American Institute of Physics, Physics of Plasmas, 8(25), p. 083101
DOI: 10.1063/1.5036967
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We predict that electrons in an ion channel can gain ultra-relativistic energies by simultaneously interacting with a laser pulse and, counter-intuitively, with a decelerating electric field. The crucial role of the decelerating field is to maintain high-amplitude betatron oscillations, thereby enabling constant rate energy flow to the electrons via the direct laser acceleration mechanism. Multiple harmonics of the betatron motion can be employed. Injecting electrons into a decelerating phase of a laser wakefield accelerator is one practical implementation of the scheme. ; Comment: 7 pages, 4 figures. Keywords: Direct Laser Acceleration, Betatron Oscillations, Longitudinal Electric Field, Ion Channels, Plasma Bubbles