Analysis of superconducting cavity quench events at SSRF

Quench is important and dangerous to superconducting RF cavities. This paper illustrates the mechanism of quench and how a quench detector works, and analyzes the quench events happening during beam operations and cavity conditioning. We find that the quench protection is mostly triggered by some reasons such as fluctuation of cavity voltage, multipacting or arc, rather than a real cavity thermal breakdown. The results will be beneficial to optimize the operation parameters of superconducting cavities, to discover the real reasons for beam trip by quench interlock, and to improve the operation stability of superconducting RF systems.     

生物质利用新途径:多元醇催化合成可再生燃料和化学品

日益严重的全球性能源和环境问题促使开发利用可再生的生物质资源成为当前研究的一个热点.本文概述了生物质基多元醇合成燃料和化学品来实现生物质转化利用的一些最新进展,特别是集中介绍了甘油和山梨醇等多元醇催化水相重整合成氢气和液体烃等燃料、催化选择氢解和氧化合成高附加值化学品或化学中间体等方面的进展,分析了存在的问题和可能的解决措施以及今后的发展趋势,指出生物质基多元醇将成为今后合成可再生燃料和化学品的新型平台分子.     

生物质利用新途径:多元醇催化合成可再生燃料和化学品

日益严重的全球性能源和环境问题促使开发利用可再生的生物质资源成为当前研究的一个热点.本文概述了生物质基多元醇合成燃料和化学品来实现生物质转化利用的一些最新进展,特别是集中介绍了甘油和山梨醇等多元醇催化水相重整合成氢气和液体烃等燃料、催化选择氢解和氧化合成高附加值化学品或化学中间体等方面的进展,分析了存在的问题和可能的解决措施以及今后的发展趋势,指出生物质基多元醇将成为今后合成可再生燃料和化学品的新型平台分子.     

Studies of an LL-type 500 MHz 5-cell superconducting cavity at SINAP

A low loss- (LL) type 500 MHz 5-cell superconducting niobium prototype cavity with a large beam aperture has been developed successfully including the optimization, the deep drawing and electron beam welding, the surface treatment and the vertical testing. The performance of the fundamental mode was optimized and the higher order modes were damped by adopting an enlarged beam pipe for propagation. Surface preparation or treatment including mechanical polishing, buffered chemical polishing and high pressure rinsing with ultra-pure water and so on was carried out carefully to ensure a perfect inner surface condition. The vertical testing results show that the accelerating voltage higher than 7.5 MV was obtained while the quality factor was better than 1× 10⁹ at 4.2 K. No obvious multipacting or field emission was found during the test. However, a quench happened while increasing the field a little higher than 7.5 MV that at present limited the cavity performance.     

生物质利用新途径:多元醇催化合成可再生燃料和化学品

日益严重的全球性能源和环境问题促使开发利用可再生的生物质资源成为当前研究的一个热点。本文概述了生物质基多元醇合成燃料和化学品来实现生物质转化利用的一些最新进展,特别是集中介绍了甘油和山梨醇等多元醇催化水相重整合成氢气和液体烃等燃料、催化选择氢解和氧化合成高附加值化学品或化学中间体等方面的进展,分析了存在的问题和可能的解决措施以及今后的发展趋势,指出生物质基多元醇将成为今后合成可再生燃料和化学品的新型平台分子。     

Design and simulation of a new type of 500 MHz single-cell superconducting RF cavity

This paper illustrates the design and simulation of a unique 500 MHz single-cell superconducting radio frequency cavity with a fluted beam pipe and a coaxial-type fundamental power coupler. The simulation results show that the cavity has a high r/Q value, a low peak surface field and a large beam aperture, so it can be a candidate cavity for high current accelerators. With the help of a fluted beam tube, almost all the higher order modes can propagate out of the cavity, especially the first two dipole modes, TE₁₁₁ and TM₁₁₀, and the first higher monopole mode, TM₀₁₁. The external quality factor of the coaxial fundamental power coupler is optimized to 1.2×10⁵, which will be useful when it is applied in the light source storage ring.     

Demagnetizing factors in patterned CoNiFe films with rectangular elements

CoNiFe patterned films with rectangular elements, all 600-nm wide but of different lengths, were fabricated and investigated by ferromagnetic resonance experiment and micromagnetic simulation. An in-plane magnetic uniaxial anisotropy was exhibited, and its value increases with the increase of the aspect ratio of the elements, which was fitted by the model, including a quasi-ellipsoid demagnetizing field and a non-uniform demagnetizing field. The relative importance of the nonuniform demagnetizing field decreased from 0.26 to 0.16 with the increase of the length-width aspect ratio of the patterned element from 1.5 to 10. The demagnetizing factors in the three principal axes were determined from the experimental data of ferromagnetic resonance, which agreed reasonably well with the values calculated by micromagnetic simulation. The calculation also indicated that the interaction between elements could be neglected when the edge-to-edge spacing between neighboring elements was larger than 3 μm in our patterned films.     

反应条件对Pt/SAPO-11催化油脂一步加氢制异构烷烃的影响

在固定床反应器中,以大豆油为模型原料,研究了反应温度、压力、氢油比和空速等条件对Pt/SAPO-11催化油脂一步加氢制异构烷烃反应的影响,并分析了反应中间产物、气体产物(CO,CO₂)及烷烃终产物的变化趋势. 结果表明,高温、低压或低氢油比可抑制酯、羧酸和醛的氢解以及醇的生成,促进油脂脱氧选择性地向脱羧和脱羰方向进行;异构烷烃收率随温度升高或空速减小而先增加后下降,但反应压力和氢油比的影响不大. 另外,对油脂一步加氢过程可能的反应历程进行了讨论.     

上海光源500MHz超导腔水平测试

上海光源是能量为3.5 GeV的第三代先进中能同步辐射光源,其储存环上安装了三台超导高频腔补偿电子因同步辐射等原因丢失的能量。为保障上海光源的长期稳定高效运行,中国科学院上海应用物理研究所和上海市低温超导高频腔技术重点实验室共同研制了具备低高次模损失参数和可承受更高入射功率的新型500 MHz超导腔,作为上海光源在线运行超导高频腔的备用腔。超导铌腔经低温垂直测试达到所需加速性能后,需要与高功率输入耦合器、高次模吸收器、低温恒温器等集成并完成水平测试,获得超导腔模组的加速性能、低温性能和真空性能。介绍了超导腔备用腔的研制、集成和测试过程,采用文丘里(Venturi)校准法获得模组的静态功耗反应模组的低温性能,并通过高功率测试获得了超导腔备用腔模组的加速性能。测试结果表明:自主研制的500 MHz超导腔备用腔满足上海光源的工作需求,在超导腔的加速腔压为2.0 MV时,无载品质因数为1.2×109 @4.2 K,且低温模组的静态热损耗为36.1 W。