Rotation of focal plane of magnetic analyzer in an isotope ratio mass spectrometer using curved shims

The inclination of focal plane from beam axis of the magnetic sector analyzer in an isotopic ratio mass spectrometer is an important design feature. For a stigmatic geometry mass spectrometer, the focal plane is normally inclined by an angle of ∼25° with respect to the principal trajectory which presents various complications in case the number of collectors is more than five. An attempt has been made by us to rotate this plane along a line normal to the principal trajectory (by using shims on exit side of magnetic analyzer) resulting in ease of design for the collector system. This paper presents theoretical explanation, computer simulation and experimental results on this development. Simulated results on optimum shim curvature are in good agreement with experimental data.

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► This work includes the focal line slope determination on a thermal ionization mass spectrometer by theoretical calculations and computer simulations.
► Based on the theoretical and simulation results, iterative experiments have been conducted to find final parameters for the desired objective of rotation of focal line along normal to the principal beam axis.
► The final parameters were further confirmed by recording peak shapes on the actual setup.