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7月5日交流报告

来源： 发布时间：2017-07-04【字体：大 中 小】

           　　临界密度气体靶技术交流会 

　　时间： 7月5日下午16点  

　　地点：上海光机所创新南楼三楼会议室  

　　演讲人：François Sylla博士 

　　演讲题目：Laser ion acceleration: exploring the potentialities of the nearcritical regime with dense gas jets 

　　New gas targets with unique properties of size and density have been recently developed at the Laboratoire d'Optique Appliquée (France) to explore the physics of laser ion acceleration within in a wide range of plasma density [1]. With these versatile systems, when the laser pulse duration is comparable to the inverse electron plasma frequency (peak density of few percent of the critical density nc), ion acceleration is observed in the transverse direction. Energy distributions with cutoff energies of 200 keV are obtained, and a striking energy gap appears consistently for all the shots in a given density range. Acceleration results in this case from a combination of target normal sheath acceleration and Coulomb explosion of a filament formed around the laser pulse propagation axis [2]. In this condition, a new mechanism by which the flow of relativistic electrons strongly magnetize the boundary between the plasma and the non-ionized gas is unveiled, leading to magnetic field up to 10- 100 Tesla (micro-Tesla in astrophysical conditions) [3]. At slightly higher peak density, when the gradient scale length is increased, ion acceleration is suppressed and fundamental electromagnetic structures (soliton/vortex) appear and they were optically identified for the first time [4]. Dependences of these structures on the laser depletion length are also experimentally demonstrated. Finally, close to the critical density, the efficient laser selffocusing leads to a localized energy deposit, that entails an ultrafast electron expansion (within one picosecond) and the growth of an intense magnetic dipole heating further the electrons [5]. This mechanism in particular bears exciting promise for efficient laser ion acceleration at high repetition rate [6] and drives present research effort carried out by SourceLAB and its academic partner LOA.  

　　[1].    Sylla et al., Rev. Scien. Instr., 83, 033507 (2012).  

　　[2].    Lifschtiz et al., New Jour. of Phys., 16, 033031 (2014).  

　　[3].    Flacco et al., Nature Physics, 11, 409 (2015).  

　　[4].    Sylla et al., Phys. Rev. Lett., 108, 115003 (2012). 

　　[5].    Sylla et al., Phys. Rev. Lett., 110, 085001 (2013). 

　　[6].    Nakamura et al., Phys. Rev. Lett., 105, 135002 (2010). 

演讲人简介： Dr. François Sylla Email: sylla@sourcelab-plasma.com 

　　laser plasma physicist and CEO-CTO at SourceLAB- Laser Plasma Technologies 

　　Visit http://www.sourcelab-plasma.com  

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