METHOD AND APPARATUS FOR IMPROVED SENSITIVITY IN A MASS SPECTROMETER
摘要
<p>Ions are generated in a high pressure region and are passed into a vacuum chamber having an inlet and an exit aperture. The configuration of the inlet aperture and the pressure difference between the high pressure region and the vacuum chamber provides a supersonic free jet expansion that has a barrel shock of predetermined diameter. At least one ion guide is provided between the inlet and exit apertures having a predetermined cross-section defining an internal volume wherein the cross-section of the at least one ion guide is sized to be at least 50% of the predetermined diameter of the barrel shock of the supersonic free jet expansion. An RF voltage is provided to the at least one ion guide. Radial gas conductance is reduced in a first section of the at least one ion guide for damping shock waves resulting from the supersonic free jet expansion.</p>
