EAST等离子体Mo Ⅴ-Mo ⅩⅧ极紫外光谱的识别

Line identification of extreme ultraviolet spectra of Mo Ⅴ to Mo ⅩⅧ in EAST tokamak

磁约束聚变等离子体中高Z杂质的存在给等离子体的约束状态带来不同程度的影响.EAST装置第一壁是钼瓦,不可避免地,等离子体与壁相互作用会使钼进入等离子体成为高Z杂质.本文利用EAST托卡马克装置快速极紫外杂质谱仪系统实现了对5—500Å(1Å=0.1 nm)波段范围内杂质线光谱进行同时监测.结合EAST等离子体低、中Z杂质的特征谱线对波长进行原位标定,基于NIST数据库和已有实验数据进行对比,并利用归一化谱线强度随时间演化行为,对较低电子温度(T_(e0)=1.5 keV)等离子体中5—485Å波段范围内由瞬态钼杂质溅射产生的钼光谱进行了系统性识别.在15—30Å和65—95Å波段范围观测到分别由电离态Mo^(19+)-Mo^(24+)(MoⅩⅩ-MoⅩⅩⅤ),Mo^(16+)-Mo^(29+)(Mo ⅤⅦ-MoⅩⅩⅩ)组成的未分辨跃迁系.而且在EAST上观测并识别出27—60Å和120—485Å波段范围内低价钼离子(Mo^(4+)-Mo^(17+))的多条谱线(MoⅤ-Mo ⅩⅧ).这些谱线包含多条强度较强且独立的禁戒线和共振线,例如Mo Ⅻ(329.414Å,336.639Å,381.125Å),Mo ⅩⅢ(340.909Å,352.994Å),Mo ⅩⅣ(373.647Å,423.576Å),Mo ⅩⅤ(50.448Å,57.927Å,58.832Å);还观测到27—32Å波段范围内6条新的钼谱线,即(27.21±0.01)Å,(27.37±0.01)Å,(28.99±0.01)Å,(30.81±0.01)Å,(31.54±0.01)Å,(31.83±0.01)Å,并推断这6条谱线可能是Mo ⅩⅤ-MoⅩⅧ谱线.同时确定了12条用于杂质输运物理研究的谱线.这些谱线的识别不仅丰富了钼原子数据库,还为EAST托卡马克开展高Z杂质行为以及输运物理的研究提供了坚实基础.

The presence of high-Z impurities in magnetically confined fusion devices has different influences on the confinement property of the plasma due to the high cooling rate of high-Z impurities.The first wall of EAST is equipped with molybdenum tiles,molybdenum particles sputtered from inevitable plasma-wall interaction enter into the plasma and become high-Z impurity.In this paper,four fast-time-response extreme ultraviolet(EUV)spectrometers,a system which is upgraded in the EAST 2021 campaign,are used to monitor the line emission from impurity ions in the 5-500Åwavelength range simultaneously.The in-situ wavelength calibration is carried out accurately using several well-known emission lines of low-and medium-Z impurity ions.The observed spectral lines are carefully identified based on the National Institute of Standards Technology(NIST)database,previously published experimental data and the time evolution of the normalized line intensity of emission lines from impurity ions.At the lower electron temperature(T_(e0)=1.5 keV),the EUV spectra emitted from molybdenum ions in the range of 5-485Åare systematically identified in EAST discharges accompanied with spontaneous sputtering events.As a result,two unresolved transition arrays of molybdenum spectra composed of Mo^(19+)-Mo^(24+)(MoⅩⅩ-Mo ⅩⅩⅤ)and Mo^(16+)-Mo^(29+)(Mo ⅩⅦ-Mo ⅩⅩⅩ)are observed in the ranges of 15-30Åand 65-95Å.In addition,several spectral lines of lower molybdenum ions of Mo^(4+)-Mo^(17+)(Mo Ⅴ-MoⅩⅧ)in the ranges of 27-60Åand 120-485Åare observed and identified on EAST for the first time,including a few strong and isolated forbidden and resonant lines,e.g.Mo Ⅻ at 329.414Å,336.639Åand 381.125Å,Mo ⅩⅢat 340.909Åand 352.994Å,Mo ⅪⅤ at 373.647Åand 423.576Å,Mo XV at 50.448Å,57.927Åand 58.832Å.Six spectral lines are newly observed in the range of 27-32Å,i.e.(27.21±0.01)Å,(27.37±0.01)Å,(28.99±0.01)Å,(30.81±0.01)Å,(31.54±0.01)Åand(31.83±0.01)Å,which may be MoⅩⅤ-Mo ⅩⅧ spectral lines.As a result,twelve strong and isolated spectral lines are chosen in routine observation for impurity transport physical study.The identification of these spectral lines not only enriches the molybdenum atom database,but also provides a solid experimental data base for magnetically confined devices to study the behavior and transport in core and edge plasmas of high-Z impurity.