WIEN: Simulation of Wien Filters
The Wien filter program calculates optical properties of columns that contain a Wien filter and any combinations of electrostatic and magnetic round lenses, and electrostatic and magnetic quadrupole lenses. The WIEN program uses as input a set of imaging conditions specified by the user, together with the field functions of the round lenses, quadrupole lenses and Wien filters. These element fields are computed with MEBS SOFEM and 3D software packages. The axial field functions are fitted with Hermite series to enable the field functions and their high-order derivatives to be computed accurately, which is an important requirement to ensure that the computed aberrations are meaningful.
The first-order optical properties are computed by numerical solution of the paraxial ray equation. The aberrations are computed by evaluating a differential algebra raytrace. The aberrations include second and third-order aberrations, and 1st order chromatic. The program can handle both Gaussian round-beam and shaped-beam systems. The output is the computed optical properties, including a table of the first-order optical properties and tables of the computed aberration coefficients. This output can subsequently be displayed graphically using the post-processing routines, which plots aberration spot diagrams.
The program will compute the first-order optical properties for any setting of the electric and magnetic deflection parts of the Wien filter. This enables the required strength of the deflectors to be chosen to give the desired deflection of the return beam. For the primary beam, the user can set the strength of the electrostatic dipole field and the program will adjust the strength of magnetic dipole field in the filter in order to satisfy the Wien condition to allow the beam to pass through the filter with zero net deflection. WIEN has a Graphic User Interface (GUI), which affords a better understanding and control of the system and its parameters during the analytical and design procedures.
If you are interested in the WIEN package, please contact us at info@electronoptica.com.