High-Accuracy Field Description of Particle Spectrographs,
Abstract
For high-resolution spectrographs with large phase space acceptance the
hardware correction of all the relevant aberrations requires so many multipole elements
that software correction methods are often more adequate. In this case, the obligatory
computation of the higher-order transfer map becomes feasible if the (three-dimensional)
magnetic field within the spectrograph can be approximated with sufficient accuracy
in an analytical form. For this purpose, we present an approach that allows the use of
midplane measurements or alternatively measurements in several planes resulting in a
global Maxwellian field that suppresses local measurement inaccuracies. It is based on
a modified charge density method generating the magnetic field by a superposition of
Gaussian charge distributions. The accuracy of the method is assessed through test
cases for which analytical solutions of the field components are known. A maximum
relative inaccuracy of the magnetic field in the midplane smaller than $\pm 10^{-4}$ is
obtained in the relevant field area. In addition, we obtain a good agreement comparing
the multipole content of the analytical field solution with the one of the approximated
field.
R. Degenhardt, M. Berz, Nuclear Instruments and Methods
A427, 151-156 (1999)
Download
Click on the icon to download the corresponding file.
Download Adobe PDF version (438130 Bytes).
Download Postscript version (2664933 Bytes).
Go Back to the reprint server.
Go Back to the home page.
This page is maintained by Kyoko Makino. Please contact her if there are any problems with it.