Design and development of a prototype of superconducting compact cyclotron

本工作是在1991年和1992年进行的。超导回旋加速器的原型一直保存在京都大学化学研究所。对于10兆电子伏的质子，回旋加速器的磁极半径为15.5厘米，束缚重约4吨。1991年，我们进行了原型机的运输和安装，并在九州大学建立了一个研究机构。通过计算设计了最佳磁场，并对平衡轨道和加速轨道上的束流特性进行了检验。通过最小二乘分析确定了等时聚焦的最佳条件。这些结果发表在1991年的一次研讨会上。为了对回旋加速器磁体进行测试，还构造了一个带翻转线圈的磁场测量系统。1992年，我们对中心区域进行了设计计算，以获得离子源注入光束的最佳条件。在目前的工作中，我们的目标是在约3.2 t的高磁场下构建无修整线圈的原型，这将要求设计计算的精度很高，因此开发了用于三维模拟的程序代码。作为最佳的束流加速条件，确定了电极形状、束流注入的电压和初始相位。为了测试回旋加速器磁体，我们通过辐射和传导对低温恒温器中液氦储存库的热流进行了估算，发现使用优化后的电源引线可将液氦的消耗降至3.6 l/h左右。从这个项目的工作中，我们发现了进一步研究的可行性。

The present work has been performed in 1991 and 1992. A prototype of superconducting cyclotron had been kept in custody at the chemical research institute, Kyoto University. The cyclotron has a pole of 15.5 c m in radius for 10 MeV protons and the yoke of about 4 ton. In 1991 we have carried out a transportation and an installation of the prototype, and established a research structure a Kyushu University. Calculations have been carried out t o design the optimum magnetic field and to examine the beam properties in equilibrium and accelerated orbits. The field shape has been determined through least-square analyses for an optimum condition for isocronous and focusing. These results were published in a symposium in 1991. A magnetic-field measurement system has also been constructed with flip-coils in order to test the cyclotron magnet. In 1992 we have performed a design calculation of the central region to obtain an optimum condition for beam injection from the ion source. In the present work we are aiming at the construction of prototype with no trimming coils under a high magnetic field of about 3.2 T. This should require a high accuracy i n the design calculations, so a program-code has been developed for 3-dimensional simulations. As an optimum condition for beam accelerations have been determined the shape of electrodes, and the voltage and the initial phase for beam injection. In order to test the cyclotron magnet we estimated the heat flow into the liquid-helium reservoir in cryostat by radiation and conduction, and found the consumption of liquid-helium can be minimized to about 3.6 l/hour by using the optimized power-leads. From the work in this project we have found the feasibility for further investigations.