Secondary electron time detector for mass measurements at CSRe

The Isochronous Mass Spectrometry is a high accurate mass spectrometer. A secondary electrons time detector has been developed and used for mass measurements. Secondary electrons from a thin carbon foil are accelerated by ail electric field and deflected 180 degrees by a magnetic field onto a micro-channel plate. The time detector has been tested with alpha particles and a time resolution of 197 ps (FWHM) was obtained in the laboratory. A mass resolution around 8 x 10(-6) For Delta m/m was achieved by using this time detector in a pilot mass measurement experiment.

Progress on the RFQ1L and LPT

The SHANS spectrometer is under construction in the Institute of Modern Physics, Chinese Academy of Science. The RFQ cooler and buncher RFQ1L is one of the key devices in the SHANS. To perform direct mass measurement, the Lanzhou Penning Trap LPT is also under construction. In this symposium, the principle of the SHANS, the status of RFQ1L and LPT and some primary test results will be reported.

超重谱仪充气段及其初步调试

论文介绍了超重充气谱仪的基本原理及此类装置的国际现状，在此基础上，对中国科学院近代物理研究所超重谱仪充气段的基本情况进行了描述。本工作采用离线和在线的方法对超重谱仪充气段进行了调试。在离线实验中，通过改变α源及探测装置的位置，确定了谱仪的接收度，得到了谱仪对不同能量及发散度的α粒子的传输效率，测试了充气对谱仪传输效率的影响，并对靶厚与传输效率间的关系进行了模拟研究。根据离线实验的结果，对谱仪进行了合理的改进。在线实验利用重离子束流轰击薄靶并观测靶反冲核的方法，确认了束流监测装置的最佳探测器和最佳安装位置，测试了谱仪对一些靶反冲核的传输效率。通过初步调试，测试了该超重谱仪充气段的一些基本性能，测量了谱仪的一些相关参数，为其投入今后的物理实验研究提供了必要的经验和参考

超重谱仪中冷却聚束器RFQ1L的模拟研究

对超重核和超重元素越来越多的探索和研究，以及对远离β稳定线奇异核的精细研究，都迫切地需要低能量、高品质的放射性束流。然而，由原子核反应产生的放射性束流普遍具有能量分散大、发射度大以及束流斑点大的缺点，因此，对放射性次级束流进行进一步的操控成为深入研究的必需条件。充有缓冲气体的RFQ冷却聚束器是适合这项任务的最佳选择。它不但可以高速度、高效率地提高束流的品质，而且适用于所有的核素。这项技术在上世纪末蓬勃地发展起来，现在已经成为世界各主要实验室进行放射性次级束流操控的必备实验装置。在中国科学院近代物理研究所，一台正在研制的专用于研究长寿命核素的超重核研究谱仪中就使用了RFQ冷却聚束器来冷却、约束和储存离子。论文首先简单介绍了近代物理研究所超重谱仪的情况和国际上RFQ冷却聚束器的研究情况，其次阐述了RFQ冷却聚束器相关原理，然后重点论述了用SIMION程序进行模拟的方法和对RFQ1L冷却段的模拟情况，并对模拟结果进行了讨论，接着，讨论了计算机无法模拟的一些因素，重点讨论了气体击穿问题，最后，对本论文的工作进行了总结，并对下一步工作进行了展望望。对RFQ1L冷却段的模拟和气体击穿问题是本论文的两个重点。冷却段的模拟是以为例进行的。通过改变缓冲气体压强、入射离子能量以及轴向电场梯度，得到了离子在RFQ冷却聚束器中不同的运动情况，得到了一些有意义的结论，有助于设备的设计和工作点的选择。另外，RFQ冷却聚束器的工作区域，正好位于缓冲气体最容易被击穿的范围，再加上射频的影响，因此气体击穿问题成为制约工作点选择的一个非常重要的因素。本文对此也作了详细的讨论

RFQ冷却聚束器RFQ1L的研制

SHANS (Spectrometer of Heavy Atoms and Nuclear Structure，重原子和核结构研究谱议)正在建设中，它不但可以直接鉴别离子的电荷数Z和质量数A，而且还将在核结构和核衰变的精细研究方面发挥重要作用。RFQ冷却聚束器RFQ1L和彭宁离子阱LPT是其中的两个重要组成部分。 RFQ冷却聚束器RFQ1L的主要目的是收集经过充气反冲谱议分离后的反应产物，然后经过冷却、聚束，使原来品质很差的束流转化为能量单一、发射度小、束斑很小的高品质束流。现在已经顺利完成了模拟、设计、机械加工和机械安装等工作，其中机械安装部分是本论文的主要工作之一。经过近半年的时间，我们克服了种种困难，高质量地完成了RFQ1L的机械安装工作。各种测量综合显示：各部件间的位置精度达到了±0.5 mm；真空系统的真空度达到了1.7×10-4 Pa，系统压升率为(0.04±0.02) Pa/h；各电极间的绝缘效果和导电效果良好。彭宁离子阱LPT的主要目的是直接高精度测量原子核的质量。质量是原子核的一个最基本属性，对检验和拓广现有核理论、研究核天体物理中的核反应过程和基本常数具有非常重要的作用。控制系统在LPT中起着至关重要的作用。控制系统的设计和实现也是本论文的另一个主要工作。本论文详细论述了LPT的控制系统LPTCtrlSys的基本要求、硬件和软件布局情况

dd→αK+K-反应截面在ANKE/COSY上的测量

ANKE谱仪是位于冷却储存环COSY上的一个内靶实验终端，在它的针对物理目标中，研究靠近 产生阈的共振态a0(980)/f0(980)是一个主要的内容。在通过强相互作用反应对a0/f0进行测量时，初态会选择使用不同的同位旋组合，也就是使用pp、 pn、pd和dd反应。本实验完成于2006年的4、5月间，是一个使用COSY所能提供的最大束流动能Td = 2.273 GeV的dd道反应，它比 产生阈高Q = 39 MeV。在实验中探测了αK+符合事件，结合使用丢失质量分析方法就可以对反应链dd → αf0 → αK+K- 以及其中的f0(980)共振态进行研究。 作为本文的主要内容这个实验，是在Monte - Carlo模拟的帮助下准备后，在4个星期的束流时间里完成的。在实验完成后，数据分析主要集中在对稀有的αK+事件进行鉴别。 ANKE的射程望远镜阵列针对K+介子的鉴别做过优化，在它的帮助下K+就可以通过飞行时间、能量损失方法，以及探测延迟发射的K+衰变产物而被挑选出来。而与之关联的α粒子则是通过它们相对于K+介子的定时点进行鉴别的，α和K+的动量及轨迹由在相应多丝正比室上测量到的径迹信息重建。由此，就可以通过使用丢失质量方法鉴别出实验中没有测量的K-介子。最终所得的αK+丢失质量谱在K-介子质量区域内呈现一个峰，其中包含大约15个事件。由这些αK+K-事件可以得到总的反应截面σtot = (9 ± 3sta ± 5sys) pb。 同位旋破缺反应dd → α(π0η) 的截面由测量得到的σtot (dd → αK+K-)值推出，进而它也给出了在WASA-at-COSY上观察这个过程所要求的最短束流时间。因为这个反应被认为主要是源于通过KK中间态的f0 → a0转化，所以它对于确定出轻标量介子a0(980)/f0(980)的结构扮演着格外重要的角色

超重谱仪充气段及其初步调试

论文介绍了超重充气谱仪的基本原理及此类装置的国际现状，在此基础上，对中国科学院近代物理研究所超重谱仪充气段的基本情况进行了描述。本工作采用离线和在线的方法对超重谱仪充气段进行了调试。在离线实验中，通过改变α源及探测装置的位置，确定了谱仪的接收度，得到了谱仪对不同能量及发散度的α粒子的传输效率，测试了充气对谱仪传输效率的影响，并对靶厚与传输效率间的关系进行了模拟研究。根据离线实验的结果，对谱仪进行了合理的改进。在线实验利用重离子束流轰击薄靶并观测靶反冲核的方法，确认了束流监测装置的最佳探测器和最佳安装位置，测试了谱仪对一些靶反冲核的传输效率。通过初步调试，测试了该超重谱仪充气段的一些基本性能，测量了谱仪的一些相关参数，为其投入今后的物理实验研究提供了必要的经验和参考

电制冷Si-PIN X射线谱仪的研制

X射线谱仪以其多用途、无损、操作简单、快速、价格低廉和运行费用很低等优点，己经成为应用最为广泛的多元素分析仪器。采用液氮冷却的X射线谱仪在荧光分析技术领域得到广泛的应用和普遍认可。液氮制冷的一个主要缺点是必须有一个液氮存储罐作为完整谱仪的一部分。从而，在实际应用中受到液氮价格贵和液氮供应厂少的限制，大大地制约了该种谱仪的进一步推广使用。如果能采用另外的技术得到足够低的温度，在此温度下探测器具有极低的漏电流，也可使X射线谱仪有极低的噪声和相当好的能量分辨率；因此克服上述限制就成为一个有重要意义的课题方向。本文在国内首次实现采用半导体电制冷技术对平面离子注入（Si一PIN）探测器制冷，降低探测器漏电流至10~(-13)以下，配合低噪声脉冲光反馈前放，成功地使得整个x射线谱仪能量分辨率达到262eV（对~(55)Fe的Mn Kα K射线）。虽然电制冷X射线谱仪的分辨率没有采用液氮冷却的好，但是它的性能已足够在包括利用X射线能量分离进行荧光分析等多种应用所需。考虑到元素周期表中钾元素以上的毗邻两元素的Ka特征X射线的能量差在380eV以上；例如，K和Ca的峰线宽分别是243eV和245 eV，由此得到电制冷X射线谱仪己可完成对K, C a和更高Z的元素进行能散荧光分析工作。并且，液氮罐的取消可方便的设计在野外使用的便携式X射线荧光分析设备。 文中全面介绍了X射线谱仪的各个组成部分和其背景知识。并详细描述了探测器系统、电制冷系统和低噪声电子学系统，充分展示了研制X射线谱仪的关键所在。最后给出了电制冷X射线谱仪的测试结果和应用设计。

High-throughput characterization of heterogeneous catalysts by temperature-programmed analysis method

A multistream reactor for high-throughput examining the surface acidity by NH3-TPD method by application of multistream mass spectrometer screening (MSMSS) technique has been developed. This method allows for examining the surface acidity of 10 catalyst samples in about 6 h, which is an improvement over the traditional process. The demonstration of the feasibility of high-throughput TPD can be significant in convincing the hardened traditionalists in the heterogeneous catalysis community that, combinatorial methods indeed should have an important place in scientific catalyst research and development. The developed method could also be used for almost all the temperature-programmed analysis theoretically with careful designed multistream reactors. (C) 2003 Elsevier B.V. All rights reserved.

Phosphoproteome analysis of mouse liver using immobilized metal affinity purification and linear ion trap mass spectrometry

Since protein phosphorylation is a dominant mechanism of information transfer in cells, there is a great need for methods capable of accurately elucidating sites of phosphorylation. In recent years mass spectrometry has become an increasingly viable alternative to more traditional methods of phosphorylation analysis. The present study used immobilized metal affinity chromatography (IMAC coupled with a linear ion trap mass spectrometer to analyze phosphorylated proteins in mouse liver. A total of 26 peptide sequences defining 26 sites of phosphorylation were determined. Although this number of identified phosphoproteins is not large, the approach is still of interest because a series of conservative criteria were adopted in data analysis. We note that, although the binding of non-phosphorylated peptides to the IMAC column was apparent, the improvements in high-speed scanning and quality of MS/MS spectra provided by the linear ion trap contributed to the phosphoprotein identification. Further analysis demonstrated that MS/MS/MS analysis was necessary to exclude the false-positive matches resulting from the MS/MS experiments, especially for multiphosphorylated peptides. The use of the linear ion trap considerably enabled exploitation of nanoflow-HPLC/MS/MS, and in addition MS/MS/MS has great potential in phosphoproteome research of relatively complex samples. Copyright (C) 2004 John Wiley Sons, Ltd.

Separation and identification of compounds in Rhizoma chuanxiong by comprehensive two-dimensional liquid chromatography coupled to mass spectrometry

A comprehensive two-dimensional liquid chromatographic separation system based on the combination of a CN column and an ODS column is developed for the separation of components in a traditional Chinese medicine (TCM) Rhizoma chuanxiong. Two columns are coupled by a two-position, eight-port valve equipped with two storage loops and controlled by a computer. The effluent is detected by both the diode array detector and atmospheric pressure chemical ionization (APCI) mass spectrometer. More than 52 components in the methanol extract of R. chuanxiong were resolved and 11 of them were preliminary identified according to their UV and mass spectra. (C) 2004 Elsevier B.V. All rights reserved.

Quantified MS analysis applied to combinatorial heterogeneous catalyst libraries

A high-throughput screening system for secondary catalyst libraries has been developed by incorporation of an 80-pass reactor and a quantified multistream mass spectrometer screening (MSMSS) technique. With a low-melting alloy as the heating medium, a uniform reaction temperature could be obtained in the multistream reactor (maximum temperature differences are less than 1 K at 673 K). Quantification of the results was realized by combination of a gas chromatogram with the MSMSS, which could provide the product selectivities of each catalyst in a heterogeneous catalyst library. Because the catalyst loading of each reaction tube is comparable to that of the conventional microreaction system and because the parallel reactions could be operated under identical conditions (homogeneous temperature, same pressure and WHSV), the reaction results of a promising catalyst selected from the library could be reasonably applied to the further scale-up of the system. The aldol condensation of acetone, with obvious differences in the product distribution over different kind of catalysts, was selected as a model reaction to validate the screening system.

Multiphoton ionization of pyrrole-water mixed clusters

Multiphoton ionization of the hydrogen,bonded pyrrole-water clusters (C4H5N)(n)(H2O)(m) is studied with a reflectron-time of flight mass spectrometer at 355 mn. With increasing partial concentration of pyrrole in a gas mixture source, a series of poly-pyrrole-water binary-mixed cluster ions can be observed, including unprotonated cluster ions [(C4H5N)(x)(H2O)(y)](+), protonated cluster ions [(C4H5N)(x)(H2O)(y)](+) and dehydrogenated cluster ions [(C4H4N)(C4H5N)(x)(H2O)(y)](+). Ab initio calculations of their structures, bond strengths, charge distributions and reaction energies are carried out. Stable structures of these clusters are obtained from the calculations. A probable formation mechanism of the cluster ions [(C4H5N)(x)(H2O)(y)](+), [(C4H5N)(x)(H2O)(y)]H+ and [(C4H4N)(C4H5N)(x) (H2O)(y)](+) is supposed to be the ionization of clusters followed by dissociation.

Mass resolved MPI spectra of methyl iodide in the 430-490 nm region

The mass resolved multiphoton ionization (MPI) spectra of methyl iodide were obtained in the 430-490 nm region using a time-of-flight (TOF) mass spectrometer. They have the same vibrational structure, which testifies that the fragment species, in the wavelength region under study, are from the photodissociation of multiphoton ionized molecular parent ions. Some features in the spectra are identified as three-photon excitations to 6p and 7s Rydberg states of methyl iodide. Two new vibrational structures of some Rydberg states are observed. The mechanism of ionization and dissociation is also discussed. (C) 2001 Elsevier Science B.V. All rights reserved.

Proton transfer reactions within the pyridazine-methanol cluster ion

The multiphoton ionization of the hydrogen-bonding cluster pyridazine-methanol (C4H4N2-CH3OH) was studied using a time-of-flight mass spectrometer at the wavelengths of 355 and 532 nm. At both wavelengths, a series of protonated C4H4N2-(CH3OH)(n)-H+ cluster ions were obtained. Relevant ab initio calculations were performed with HF and B3LYP methods. Equilibrium geometries of both neutral and ionic C4H4N2-CH3OH clusters, and dissociation channels and dissociation energies of ionic clusters, are presented. The results show that when C4H4N2-CH3OH is vertically ionized, C4H4N2H+ and CH3O are the dominant products via proton transfer reaction. A high energy barrier makes another channel corresponding to the production of C4H4N2H+ and CH2OH disfavored. (C) 2002 Elsevier Science B.V. All rights reserved.