Focusing and stabilizing laser-plasma-generated electron beams with magnetic devices

External magnetic devices have been successfully tested to control the divergence and pointing stability of subrelativistic electron beams accelerated by ultrashort laser pulses in a nitrogen plasma (electron density of similar to 10(19) cm(-3)). Different configurations of the magnetic devices have been studied, and their effects ate discussed in detail. The analysis is also supported by the results of ray-tracing simulations using the first-order trajectory equation in the magnetic field configurations. This simple method of improving beam stability will be particularly useful for applying laser-generated ultrashort electron beams to high-dose radiobiological studies. (C) 2014 The Japan Society of Applied Physics