Field quality measurements of spare TRISTAN insertion quadrupole magnet with yoke added

A spare TRISTAN insertion quadrupole magnet was subjected to field quality measurements. The magnet was yoked and tested at 4.2 K. Comparisons were conducted on the transfer functions of the yoked magnet and the original iron-free magnet. The yoked magnet exhibited a transfer function of 23.67 T/m/kA, with the yoke adding a maximum of 15% to the quadrupole field. An increase was observed in the normal 12-th pole when the magnets were energized.