HIMAC synchrotron magnets

HIMAC is a heavy ion medical accelerator in Chiba now under construction at NIRS (National Institute of Radiological Sciences). The first beam is expected at the end of 1993. The dipole and quadrupole magnets of the synchrotron have demountable pole end pieces. The integrated field of all the dipoles of the synchrotron ring were adjusted with a precision of ±0.8×10^-4 at 1 T by field measurements. Deviations in the integrated field of each dipole were also measured at different excitation levels. By proper location of the dipoles to reduce 3rd and 4th harmonics of the error distribution in the ring, the closed orbit distortion (COD) due to the harmonic errors was estimated to be less than 2.7 mm over the entire excitation range. The shims at the ends of the quadrupole poles were adjusted to obtain a gradient length product that was uniform to within 8×10^-3 at low field and 3×10^-3 at high field over a width of 244 mm along the horizontal axis