The reverse geometry SHRIMP is based on ion optical designs by
Matsuda (1990) to minimize third-order aberrations. The design
of the SHRIMP RG yields approximately four times the mass resolution
for the same slit sizes compared to SHRIMP II.
SHRIMP RG was completed in 1997 however it was apparent that
the instrument was not performing as well as it should. The voltages
on the electrostatic quadrupole lenses were very different to
the theoretical voltages and good peak shapes could only be obtained
by severely limiting the beam divergence. After lengthy examination
of the input parameters it was found that the RG electrostatic
lenses were clamping the beam too hard and were not consistent
with the expectation of Matsuda’s design. Following the
re-design of the lenses, the voltages for the quadupole lenses
were close to theoretical and high mass resolution could be readily
obtained.
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