1.3 GHz超导腔的电化学青铜法铌三锡镀膜技术

由于射频超导腔具有高品质因数Q₀,大束流孔径等诸多优势,已被加速器行业广泛应用。目前纯铌腔的性能已经接近理论极限,使用Nb₃Sn薄膜腔代替纯铌腔是突破这一限制的有效手段。铌三锡具有较高的超导转变温度和过热磁场,理论预期可以大幅度提高SRF腔体工作温度和加速梯度。目前,Nb₃Sn薄膜制备技术蓬勃发展,其中锡蒸汽扩散法已经比较成熟,已制备出初步满足工程需求的铌基铌三锡薄膜射频超导腔。但是由于反应温度在1100℃以上,锡蒸汽扩散法无法摆脱纯铌基底,因此不可避免地在机械稳定性、导热性等方面有缺陷,难以满足未来高可靠性加速器的应用。青铜法广泛应用于铌三锡线缆的制备,热处理温度不高于700℃,具有制备铜基铌三锡镀膜腔的潜力。此外,电化学镀膜与其他方式相比,具有成本低、反应过程容易控制、常温常压等明显优势。本工作将上述两种工艺结合起来,研究了电化学方式在1.3 GHz铌基超导腔上镀青铜前驱体,之后热处理合成铌三锡薄膜腔。垂测结果表明,4.2 K下的薄膜腔本征Q₀为6×10⁸左右且仍具很大提升...     

C-ADS超导轮辐腔Spoke021的电磁设计与优化

为满足C-ADS项目建设对超导轮辐腔Spoke021的需求,对Spoke021进行了详细的电磁参数优化。对Spoke021的参数化模型进行参数扫描,针对腔体的关键电磁特征量寻找可能存在的极值,详细分析、解释了优化过程中各个参数发生变化的物理意义。在Spoke021各参数达到最终优化值时,表征腔体性能的两个关键比值分别为:E_p/E_(acc)=3.14,Bp/E_(aCC)=4.77 mT/(MV/m)。考虑到次级电子倍增(Multipacting,MP)对Spoke021运行中所能达到的性能指标有很重要影响,对腔体的MP进行了建模分析。结果表明,当Spoke021工作在E_(acc)=10 MV/m情况下,没有发生MP,优化得到的参数可以满足Spoke021工程设计的需要;最后计算了腔体的TTF曲线,表明该腔体具有较宽的速度接受度。     

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

A superconducting squeezed type half-wave resonator(HWR)ofβ=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.     

162.5 MHz高功率耦合器测试腔体设计

功率耦合器是粒子加速腔射频功率馈送的关键部件。耦合器在安装至加速腔之前,必须进行常温高功率测试和锻炼,以检验加工工艺和设计指标,提高其射频性能。详细介绍了中国科学院近代物理研究所ADS25 MeV加速器样机162.5 MHz耦合器测试平台的改进设计。针对原有接触式测试锻炼方式的不足,提出非接触式测试锻炼方案。对耦合器测试锻炼过程进行了物理抽象,采用理论模拟的方法分析测试腔体功率传输。基于分析结果设计了低损耗、宽通带、多用途的非接触式耦合器测试腔体。该腔体可实现20 kW测试功率下60 W左右的腔体损耗和15 MHz-3 dB带宽。Fundamental power couplers (FPC) are crucial components for feeding RF power to the accelerating cavities. Before being installed on the accelerating cavity, a coupler must be tested and conditioned at room temperature to check its fabrication quality, to verify its design specifications, and improve its RF performance. This paper thoroughly introduced the design of a test stand for the 162.5 MHz coupler of ADS 25 MeV demo facility at IMP, CAS. In order to overcome the shortcomings of the original contacting test method, a noncontacting test scheme was proposed. A physical model was built for the the coupler test and the test cavity power transmission was analyzed theoretically. Based on the analysis results, a low-loss, wide-passband and multipurpose non-contacting coupler test cavity was designed. With the new test cavity, a power loss of around 60W and a -3 dB bandwidth of 15 MHz at a test power of 20 kW was achieved.     

Electromagnetic characteristics of the CH cavity

In this paper, we present the RF simulation, the fabrication and the normal RF test of a six-cell copper model cross bar H mode (CH) cavity. The CH cavity was researched and developed at the Institute of Modern Physics for Injector II of the superconducting linac of the accelerator driven system of China, operating at a frequency 162.5 MHz, β=0.065. The deep drawing and electron beam welding were employed to fabricate this cavity, which would be used to develop the superconducting CH cavity in the future. The results of the normal RF test agree with the simulation of the electromagnetic properties, such as the electric field distribution on the cavity axis, frequency and Q factor.