Stretched wire set-up

Schematic of a stretched-wire set-up.
The stretched-wire technique allows for a very accurate measurement of the first and second field integral of the full length of an insertion device. It is based on the induction of a voltage when a coil is moved in a magnetic field or when a stationary coil is placed in a field that changes with time. For the stretched-wire technique, a long wire is installed along the electron beam axis of the undulator. This wire is part of a one-loop coil. The return path of this coil is positioned well away from the magnetic field and is kept stationary. The stretched section is then moved within the magnetic field, cutting the flux and so inducing a voltage within the coil. Depending on the direction of movement, the horizontal or vertical component of the field integrals can be measured. The FS-US Magnetic Measurement Lab is equipped with two stretched wire stands that can measure on insertion devices of up to 5 m length but can also be used for the characterization of individual block magnets.

Further literature: James A. Clarke: “The Science and Technology of Undulators and Wigglers”, Oxford University Press, 2004

Contact: P. Neumann