Supersonic Annular Nozzle as a Differential Barrier

Supersonic annular nozzles were used as a means of maintaining vacuum pressure differentials between two points, without the use of solid barriers or small constrictions as a mechanism for injection of ion beams into gases. Ambient atmospheric air was expanded into a small stilling chamber; this air was then expanded so as to form an annular supersonic stream in a chamber which was pumped by a six‐stage steam jet ejector. With a center opening of 1.25 in. diameter and the air stream expanding into 15 mTorr, an optimized nozzle will produce, under small loads, a pressure of 3 mTorr upstream of the opening. With a nozzle of center opening 0.5 in. in diameter expanded into 15 mTorr, an upstream pressure of 0.9 mTorr can be maintained.