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Experimental Characterization of a Genetic Algorithm-Optimized Nonlinear Transmission Line for High Power RF Generation
J. Stephens;T. Wright;D. Saheb;L. Silvestre;W. Hendricks;N. Black;J. Mankowski;J. Dickens;A. Neuber;E. Schrock;J. Schrock
A numerical model of a dispersive, discrete-element nonlinear transmission line (NLTL) employing saturable inductors is reported and demonstrated to qualitatively reproduce the experimentally measured output of an NLTL. This numerical model is used with a genetic algorithm (GA) to optimize RF output power by varying the number of turns on each inductor at each stage and capacitance at each stage o...Show More
Characterization of Solid-State Nonlinear Transmission Line PCB for RF Production
Travis Wright;David Saheb;Jacob Hoebelheinrich;John Mankowski;James Dickens;Andreas Neuber;Emily Schrock;James Schrock;Jacob Stephens
A discrete-element, printed circuit board (PCB)-based nonlinear transmission line was investigated to characterize its RF output characteristics for varying dc bias current and input pulse voltage. The device demonstrated both forward-wave and backward-wave RF formation, with each mode of operation exhibiting RF frequency and power characteristics. The forward-wave operational mode yielded a wider...Show More
Benchmarking the Suitability of Novec™ 4710 for Application in Flux Compression Generators
Nathan Fryar;Kirk Schriner;Jacob Stephens;James Dickens;Andrew Young;Andreas A. Neuber
An experimental study evaluated the feasibility of replacing traditional insulating gases such as SF6 with C4F7N (3M, Novec 4710) in flux compression generator (FCG) applications. Currently available data indicate that Novec 4710 could offer certain performance benefits over SF6. However, the available literature is focused on low frequency (50–60 Hz) and dc at static pressures. To evaluate the pe...Show More
Effect of Approach Speed and Electrode Geometry on Electrostatic Discharges Off Floating Dielectrics
B. Esser;Z. Cardenas;J. T. Mockert;J. C. Stephens;J. C. Dickens;J. J. Mankowski;A. A. Neuber;D. Friesen;D. Hattz;C. Nelson
With the damaging effects of electrostatic discharges (ESDs), it is important to study them within various parameter regimes relevant to real-world scenarios. One such scenario studied here is a floating dielectric with no nearby ground plane with a grounded object approaching at a high rate of speed. One may encounter this scenario when moving objects by hand. Discharge current and radiated field...Show More
Investigation of Multipactor in X-Band Waveguide Filters
D. Wright;A. Gregory;H. Spencer;J. Mankowski;J. Stephens;J. Dickens;A. Neuber
2023 IEEE International Conference on Plasma Science (ICOPS)
Year: 2023 | Conference Paper |
The increased need for multi-carrier signals and higher power requirements has made it essential to study the multipactor (MP) phenomenon in practical structures. A 3-stage rectangular waveguide filter has been designed and implemented in a plug-and-play test fixture for X-band frequencies. The test source for this system is a coaxial magnetron, which yields a peak power output of 150 kW at a freq...Show More
Progress Understanding Anode-Initiated Vacuum Insulator Flashover
M. Hopkin;W. Brooks;R. Clark;J. Dickens;Z. Echo;R. Goeke;J. Mankowski;C. Moore;A. Neuber;J. Stephens
2023 IEEE International Conference on Plasma Science (ICOPS)
Year: 2023 | Conference Paper |
There is often a dielectric separation barrier between vacuum and water-containing (or oil-containing) sections in pulsed power systems. This barrier must successfully hold off electrical breakdown as the applied electrical pulse is rising and delivering electrical energy to the downstream load. While breakdowns during the falling end of the pulse are somewhat understood to be electron cascade and...Show More
Multipactor Suppression Schemes in X-Band Waveguide Via Surface Modifications
H. Spencer;D. Wright;A. Gregory;J. Stephens;J. Mankowski;J. Dickens;A. Neuber
2023 IEEE International Conference on Plasma Science (ICOPS)
Year: 2023 | Conference Paper |
Multipactor (MP) suppression is essential as more powerful signal sources in smaller form factors are needed. This study utilizes a high-power X-band system with plug-and-play features allowing for quick testing of different surface modifications.’ The presented work uses phase and power diagnostics to detect the onset of MP.Show More
High Power Microwave Breakdown of C4F7N (Novec 4710) Gas Mixtures
Brandon Bywater;John Mankowski;James Dickens;Andreas Neuber;Matthew Capps;Jacob Stephens
2023 IEEE Pulsed Power Conference (PPC)
Year: 2023 | Conference Paper |
Sulfur Hexafluoride’s (SF6) high dielectric strength makes it heavily relied upon as a high voltage insulating medium. However, its atmospheric lifetime of 3,200 years and overall high global warming potential has motivated a search for alternatives. One possible alternative, C4F7N (NOVEC 4710) features a dielectric strength more than twice that of SF6 yet features an atmospheric lifetime one-hund...Show More
Experimental Demonstration of a Compact, High Average Power, Pulsed Power Driver for Printed-Circuit Board Nonlinear Transmission Lines
David Saheb;Travis Wright;John Mankowski;James Dickens;Andreas Neuber;Emily Schrock;James Schrock;Jacob Stephens
Nonlinear transmission lines (NLTLs) are a promising technology for high power microwave (HPM) generation. However, NLTLs are also typically characterized by relatively short RF pulse widths, on the order of tens to hundreds of nanoseconds. One approach to increasing the overall average microwave power is the application of short excitations in very high pulse repetition frequency, thus yielding a...Show More
Air Core Transformers for Use in Flux Compression Generator Power Conditioning
2023 IEEE Pulsed Power Conference (PPC)
Year: 2023 | Conference Paper |
Flux compression generators (FCGs), are unable to drive high impedance loads efficiently. To ensure that the output from an FCG can drive a high impedance load, an impedance transformation is necessary. This impedance transformation is known as the power conditioning stage of the FCG. Air core transformers were developed to eventually be used as a power conditioning stage for an FCG. Two types of ...Show More
Methods for Mapping of Surface Charge Density on Arbitrary Dielectric Objects
John Mockert;John Mankowski;Benedikt Esser;Donald Friesen;Blake Havens;David Hattz;James Dickens;Crystal Nelson;Jacob Stephens;Andreas Neuber
2023 IEEE Pulsed Power Conference (PPC)
Year: 2023 | Conference Paper |
A system to map surface charge densities on dielectric objects – e.g. PTFE, PMMA, and PA6 – is described to study maximum surface charge limits discharge and decay characteristics. Two electromechanical movements are used to achieve these goals: a three-axis robotic arm with an electrostatic probe and a three-axis auxiliary movement fitted with a current viewing resistor and laser displacement sen...Show More
A 1D1V Continuum Vlasov–Poisson Multipactor Analysis From Onset to Saturation Across the Entire First-Order Multipactor Regime
Luke Silvestre;Jacob Stephens;James Dickens;John Mankowski;Andreas Neuber;Ravindra P. Joshi
This report employs a Vlasov–Poisson model to elucidate fundamental electron phase–space mechanics of a multipactor discharge from onset to saturation. At the onset of multipactor, the electron phase–space is primarily defined by sharp features in both the physical space and energy space. With increasing electron density, space-charge effects lead to debunching of the swarm in phase–space. The tem...Show More
RF Output Power Detection of the RADAN MG-4 Microwave Generator
Nicholas Harrison;Kaylee Allen;James C. Dickens;Andreas A. Neuber;John Mankowski
2022 IEEE International Power Modulator and High Voltage Conference (IPMHVC)
Year: 2022 | Conference Paper |
The RADAN series-based MG-4 Microwave Generator is a compact, high power microwave system developed by the Institute of Electrophysics in Ekaterinburg. The system features the RADAN high voltage generator which is a SINUS-series device featuring a Tesla transformer charger and a Blumlein pulse forming line. The MG-4 microwave head is a mm-band relativistic backward wave oscillator (BWO) that opera...Show More
Assessing the Role of Photon Processes in Facilitating Radio Frequency Breakdown of Air at Atmospheric Pressure in Millimeter Gaps
Xiaoli Qiu;Benedikt Esser;Ivan Aponte;John Mankowski;James C. Dickens;Andreas A. Neuber;Ravi P. Joshi
The behavior of the breakdown electric field versus gap lengths (in the 1–5-mm range) and at different frequencies in the 1–80-MHz span, has been studied numerically at atmospheric pressure. Unlike previous studies of radio frequency (RF) breakdown, the role of photon-emission processes is explicitly included and shown to be important for large-area electrode configurations. Numerical analysis bas...Show More
Evaluation of Explosive Emission Carbon Fiber Cathodes for High-Power Microwave Devices
Tyler Buntin;Matthew Abide;Andreas Neuber;James Dickens;Ravindra Joshi;John Mankowski
Most high-power microwave (HPM) sources, such as the magnetically insulated transmission line oscillator (MILO) being developed at Texas Tech, utilize cold cathodes that generate electrons via explosive emission. Highly emissive cathodes such as the presented can generate current densities and currents greater than 1 kA/cm 2 and 10 kA, respectively, which are required for devices that can output r...Show More
Sensitivity of Multipactor on Variations in SEY using a Continuum Vlasov-Poisson Model
L. Silvestre;R. Joshi;J. Stephens;J. Dickens;J. Mankowksi;A. Neuber
2022 IEEE International Conference on Plasma Science (ICOPS)
Year: 2022 | Conference Paper |
The impact of secondary electron yield (SEY) variations on multipactor in a parallel plate geometry is probed. In this contribution, electron swarm dynamics are simulated via the continuum approach across a variety of SEY curves. The objective is to determine which changes and shifts in the SEY curve are most sensitive to the final multipactor outcome. For instance, will a variation in the maximum...Show More
Exploring the Basic Physical Mechanisms of Cathode- and Anode-Initiated High-Voltage Surface Flashover
William Brooks;Raimi Clark;Jacob Young;Matthew Hopkins;James Dickens;Jacob Stephens;Andreas Neuber
Surface flashover in vacuum imposes a substantial physical limit on modern, large-scale pulsed power. One of the ramifications is a minimum size requirement for new machines, which in itself becomes a hard barrier to the modernization and improvement of existing infrastructure. Pulsed power topologies require the physical mechanisms of both anode- and cathode-initiated flashover to be considered. ...Show More
Optically Activated In-Waveguide Semiconductor Attenuators for the Controllable Isolation of Ka-Band Microwaves
A. T. Hewitt;B. Esser;R. P. Joshi;J. Mankowski;J. Dickens;A. Neuber;R. Lee;J. Stephens
Three different isolator topologies utilizing photoconductive (PC) elements are explored for their application as a controllable attenuator for a Ka-band radar system. Network analyzer measurements are reported for each geometry in the unilluminated case, while a high-speed, high dynamic range heterodyne detection apparatus is used to measure the transient attenuation behavior of the isolators whe...Show More
Lightning Current Propagation in Electrical Conduit
William Brooks;Micah Lapointe;Landon Collier;John Mankowski;James Dickens;David Hattz;Neil Koone;Andreas Neuber
Investigation of lightning strikes to conductors ran through long spans of rigid steel conduit was performed. An overdamped-exponential current waveform with controlled peaks and rise rates was used to inject simulated lightning strikes. The impact of the length of wire, length of conduit, grounding location/s, and load type was investigated. Breakdown of 600 V, 12 AWG, THHN insulated wire (3.23 m...Show More
High Power Multipactor Suppression in X-Band Waveguide
A. Gregory;Z. C. Shaw;D. Wright;J. Mankowski;J. Dickens;A. Neuber
The multipactor effect is detrimental in space-based RF systems through detuning, heating, and causing permanent component damage. Studying thresholds and suppression of multipactor utilizing surface geometries in structures akin to WR-90 waveguide are of specific interest in the presented work. Operating in the dominant TE10 mode, a copper stepped impedance transformer transitions the waveguide t...Show More
Surface Charge Distribution Mapping Using an Electrostatic Probe
Micah LaPointe;Benedikt Esser;Ivan Aponte;Zachary Cardenas;James Dickens;John Mankowski;Jacob Stephens;Donald Friesen;Crystal Nelson;Neil Koone;David Hattz;Andreas Neuber
Undesired accumulation of charge on dielectric materials causing electrostatic discharges can be an issue in pulsed power systems and electrical systems in general. As such, an understanding of surface charge distribution, charge accumulation, and decay is required. An in-house no-contact electrostatic probe designed with a 2 mm resolution was fabricated to measure and map surface charge distribut...Show More
Sensitivity of PBX 9501 and PBX 9502 to Milling Operations
Joshua Williams;Ethan Weeks;Raimi Clark;Scott Watkins;James Dickens;John Mankowski;Jacob Brinkman;Andreas Neuber
2021 IEEE Pulsed Power Conference (PPC)
Year: 2021 | Conference Paper |
Explosive driven pulsed power performance benefits from modern polymer-bonded explosives. In practical application, high precision in the dimensional shape is required, and high machining speeds are desired. The limits of machining speed, driven mainly by the thermal response of the energetic material, are investigated. Specifically, the thermal response of PBX 9501 (95% HMX, 2.5% Estane, 2.5% BDN...Show More
Effect of Humidity on Charge Decay in Varying Atmospheric Gases
Zachary Cardenas;Ben Esser;Ivan Aponte;James Dickens;John Mankowski;Jacob Stephens;Donald Friesen;Crystal Nelson;Neil Koone;David Hattz;Andreas Neuber
2021 IEEE Pulsed Power Conference (PPC)
Year: 2021 | Conference Paper |
Characterization of surface charge decay for varying materials – PTFE, Acrylic, and metals – of 100 mm diameter, radially symmetric bodies was performed. In a gaseous environment, charged materials will lose their charge depending on gas type, humidity, and other environmental factors. Eventually, the charge will be (1) neutralized by ions or electrons in the surrounding gas (2) distributed by con...Show More
Explosive Emission Cathode Evaluation for a Magnetically Insulated Line Oscillator
T. Buntin;M. Abide;J. Dickens;A. Neuber;R. Joshi;J. Mankowski
2020 IEEE International Conference on Plasma Science (ICOPS)
Year: 2020 | Conference Paper |
Most high power microwave sources, such as the Magnetically Insulated Transmission Line Oscillator (MILO) being developed at Texas Tech, utilize cold cathodes that generate electrons via explosive emission. These highly emissive cathodes can generate current densities and currents greater than kA/cm2 and 10 kA, respectively which are required for devices that can output RF power greater than 100 M...Show More
High Power 2.85 GHz GaN RF Source for Direct Detection of Multipactor Research
Benedikt Esser;Zachary Shaw;James C. Dickens;Andreas A. Neuber
2020 IEEE International Conference on Plasma Science (ICOPS)
Year: 2020 | Conference Paper |
A pulsed 2.85 GHz RF source design with high average power is presented for use as the principle exciter in an experiment to directly detect multipactor. With a rated output power of 700 W each in long pulse mode (∼ 100 □s), four Cree GaN HEMTs are used to achieve a maximum of 2.8 kW rated output. A fifth HEMT is used to drive the four output devices with approximately 40 W each. A free running VC...Show More
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