# Compact Design and Impact Ionization: Utilizing Small-Sized Thyristors in a 4-Stage Marx Generator
)2 Institute for Pulsed Power and Microwave Technology, KIT--Karlsruhe Institute of Technology, 7634 Karlsruhe, Germany; georg.mueller@kit. module, thyratron, or thyristor [3]. Thyratrons, in particular, stand out for their ability to control switching characteristics with precision. This, along with their rapid switching times and strong reliability, makes them well-suited for applications requiring high-current and high-voltage delivery. However, despite these advantages, thyratrons also present significant drawbacks, including complex triggering and biasing electronics, high costs, and limited market availability [4]. As a result, there is growing interest in exploring alternative systems that utilize different technologies to provide more reliable and cost-effective solutions. Insulated gate bipolar transistors (IGBTs) are widely used for high-power switching applications. However, their rise time is not optimal for applications requiring extremely fast transitions. To address the need for high-voltage nanosecond pulses, a microsecond-scale, solid-state pulse charger design with IGBTs has been proposed, as outlined in [5]. This design employs IGBTs in a parallel configuration within the pulse charger, enhancing their ability to manage the high power needed for generating rapid and repeated pulses. However, this solution can be impractical for use in applications demanding tens of kilovolts and kiloamperes because of its excessive bulkiness. Another alternative for generating high-voltage pulses is the inductive adder [6], a solid-state modulator that generates such pulses using multiple transformers set in series, each with a 1:1 turn ratio. This system integrates key elements, such as semiconductor switches (e.g., IGBTs or MOSFETs) to regulate pulse timing, capacitors for energy storage, diode clamps to mitigate voltage spikes, and gate drive circuits for switch control. The inductive adder's modular architecture enables scalable configurations, simplifying both maintenance and adaptation to diverse requirements. However, these adders tend to be bulky, which can restrict their application in environments with limited space, where they would need to fit into existing systems. Furthermore, the transformers within these systems may encounter magnetic saturation if their capacity is exceeded, adding complexity to the design. Expanding the number of modules also raises overall impedance, complicating impedance matching and requiring additional adjustments as system specifications evolve. In contrast, Marx generators based on semiconductor switches have emerged as a promising solution for delivering high-voltage nanosecond pulses. With the advancement of wide-bandgap semiconductor technology, commercial silicon carbide (SiC) MOSFETs have emerged as a promising alternative, offering faster switching speeds and lower losses compared to silicon-based IGBTs, particularly in high-voltage and high-power applications [7]. By utilizing SiC MOSFETs optimized for fast switching capabilities, Marx generators can achieve fast rise and fall times while still providing high-voltage and current outputs [8]. A key benefit of this approach is the reliance on COTS devices, which minimizes current paths, leading to reduced inductance and improved switching speeds. However, this also subjects components to considerable stress, potentially compromising reliability and longevity. Additionally, scaling the generator to attain higher voltage levels by incorporating additional stages increases system complexity, enlarges the overall physical footprint, and introduces synchronization challenges between stages. In accelerator environments, solid-state thyristor switches demonstrate dependable performance [9] by simultaneously providing a combination of high reliability, moderate switching speed, and low conduction losses. As solid-state devices, they offer extended operational lifetimes and come in a wide range of voltage and current ratings [10].