We provide here an update on the status of ferratron development. The ferratron is a high-voltage, fast risetime, gas switch with low-jitter and high repetition rate. It is triggered by the emission of electrons from a ferroelectric device. It may be suitable for phased arrays due to it's low jitter. We have designed and built a test chamber for measuring the output of the ferratron. The test chamber is designed to launch a fast-risetime wave into an electrically large coaxial structure.
Jane Lehr, Sean Ahern, Michael Abdalla, Mike Skipper, Samuel Romero, John Gaudet, Jeffrey Burger, Jon Hull, Fred Gruner, Brett Cockerham, C. Jerald Buchenauer
Fast rising, high-voltage, low jitter trigger pulses have been in high demand for a variety of applications. A recent application required triggering a compact Marx generator with very low trigger jitter. The lateral gallium arsenide photoconductive semiconductor switch (PCSS) being developed at the Air Force Research Laboratory (AFRL) has been implemented in this application. PCSS technology is an attractive solution because of the very low trigger jitter, high voltage switching capability and inherent trigger isolation properties. The PCSS has been packaged into an integrated unit for triggering a Marx generator. The Photoconductive Trigger Generator (PTG-30) requires external 24 VDC, TTL trigger and pressurized insulating gas for operation. Performance characteristics of the PTG-30 are variable output voltage from 5 to 13 kV, in four discrete steps. At maximum output voltage, the pulse risetime is approximately 350 pS. The high-voltage output pulse has an average of 22 ps rms temporal switching jitter with respect to a fast-rising trigger signal. The PTG-30 incorporates all required support components internal to the unit, including: laser diode and driver assembly, solid state FET-based pulse modulator, high-voltage DC to DC converter, and a pulse forming line. The versatility of this unit also allows for direct connection to a variety of antennas and other loads. This paper will discuss the manufacture and performance characteristics of the PTG-30 as well as experimental results from triggering a coaxial Marx generator.
KEYWORDS: Switches, Ceramics, Dielectrics, Picosecond phenomena, Electrodes, Prototyping, Resistors, Directed energy weapons, High power microwaves, Analytical research
Low jitter, triggered spark gap switches are highly desirable components for a wide variety of High Power Microwave applications. In particular, this switch enables a wide range of new applications ranging from protection circuitry to high power transient arrays that are currently technically infeasible with the considerable jitter associated with high power switches. The device presently under advanced development is a novel triggering scheme using a ferroelectric ceramic as the electron source coupled with a high gas flow rate which allows reliable triggering at low trigger voltages, even at high repetition rates. The switch chamber is tailored to reduce field stresses and provide a low inductance current path with a very compact geometry. The high gas flow rate allows the replacement of the gas in the discharge region within the time scale necessary to sustain the required repetition rates of up to 1000 Hz.
High Power Impulse generation depends strongly on both the voltage and the rate of voltage rise which is applied to the radiating structure. Thus, placing the peaking switch at the apex of the antenna optimizes the transient radiating system. Liquids are prime candidates for the peaking switch media because of their high dielectric strength and its compatibility with lensing structures.
The generation of Ultra-Wide Band Pulses nanoseconds is a challenging problem that involves generating pulses with 100 pico-second rise times and voltage of 500 kV with pulse widths of the order of less than one to a few nanoseconds. A critical step involves switching high voltages with precision. The use of both gas and oil for the switching insulating medium have been accomplished with varying results. The Phillips Laboratory is pursuing both media in the gas switched Hindenburg series of pulsers and in the study of oil switches that promise good performance in compact packages. This paper reports on progress in gas switching associated with the new H-5 pulser and with the use of earlier Hindenburg pulsers to investigate the UWB properties of oil switches. We compare the design strategies and techniques of oil and gas switching in the context of pulsers of interest.
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