Ultra-high gradient compact accelerator developments

Continued development of relatively compact, although not quite 'table-top', lasers with peak powers in the range up to 100 TW has enabled laser-plasma-based acceleration experiments with amazing gradients of up to 1 TV/m. In order to usefully apply such gradients to 'controlled' acceleration, various hurdles need to be overcome. The main one is that of well-synchronized injection into a sub-mm to micron wavelength plasma wave. The talk will describe the various physics regimes of laser wakefield acceleration, and the two classes of experiments being pursued. One is that of atmospheric-density plasmas, non-linear wakefields with extreme gradients (hundreds of GV/m)and 'internal injection' of few-femtosecond electron bunches. A second class involves modest-density plasmas,wakefields of order 1 GV/m and external injection of (sub)-ps bunches. The state-of-the-art of these experiments will be covered, including the progress on plasma waveguiding of TW pulses over many diffraction lengths. The talk will also provide an outlook for the coming few years. This part includes proposed schemes for improvements in the area of injection, such as 'all-optical' injection and injection based on GV/m 'pulsed-DC' photoguns.