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 >1019cm%3). Different configurations of the magnetic devices have been studied, and their effects are 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. © 2014 The Japan Society of Applied Physic