INFLUENCE OF THE FRINGING FIELD LENGTH ON THE SEPARATED HE-4 D-2 PEAKSHAPE OF A HIGH-RESOLUTION QUADRUPOLE MASS-SPECTROMETER/

The influence of the fringing held length on the separated He-4/D-2 pe ak shape was experimentally studied by using a high-resolution quadrup ole mass spectrometer (QMS) that adopts the second stability zone (zon e II) in the Mathieu diagram. The fringing fields arise on the inlet a nd outlet of the quadrupole, where the traveling ions receive the conf used static and dynamic forces. Therefore, the fringing field length s trongly influences the performance of the high-resolution QMS. The inl et and outlet fringe lengths were changed by moving an ion source and a detector, respectively. It was concluded that the resolution, sensit ivity and peak disturbance were improved by decreasing the inlet and o utlet fringe lengths.