Laser-driven electron acceleration and future applications to compact light sources

Laser-driven plasma accelerators are gaining much attention by the advanced accelerator community due to the potential these accelerators hold in miniaturizing future high-energy and medium energy machines. In the laser wakefield accelerator (LWFA), the ponderomotive force of an ultrashort high-intensity laser pulse excites a longitudinal plasma wave or bubble. Due to huge charge separation, electric fields created in the plasma bubble can be several orders of magnitude higher than those available in conventional microwave and RF-based accelerator facilities, which are limited (up to ∼ 100 MV/m) by material breakdown. Therefore, if an electron bunch is injected into the bubble in phase with its field, it will gain relativistic energies within an extremely short distance. Here, in the LWFA, we show the generation of high-quality and high-energy electron beams up to the GeV-class within a few millimeters of gas-jet plasmas irradiated by tens-of- terawatt ultrashort laser pulses. Thus, we realize approximately four orders of magnitude acceleration gradients, higher than available by conventional technology. As a practical application of the stable high-energy electron beam generation, we are planning on injecting the electron beams into a fewmeter-long conventional undulator in order to realize compact X-ray synchrotron (immediate) and Free Electron Laser (future) light sources. Stable laser-driven electron beam and radiation devices will surely open a new era in science, medicine, and technology and will benefit a larger number of users in those fields.