APPLICATION OF A MAGNETRON GLOW-DISCHARGE TO DIRECT SOLID SAMPLING FOR MASS-SPECTROMETRY

The behavior of a planar magnetron glow discharge used as a sampling device and ion source for mass spectrometry of conducting solids is examined. Low-pressure operation of the magnetron allows efficient sputtering and ion production from conducting samples. Interfacing the magnetron with the mass spectrometer is simplified by low-pressure magnetron operation. A special sample holder allows up to five sample plugs to be analyzed without the source chamber vacuum being broken. Sample ion current is not found to be a simple function of discharge current, but is a strong function of sample axial position relative to the mass spectrometer sampling cone. The mass spectrometer sampling cone orifice diameter may be varied from 0.5 to 5.0 mm. A cone orifice diameter of 2.0 mm yields optimum analytical conditions. Determination of Al at the 3-5% level in a series of NIST Zn-base alloy standards yields a straight-line analytical curve, suggesting the potential application of the device to high-precision analyses of alloys.