Multimegavolt Laser-Triggered Gas Switching With a Green Laser and Beam Transport Through Water

Ultraviolet (UV) laser-triggered gas switching using laser beams at 266 nm has greatly improved the simultaneity of many large multimodule accelerators. This UV beam however cannot be transmitted significant distances through water or oil. Since the switches in these accelerators are typically submerged in water or oil, the laser beams are often conveyed to the switches through gas-filled “laser crossover tubes.” These crossover tubes are difficult to field grade properly and are subject to frequent mechanical and electrical failures in the pulse-power environment. We have demonstrated that a 4.6-MV multistage gas switch insulated with $\hbox{SF}_{6}$ can be triggered with a jitter of less than 10 ns using 110-mJ pulses of a green (532-nm) laser beam that has been transported through 67 cm of 1- $\hbox{M}\Omega\hbox{-cm}$ water on its way to the switch. These results may allow elimination of the laser crossover tubes in future accelerators.