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
自2021年11月以来,火星离子与中性粒子分析仪(Mars Ion and Neutral Particle analyzer,MINPA)持续开展火星空间中离子观测,积累了丰富的科学数据.尽管观测过程中仪器背景信号整体较弱,但在离子信号强度较低的时段,其对离子结构的识别...自2021年11月以来,火星离子与中性粒子分析仪(Mars Ion and Neutral Particle analyzer,MINPA)持续开展火星空间中离子观测,积累了丰富的科学数据.尽管观测过程中仪器背景信号整体较弱,但在离子信号强度较低的时段,其对离子结构的识别和参数计算仍可能产生一定影响.为提高数据的科学适用性,本文系统分析了MINPA离子背景信号的统计特征,揭示其能量分布均匀、方位角与质量组依赖性强、具有随时间演化的特性,并指出不同通道间存在明显差异.基于此,提出了一种根据统计特征的动态背景剔除方法,结合典型观测数据对其有效性进行验证.结果表明,该方法在去除背景干扰、提取真实离子信号方面具有良好效果,特别是在弱信号条件下显著提升了体速度与温度等关键参数的反演精度.本研究为MINPA离子数据的科学研究提供了可靠支撑.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
文摘自2021年11月以来,火星离子与中性粒子分析仪(Mars Ion and Neutral Particle analyzer,MINPA)持续开展火星空间中离子观测,积累了丰富的科学数据.尽管观测过程中仪器背景信号整体较弱,但在离子信号强度较低的时段,其对离子结构的识别和参数计算仍可能产生一定影响.为提高数据的科学适用性,本文系统分析了MINPA离子背景信号的统计特征,揭示其能量分布均匀、方位角与质量组依赖性强、具有随时间演化的特性,并指出不同通道间存在明显差异.基于此,提出了一种根据统计特征的动态背景剔除方法,结合典型观测数据对其有效性进行验证.结果表明,该方法在去除背景干扰、提取真实离子信号方面具有良好效果,特别是在弱信号条件下显著提升了体速度与温度等关键参数的反演精度.本研究为MINPA离子数据的科学研究提供了可靠支撑.
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.
