HV Storage Capacitors for High Current Pulse Power Applications

High Energy accelerators and colliders are becoming increasingly compact and switching devices such as thyratron tubes are replaced by solid state switches such as IGBT, IGCT and MOSFET devices, operating at voltages of 3KV to 6.0+KV with peak currents of 0.5-6.0+KA. Klystron modulators built with various topologies require HV energy storage capacitors that can operate at the same voltage and current as the switching devices. When combining HV, high dV/dt and high di/dt, the choice of capacitors is reduced to select Multi Layer Ceramics and wound polymer film capacitors. HV high capacitance MLC capacitors meet surface mount and temperature requirements but they are large, heavy, they are subject to cracking from large electrostrictive forces and are prohibitively expensive. Metallized film capacitors have superior capacitance stability with voltage and temperature, but they are also relatively large, they have higher ESL and ESR, contributing to voltage droop and under high dV/dt and di/dt pulse conditions, loss of termination can occur which increases ESR. Commercial Applications and Other Benefits: This Phase I SBIR proposal addresses the development of solid-state Polymer-Multi- Layer (PML) capacitors, for use in high dV/dt pulse power applications. PML capacitors comprise thin, high temperature polymer dielectrics with breakdown strength greater than 1000V/m. A large area (10sq.ft.) mother capacitor material with 1000s of capacitor layers is formed using an in-line, non-contact fabrication process. A mother capacitor sheet can be segmented into 10s, 100s, or 1000s of capacitor chips depending on capacitor rating. Like metallized film capacitors, PML capacitors have stable dielectric properties with voltage and temperature and are self-healing. The PML dielectrics can withstand temperatures in excess of 260oC, they have a prismatic shape with low ESL, the massively parallel electrode structure results in low ESR and the energy density is at least 10X that of film capacitors. The proposed development will address prototype fabrication and testing of PML capacitors designed specifically for HV pulse power applications. Capacitors with a rating of 5F/5KV will be produced in the Phase I program and will be tested using short term accelerated dV/dt and di/dt tests to demonstrate 10KA peak current performance. Packaging and long term accelerated tests to demonstrate reliability and life under various application conditions will be addressed in the Phase II program.