Development of a Custom Spiral Generator Winding Machine

Spiral generators are pulsed-power devices than can produce high-voltage pulses in an ultra-compact form factor. The spiral generator acts as energy storage device, voltage multiplier, and RF source all in one system. A slower input charge is converted to a high voltage pulse on the order of hundreds of nanoseconds in pulse width. The construction is typically comprised of two conductive foils that are separated by dielectric films that are then wound in a spiral around a cylindrical core. The spiral generator's electrical characteristics are controlled directly through the geometry of the material stack and core size. While historically initiated using spark gaps as closing switches, the advancement of solid-state switching devices, such as SiliconCarbide (SiC) transistors, has enabled spiral generators to become completely solid-state. This improves repetition rate and jitter by several orders of magnitude. Since the holdoff voltage of solidstate switches is much lower than that of plasma switches, the charge voltage, and therefore the output voltage, is lower. The output voltage and power may be increased by adding turns and/or increasing the capacitance by using ultra-thin dielectric films. Ultra-thin films present many challenges to handling and integrating into the spiral generator. Significant care must be taken to ensure desired characteristics are achieved and not altered by wrinkles, dust, misalignment, and film quality. Mechanical accuracy and robustness of the spiral winding machinery becomes critical to realize uniform transmission line impedance and prevent voltage breakdown between layers. A custom spiral generator winding machine has been constructed to improve the overall spiral generator manufacturing process across a span of materials, down to dielectric films as thin as 0.3 mil. The machine incorporates features to improve the manufacturing process, such as laser film alignment, tension controlled bobbins, and integrated control panel. The bobbins can handle material spools and manage tension control with widths from 2 to 18 inches. The design considerations and improvements to spiral generator performance will be discussed.