dc septum magnet based on permanent magnet for next-generation light sources

This paper presents a dc septum magnet based on a permanent magnet that we developed as an injection magnet for next-generation light sources. Permanent-magnet based magnet devices are regarded as one of the key technologies for next-generation light sources as they are expected to consume less power, occupy less space, and cause fewer failures than conventional electromagnets that require power sources. The injection magnets, including the dc septum magnet, are often restricted to a limited space, and consume large amounts of power. Thus, the advantage of building such a magnet using a permanent magnet should be as important as that of building main magnets. We designed and fabricated a permanent-magnet based dc septum magnet with a thin septum plate of 7 mm thickness, and confirmed that the measured gap and leakage fields agreed well with the design values. The permanent-magnet specific issues such as a variable-field mechanism, demagnetization and temperature dependence, are also solved. Furthermore, we explored the numerical study for reducing the septum thickness, and verified that the double-septum structure enabled a reduction in the overall septum thickness, while keeping adequate magnetic shielding.