成大物理系徽
凝態組博士班專題討論 (Seminar)
演講題目: 3D PIC Simulations Of Monoenergetic Electron Generation Via LWFA For 5 To 25TW Lasers
演講人: Dr. Frank S. Tsung
UCLA
演講時間: 2005 年 12 月 8 日
星期四  下午 1 : 40
演講地點: 國家理論科學研究中心二樓演講廳(R203)
內容摘要:  
Recently, we reported the observation of a low emittance, monoenergetic electron bunch with .5nC of charge at a central energy of 240 MeV [1] in PIC simulations in which a 16.5TW, 50fs laser propagated through nearly .5 cm of 3x10$^{18}$ cm$^{-3}$ preformed plasma channel. In addition, electrons out to 840 MeV were seen if the laser propagated through .8 cm of the same plasma. The simulations showed that self-injection occurs after the laser intensity increases due to a combination of photon deceleration, group velocity dispersion, and self-focusing. The monoenergetic beam is produced because the injection process is clamped by beam loading and the rotation in phase space that results as the beam dephases. Nearly simultaneously[2-4], three experimental groups from around the world reported the generation of near nanocoulomb of low emittance, high quality electron beams using similar laser parameters reported in our simulations. Using the 3D particle-in-cell code OSIRIS we have modeled each of these experiments. Although these simulations and experiments use a wide range of plasma parameters, laser powers and spot sizes, we find that key aspects of how the monoenergetic electrons are generated are universal. We describe the physics mechanisms behind the mono-energetic beam production and the details of each simulation. We also comment on how the energy and beam quality can be improved in the future.

[1] F. S. Tsung et al, Phys. Rev. Lett, 93:185002 (2004).
[2] S. P. D. Mangles et al, Nature, 431:535 (2004).
[3] C. G. R. Geddes et al, Nature, 431:538 (2004).
[4] J. Faure et al, Nature, 431:541 (2004).