Development of the edge-focusing wiggler for SASE

We propose a novel concept to make a low-error wiggler to be used for self-amplified spontaneous emission. Magnetization errors of permanent magnet blocks can be reduced by using a pair or quartet of magnet pieces quarried out of a single raw block of permanent magnet. The concept has been tested experimentally using magnet blocks for a trial model of the edge-focus wiggler, which can produce a focusing field as high as 1 T/m in the wiggler. The errors in the magnetization of magnet blocks were considerably reduced. This was calculated with the vertical magnetization axis with which it is easier to measure three components of the magnetic field, and the measured values are reliable. It has been experimentally confirmed that the concept works well.