Secondary electron yield reduction by femtosecond pulse laser-induced periodic surface structuring
Secondary electron yield reduction by femtosecond pulse laser-induced periodic surface structuring
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DOI：
10.1016/j.surfin.2021.101179
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发表时间：
2021-05-28
影响因子：
6.2
通讯作者：
Masullo, M. R.
中科院分区：
文献类型：
--
作者：
Nivas, J. J. J.;Valadan, M.;Masullo, M. R.
电子云现象是高强度正粒子加速器中束流不稳定的原因之一。在所提出的减轻或控制这种有害影响的技术中，真空室表面的微米/纳米几何修改有望减少发射的二次电子的数量。飞秒激光表面结构化可以轻松制造激光诱导周期性表面结构（LIPSS），并应用于多个领域，但尚未经过二次电子发射减少测试。在这项研究中，使用线性和圆偏振飞秒激光脉冲对铜样品进行这种处理。研究了形成的表面纹理对二次电子产率（SEY）的影响。我们通过 SEM、AFM、拉曼和 XPS 分析研究形态特性和化学成分。使用线偏振光进行表面修饰比使用圆偏振光更有效，可以显着降低SEY。尽管与标准激光诱导表面粗糙化方法相比，SEY 最大值仅降至约 1.7 的值，但飞秒-LIPSS 工艺能够限制材料烧蚀以及不需要的灰尘的产生，并大幅减少表面重新沉积的纳米粒子的数量，这对于粒子加速器中的应用是不利的。此外，调节测试表明，在电子辐照剂量高于 10 (3) C/mm(2) 时，LIPSS 处理的 Cu 可以达到低于 1 的 SEY 值。
The electron-cloud phenomenon is one cause of beam instabilities in high intensity positive particle accelerators. Among the proposed techniques to mitigate or control this detrimental effect, micro-/nano-geometrical modifications of vacuum chamber surfaces are promising to reduce the number of emitted secondary electrons. Femtosecond laser surface structuring readily allows the fabrication of Laser Induced Periodic Surface Structures (LIPSS) and is utilized in several fields, but has not yet been tested for secondary electron emission reduction. In this study, such treatment is carried out on copper samples using linearly and circularly polarized femtosecond laser pulses. The influence of the formed surface textures on the secondary electron yield (SEY) is studied. We investigate the morphological properties as well as the chemical composition by means of SEM, AFM, Raman and XPS analyses. Surface modification with linearly polarized light is more effective than using circularly polarized light, leading to a significant SEY reduction. Even though the SEY maximum is only reduced to a value of similar to 1.7 compared to standard laser-induced surface roughening approaches, the femtosecond-LIPSS process enables to limit material ablation as well as the production of undesired dust, and drastically reduces the number of redeposited nanoparticles at the surface, which are detrimental for applications in particle accelerators. Moreover, conditioning tests reveal that LIPSS processed Cu can reach SEY values below unity at electron irradiation doses above 10 (3) C/mm(2).