Magnetically assisted self-injection and radiation generation for plasma   based acceleration
  It is shown through analytical modeling and numerical simulations that external magnetic fields can relax the self-trapping thresholds in plasma based accelerators. In addition, the transverse location where self-trapping occurs can be selected by adequate choice of the spatial profile of the external magnetic field. We also find that magnetic-field assisted self-injection can lead to the emission of betatron radiation at well defined frequencies. This controlled injection technique could be explored using state-of-the-art magnetic fields in current/next generation plasma/laser wakefield accelerator experiments. 
J. Vieira, J.L. Martins, V.B. Pathak, R.A. Fonseca, W.B. Mori, L.O.   Silva
physics.plasm-ph physics.acc-ph