The Magnetron Gauge: A Cold-Cathode Vacuum Gauge

A cold-cathode ionization gauge with axial magnetic field is described which is capable of measuring pressure in the range 10 −3 to 10 −12 mm Hg and is primarily useful in the range above 5 × 10 −10 mm Hg. The gauge is operated with an anode voltage of 6 kilovolts and a magnetic field of 1000 gauss. The relationship between ion current and pressure is linear in the pressure range 10 −4 to 5 × 10 −10 mm Hg; at lower pressures the relationship i + = cP 1.7 obtains. In the linear region the ion current per unit pressure is given by i + (amperes) [Formula: see text](mm Hg) for nitrogen (i.e., a sensitivity about 45 times greater than obtainable with a thermionic triode gauge).