先进软磁材料在脉冲加速器束流精细时间结构测量中的应用研究

The beam intensity measurement is one of main tasks in the acclerator diagnostics. The accurate measurement and optimization of the beam time structure play an importance role in the study of the accelerator physics and the expanding beam application. To meet the requirement of the time structure measurement in pulsed accelerators, we will start from the evaluation of the permeability and magnetic loss of amorphous and nanocrystal alloy and the annealing process in different magnetic fields. Then we will focus on the study of the coil size, turns of wires on the coil, wiring methods, impedance matching network, the relation of the beam position and the monitor sensitivity. A comparison between the normal Rogowski Coil or transformers filled with silicon steel sheet and these new type current sensors will be made to verify the utilization of magnetic alloy ribbons in the wide-band current transformers for the accurate time structure measurement in pulsed accelerators. According to the international published papers and based on the former work, we can foresee a high cut off frequency of over 350MHz will be achieved on the new type current monitors, which will show its superiority in the fields of beam energy measurements via TOF, the co-check the beam loss with the other BLM sensors, the study of particle dynamics, and the machine protection.

束流流强测量是加速器束流诊断主要任务之一，精确测量、优化束流时间结构对加速器物理研究及束流扩展应用具有重要意义。针对脉冲加速器束流精细时间结构的测量需求，本项目从先进软磁材料——非晶、纳米晶磁合金的导磁率和磁损耗的频响曲线测量、退火工艺的改进等方面入手，围绕无源互感型电流探头的线圈尺寸、绕线匝数和工艺、阻抗匹配网络、束流位置与探头灵敏度关系等问题展开研究，并与传统的罗氏线圈和以硅钢片、坡莫合金、铁氧体等磁性材料加载的互感型电流探头进行性能比较，探索采用非晶、纳米晶磁合金环绕制的宽带电流互感器在脉冲加速器精细时间结构测量上的应用。根据国外相关文献和申请人前期工作基础，采用这种新型软磁合金材料制成的电流探头，预期能达到更宽的带宽（>350MHz），在高频快脉冲电流时间结构测量上具有独特的优势，并可在束流能量TOF测量、束损信息校核、粒子动力学研究、机器保护等方面有更广泛的应用。

本项目针对脉冲加速器束流精细时间结构的测量需求，从先进软磁材料——非晶、纳米晶磁合金的磁导率、矫顽力、剩余磁感应强度、磁致伸缩系数等特征磁性能参数入手，考察可用于快脉冲束流测量的软磁合金环的退火工艺，围绕无源互感型电流探头的线圈尺寸、绕线匝数、阻抗匹配网络等问题展开研究，探索采用铁基纳米晶磁合金环绕制的宽带电流互感器在脉冲加速器精细时间结构测量上的应用。采用这种经过特定退火工艺处理的软磁合金材料，本项目已成功研制出一系列快脉冲电流探头，带宽上限可达到350MHz以上，最高达到了850MHz，标称灵敏度为1.25V/A和2.5V/A，并根据测试需求，利用CST仿真，设计了一套50Ω阻抗匹配同轴标定腔。该快脉冲电流探头能够进行高频快脉冲电流时间结构的测量，造价低廉，具有完全自主知识产权，并可在束流能量TOF测量、束损信息校核、粒子动力学研究、机器保护等方面有更广泛的应用。