years; Gauss normal polarity epoch, 2.4±0.1 to 3.35±0.1 million years; Gilbert reversed polarity epoch, 3.35±0.1 million years to (?). A brief interval of normal polarity (the Olduvai event) occurs within the Matuyama reversed epoch at about 1.9 m.y., and a brief interval of reversed polarity (the Mammoth event) occurs within the Gauss normal epoch at about 3.06 m.y. Data for twelve units from eastern California and Nevada, reported here for the first time, are particularly useful in defining the Gauss-Gilbert boundary and for recognizing the Mammoth event.