Sextupole winding in a dipole magnet gap for a storage ring

In special synchrotrons a controllable sextupole field is required in the bending dipole magnets. One of them is NewSUBARU, a 1.5 GeV synchrotron light source. It has inverse dipole (bending) magnets to control the linear momentum compaction factor. It has to have a controllable sextupole at the position of the inverse bend for an independent control of its horizontal chromaticity and its higher order momentum compaction factor while keeping enough dynamic aperture. The inverse bend is a normal conducting C-type magnet whose bending angle, maximum field strength, yoke length and magnet gap are - 8 degrees, 1.554 T, 444 mm and 40 mm, respectively. The height of vacuum chamber in it is 28 mm, smaller than that in a normal bending magnet, while the magnet gaps are the same. This is because the vertical beta function at the inverse dipole is smaller. A pair of water-cooled coil sheets, which produce a sextupole field, are set at the space between the chamber and the pole face. Its thickness, the maximum current and the maximum sextupole field are 4.4 mm, 154 A and 70 T/m/sup 2/, respectively.