Discharge characteristics of magnetron cells with different lengths in ultrahigh vacuum
ABSTRACT Discharge characteristics of several magnetron cells have been measured at different experimental conditions. The cell diameter was always 27 mm, while the length was between 13 and 50 mm. The voltage was varied between 1 and 8 kV. The magnetic field and pressure were constant at 0.13 T and 1×10−8 mbar, respectively. The maximum current through the cell was found to be a strong function of the cell length. A maximum was observed at the cell length of about 20 mm followed by a minimum at about 35 mm. The behaviour was explained by variations in the space charge formed within the discharge volume.
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ABSTRACT: In high-vacuum measurement, cold-cathode ionization gauges have been widely used due to their unique advantages such as being simple and robust, low outgassing, x-ray effects, and so on. But during the measuring process, they show that a considerable pump effect, contamination buildup, and the heating and sputtering of the electrode surface from discharge can also become a serious problem at higher measured pressures. In such circumstances, pulsed operation is a good solution. However, the lowest measurable pressure of cold-cathode ionization gauges in pulsed operation is hard to extend, which limits its application. But if the measurable range of the cold-cathode gauge is divided into two regions, the low-pressure region where it is operated in dc discharge mode to ensure its lowest measurable pressure and the high-pressure region where it is operated in pulsed-discharge mode to reduce its above disadvantages at high pressures, the problem can be well solved. This article describes a pulsed high-voltage generating circuit controlled by a single-chip CPU to perform such a hybrid discharge in an inverted-magnetron gauge. With this circuit, the following problems of an inverted-magnetron gauge were investigated: the difference between pulsed-discharged mode and dc discharge mode, one method of extending the low measurable pressure limit in pulsed-discharge mode, the volt-current characteristics at different pressures, and constant-current pulsed-discharge measurement at pressures above 2x10² Pa.Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2007; 25(2):281-284. · 1.43 Impact Factor