320 kV Marx Generator Upgrade for Particle Accelerator Systems

Legacy air-insulated Marx generators originally commissioned in the 1980s for 320 kV ion and electron accelerators suffer from erection jitter >180 ns and voltage droop >9 % across 2 µs pulses, limiting bunch charge uniformity and beam brightness. Modern solid-state Marx upgrades replace spark gaps with series-stacked 1.7 kV silicon carbide MOSFET boards while preserving existing column geometry and charging infrastructure.

Each stage comprises twelve parallel MOSFETs with integrated 4 nF ceramic storage capacitors and active voltage balancing via individual gate-zener clamps. Triggering uses a single fiber-optic pulse distributed through a compensated delay tree with 6 ps channel matching, achieving simultaneous turn-on across 96 stages and erection jitter below 4.2 ns. Rise time (10–90 %) is reduced from 420 ns to 68 ns through minimized stage inductance (<28 nH) and optimized wavefront shaping resistors.

Voltage droop is compensated by a two-part strategy: stage capacitors are deliberately oversized to 5.2 nF providing <2.8 % natural droop, while a fast tail-biter circuit injects an additional 180 A current ramp during the last 800 ns of the flat-top, maintaining ±0.6 % regulation into 1.4 A beam load. Total pulse energy is 28 kJ at 40 ppm repetition rate.

Erection reliability exceeds 99.9997 % through triple-redundant trigger paths per stage and automatic faulty-stage bypass using high-speed thyristors that short defective boards in <1.1 µs. Post-fault operation continues at 308 kV until scheduled maintenance.

Seismic and acoustic hardening uses carbon-fiber support struts and viscoelastic damping pads that reduce mechanical resonance amplitude by 46 dB, eliminating the stage-to-stage timing drift previously observed during cooling tower operation.

Upgrade kits reuse the original oil-free ceramic column and charging resistors, allowing replacement in a single 14-day shutdown window including high-pot testing. These solid-state Marx systems routinely deliver 320 kV pulses with 0.42 % flat-top stability and <3.8 ns jitter in high-energy physics injectors and industrial linacs, increasing beam transmission efficiency by 28 % and reducing emittance growth by 41 % compared to spark-gap predecessors.