A SOURCE OF HIGH-ENERGY OXYGEN IONS WITH A COLD HOLLOW-CATHODE

A compact gas-discharge source of oxygen ions with an unlimited durati on of continuous operation is described. Ions are produced in a steady -state self-sustained low-pressure discharge. The discharge chamber co ntains a hollow cold cathode with closed ends and an anode in the form of two tubes inserted into the central openings in the end cathode wa lls, so that they reach the internal surface of the cathode. External ring-shaped magnets create diverging magnetic fields of up to 20 mT in the region where the anode tubes enter the cathode hollow. The source parameters are as follows: 270-320 V (discharge voltage), 0.3-0.8 A ( discharge current), and 0.01-0.015 Pa m(3) s(-1) (oxygen flow rate). A beam of oxygen ions with a current and energy of up to 12 mA and 25 k eV, respectively, is extracted through the emission aperture measuring 2 x 40 mm. The ratio between the concentrations of O-2(+) and O+ ions in the beam is 2-3.