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.     

Investigation on the fabrication of the 3rd harmonic superconducting cavity for the SSRF storage ring

A third harmonic superconducting niobium cavity has been proposed for installation in the Shanghai Synchrotron Radiation Facility （SSRF） storage ring to improve the Touschek lifetime. In order to investigate the feasibility of the superconducting cavity fabrication indigenously and the possibility to master the fabrica tion techniques, cavities were fabricated from copper and niobium sheets by deep drawing and electron-beam welding, and a series of measurements, such as resonant frequency, shape dimensions and wall thickness, were carried out during this process. After analysis of various problems existing in the fabrication process, technique improvements were proposed, and finally the precise shape as designed and resonant frequency within 1.2 MHz were achieved for the new completed cavities. In addition, full annealing was finally proved to be a good cure for niobium sheets＇ tearing up during deep drawing. By fabricating niobium cavities successfully, some problems to the next step were cleared. This paper introduces the process of cavity fabrication and its technique improvements towards forming, and the initial vertical test result of niobium cavity is also presented.     

Design of a higher harmonic cavity for the SSRF storage ring

Higher harmonic cavity used in the third generation synchrotron light source increases the Touschek lifetime. The higher harmonic cavity of Shanghai Synchrotron Radiation Facility (SSRF) is a 1.5GHz passive superconducting cavity. Its higher order modes (HOM) are extracted by a ferrite HOM damper out of the cryostat. Multi-cell cavity is chosen concerning the voltage. The harmonic cavity dynamics, beam dynamics with passive harmonic cavity and the design of single cell cavity are included in this paper.     

Digital prototype of LLRF system for SSRF

This paper describes a field programming gate array (FPGA) based low level radio frequency (LLRF) prototype for the SSRF storage ring RF system. This prototype includes the local oscillator (LO), analog front end, digital front end, RF out, clock distributing, digital signal processing and communication functions. All feedback algorithms are performed in FPGA. The long term of the test prototype with high power shows that the variations of the RF amplitude and the phase in the accelerating cavity are less than 1% and 1° respectively, and the variation of the cavity resonance frequency is controlled within ±10 Hz.     

二氢卟吩P6醚类衍生物的合成

以蚕沙糊状叶绿素经酸碱降解制得的二氢卟吩P6三甲酯(2)为关键中间体,设计合成了9个二氢卟吩P6醚类衍生物3a～3e和4b～4e,用UV、IR、^1H、NMR、FAB-MS和元素分析确证了它们的结构。     

不同溶剂体系中改性氢氧化镁的分散行为

研究了不同的表面改性剂对超细氢氧化镁的表面改性.并分别以水和乙醇为溶剂,研究了表面改性后氢氧化镁的分散行为.实验结果表明,以水为溶剂的体系,六偏磷酸钠分散性能最好,而以乙醇为溶剂,硅烷偶联剂KH-550分散性能最好,其用量为基体量的5%左右,可使制备的超细氢氧化镁粒径达到0.2 μm尺度以下.试验结果对进一步认识超细氢氧化镁的性质及其应用具有重要意义.     

THE POLYMERIZATION OF EPICHLOROHYDRIN WITH Nd(i-oPr)_3-Al(i-Bu)_3 SYSTEM

Epichlorohydrin (ECH) was polymerized with a rare earth catalytic system: Nd (i-OPr)_3-Al (i-Bu)_3. The effects of Al/Nd molar ratio, solvents, the polymerization time and temperature,the aging time and temperature of the catalyst preparation were studied. The results showed thatat a low Al/Nd molar ratio (4) of the Nd(i-OPr)_3-Al(i-Bu)_3 system ECH polymerized at a lowtemperature (248K) with a high conversion. The average molecular weight ofpolyepichlorohydrin (PECH) ranged from 1×10~5 to 3×10~5.     

离子色谱法在中药化学成分分析中的应用进展

离子色谱作为一种新型高效液相色谱技术, 最初主要应用于测定样品中的阴阳离子含量, 如今发展为应用于有机酸、生物胺、糖类等化合物的组成及含量测定. 离子色谱法具有操作简便、灵敏度高以及选择性好等优点, 因此, 目前离子色谱法已在能源、环境、地质、食品、药物等领域得到了广泛应用. 总结了近年来离子色谱在中药金属离子、无机阴离子、有机酸、糖类成分的研究进展, 为离子色谱法分析中药化学成分提供了参考.     

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.