Test results of spare TRISTAN insertion quadrupole magnet with yoke added in superfluid helium

One of the TRISTAN insertion quadrupole magnets, iron-free magnet with an inner aperture of 140 mm and a length of 1.45 m, was tested at 1.8 K with a thick iron yoke assembled around the magnet. Two testing cycles were performed, and during the first test, the magnet current reached 5086 A after six training quenches, which corresponds to 94% of the short sample critical current. After warming up to room temperature, the second test was performed where the magnet current reached 5067 A without a training quench. The current was almost the same as the maximum current during the first test, indicating that the previous training effect was not lost after warmed up to room temperature.