A fast-closing vacuum valve for the Berkeley 88-inch cyclotron

A fast-closing vacuum valve has been built to protect the Berkeley 88 inch cyclotron against radioactive contamination during bombardments of highly radioactive targets. A 2.5 cm diameter through-hole can be vacuum sealed in approximately 3 ms by means of a wedge-shaped teflon gate which is moved into the closed position by the pressure created from an explosive charge. This charge can be triggered by a fast electronic signal from an ion gauge, a helium leak detector or other suitable gas analyzer. Response times of an ion gauge at 10-5-10-4 torr to a sudden pressure increase have been measured to be approximately 1 ms. (Auth.)