LLRF超导腔体控制系统的测试

中国科学院近代物理研究所自主研发的ADS注入器Ⅱ第一代高频低电平(LLRF)控制系统,工作频率为162.5 MHz;LLRF系统是由基于I/Q采样的正交解调技术构成的全数字闭环反馈控制系统,其主要功能是实现超导腔腔体电压幅值稳定控制、相位稳定控制与腔体谐振频率控制;LLRF控制系统在液氦温区超导腔上进行了系统稳定度和性能的在线测试,根据实验数据计算得超导腔体电压幅度稳定度为±3.4‰,相位稳定度为±0.3°,腔体表面峰值电场(Epk)能长时间稳定在25.1 MV/m。通过实验测试,检验了LLRF控制系统的性能,并对测试过程中出现的问题进行了分析,为将来超导腔LLRF控制系统运行积累了经验。     

A vertical test system for China-ADS project injector Ⅱ superconducting cavities

To test superconducting cavities, a vertical test system has been designed and set up at the Institute of Modern Physics (IMP). The system design is based on VCO-PLL hardware and the NI Labview software. The test of the HWR010#2 superconducting cavity shows that the function of this test system is satisfactory for testing the low frequency cavity.     

A vertical test system for China-ADS project injector II superconducting cavities

To test superconducting cavities, a vertical test system has been designed and set up at the Institute of Modern Physics （IMP）. The system design is based on VCO-PLL hardware and the NI Labview software. The test of the HWR010#2 superconducting cavity shows that the function of this test system is satisfactory for testing the low frequency cavity.     

HIRFL高频腔体功率耦合匹配实验研究

 介绍了HIRFL主加速器SSC高频腔体功率馈入耦合匹配系统的研究，实验结果表明，通过改变耦合环角度可更好地实现高频腔体和高频发射机之间的匹配，提高了高频腔体电压和高频发射机的工作效率。     

Optimization of the three-dimensional electric f ield in IH-DTL

The tuning process of the three-dimensional electric field near the beam axis is very important in the optimization of the Interdigital H-mode Drift Tube Linac (IH-DTL). The tuning of the longitudinal field distribution, the Kilpatrik (Kp) factor, and the transverse dipole field have been discussed in detail, combined with the radio-frequency tuning process of the 53.667 MHz short IH-DTL cavity, which was designed to accelerate ²³⁸U³⁴⁺ from 0.143 MeV/u to 0.289 MeV/u in the SSC-Linac injector project at the Institute of Modern Physics. The flatness criterion and the tube tuning method are discussed in order to meet the beam dynamics requirements. In the tube tuning process, the energy gain error in the cells should be reduced to less than ±2%, and the Kp factor should be reduced to 1.6. The transverse dipole field and the method that uses a "plunger" to dismiss this dipole field are evaluated. The experience gained from the first cavity optimization benefits the tuning process of the three remaining IH-DTL cavities in the SSC-Linac project.     

Mechanical design and analysis of a low beta squeezed half-wave resonator

A superconducting squeezed type half-wave resonator （HWR） of β=0.09 has been developed at the Institute of Modern Physics, Lanzhou. In this paper, a basic design is presented for the stiffening structure for the detuning effect caused by helium pressure and Lorentz force. The mechanical modal analysis has been investigated the with finite element method （FEM）. Based on these considerations, a new stiffening structure is proposed for the HWR cavity. The computation results concerning the frequency shift show that the low beta HWR cavity with new stiffening structure has low frequency sensitivity coefficient df/dp and Lorentz force detuning coefficient KL, and stable mechanical properties.     

R&D of an LLRF control system for a 162.5 MHz radio frequency system

This paper describes a low level radio frequency control system that was developed by the Institute of Modern Physics Chinese Academy of Sciences, and will be used in Injector of the China-ADS project. The LLRF control system consists of an RF modulated front end, fast analog-to-digital converter (ADC) modules, and a digital signal processing board based on a field programmable gate array. The system has been tested on a room temperature cavity with 12-hr, and the results illustrate that the stability of amplitude and phase achieved ±0.32% and ±0.35 degrees, respectively.     

Structural analysis of quarter-wave resonators in IMP

The taper-shaped superconducting quarter wave resonators with frequency of 80.5 MHz, β of 0.041 and 0.085 have been pre-researched. The radio frequency (RF) design of the cavities has been completed, and the structural design is also an important aspect which will be discussed in the following. The frequency shift caused by the etching effects of the surface treatment, the helium bath pressure and the Lorentz force, and the mechanical modes caused by the microphonic excitation have been analyzed. The results show that the frequency variation from the Lorentz force is not serious and stiffening rings are explored aimed at decreasing the deformation brought by the helium pressure and microphonic excitation.     

一种新型高频幅度稳定装置

 介绍了兰州重离子研究装置主加速器(SSC)使用的一种新型高频幅度稳定装置,与原有的高频幅度稳定装置相比,新装置采用了双环稳定控制模式,并引入单片机控制处理模块,实际运行实验结果稳定度达到±6×10^-4量级。     

f=325MHz,β=0.52双柱超导Spoke腔电磁设计

中国科学院近代物理研究所设计的工作频率为325 MHz、最优β为0.52的双柱超导Spoke腔的电磁已经完成。详细地描述了Spoke基部横截面形状和大小对腔体射频性能的影响,采用了跑道形来取代通常的圆形Spoke基部截面。从归一化峰值电磁场和分路阻抗两方面出发,比较了横截面为横向跑道和纵向跑道的Spoke基部。Spoke基部横截面的形状为横向跑道时能得到较好的射频参数,满足中国ADS(C-ADS)的工程需求。最后利用CST粒子工作室对得到的腔体进行了二次电子倍增分析,在工作电压附近不存在二次电子倍增,验证了该腔体形状的可行性。