MAGNETIC-FIELD FEATURES OF VARIOUS MAGNETIC-CIRCUITS ON THE SEXTUPOLEMAGNET

In this study, two adjacent sextants were partially cut from one side of a sextupole magnet in order to accommodate the electron beam bendin g chamber associated with a three x-ray beam dine chamber. The yoke cu tting of these two sextants creates a different magnetic circuit which induces several forbidden fields. Meanwhile, the fundamental strength of this magnetic circuit is less than that of the normal on cut sextu pole magnets in the storage ring. An induced forbidden field and the l essened sextupole strength originated from the saturation effect occur ring at the magnet's yoke cutting side. Therefore, an extra closed-loo p magnetic circuit is added across the two adjacent sextants to compen sate for the yoke's smaller core area. This extra magnetic circuit can eliminate the saturation effect which induces asymmetric field behavi or. It can also compensate for the lessened sextupole strength. In thi s work, the field distribution for various excitation currents related to the three magnetic circuits were measured. The field measurement r esults with various excitation currents tell us that the field saturat ion phenomena create the asymmetry field, forbidden field, and the les sened sextupole strength of the yoke cut magnetic circuit.