Ultrashort pulse filamentation and monoenergetic electron beam production in LWFAs

作者：Thomas A G R^*; Mangles S P D; Murphy C D; Dangor A E; Foster P S; Gallacher J G; Jaroszynski D A; Kamperidis C; Krushelnick K; Lancaster K L; Norreys P A; Viskup R; Najmudin Z

来源：Plasma Physics and Controlled Fusion, 2009, 51(2): 024010.

DOI：10.1088/0741-3335/51/2/024010

In the experiments reported here, the filamentation of ultrashort laser pulses, due to non-optimal choice of focusing geometry and/or electron number density, has a severely deleterious effect on monoenergetic electron beam production in laser wakefield accelerators. Interactions with relatively small focal spots, w(0) < lambda(p)/2, and with pulse length c tau approximate to lambda(p), incur fragmentation into a large number of low power filaments. These filaments are modulated with a density dependent size of, on average, close to lambda(p). The break-up of the driving pulse results in shorter interaction lengths, compared with larger focal spots, and broad energy-spread electron beams, which are not useful for applications. Filamentation of the pulse occurs because the strongly dynamic focusing (small f-number) of the laser prevents pulse length compression before reaching its minimum spot-size, which results in non-spherical focusing gradients.

• 出版日期2009-2