Ionization Pump

The authors of the note reviewed*) describe a high-vacuum ionization pump with a high pumping speed. Unlike ordinary high-vacuum mercury-vapor pumps, this pump has no working fluid. In it, gas molecules are ionized and directed into the region of high pressure by electric and magnetic fields. Ionization of the molecules is produced in a gas discharge, which is collimated by a magnetic field of strength about 1300 oersteds. The discharge is bounded on one side by a heated tungsten cathode, and on the other side by a cold reflecting cathode. The pumped gas enters the discharge through the gaps between the turns of a spiral, which serves as the anode and through which a current is passed, creating an axial magnetic field. The ions formed, owing to the existence of a potential gradient in the plasma, are directed toward the cathodes, where they are neutralized and can be removed by a forepump.

The limiting pressure obtained in pumping with this pump was of the order of \(10^{-6}\) mm Hg at a pumping speed of \(3000 \div 7000\) l/sec.

The highest pressure at which operation of the pump can be started is \(10^{-2}\) mm Hg.

L. Kh.

) J. S. Foster, E. O. Lawrence and E. J. Lofgaeen, Phys. Rev. 89*, 338 (1953).