Conceptual Design of a 5 T 200 mm 1 T/s Ramping NbTi Synchrotron Magnet for Cancer Treatment

Recently, a collaborative research to develop an all-superconducting synchrotron system for cancer treatment was embarked by a team led by Electronics and Telecommunications Research Institute in Korea. The system requires a 5 T dipole magnet with a uniform field region in cylindrical shape of 130 mm in diameter and 3000 mm in length, and operates at a ramping rate of 1 T/s. As the first step of the project, this paper presents a conceptual design of the magnet that consists of six single-layer cosine windings made of the NbTi Rutherford cable. Key design results include: (1) spatial field uniformity, \Delta B/B < 2\times 10^{-4} within a target space of |r|< 65 mm; (2) total ac loss of the entire coils, 297 J per cycle for a normal operation of 1 T \rightarrow 5 T \rightarrow 1 T at the 1 T/s ramping rate; (3) ac-loss-oriented cryogenic load of 23 W; (4) peak temperature of 4.9 K within the magnet during the consecutive normal operation; (5) enthalpy margin of 2.1 mJ/cm^3 with the current sharing temperature of 5.65 K; and (6) adiabatic temperature rise of 87 K upon a quench.