Phase error reduction in ILSF undulators using a genetic algorithm for sorting the magnetic blocks

The insertion device for the Iranian light source facility (ILSF), a 3 GeV third-generation light source, is in the design and construction phase. Insertion devices incorporate up to several thousand magnetic blocks to generate a sinusoidal magnetic field. The primary sources of limitations in the spectral flux and brilliance are the different remanence magnetizations for each magnet block, which are unavoidable. The magnetic field error affects the phase radiation and path of the electron, as well as other issues. The phase error directly affects the relative intensity of the radiation; thus, the intensity decreases with an increase in the phase error. These magnets must be measured and appropriately sorted to minimize phase errors. This study used genetic algorithms on an ILSF's pure permanent magnet undulator as a sorting technique to minimize phase error. The genetic algorithm was implemented using the Wolfram programming language. The optimal magnetic sorting achieved through a genetic algorithm reduces the phase error to 8.78°, which is an 82.9% decrease compared to a random magnetic block setup (51.41°). As a result, the relative intensity increases to 0.98, representing a 104% rise over the random arrangement (0.48), and the electron beam deviation from the undulator axis drops by 90%, from 81.66 μm to 7.93 μm.