Reconstructive Correction of Aberrations in Nuclear Particle Spectrographs
AbstractA new method is presented that allows the reconstruction of trajectories in
particle spectrographs and the reconstructive correction of residual
aberrations that otherwise limit the resolution. Using a computed or fitted
high order transfer map that describes the uncorrected aberrations of the
spectrograph, it is possible to calculate a map via an
analytic recursion relation that allows the computation of the corrected data
of interest like reaction energy and scattering angle as well as the
reconstructed trajectories in terms of position measurements in two planes near
the focal plane. The technique is only limited by the accuracy of the position
measurements, the incoherent spot sizes, and the accuracy of the transfer map.
In practice the method can be expressed as an inversion of a nonlinear map
and implemented in the differential algebraic framework. The method is
applied to correct residual aberrations in the S800 spectrograph which is under
construction at the National Superconducting Cyclotron Laboratory at Michigan
State University and to two other high resolution spectrographs.
M. Berz, K. Joh, J. A. Nolen, B. M. Sherrill, A. F. Zeller,
Physical Review C 47,2 (1993) 537-544
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