敞开式离子化质谱(ambient mass spectrometry,AMS)是近年来新兴的一种无需或者只需很少样品前处理步骤,在敞开的大气压环境中可直接对物体表面物质进行离子化的质谱分析技术。本实验室基于敞开式离子源实时直接分析(direct analysis in...敞开式离子化质谱(ambient mass spectrometry,AMS)是近年来新兴的一种无需或者只需很少样品前处理步骤,在敞开的大气压环境中可直接对物体表面物质进行离子化的质谱分析技术。本实验室基于敞开式离子源实时直接分析(direct analysis in real time,DART),进行了多方面的研究。主要包括三个方面:第一,应用研究,将简单的样品前处理技术和DART-MS结合,建立了有针对性的快速检测方法;第二,实现正相液相色谱(normal phase liquid chromatography,NPLC)和DART-MS的在线联用,解决了NPLC-MS联用中正相色谱流动相不利于样品离子化的问题,并利用该方法对NPLC分离的手性化合物进行了有效检测;第三,构建了一套新的AMS装置—等离子体辅助多波长激光解吸离子化质谱(plasma assisted multiwavelength laser desorption ioniza-tion mass spectrometry,PAMLDI-MS)。该装置将激光解吸附和等离子体辅助离子化技术相组合,并且将其与简单的TLC快速分离结合,对一些小分子混合物进行了分离检测;实验室还借助简单的铅笔芯中石墨涂覆的滤纸作为PAMLDI-MS的进样基底,发现石墨涂覆的滤纸对于待测样品有很好的基质辅助信号增强作用。展开更多
The ^(232)Th(n,f)cross section is very important in basic nuclear physics and applications based on the Th/U fuel cycle.Using the time-of-flight method and a multi-cell fast-fission ionization chamber,a novel measurem...The ^(232)Th(n,f)cross section is very important in basic nuclear physics and applications based on the Th/U fuel cycle.Using the time-of-flight method and a multi-cell fast-fission ionization chamber,a novel measurement of the^(232)Th(n,f)cross sec-tion relative to^(235)U in the 1–200 MeV range was performed at the China Spallation Neutron Source Back-n white neutron source(Back-n).The fission event-neutron energy spectra of^(232)Th and^(235)U fission cells were measured in the single-bunch mode.Corrected 232Th/235U fission cross-sectional ratios were obtained,and the measurement uncertainties were 2.5–3.7%for energies in the 2–20 MeV range and 3.6–6.2%for energies in the 20–200 MeV range.The^(232)Th(n,f)cross section was obtained by introducing the standard cross section of^(235)U(n,f).The results were compared with those of previous theoreti-cal calculations,measurements,and evaluations.The measured 232Th fission cross section agreed with the main evaluation results in terms of the experimental uncertainty,and 232Th fission resonances were observed in the 1–3 MeV range.The present results provide^(232)Th(n,f)cross-sectional data for the evaluation and design of Th/U cycle nuclear systems.展开更多
The properties of an atmospheric-pressure collisional plasma sheath with nonextensively distributed electrons and hypothetical ionization source terms are studied in this work. The Bohm criterion for the magnetized pl...The properties of an atmospheric-pressure collisional plasma sheath with nonextensively distributed electrons and hypothetical ionization source terms are studied in this work. The Bohm criterion for the magnetized plasma is extended in the presence of an ion–neutral collisional force and ionization source. The effects of electron nonextensive distribution, ionization frequency, ion–neutral collision, magnetic field angle and ion temperature on the Bohm criterion of the plasma sheath are numerically analyzed. The fluid equations are solved numerically in the plasma–wall transition region using a modified Bohm criterion as the boundary condition. The plasma sheath properties such as charged particle density, floating sheath potential and thickness are thoroughly investigated under different kinds of ion source terms, contributions of collisions, and magnetic fields. The results show that the effect of the ion source term on the properties of atmosphericpressure collisional plasma sheath is significant. As the ionization frequency increases, the Mach number of the Bohm criterion decreases and the range of possible values narrows. When the ion source is considered, the space charge density increases, the sheath potential drops more rapidly,and the sheath thickness becomes narrower. In addition, ion–neutral collision, magnetic field angle and ion temperature also significantly affect the sheath potential profile and sheath thickness.展开更多
The B2-Eirene （SOLPS 4.0） code package is used to investigate the plasma parallel flow, i.e., the scrape-off layer （SOL） flow, in the experimental advanced superconducting tokamak （EAST） divertor. Simulation res...The B2-Eirene （SOLPS 4.0） code package is used to investigate the plasma parallel flow, i.e., the scrape-off layer （SOL） flow, in the experimental advanced superconducting tokamak （EAST） divertor. Simulation results show that the SOL flow in the divertor region can exhibit complex behaviour, such as a high Mach flow and flow reversal in different plasma regimes. When the divertor plasma is in the detachment state, the high Mach flow with approaching or exceeding sonic speed is observed away from the target plate in our simulation. When the divertor plasma is in the high recycling ~tate, the flow reversM with a ~mall Mach number （IMI 〈 0.2） is observed near the X-point along the separatrix region. The driving mechanisms for the high Mach flow and the reversed flow are analysed theoretically through momentum and continuity equations, respectively. The profile of the ionization sources is shown to be a possible formation condition causing the complex behaviour of the SOL flow. In addition, the effects of the high Mach flow and the flow reversal on the impurity transport are also discussed in this paper.展开更多
An experiment facility has been set up for the study of metal cluster compounds in our laboratory, which consists of a nano-electrospray ionization source, an ion transmission and focus system, and a reflectron time-o...An experiment facility has been set up for the study of metal cluster compounds in our laboratory, which consists of a nano-electrospray ionization source, an ion transmission and focus system, and a reflectron time-of-fight mass spectrometer. Taking advantage of the nano-electrospray ionization source, polyvalent ions are usually produced in the ＂ionization＂ process and the obtained mass resolution of the equipment is over 8000. The molecular ion peaks of metal cluster compounds [Au20（PPhpy2）10Cl2]（SbF6）4, where PPhpy2=bis（2- pyridyl）phenylphosphine, and [AuaAg2（C）L6]（BF4）4, where L=2-（diphenylphosphino）-5- methylpyridine, are distinguished in the respective mass spectrum, accompanied by some fragment ion peaks. In addition, the mass-to-charge ratios of the parent ions are determi- nated. Preliminary results suggest that the device is a powerful tool for the study of metal cluster compounds. It turns out that the information obtained by the instrumentation serves as an essential supplement to single crystal X-ray diffraction for structure characterization of metal cluster compounds.展开更多
文摘敞开式离子化质谱(ambient mass spectrometry,AMS)是近年来新兴的一种无需或者只需很少样品前处理步骤,在敞开的大气压环境中可直接对物体表面物质进行离子化的质谱分析技术。本实验室基于敞开式离子源实时直接分析(direct analysis in real time,DART),进行了多方面的研究。主要包括三个方面:第一,应用研究,将简单的样品前处理技术和DART-MS结合,建立了有针对性的快速检测方法;第二,实现正相液相色谱(normal phase liquid chromatography,NPLC)和DART-MS的在线联用,解决了NPLC-MS联用中正相色谱流动相不利于样品离子化的问题,并利用该方法对NPLC分离的手性化合物进行了有效检测;第三,构建了一套新的AMS装置—等离子体辅助多波长激光解吸离子化质谱(plasma assisted multiwavelength laser desorption ioniza-tion mass spectrometry,PAMLDI-MS)。该装置将激光解吸附和等离子体辅助离子化技术相组合,并且将其与简单的TLC快速分离结合,对一些小分子混合物进行了分离检测;实验室还借助简单的铅笔芯中石墨涂覆的滤纸作为PAMLDI-MS的进样基底,发现石墨涂覆的滤纸对于待测样品有很好的基质辅助信号增强作用。
基金supported by the National Natural Science Foundation of China(Nos.11675155,11790321,and 12075216)the National Key Research and Development Plan(No.2016YFA0401603).
文摘The ^(232)Th(n,f)cross section is very important in basic nuclear physics and applications based on the Th/U fuel cycle.Using the time-of-flight method and a multi-cell fast-fission ionization chamber,a novel measurement of the^(232)Th(n,f)cross sec-tion relative to^(235)U in the 1–200 MeV range was performed at the China Spallation Neutron Source Back-n white neutron source(Back-n).The fission event-neutron energy spectra of^(232)Th and^(235)U fission cells were measured in the single-bunch mode.Corrected 232Th/235U fission cross-sectional ratios were obtained,and the measurement uncertainties were 2.5–3.7%for energies in the 2–20 MeV range and 3.6–6.2%for energies in the 20–200 MeV range.The^(232)Th(n,f)cross section was obtained by introducing the standard cross section of^(235)U(n,f).The results were compared with those of previous theoreti-cal calculations,measurements,and evaluations.The measured 232Th fission cross section agreed with the main evaluation results in terms of the experimental uncertainty,and 232Th fission resonances were observed in the 1–3 MeV range.The present results provide^(232)Th(n,f)cross-sectional data for the evaluation and design of Th/U cycle nuclear systems.
基金supported by National Natural Science Foundation of China(Nos.11975062,11605021 and 11975088)the China Postdoctoral Science Foundation(No.2017M621120)。
文摘The properties of an atmospheric-pressure collisional plasma sheath with nonextensively distributed electrons and hypothetical ionization source terms are studied in this work. The Bohm criterion for the magnetized plasma is extended in the presence of an ion–neutral collisional force and ionization source. The effects of electron nonextensive distribution, ionization frequency, ion–neutral collision, magnetic field angle and ion temperature on the Bohm criterion of the plasma sheath are numerically analyzed. The fluid equations are solved numerically in the plasma–wall transition region using a modified Bohm criterion as the boundary condition. The plasma sheath properties such as charged particle density, floating sheath potential and thickness are thoroughly investigated under different kinds of ion source terms, contributions of collisions, and magnetic fields. The results show that the effect of the ion source term on the properties of atmosphericpressure collisional plasma sheath is significant. As the ionization frequency increases, the Mach number of the Bohm criterion decreases and the range of possible values narrows. When the ion source is considered, the space charge density increases, the sheath potential drops more rapidly,and the sheath thickness becomes narrower. In addition, ion–neutral collision, magnetic field angle and ion temperature also significantly affect the sheath potential profile and sheath thickness.
基金Project supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No.085FCQ0123)the Chinese National Fusion Project for ITER (Grant No.2009GB106001)
文摘The B2-Eirene （SOLPS 4.0） code package is used to investigate the plasma parallel flow, i.e., the scrape-off layer （SOL） flow, in the experimental advanced superconducting tokamak （EAST） divertor. Simulation results show that the SOL flow in the divertor region can exhibit complex behaviour, such as a high Mach flow and flow reversal in different plasma regimes. When the divertor plasma is in the detachment state, the high Mach flow with approaching or exceeding sonic speed is observed away from the target plate in our simulation. When the divertor plasma is in the high recycling ~tate, the flow reversM with a ~mall Mach number （IMI 〈 0.2） is observed near the X-point along the separatrix region. The driving mechanisms for the high Mach flow and the reversed flow are analysed theoretically through momentum and continuity equations, respectively. The profile of the ionization sources is shown to be a possible formation condition causing the complex behaviour of the SOL flow. In addition, the effects of the high Mach flow and the flow reversal on the impurity transport are also discussed in this paper.
文摘An experiment facility has been set up for the study of metal cluster compounds in our laboratory, which consists of a nano-electrospray ionization source, an ion transmission and focus system, and a reflectron time-of-fight mass spectrometer. Taking advantage of the nano-electrospray ionization source, polyvalent ions are usually produced in the ＂ionization＂ process and the obtained mass resolution of the equipment is over 8000. The molecular ion peaks of metal cluster compounds [Au20（PPhpy2）10Cl2]（SbF6）4, where PPhpy2=bis（2- pyridyl）phenylphosphine, and [AuaAg2（C）L6]（BF4）4, where L=2-（diphenylphosphino）-5- methylpyridine, are distinguished in the respective mass spectrum, accompanied by some fragment ion peaks. In addition, the mass-to-charge ratios of the parent ions are determi- nated. Preliminary results suggest that the device is a powerful tool for the study of metal cluster compounds. It turns out that the information obtained by the instrumentation serves as an essential supplement to single crystal X-ray diffraction for structure characterization of metal cluster compounds.
