The so-called “self-guided” regime of laser wakefield acceleration has been experimentally explored. It is shown that short but intense laser pulses can be self-guided by the wake over tens of Rayleigh length by creating a bubble-like wakefield structure . The density and power scaling of the onset of self-trapping of plasma electrons in such self-guided wakes has been experimentally determined . To enable electron injection into wakes below these threshold values, inner-shell ionization of trace atoms has been employed . Combining self-guiding in the bubble regime with ionization-induced trapping has led to the generation of ~ 1.5 GeV electron sin ~ 1.5 cm long 1.4×1018cm−3 density plasma .
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