The undulator yokes are mounted on a C-shaped
support allowing an easy access to the undulator gap. The
support is made of a non-magnetic steel. Mechanical
properties of the support are sufficient to keep strong
ponderomotive forces, the gap change is less than 0.01
mm at a maximum field. The main coil consists of four layers, and each layer
consists of 16 turns. The windings are made of a
squared-shape copper pipe (8.5x8.5 mm) with a cooling
channel of 5.3 mm diameter. The maximum current in
the winding is 435 A (current density 8.7 A/mm²). Maximum heat deposition per undulator period is 2.54
kW. Each regular coil has an additional correction
winding to provide fine regulation of the magnetic field.
The number of turns in the correction winding is equal
to 270, and wire diameter is 1 mm. The corrector
winding allows to regulate the number of Amper·turns
inside 2% of maximum value of the main winding. The
correction coils permit to compensate a perturbation of
the magnetic field related to an imperfection of magnetic
system at its construction.
The coils of two end poles differ from the coils of
regular periods, and consist of 8 and 36 turns for the first
and the second pole, respectively. End-pole coils have
also the correcting winding for fine adjustment of the
magnetic field
magnetic field