ION SOURCES FOR MASS SPECTROMETERS
1328882 Ion sources UNITED KINGDOM ATOMIC ENERGY AUTHORITY 28 April 1971 [6 May 1970] 21955/70 Heading H1D An ion source for a mass spectrometer comprises an ionizing region 1, and successively spaced therefrom, a first electrode 3, a second electrode 4, a focusing electrode 5 and a collimating electrode 6, all said electrodes having slits for the passage of ions, the arrangement being such that after a cross-over in the plane of the first electrode 3, a virtual image is formed on the incident side of the second electrode 4, from which electrode a divergent beam leaves and is acted upon by focusing electrode 5 to provide at the collimating electrode 6 a beam whose width is only slightly greater than the width of the slit therein. At the collimating slit the beam may form a real image or be slightly divergent.