Advancing high power microwave spark-gap technology : design and analysis of a coaxial ringdown oscillator

High-power microwave (HPM) systems play a significant role in radiated Intentional Electromagnetic Interference (IEMI) technologies. Generating high peak voltages allows HPM systems to produce powerful electromagnetic pulses. However, their development is limited by challenges in achieving high peak voltages within a target frequency band. The source in an HPM system generates the initial high-power electromagnetic pulses that are shaped and radiated. HPM sources, such as switched oscillators (SOs), rely on spark-gap switches that underperform in voltage thresholds, limiting their range and effectiveness. Coaxial ringdown oscillators (CROs), a variation of SOs, operate within a coaxial geometry to generate high-power electromagnetic pulses. Current CRO designs can only withstand breakdown voltages up to 100 kV, which limit peak output voltages, and a suboptimal Q-factor (Q) values, which reduces the amount of energy coupled to a target at a specific frequency. Therefore, the aim of this thesis is to design, fabricate, test, and evaluate a novel CRO using a systematic methodology to optimize its performance, increase peak voltage, and enhance Q.To better understand the limitations of existing systems and guide the development of the CRO, a review of relevant literature was conducted. The literature review identifies challenges in SO design, including limitations in the performance of various insulating gases. Insulation gases directly impact the achievable peak electric fields and pulse repetition frequency with most SO prototypes failing to exceed 100 kV in peak voltage, which limits their range of effectiveness. Fundamental limitations in current CRO designs are scalability for high-voltage applications, and low Q. The proposed solution is a novel CRO design incorporating a high-pressure hydrogen spark-gap switch, optimized to use a high breakdown voltage and operate at a narrowband center frequency with a high Q. The design utilizes a three-conductor system with a high-voltage middle conductor, an inner conductor for post-breakdown pulse transmission, and a grounded outer conductor. Full-wave electromagnetic simulations in conjunction with genetic algorithms (GAs) were used to optimize the CRO design for high Q values while minimizing losses to peak output voltage. Experimental results confirm that the CRO achieves significant improvements in peak voltage and Q value compared to state-of-the-art designs. A breakdown voltage was achieved that exceeds the previous peak by 200%, while the measured Q exceeds the highest recorded value by 20%. Simulated peak voltages and waveforms align closely with experimental data. The novelty of this research lies in its integration of a high-pressure hydrogen spark gap switch and a helical antenna, which collectively improve breakdown voltage, Q, and mitigate conductor build up issues. The CRO design successfully addresses the big-picture HPM challenges by generating more powerful and reliable electromagnetic pulses, extending the operational range. This advancement in HPM technology has potential application not only in IEMI but also other high-power systems requiring efficient, high-voltage pulse generation, thereby offering practical solutions to real-world problems.

Name thesis:degree_name

M.S. (Master of Science)

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Electrical Engineering (UMKC)

Grantor

University of Missouri--Kansas City

Year dc:date.issued

2024

Author dc:creator

• Murphy, Tyler John

Advisor dc:contributor.advisor

• Durbhakula, Kalyan C.

Language dc:language.iso

en_US

Handle dc:identifier.uri

https://hdl.handle.net/10355/110173

OAI identifier oai:identifier

oai:mospace.umsystem.edu:10355/110173