Research to built a compact system to shape irradiation field for the particle cancer therapy

点击翻译按钮获取中文摘要

In order to build a compact irradiation system for the particle cancer therapy, we fabricated a magnet to scan the beam in a plane perpendicular to the beam axis. The magnet consists of two sets of air core coils. We used the high temperature superconducting wire of the material Bi2223 which has a large margin in operating temperature. In the design, numerical analyses were performed on the magnetic fields, the cooling system and supporting frame against the electromagnetic force. Coils showed superconductivity in10 hours by conduction cooling with a single stage GM cooler. Critical currents of coils were measured to be higher than 250A at 20K as expected. No damages were observed during winding. Magnetic field was measured along the center line of each coil. The results agreed very well with the numerical calculations. An alternating current (AC) power supply was constructed with an inverter, an induction motor and a generator. Coils were excited in series with condensers. The AC power loss of coils was measured at 10, 15 and 20 Hz. The power loss per cycle is independent of the frequency. This shows the loss is the hysteretic one which is characteristic to high temperature superconductors. The loss shows 2.4^<th> power dependence on exciting currents. This phenomenon is same as that reported for low magnetic field cables. There have been few reports on the AC loss studies at high magnetic fields. Present results give the invaluable information towards future applications in cancer therapy systems, accelerators, etc.