Quasi-stable injection channels in a wakefield accelerator
  The influence of initial position on the acceleration of externally-injected electrons in a plasma wakefield is investigated. Test-particle simulations show previously unobserved complex structure in the parameter space, with quasi-stable injection channels forming for particles injected in narrow regions away from the wake centre. Particles injected into these channels remain in the wake for a considerable time after dephasing, and as a result achieve significantly higher energy than their neighbours. The result is relevant to both the planning and optimisation of experiments making use of external injection. 
Mara Wiltshire-Turkay, John P. Farmer, and Alexander Pukhov
physics.plasm-ph physics.acc-ph