Categories of exhibits
Source Ion Beam Focusing Lenses
Exhibit no. 866
Double-focusing magnetic sector instruments can be used to perform MS/MS analyses. In these experiments, the electric and magnetic sectors are scanned together. For instance, ion decompositions in the first field-free region (between the ion source and the first sector) can be used to measure product ion spectra. Ions leaving the ion source are accelerated to kinetic energy that depends on the accelerating potential. All ions with the same number of charges will have the same kinetic energy. After fragmentation, the product ions will have the same velocity as the precursor. If it were possible to select ions according to their velocities, it would also be possible to determine which product ions were formed from a precursor with a known velocity. This is achieved by scanning B and E together, always keeping a constant B/E ratio.
The exhibit is a source focus lens and gas cell assembly from the first field-free region of ZAB EQ double-focusing mass spectrometer with the reversed (BEQ) geometry. The instrument was manufactured by VG Analytical Ltd. in 1986. The lens was used to refocus an image of the ion source fixed slit onto the adjustable object slit. The first field-free region gas cell was positioned immediately in front of the adjustable object slit in the ion source housing. The cell was used for collisional activation B/E, B2/E and V (Barber-Elliott) scans. The assembly was supported by four ceramic rods retained by circlips at their ends.
