Near-Ideal Dechirper for Plasma-Based Electron and Positron Acceleration Using a Hollow Channel Plasma

Plasma-based electron or positron wakefield acceleration has made great strides in the past decade. Currently, one major challenge for its applications to coherent light sources and colliders is the relatively large energy spread (few-percent level) of the accelerated beams. This energy spread is usually dominated by a longitudinally correlated energy chirp induced by the wakefield. It is highly desirable to have a systematic method for reducing this spread to less than or similar to 0.1% and, at the same time, maintaining the beam emittance. Here, a near-ideal dechirper based on a low-density hollow channel plasma is proposed and tested through large-scale three-dimensional particle-in-cell simulations. The theoretical analyses and simulations confirm that the positively correlated energy spread (chirp) of the electron or positron beam from a plasma accelerator can be significantly reduced by its self-wake in the hollow plasma channel from a few percent down to less than or similar to 0.1% without noticeable beam emittance growth. Such a near-ideal dechirper may significantly improve the beam quality of plasma-based accelerators; thus paving the way for their applications to future compact free-electron lasers and colliders.