Theoretical study on characteristics of high voltage Child-sheath of mixed D+ and Ti2+ plasmas
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摘要: 建立了混合多组分等离子体高压查尔特鞘层动力学模型，数值研究了氘钛等离子体高压查尔特鞘层特性。理论与数值研究结果表明，提升D+离子比例、降低D+离子及Ti2+离子入鞘速度、降低等离子体密度等方式，均会有效增加鞘层厚度，并降低靶面场强幅值，这些方式有利于离子汇聚传输和降低靶面击穿风险。随加速电压的增加，离子引出稳定工作区域范围呈现先增加后减小的趋势。增加D+离子比例、减小D+离子及Ti2+离子入鞘速度，均会显著增加离子引出稳定工作区域范围。Abstract: A dynamic model for high voltage Child-sheath of mixed multi-component plasmas is built up, and the characteristics of high voltage Child-sheath of mixed D+ and Ti2+ plasmas is numerically studied. The theoretical and numerical results demonstrate as follows. The depth of Child-sheath will increase and electric field intensity on target will decrease by increasing the ratio of D+ to Ti2+, decreasing the sheath-entering velocity of D+ or Ti2+, and decreasing the density of mixed plasmas. Through the above ways, ions could achieve convergent transportation and breakdown risk on target could also be reduced. As the increase of accelerating voltage, the range of stable ion-extraction operating region will firstly increase and then decrease. By increasing the ratio of D+ to Ti2+ and decreasing the sheath-entering velocity of D+ or Ti2+, the range of stable ion-extraction operating region could be notably increased.
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Key words:
- mixed multi-component plasmas /
- high voltage Child-sheath /
- dynamic model
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图 1 氘钛等离子体中性区域和高压鞘层区域示意图
Figure 1. Schematic of neutral region and high voltage sheath of mixed D+ and Ti2+ plasmas
图 2 鞘层厚度及靶面场强随等离子密度变化关系
Figure 2. Sheath depth and electric-field strength as a function of ion density
图 3 鞘层厚度及靶面场强随D+离子占比变化关系
Figure 3. Sheath depth and electric-field strength as a function of D+ proportion
图 4 鞘层厚度及靶面场强随D+入鞘速度变化关系
Figure 4. Sheath depth and electric-field strength vs sheath-entering velocity of D+
图 5 鞘层厚度及靶面场强随Ti2+入鞘速度变化关系
Figure 5. Sheath depth and electric-field strength vs sheath-entering velocity of Ti2+
图 6 鞘层厚度及靶面场强随加速电压变化关系
Figure 6. Sheath depth and electric-field strength as a function of accelerating voltage
图 7 组分电流密度随电压变化关系（保持鞘层厚度不变）
Figure 7. Current density components vs voltage (fixed sheath depth)
图 8 等离子体密度和总电流密度随电压变化关系（保持鞘层厚度不变）
Figure 8. Total current density and interface plasma density vs voltage (fixed sheath depth)
图 9 组分电流密度随加速电压变化关系（保持靶面场强不变）
Figure 9. Current density components vs voltage (fixed Emax)
图 10 等离子体密度及总电流密度随加速电压变化关系（保持靶面场强不变）
Figure 10. Total current density and interface plasma density vs voltage (fixed Emax)
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