Electromagnetically driven, fast opening and closing gas jet valve

The design and performance are presented of an electromagnetically driven gas valve [M. Krishnan, J. Wright, and T. Ma, Proceedings of the 13th Advanced Accelerator Concepts Workshop, Santa Cruz, CA, AIP Conf. Proc. No. 1086 (AIP, New York, 2008)] that opens in < 100 mu s, closes in < 500 mu s, and can operate at pressures of similar to 1000 psia to drive supersonic nozzles. Such a valve has applications to laser-plasma accelerators, where the fast opening and closing would allow sharper edges to the flow and also allow higher rep-rate operation without loading the vacuum chamber. The valve action is effected by a flyer plate accelerated by the electromagnetic impulse of a low inductance, spiral wound, strip-line coil driven by a capacitor. Gas flows out of the valve when the seal between this flyer plate and the valve seat is broken. The electromagnetic force greatly exceeds the restoring forces provided by a spring and the gas pressure against the valve seat. Piezoresistive sensor and laser interferometer measurements of flow show that the valve opens in similar to 100 mu s for all pressures up to 800 psia. The closing time is 500 mu s, set by the spring constant and mass. The prototype valve has been operated with helium at 0.5 Hz and at 500 psia for similar to 1 hour at a time with no cooling.