Search

We study the physics of water switching at 4 to 5 MV as part of Sandia's Z-Refurbishment program. We present time histories of the light emitted by two sets of water switches and correlate the light emission to the accelerator power pulse. Framing camera images demonstrate how the initial "bushy" streamers collapse to narrow current channels at late time. Spectroscopy of the water switches indicates that the early-time streamers are already hot-dense blackbodies with temperatures between 7000 K and 9000 K. Late time hydrogen emission lines allow estimates of electron densities at that time ranging from 0.2 to 2 x 1018/cm3. [ABSTRACT FROM AUTHOR]

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 SF6 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-MΩ-cm water on its way to the switch. These results may allow elimination of the laser crossover tubes in future accelerators. [ABSTRACT FROM AUTHOR]