J. W. Walter

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We are fabricating and testing several different types of cathodes for the same vircator driven by a single shot Marx generator and pulse forming line (300 kV, 60 ns, 30 Omega). The cathodes types, each with an emitting area of ~32 cm<sup>2</sup>, include the original velvet with a new geometry, carbon fiber, pin-array, and an array of all metal cathodes.(More)
The high-power-microwave (HPM) sources currently under development typically require constant pumping to maintain the high vacuum levels required for operation. This pumping is often done with either a cryo- or turbopumping system, either of which would be difficult to deploy in a compact portable system. A compact sealed-tube virtual cathode oscillator(More)
Many high-power electron devices utilize cold-cathode diodes to generate intense electron beams. These cold cathodes have the advantage of being capable of supplying several kiloamperes of current spread over a large cross section without the need for auxiliary components such as a heater supply. However, they suffer from many known problems such as(More)
An inexpensive and mobile array of Pulsed Ring Down Sources (PRDS) were required to verify previous simulation results. Initial attempts to use a stacked MosFET circuit as a closing switch were unsuccessful due to the additional series inductance of the MosFET stack lowering the frequency of the oscillation on the coaxial radiator. Experimental results(More)
Summary form only given.Recent attention to impulse antenna phased array has necessitated the need to develop a reliable high voltage, high repetition rate switch that will operate with ultra low jitter. An ideal jitter of a small fraction of the rise time is required to accurately synchronize the array to steer and preserve the rise time of the radiated(More)
Summary form only given. High-power transient RF transmitters are currently being developed for multiple applications. One potential high- power pulsed source being considered is the pulsed ring- down source (PRDS). In a typical PRDS, electrical energy that is stored in the device structure is discharged through a switch, generating a damped ringing(More)
Recent attention to impulse antenna phased array has necessitated the need to develop a reliable high-voltage high-repetition-rate switch that will operate with ultralow jitter. An ideal jitter of a small fraction of the rise time is required to accurately synchronize the array to steer and preserve the rise time of the radiated pulse. This paper presents(More)
This paper presents a study on gas evolution of three different anode materials in vacuum sealed tubes under UHV conditions. The experimental apparatus consists of a high-power microwave (HPM) virtual-cathode oscillator (vircator) driven by a 200 ns, 80 J, 225 kV low-impedance Marx Generator. Plasma expansion due to explosive electron field emission has(More)
An explosively driven High Power Microwave (HPM) source has been developed that is based on the use of a Flux Compression Generator (FCG) as the primary driver. Four main components comprise the HPM system, and include a capacitor-based seed energy source, a dual-staged FCG, a power conditioning unit and an HPM diode (reflex-triode vircator). Volume(More)
Current research at Texas Tech University is focused on the development of a High-Power Pulsed Ring-Down Source (PRDS) Antenna Array. Previously, a Monte Carlo based analysis was conducted in order to predict the array performance based upon the estimated switching jitter between elements [1]. This analysis showed good performance for jitter times between 0(More)