Performance of Self-Closing Diverter Switches for ZR/Z20 Marx and Intermediate Store Protection

The ZR refurbishment project [1] at Sandia National Laboratories (SNL) required a set of diverter switches to protect the Marx generators and intermediate storage (IS) capacitors from Marx pre-fire and/or laser triggered output switch (LTS) no-fire. Thirty-six such diverters, one for each Marx-IS set, will need to operate reliably over the full range of Marx charge voltages and LTS anticipated closure times. Operating voltage is up to 6 MV. A self-closing oil switch diverter was selected and design work began in late 2002. The first diverter (Phase I or just PI) was delivered in the summer of 2003 and tested on SNL's Z20 test-bed. Based on test results, operational experience and overall project budgetary concerns, it was decided to re-design the diverter, resulting a simpler, less costly switch. This new self- closing oil switch (Phase II or P2) was fielded at SNL on the Z20 test-bed in late 2004. Both designs include adjustable electrodes to control the closure time. Also incorporated is a mechanical clamp that minimizes or shorts the oil gap until Marx charge is complete. Both diverters feature liquid resistors sized to safely absorb the energy stored in the Marx or IS. This paper describes the design and test results from these diverters.