Promise and challenges for plasma-based accelerators for science applications

Plasma-based accelerators, powered either by lasers or charged particle beams, are able to sustain ultra-high accelerating gradients, orders of magnitude higher than conventional metallic structures, enabling compact accelerators. In addition, plasma accelerators naturally accelerate ultra-short (femtosecond) beams, a fraction of the plasma wavelength. Hence plasma-based accelerators are of interest for applications that require compactness and high peak beam currents. Using triggered injection techniques, generation of electron beams from the background plasma can yield beams with sub-micron normalized transverse emittances and, therefore, high beam brightness. These beam characteristics make plasma accelerators attractive for a variety of applications, including future linear colliders and light sources. In this talk I will review recent advances and research directions in the field of plasma accelerators, as well as the challenges for realizing applications of this accelerator technology.