Flying cavity: micro-bunching of protons for electron acceleration

While conventional particle accelerators have been used in the past to answer fundamental physical questions, their technical limits have been reached. An intrinsically different approach is provided by plasma-based accelerators. Utilizing the properties of a plasma, acceleration gradients which are orders of magnitude higher compared to conventional accelerators can be achieved. Recent experiments have shown utilization of a long proton bunch provided by CERN’s Super Proton Synchrotron (SPS). In the experiment, a long proton bunch is co-propagated through a 10 m long gas vapor together with a laser pulse which ionizes the gas and creates an electron plasma column. With the help of the self‑modulation instability (SMI) the long proton bunch is sliced in micro‑bunches driving plasma wakes. Thus wakes allow the acceleration of electrons up to several gigaelectronvolts over a short distance.

Our work presented in the video depicts a simulation for the generation of micro‑bunches by the SMI. It was carried by utilizing the ponderomotive guiding center solver (PGC), a reduced solver for the particle-in-cell (PIC) algorithm, which models kinetic effects on the scales of the plasma frequency. Due to the physical parameters like the ratio of the plasma frequency vs the laser frequency and the propagation distance, full scale simulation are not feasible and would required 107 computational costs.

For more information, see E. Adli et al., Acceleration of electrons in the plasma wakefield of a proton bunch, Nature 561, p. 363–367 (2018), available here.