Plasmas containing ion beams have various applications both in plasma technology and in fundamental research. The ion beam energy and flux are the two factors characterizing the beam properties. Previous studies have ...Plasmas containing ion beams have various applications both in plasma technology and in fundamental research. The ion beam energy and flux are the two factors characterizing the beam properties. Previous studies have not achieved the independent adjustment of these two parameters. In this paper, an ion-beam-background-plasma system was produced with hotcathode discharge in a double plasma device separated by two adjacent grids, with which the beam energy and flux ratio （the ratio between the beam flux and total ion flux） can be controlled independently. It is shown that the discharge voltage （i.e., voltage across the hot-cathode and anode） and the voltage drop between the two separation grids can be used to effectively control the beam energy while the flux ratio is not affected by these voltages. The flux ratio depends sensitively on hot-filaments heating current whose influence on the beam energy is relatively weak, and thus enabling approximate control of the flux ratio展开更多
Quark interactions with topological gluon fields in quantum chromodynamics can yield local P and CP violations that could explain the matter–antimatter asymmetry in our universe. Effects of P and CP violations can le...Quark interactions with topological gluon fields in quantum chromodynamics can yield local P and CP violations that could explain the matter–antimatter asymmetry in our universe. Effects of P and CP violations can lead to charge separation under a strong magnetic field, a phenomenon called the chiral magnetic effect(CME).Early measurements of the CME-induced charge separation in heavy ion collisions are dominated by physics backgrounds. This report discusses the recent innovative efforts in eliminating those backgrounds, namely by eventshape engineering, invariant mass dependence, and reaction and participant plane comparison. The backgroundfree CME measurements using these novel methods are presented.展开更多
长江三角洲在经济高速发展的同时,经历了较为严重的大气污染,受到了越来越多的关注.本研究于2009年4月(代表春季)、7月(代表夏季)和10月(代表秋季)在临安区域本底观测站使用低流量大气颗粒物采样器(FRM Omni sampler,BGI Inc.,USA)同步...长江三角洲在经济高速发展的同时,经历了较为严重的大气污染,受到了越来越多的关注.本研究于2009年4月(代表春季)、7月(代表夏季)和10月(代表秋季)在临安区域本底观测站使用低流量大气颗粒物采样器(FRM Omni sampler,BGI Inc.,USA)同步采集了PM_(2.5)和PM_(1.0)样品,并用离子色谱(IC)分析了样品中的水溶性无机离子(阴离子:F^-,Cl^-,NO_3^-,SO_4^(2-);阳离子:Na^+,NH_4^+,K^+,Mg^(2+),Ca^(2+)).结果表明:临安区域本底站PM_(2.5)和PM_(1.0)中水溶性无机离子总浓度夏季最低.NH_4^+、SO_4^(2-)和NO3-是最主要的无机离子,在PM_(2.5)中占水溶性无机离子总浓度的比值分别为78%(春季),85%(夏季)和80%(秋季),在PM_(1.0)中占水溶性无机离子总浓度的比值分别为78%(春季),83%(夏季),79%(秋季).NH_4^+和SO_4^(2-)的摩尔比均>2,表明SO_4^(2-)完全被NH_4^+中和,可能主要以(NH4)_2SO_4的形态存在.PM_(2.5)和PM_(1.0)中NO_3^-/SO_4^(2-)质量比的变化范围分别为0.31~0.84和0.44~0.63,说明临安市以固定源污染为主.展开更多
基金supported by National Natural Science Foundation of China(Nos.11575183,11175177)
文摘Plasmas containing ion beams have various applications both in plasma technology and in fundamental research. The ion beam energy and flux are the two factors characterizing the beam properties. Previous studies have not achieved the independent adjustment of these two parameters. In this paper, an ion-beam-background-plasma system was produced with hotcathode discharge in a double plasma device separated by two adjacent grids, with which the beam energy and flux ratio （the ratio between the beam flux and total ion flux） can be controlled independently. It is shown that the discharge voltage （i.e., voltage across the hot-cathode and anode） and the voltage drop between the two separation grids can be used to effectively control the beam energy while the flux ratio is not affected by these voltages. The flux ratio depends sensitively on hot-filaments heating current whose influence on the beam energy is relatively weak, and thus enabling approximate control of the flux ratio
基金supported in part by the National Natural Science Foundation of China(No.11747312)the U.S.Department of Energy(No.de-sc0012910)
文摘Quark interactions with topological gluon fields in quantum chromodynamics can yield local P and CP violations that could explain the matter–antimatter asymmetry in our universe. Effects of P and CP violations can lead to charge separation under a strong magnetic field, a phenomenon called the chiral magnetic effect(CME).Early measurements of the CME-induced charge separation in heavy ion collisions are dominated by physics backgrounds. This report discusses the recent innovative efforts in eliminating those backgrounds, namely by eventshape engineering, invariant mass dependence, and reaction and participant plane comparison. The backgroundfree CME measurements using these novel methods are presented.
文摘长江三角洲在经济高速发展的同时,经历了较为严重的大气污染,受到了越来越多的关注.本研究于2009年4月(代表春季)、7月(代表夏季)和10月(代表秋季)在临安区域本底观测站使用低流量大气颗粒物采样器(FRM Omni sampler,BGI Inc.,USA)同步采集了PM_(2.5)和PM_(1.0)样品,并用离子色谱(IC)分析了样品中的水溶性无机离子(阴离子:F^-,Cl^-,NO_3^-,SO_4^(2-);阳离子:Na^+,NH_4^+,K^+,Mg^(2+),Ca^(2+)).结果表明:临安区域本底站PM_(2.5)和PM_(1.0)中水溶性无机离子总浓度夏季最低.NH_4^+、SO_4^(2-)和NO3-是最主要的无机离子,在PM_(2.5)中占水溶性无机离子总浓度的比值分别为78%(春季),85%(夏季)和80%(秋季),在PM_(1.0)中占水溶性无机离子总浓度的比值分别为78%(春季),83%(夏季),79%(秋季).NH_4^+和SO_4^(2-)的摩尔比均>2,表明SO_4^(2-)完全被NH_4^+中和,可能主要以(NH4)_2SO_4的形态存在.PM_(2.5)和PM_(1.0)中NO_3^-/SO_4^(2-)质量比的变化范围分别为0.31~0.84和0.44~0.63,说明临安市以固定源污染为主.
