Abstract
Laser wakefield accelerator is expected to be one of the novel accelerators for a new energy frontier and
an ultrashort electron source for many attractive applications such as ultrafast electron microscopy. In
recent studies, pointing stability of an electron beam emitted from laser wakefield acceleration has been
extremely improved by applying an external magnetic field to preplasma. Emission direction of the
electron beam can be controlled by the direction of the magnetic field. This stable and controllable
electron beam can be a precise injector of staged laser wakefield acceleration and the energy spectrum of
electron bunch can be modified by further acceleration and phase rotation in next wakefield. Also
conventional beam optics is available for such stable electron beam. We are developing a reliable laser
wakefield accelerator/electron source based on staged laser wakefield acceleration and new ultrashort
electron bunch transport system with conventional beam optics towards practical use.
