RESEARCH ON BEAM FLATTENING BY USING THE HIGHER HARMONIC CAVITY IN THE HIGH INTENSITY PROTON ACCELERATOR.

从缓解空间电荷效应的角度看，在高强度质子加速器中形成平坦束是必要的。二次谐振腔用于这一目的，其中需要精确地控制腔的相位到基波相位。这项计划是为了在世界上最高的质子同步加速器装置，ISIS，英国卢瑟福·阿普尔顿实验室(RAL)进行束流实验，以研究使用低输出阻抗(LOI)二次谐振腔的空间电荷效应。由于LOI腔没有束流加载，可以实现腔相位的精确控制。2005年8月，我们成功地产生了LOI系统所需的每隙12.6KV的射频电压：频率从2.6 MHz扫频到6.2 MHz，输出阻抗小于30欧姆。虽然驱动阶段的波形失真问题仍有待解决，但LOI系统已基本准备好安装到ISIS同步加速器中进行束流测试。然而，在2006年，一个关于Muon电离冷却实验(MICE项目)的新项目在RAL提出。我们到目前为止使用的试验区是为这个项目分配的，我们别无选择，只能搬到其他地方。ISIS设施的2号大厅进行了翻新，以适应我们的LOI系统。意向书的移动和所有电力线和控制线的重新布线工作于2006年10月开始。截至2007年3月底，这些工程已经完成。因此，拟议的实验研究无法进行：束流实验预计在2007财年或以后进行。

It is essential to form a flattened bunch shape in a high intensity proton accelerator from view point of mitigation of the space charge effect. The second harmonic cavity is used for this end, where precise control of the cavity phase to the fundamental one is required. This project is intended for the beam experiments at the world highest proton synchrotron facility, ISIS, Rutherford Appleton Laboratory (RAL), UK in order to investigate the space charge effects by using the low-output impedance (LOI) second harmonic cavity. Since the LOI cavity is free from beam loading, precise control of the cavity phase can be achieved.In August, 2005, we succeeded in producing a required RF voltage, 12.6kV per gap, for the LOI system : the frequency was swept at 50Hz from 2.6 to 6.2MHz, and the output impedance less than 30ohms. Although a problem on waveform distortions in the driver stage remained to be solved, the LOI system became almost ready for installation into the ISIS synchrotron for beam test.In 2006, however, a new project on the muon ionization cooling experiment (MICE project) came up at the RAL. The experimental area we have used so far was allocated for this project, and we had no choice but to move elsewhere. The Hall 2 of the ISIS facility was refurbished to accommodate our LOI system. The movement of the LOI and re-cabling of all the power lines and control lines began in October, 2006. By the end of March, 2007, these works have been completed. Therefore, the proposed experimental research could not be performed : the beam experiments are foreseen in Fy2007 or later.