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Development of Very Thin Beam Chopper with High Field Gradient for High Intensity Accelerator

用于高强度加速器的高场梯度超薄光束斩波器的开发

基本信息

批准号：
11640303
负责人：
OHMORI Chihiro
金额：
$ 2.24万
依托单位：
High Energy Accelerator Research Organization (KEK)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

Proton and ion Synchrotrons consist of an ion source, linear accelerator and synchrotron (s). Each accelerator has a different time structure and RF frequency. Usually, the beam from the ion source has the width of few hundred micro seconds and it is much longer than the time structure in the synchrotron (less than one micro second). Because of the difference on the time structure, the beam will be spread out in the synchrotron while the injection. To capture the beam for the acceleration, an adiabatic capture method is used and the beam will be bunched by the RF voltage. However, the beam loss is easily occurred during the process because of the space charge effects and others. On the high intensity proton accelerator, a beam chopper is employed to reduce the loss. So far, the beam is kicked to the transverse direction before the injection. A disadvantage of this method is the transverse halo formation by the slow rise and fall times of the chopper magnets. A new type of beam chopper using the longitudinal kick is proposed. The transverse halo formation can be avoidable by the method. The chopper is located between the RFQ and ion source. By the energy modulation of about 10%, kicked part of the beam will not be accelerated in the RFQ.We developed the chopper using a magnetic alloy which has very high permeability. The high power FET switch drives the chopper. The beam test has been performed and it was chopped with the repetition rate of 1 MHz. The chopped beam was injected and accelerated, successfully. By using the chopper, low emittance beam was also formed and it is very useful for the accelerator study.

质子和离子同步加速器由离子源、直线加速器和同步加速器组成。每个加速器都有不同的时间结构和射频频率。通常，离子源的光束宽度为几百微秒，比同步加速器中的时间结构（小于1微秒）长得多。由于时间结构上的差异，光束在同步加速器内注入时会扩散。为了捕获加速光束，采用绝热捕获方法，光束将被射频电压聚束。然而，由于空间电荷等因素的影响，在此过程中容易产生束流损耗。在高强度质子加速器上，采用了波束斩波器来减少损耗。到目前为止，在注入之前，光束被踢向横向。这种方法的缺点是由于斩波磁体的缓慢上升和下降时间而形成横向晕。提出了一种新型的纵波斩波器。该方法可避免横向光晕的形成。斩波器位于RFQ和离子源之间。通过10%左右的能量调制，束的踢出部分不会在RFQ中加速。我们使用磁导率很高的磁性合金开发了这种斩波器。高功率FET开关驱动斩波器。进行了波束测试，并以1mhz的重复频率进行了斩波。切割后的光束被成功注入并加速。利用斩波器还可以形成低发射度光束，这对加速器的研究非常有用。