Construction of compact FEM using solenoid-induced helical wiggler

Helical undulator based on partial redistribution of uniform magnetic field

“…A similar method was proposed and demonstrated many years ago in planar undulator systems with periodic planar insertions [18][19][20]. Also, helically distributed planar elements were used for creating a relatively low helical transverse magnetic field [21]. We suggest using a more convenient helical undulator based on a fully-symmetrical helical insertion [22].…”