Wire method for magnetic field measurements in long undulators

This paper is devoted to improvements of the conventional version of the pulsed wire method used for operative magnetic field control. The aim was to avoid some serious disadvantages: signal reflections from the wire ends which prevent accurate measurements, the sag of the wire which leads to wire deflection from a straight line, and complexity of the used wire-position detectors. An effective and simple wire-position detector providing accuracy up to 1 μm was designed and tested. Damping of reflected signal noise and decrease of the wire sag were achieved. It is shown that with these improvements the wire method can be applied to undulators with a length up to several meters.