Electromagnetic Shielding¶
Electric Shielding¶
Electric fields can be shielded with a Faraday cage, which may take the form of a Ground Chamber.
A Faraday cage (Wikipedia: Faraday_cage) can also filter electromagnetic radiation by disrupting the E-field component, but this is of less concern in SIMION, which is geared toward static and/or low frequency fields (not electromagnetic radiation where electric and magnetic fields are coupled).
Magnetic Shielding¶
Magnetic shielding, at least for static or low frequencies is often done with mu metal material (Mu Metals (High Permeability)) or a Helmholtz Coil.
Earth’s magnetic field can be a significant source of unwanted magnetic fields in your instrument and is often the motivation for shielding. Earth’s B-field varies in direction and by location roughly in the range 0.25-0.65 gauss (see Wikipedia: Earth%27s_magnetic_field).
You can simulate Earth’s B-field in SIMION
by adding a magnetic PA to your workbench with a uniform,
where the field is defined either in the PA itself (see Magnets)
or it is zero in the PA and defined instead in an
mfield_adjust user program segment
(like in SIMION Example: poisson/pipe_with_beam pipe_beam_bfieldearth):
simion.workbench_program()
local b = 0.5 -- gauss
function segment.mfield_adjust()
ion_bfieldx_gu = 0
ion_bfieldy_gu = 0
ion_bfieldz_gu = b
end