Tungsten has been chosen as one of the most promising candidates as the plasma-facing material in future fusion reactors. Although tungsten has numerous advantages compared with other materials, issues including dust ...Tungsten has been chosen as one of the most promising candidates as the plasma-facing material in future fusion reactors. Although tungsten has numerous advantages compared with other materials, issues including dust are rather difficult to deal with. Dust is produced in fusion devices by energetic plasma-surface interaction. The re-deposition of dust particles could cause the retention of fuel atoms. In this work, tungsten is deposited with deuterium plasma by hollow cathode discharge to simulate the dust production in a tokamak. The morphology of the deposited tungsten can be described as a film with spherical particles on it. Thermal desorption spectra of the deposited tungsten show extremely high desorption of the peak positions. It is also found that there is a maximum retention of deuterium in the deposited tungsten samples due to the dynamic equilibrium of the deposition and sputtering process on the substrates.展开更多
Samples of chemically vapor deposited(CVD)coatings of tungsten carbides W_(45)C_(55)and W_(60)C_(40)and samples of hot-rolled tungsten were exposed to deuterium(D)plasma at sample temperatures ranging from 323 to 813 ...Samples of chemically vapor deposited(CVD)coatings of tungsten carbides W_(45)C_(55)and W_(60)C_(40)and samples of hot-rolled tungsten were exposed to deuterium(D)plasma at sample temperatures ranging from 323 to 813 K,as a result of which the samples were irradiated with D ions with an energy of about 200 eV per D particle at a flux of D particles of about1.1×10^(21)D·m^(-2)·s^(-1)to a fluence of about 2×10^(24)D·m^(-2).The concentration of deuterium in these samples was examined by the D(3 He,p)4 He nuclear reaction.Based on the measured deuterium depth profiles and assuming that these profiles are determined by diffusing D atoms,the diffusion coefficients of deuterium in the CVD tungsten carbide coatings were determined.Using these diffusion coefficients,an estimate of the Arrhenius relation for the diffusion coefficients of deuterium in CVD tungsten carbide coatings was obtained:D=2.5×10^(-3)exp(-1.12 eV/kT)m~2·s^(-1),where T is temperature expressed in Kelvin,and k is the Boltzmann constant.The concentration of trapped deuterium in the bulk of CVD tungsten carbide coatings is practically independent of the stoichiometry of the coatings.It decreases from about 5×10^(-2)to about 7×10^(-4)D/(W+C)with an increase in the deuterium plasma exposure temperature from 373 to 813 K.The concentration of trapped deuterium in hot-rolled tungsten,expressed in units of the D/W atomic ratio,is more than an order of magnitude lower than the concentration of deuterium in tungsten carbides,and also decreases with increasing plasma exposure temperature.展开更多
Based on our previous work(Phys.Plasmas 25 012704(2018)),a fitting formula is given for electron-ion energy partition fraction of 3.54-MeV fusion alpha particles in deuterium-tritium(DT) plasmas as a function of plasm...Based on our previous work(Phys.Plasmas 25 012704(2018)),a fitting formula is given for electron-ion energy partition fraction of 3.54-MeV fusion alpha particles in deuterium-tritium(DT) plasmas as a function of plasma mass density ρ,electron temperature T_(e),and ion temperature T_(i).The formula can be used in a huge range of the plasma state,where ρ varies between 1.0 g/cc~10.0^(3) g/cc and both T_(e) and T_(i) change from 0.1 keV to 100.0 keV.Relativistic effect for electrons is investigated including the effect of the projectile recoil in the plasmas at T_(e)≥ 50.0 keV.The partition fraction for T_(e)>T_(i) is found to be close to that for T_(e)=T_(i). The comparisons with other fitting results are made at some plasma densities when T_(e)=T_(i),and the difference is explained.The fitting result is very close to the calculated one in most cases,which is convenient for the simulation of alpha heating in hot dense DT plasmas for inertial confined fusion.展开更多
Based on neon gas puffing, an active feedback control of H-mod plasma divertor detachment experiment was successfully operated on the EAST tokamak. During the feedback control discharge, the plasma was detached by puf...Based on neon gas puffing, an active feedback control of H-mod plasma divertor detachment experiment was successfully operated on the EAST tokamak. During the feedback control discharge, the plasma was detached by puffing neon gas and the strike point splitting phenomenon on divertor target was also clearly observed by divertor probes diagnostic.In boundary region, many neutral particle processes(atom and molecule) were happened and accompanied by their emission spectra under the detachment discharge. By studying these emission spectra, it is helpful for us to understand the role of atoms and molecules in boundary recycling, which is important for studying the physical mechanism of divertor detachment. For the Fulcher-α system(d(3 p)3Πu±→ a(2 s)3Σg+), D2 emission spectra in the range from 601 nm to 606 nm were observed, identified and fitted in the detachment experiment for the first time on the EAST, and the spectra in the Q(0–0) band(d3Πu-→ a(2 s)3Σg+) in the Q branch of the Fulcher-α system were used for detailed analysis to acquire the boundary region temperature Te(below 5eV), which could not be provided very well by other diagnostics on the EAST. An electronic version deuterium molecular spectral line database was established to identify the spectral lines and a multi-peak fitting program was developed to fit and analyze the observed spectra.展开更多
托卡马克等离子体破裂会产生逃逸电流,如不进行抑制,其携带的巨大能量将对设备造成严重破坏。本文使用DREAM程序中的流体模型,基于中国环流器二号M(HL-2M)托卡马克装置大等离子体电流放电条件,研究注入氘氩/氖混合气体对破裂逃逸电流的...托卡马克等离子体破裂会产生逃逸电流,如不进行抑制,其携带的巨大能量将对设备造成严重破坏。本文使用DREAM程序中的流体模型,基于中国环流器二号M(HL-2M)托卡马克装置大等离子体电流放电条件,研究注入氘氩/氖混合气体对破裂逃逸电流的影响。研究表明:注入氘氩/氖混合气体可以抑制最终形成的平台逃逸电流。在讨论的破裂前等离子体电流I_(p)范围内,最优条件下氩/氖在混合气体中的含量应在0.50%~0.70%,氘的注入量应在10^(20)~10^(21)m^(-3)。在这个范围外,氘氩/氖混合气体注入对逃逸电流的抑制效果都会减弱,甚至会增大逃逸电流。破裂前等离子体电流I_(p)是影响逃逸电流的关键因素。I_(p)越大,形成的逃逸电流越大,也需要注入更多的混合气体。在I_(p)高达10 MA的聚变堆级托卡马克装置上,注入混合气体的密度需要达到10^(22)m^(-3),这是目前大量气体注入(Massive Gas Injection,MGI)技术所不能达到的,通过散裂弹丸注入氘氩/氖混合物将是更加可行的方式。展开更多
为了满足核材料研究中对氘(D)滞留研究的需要,基于北京大学4.5 MV静电加速器,搭建三路探测系统的NRA分析装置,并建立氘含量及深度分布的多能点NRA方法。该方法利用D(~3He,p)~4He反应,采用多个能量(0.8~3.6 Me V)~3He^+入射,同时探测出射...为了满足核材料研究中对氘(D)滞留研究的需要,基于北京大学4.5 MV静电加速器,搭建三路探测系统的NRA分析装置,并建立氘含量及深度分布的多能点NRA方法。该方法利用D(~3He,p)~4He反应,采用多个能量(0.8~3.6 Me V)~3He^+入射,同时探测出射的p和4He,在较大的深度范围内有较好的深度分辨和较高的灵敏度。还在该系统上完成3He-D反应135°微分截面的测量,微分截面误差好于±3.9%。采用该方法进行初次样品氘含量的深度分布分析,靶为氘注入的PC-W样品以及TOKAMAK AUG偏滤器外打击点附近的CMSII-W样品。在钨样中获得的探测深度约6μm,在钨整个探测深度内的深度分辨小于1.5μm,表面可达约20 nm,其探测灵敏度约5×1019 D/m^2。该方法的分析误差除统计及拟合误差外,还包含±7.5%的实验参数测量误差。展开更多
Based on the passive spectroscopy,the D_α atomic emission spectra in the boundary region of the plasma have been measured by a high resolution optical spectroscopic multichannel analysis（OSMA） system in EAST tokama...Based on the passive spectroscopy,the D_α atomic emission spectra in the boundary region of the plasma have been measured by a high resolution optical spectroscopic multichannel analysis（OSMA） system in EAST tokamak.The Zeeman splitting of the D_α spectral lines has been observed.A fitting procedure by using a nonlinear least squares method was applied to fit and analyze all polarization π and ±σ components of the D_α atomic spectra to acquire the information of the local plasma.The spectral line shape was investigated according to emission spectra from different regions（e.g.,low-field side and high-field side） along the viewing chords.Each polarization component was fitted and classified into three energy categories（the cold,warm,and hot components） based on different atomic production processes,in consistent with the transition energy distribution by calculating the gradient of the D_α spectral profile.The emission position,magnetic field intensity,and flow velocity of a deuterium atom were also discussed in the context.展开更多
基金Supported by the National Magnetic Confinement Fusion Program under Grant No 2015GB109003the National Natural Science Foundation of China under Grant No 11675010
文摘Tungsten has been chosen as one of the most promising candidates as the plasma-facing material in future fusion reactors. Although tungsten has numerous advantages compared with other materials, issues including dust are rather difficult to deal with. Dust is produced in fusion devices by energetic plasma-surface interaction. The re-deposition of dust particles could cause the retention of fuel atoms. In this work, tungsten is deposited with deuterium plasma by hollow cathode discharge to simulate the dust production in a tokamak. The morphology of the deposited tungsten can be described as a film with spherical particles on it. Thermal desorption spectra of the deposited tungsten show extremely high desorption of the peak positions. It is also found that there is a maximum retention of deuterium in the deposited tungsten samples due to the dynamic equilibrium of the deposition and sputtering process on the substrates.
文摘Samples of chemically vapor deposited(CVD)coatings of tungsten carbides W_(45)C_(55)and W_(60)C_(40)and samples of hot-rolled tungsten were exposed to deuterium(D)plasma at sample temperatures ranging from 323 to 813 K,as a result of which the samples were irradiated with D ions with an energy of about 200 eV per D particle at a flux of D particles of about1.1×10^(21)D·m^(-2)·s^(-1)to a fluence of about 2×10^(24)D·m^(-2).The concentration of deuterium in these samples was examined by the D(3 He,p)4 He nuclear reaction.Based on the measured deuterium depth profiles and assuming that these profiles are determined by diffusing D atoms,the diffusion coefficients of deuterium in the CVD tungsten carbide coatings were determined.Using these diffusion coefficients,an estimate of the Arrhenius relation for the diffusion coefficients of deuterium in CVD tungsten carbide coatings was obtained:D=2.5×10^(-3)exp(-1.12 eV/kT)m~2·s^(-1),where T is temperature expressed in Kelvin,and k is the Boltzmann constant.The concentration of trapped deuterium in the bulk of CVD tungsten carbide coatings is practically independent of the stoichiometry of the coatings.It decreases from about 5×10^(-2)to about 7×10^(-4)D/(W+C)with an increase in the deuterium plasma exposure temperature from 373 to 813 K.The concentration of trapped deuterium in hot-rolled tungsten,expressed in units of the D/W atomic ratio,is more than an order of magnitude lower than the concentration of deuterium in tungsten carbides,and also decreases with increasing plasma exposure temperature.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0402300 and 2017YFA0403200)the National Natural Science Foundation of China(Grant No.11574034)+1 种基金the Innovation Development Foundation of China Academy of Engineering Physics(CAEP)(Grant No.CX20200029)the Science Challenge Project(Grant Nos.JCKY201612A501)。
文摘Based on our previous work(Phys.Plasmas 25 012704(2018)),a fitting formula is given for electron-ion energy partition fraction of 3.54-MeV fusion alpha particles in deuterium-tritium(DT) plasmas as a function of plasma mass density ρ,electron temperature T_(e),and ion temperature T_(i).The formula can be used in a huge range of the plasma state,where ρ varies between 1.0 g/cc~10.0^(3) g/cc and both T_(e) and T_(i) change from 0.1 keV to 100.0 keV.Relativistic effect for electrons is investigated including the effect of the projectile recoil in the plasmas at T_(e)≥ 50.0 keV.The partition fraction for T_(e)>T_(i) is found to be close to that for T_(e)=T_(i). The comparisons with other fitting results are made at some plasma densities when T_(e)=T_(i),and the difference is explained.The fitting result is very close to the calculated one in most cases,which is convenient for the simulation of alpha heating in hot dense DT plasmas for inertial confined fusion.
基金Project supported by the National Natural Science Foundation of China(Grant No.11805234)
文摘Based on neon gas puffing, an active feedback control of H-mod plasma divertor detachment experiment was successfully operated on the EAST tokamak. During the feedback control discharge, the plasma was detached by puffing neon gas and the strike point splitting phenomenon on divertor target was also clearly observed by divertor probes diagnostic.In boundary region, many neutral particle processes(atom and molecule) were happened and accompanied by their emission spectra under the detachment discharge. By studying these emission spectra, it is helpful for us to understand the role of atoms and molecules in boundary recycling, which is important for studying the physical mechanism of divertor detachment. For the Fulcher-α system(d(3 p)3Πu±→ a(2 s)3Σg+), D2 emission spectra in the range from 601 nm to 606 nm were observed, identified and fitted in the detachment experiment for the first time on the EAST, and the spectra in the Q(0–0) band(d3Πu-→ a(2 s)3Σg+) in the Q branch of the Fulcher-α system were used for detailed analysis to acquire the boundary region temperature Te(below 5eV), which could not be provided very well by other diagnostics on the EAST. An electronic version deuterium molecular spectral line database was established to identify the spectral lines and a multi-peak fitting program was developed to fit and analyze the observed spectra.
文摘托卡马克等离子体破裂会产生逃逸电流,如不进行抑制,其携带的巨大能量将对设备造成严重破坏。本文使用DREAM程序中的流体模型,基于中国环流器二号M(HL-2M)托卡马克装置大等离子体电流放电条件,研究注入氘氩/氖混合气体对破裂逃逸电流的影响。研究表明:注入氘氩/氖混合气体可以抑制最终形成的平台逃逸电流。在讨论的破裂前等离子体电流I_(p)范围内,最优条件下氩/氖在混合气体中的含量应在0.50%~0.70%,氘的注入量应在10^(20)~10^(21)m^(-3)。在这个范围外,氘氩/氖混合气体注入对逃逸电流的抑制效果都会减弱,甚至会增大逃逸电流。破裂前等离子体电流I_(p)是影响逃逸电流的关键因素。I_(p)越大,形成的逃逸电流越大,也需要注入更多的混合气体。在I_(p)高达10 MA的聚变堆级托卡马克装置上,注入混合气体的密度需要达到10^(22)m^(-3),这是目前大量气体注入(Massive Gas Injection,MGI)技术所不能达到的,通过散裂弹丸注入氘氩/氖混合物将是更加可行的方式。
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11275231 and 11575249)the National Magnetic Confinement Fusion Energy Research Program of China(Grant No.2015GB110005)
文摘Based on the passive spectroscopy,the D_α atomic emission spectra in the boundary region of the plasma have been measured by a high resolution optical spectroscopic multichannel analysis（OSMA） system in EAST tokamak.The Zeeman splitting of the D_α spectral lines has been observed.A fitting procedure by using a nonlinear least squares method was applied to fit and analyze all polarization π and ±σ components of the D_α atomic spectra to acquire the information of the local plasma.The spectral line shape was investigated according to emission spectra from different regions（e.g.,low-field side and high-field side） along the viewing chords.Each polarization component was fitted and classified into three energy categories（the cold,warm,and hot components） based on different atomic production processes,in consistent with the transition energy distribution by calculating the gradient of the D_α spectral profile.The emission position,magnetic field intensity,and flow velocity of a deuterium atom were also discussed in the context.
