Electromagnet
The energy distribution of the electrons accelarted by the e-gun is wide spreaded. The aim of the electromagnet is to provide a rough energy selector of the accelrated electrons. The principle is to force the beam through a bended section of the vaccum system. For a given magnetic field only electrons with a certain kinetic energy will be able to reach the exit window. The electromagnet is designed to work as energy selectors up to a 100keV beam. It is planned, in futur, to add slits to improve the energy selction function.
An electro-magnet supplied by a high current power supply is used to vary the magnetic field.
A bending angle of 45 degrees was chosen. In an effort to reduce the size of the metal required to form the magnet yoke, a cross section of 1 x 1 inch of 1018 steel was chosen to perform the Finite Element Analysis in the FEMM software.
Using the FEMM software, various magnetic circuit configurations, materials and input currents were tested. The design parameter was to ensure that a magnetic field of 0.02 Tesla was found at the centre of the angled tube. To check different designs, the magnetic yoke (metal) would have to be chosen alongside the solenoid (long copper wire wound in a helix around a section of the yoke) size and current.
Field Strength (Tesla) Using FEMM Software
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The wiring was also tested in the FEMM software and AWG 16 wire was chosen. The wire should be a solid strand that is enameled and capable of passing 12 Amps. The choice of wire changes the outcome and/or sizing of the magnetic circuit as the wire must be wrapped around the core and each gauge of wire has a different diameter.
Electromagnet Assembly Showing The Copper Wire Wound
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