目的 研究自偏压对射频等离子体恢复单晶第一镜反射率的影响,为未来聚变堆诊断第一镜反射率原位恢复提供重要参考和依据。方法 在实验室条件下,采用射频氩等离子体,在工作气压为1 Pa,自偏压分别为-100、-200和-300 V条件下,开展单晶钼第一镜表面Al2O3清洗实验,并通过扫描电子显微镜、紫外可见分光光度计和非接触式三维表面轮廓仪等手段对第一镜表面和光学特性进行表征。结果 当自偏压为-300 V时,射频氩等离子体清洗23 h后,第一镜表面Al2O3杂质被完全去除,镜表面平整,第一镜全反射率有效恢复,且漫反射率变化小（<1％）;当自偏压为-200 V时,射频氩等离子体清洗33 h后,第一镜表面的Al2O3杂质被完全去除,全反射率恢复到清洗前的水平;当自偏压为-100 V时,射频氩等离子体清洗354 h后,第一镜表面仍存在Al2O3杂质残留,全反射率仅恢复到清洗前的70％。结论 单晶钼材料具有良好的抗溅射能力,射频等离子体清洗对第一镜表面损伤小,清洗后第一镜漫反射率较低。且采用绝对值较高的自偏压（-300 V）,溅射第一镜杂质粒子能量高和沉积杂质溅射率高,第一镜反射率恢复效率更快;低自偏压绝对值（-100 V）条件下的溅射再沉积和低通量溅射粒子无法完全去除第一镜表面的杂质沉积。因此,单晶第一镜清洗可适当提高自偏压绝对值以提升清洗效率。
Abstract
Radio frequency (RF) plasma cleaning technology is emerging as the most promising technique for in-situ cleaning of the first mirror in future Tokamak devices. The self-bias voltage, which determines the ion energy and sputtering behavior, is a critical factor affecting the efficiency and effectiveness of RF plasma cleaning. In order to investigate the impact of self-bias on the recovery of reflectivity of single crystal first mirrors in radio frequency (RF) plasma, the work aims to provide important references and basis for the in-situ recovery of reflectivity of first mirrors in future fusion reactors. Single crystal molybdenum (Mo) samples with a (110) crystal orientation, a diameter of 25 mm, and a thickness of 4 mm were used as first mirror substrates. A 30 nm thick Al/Al2O3 film was coated on the mirror surfaces via magnetron sputtering to simulate impurity contamination in the device. In this experiment, argon (Ar) was used as the working gas with the operating pressure set at 1 Pa. The self-bias voltages were set at -100 V, -200 V, and -300 V, respectively, to clean the Al2O3 deposition on the surface of the single crystal molybdenum (Mo) first mirror. The surface morphology and optical properties of the mirrors were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), ultraviolet-visible spectrophotometry, and non-contact three-dimensional surface profiling. When the self-bias voltage was set to -300 V, complete removal of Al2O3 deposition was achieved after 23 hours of RF argon plasma cleaning. The mirror surface was restored to a flat state, and the total reflectivity of the first mirror was effectively recovered with minimal change in diffuse reflectivity (<1%). At a self-bias voltage of -200 V, the complete removal of Al2O3 deposition required 33 hours of cleaning, and the total reflectivity was restored to the level before coating of Al2O3 deposition. However, at the self-bias voltage of -100 V, even though after 354 hours of cleaning, Al2O3 deposition residues remained on the surface, and the total reflectivity only recovered to 70% of the pre-coating level. Due to the good sputtering resistance of single crystal Mo material, RF plasma cleaning had the least damage to the mirror, and the diffuse reflection coefficient was kept at a low level after cleaning. Higher absolute self-bias voltages (-300 V) enhanced the energy and sputtering rate of impurity particles, leading to faster and more complete removal of deposition and quicker reflectivity recovery. In contrast, the ion sputtering energy at low absolute self-bias (-100 V) was too low to effectively bombard and remove the impurity deposition on the surface of the first mirror. Some of the sputtered impurities were redeposited on the surface of the first mirror. These resulted in the inability to completely remove the Al2O3 deposition layer on the surface of the first mirror even after a long-time (354 h) cleaning. The low roughness and diffuse reflectance of the surface of the first mirror of single crystal molybdenum after cleaning prove that single crystal molybdenum material is an excellent candidate material for the diagnosis of the first mirror in future fusion reactors. When radio frequency plasma is used to achieve in-situ cleaning of the first mirror in future fusion reactor devices such as ITER, the absolute value of self-bias can be appropriately increased to improve cleaning efficiency.
关键词
第一镜 /
射频等离子清洗 /
反射率 /
自偏压 /
单晶Mo /
Al2O3沉积
Key words
first mirror /
RF plasma cleaning /
reflectivity /
self-bias /
single crystal Mo /
Al2O3 deposition
{{custom_sec.title}}
{{custom_sec.title}}
{{custom_sec.content}}
参考文献
[1] NAYLOR G A, SCANNELL R, BEURSKENS M, et al. The ITER Thomson Scattering Core LIDAR Diagnostic[J]. Journal of Instrumentation, 2012, 7(3): C03043-1/10.
[2] SHIMOMURA Y, The Present Status and Future Prospects of the ITER Project[J]. Journal of Nuclear Materials, 2004, 329/330/331/332/333: 5-11.
[3] LINKE J, DU J, LOEWENHOFF T, et al.Challenges for Plasma-Facing Components in Nuclear Fusion[J]. Matter and Radiation at Extremes, 2019, 4(5): 056201.
[4] STANGEBY, PETER C, The Plasma Boundary of Magnetic Fusion Devices[M]. Pennsylvania: Institute of Physics Pub, 2000: 103-105.
[5] BUSCHMANN B, SCHEIDT A, MAUSBACH M, et al.Plasma Enhanced Deposition of Corrosion Resistant High Reflectivity Mirrors[J]. Surface and Coatings Technology, 1995, 74 : 993-997.
[6] 郑灵, 赵青, 周艳. HL-2A第一镜挡板防护效果模拟[J]. 物理学报, 2011, 60(8): 085204.
ZHENG L, ZHAO Q, ZHOU Y, Simulation of Protective Effect of the Buffer on the First Mirror in HL-2A Tokamak[J]. Acta Phys. Sin., 2011, 60(8): 085204.
[7] LITNOVSKY A, VOITSENYA V, COSTLEY A, et al.First Mirrors for Diagnostic Systems of ITER[J]. Nuclear Fusion, 2007, 47(8): 833.
[8] ROCHE H, COURTOIS X, DELAPORTE P H, et al.Optimization of Laser Ablation Technique for Deposited Layer Removal on Carbon Plasma Facing Components[J]. Journal of Nuclear Materials, 2011, 415(1) : S797-S800.
[9] MARIMUTHU S, ALHAJI M, et al.Applications of Laser Cleaning Process in High Value Manufacturing Industries[J]. Developments in Surface Contamination and Cleaning: Applications of Cleaning Techniques, 2019, 11: 251-288.
[10] SIANO S, FABIANI F, CARUSO D, et al.Laser Cleaning of Stones: Assessment of Operative Parameters, Damage Thresholds, and Associated Optical Diagnostics[J]. ALT'99 International Conference on Advanced Laser Technologies. 2000, 4070: 27-38
[11] ZHOU Z, SUN W, WU J, et al.The Fundamental Mechanisms of Laser Cleaning Technology And Its Typical Applications in Industry[J]. Processes, 2023, 11(5): 1445.
[12] ZHU G, XU Z, JIN Y, et al.Mechanism and Application of Laser Cleaning: A Review[J]. Optics and Lasers in Engineering, 2022, 157: 107130.
[13] WINTER J.Wall Conditioning in Fusion Devices and Its Influence on Plasma Performance[J]. Plasma Physics and Controlled Fusion, 1996, 38(9): 1503.
[14] RAZDOBARIN A, DMITRIEV A, BAZHENOV A, et al.RF Discharge for In-Situ Mirror Surface Recovery in ITER[J]. Nuclear Fusion, 2015, 55(9): 093022.
[15] COSTLEY A.E, Key Issues in ITER Diagnostics: Problems and Solutions[J]. Review of Scientific Instruments, 1999, 70(1): 391-396.
[16] YAN R, CHEN J L, CHEN L W, et al.Cleaning of HT-7 Tokamak Exposed First Mirrors by Radio Frequency Magnetron Sputtering Plasma[J]. Plasma Science and Technology, 2014 16(12): 1158.
[17] MOSER L, MAROT L, STEINER R, et al.Plasma Cleaning of ITER First Mirrors[J]. Physica Scripta, 2017, T170: 014047.
[18] RUBEL M, MOON S, PETERSSON P, et al.First Mirror Erosion-Deposition Studies in JET Using an ITER-like Mirror Test Assembly[J]. Nuclear Fusion, 2021, 61(4): 046022.
[19] PELLEGRIN E, SICS L, REYES-HERRERA J, et al.Characterization, Optimization and Surface Physics Aspects of in Situ Plasma Mirror Cleaning[J]. Journal of Synchrotron Radiation, 2014, 21(2): 300-314.
[20] 叶超,宁兆元,江美福,等. 低气压低温等离子体诊断原理与技术[M]. 北京: 科学出版社, 2010: 70-79.
YE C, NING Z Y, JIANG M F, et al.Principle and Technology of Low Pressure and Low Temperature Plasma Diagnosis[M]. Beijing: Science Press, 2010: 70-79.
[21] SONI K, MOSER L, STEINER R, et al.Plasma Cleaning of Steam Ingressed ITER First Mirrors[J]. Nuclear Material And Energy, 2019, 21: 100702.
[22] HUTSAYLYUK V, ZADOROZHNA K, VESELIVSKA H, et al.Improvement of Wear Resistance of Aluminum Alloy by HVOF Method[J]. Journal of Materials Research and Technology, 2020, 9(6): 16367-16377.
[23] KRZYZEWSKI F, ZALUSKA-KOTUR M, KRASTEVA A, et al.Step Bunching and Macrostep Formation in 1D Atomistic Scale Model of Unstable Vicinal Crystal Growth[J]. Journal of Crystal Growth, 2017, 15: 135-139.
[24] 赵家政, 徐洮, 马良. 用EDS测量薄膜的厚度及其元素的深度分布[J]. 电子显微学报, 1998, (5): 43.
ZHAO J Z, XU Z, MA L, The Thickness of the Film and the Depth Distribution of Its Elements Were Measured by EDS[J]. Journal of Electron Microscopy, 1998, (5): 43.
[25] DMITRIEV A M, RAZDOBRAIN A G, SNIGIREV L A, et al.Pulsed Radio Frequency Plasma for Cleaning ITER First Mirrors With and Without Notch-filter and Magnetic Field[J]. Fusion Engineering and Design, 2024, 209: 114724.
[26] BEHRISCH R, ECKSTEIN W.Sputtering by Particle Bombardment: Experiments and Computer Calculations From Threshold to MeV Energies[M]. Berlin: Springer, 2007: 49-51.
[27] DMITRIEV A M, RAZDOBARIN A G, SNIGIREV L A, et al.Re-deposition of ITER-grade Be on Plasma Gun Facility QSPA-Be: Characterization & Plasma Cleaning[J]. Nuclear Materials and Energy, 2022, 30: 101111.
基金
国家自然科学基金（122753060）;中国科学院青年创新促进会会员（2022452）;安徽省自然科学基金杰青项目（2208085J40）
PDF(1790 KB)
渝公网安备 50010702501715号 渝ICP备15012534号-3
