Towards a plasma-based acceleration for non-relativistic particles

The past years have seen a growing interest in plasma-based accelerator technology since it provides a route to more compact, ecological yet powerful accelerators. Nonetheless, even well-established acceleration methods, such as Laser Wake Field Acceleration [1] and Plasma Wake Field Acceleration [2], are only applicable to particles whose velocities are close to the speed of light (relativistic particles). Heavier particles, e.g. muons, are thus excluded from the acceleration mechanism because they are produced with non-relativistic velocities, even though these particles could particularly benefit from plasma acceleration since their finite decay-time represents a challenge for conventional acceleration machines [3]. State-of-the-art techniques to sculpt the spatio-temporal spectrum of electromagnetic wave packets leading to pulses with arbitrary group velocities have been recently developed [4].

These pulses can drive superluminal ionization fronts, and are promising drivers for plasma acceleration, being able for example to circumvent dephasing. At the same time, they can propagate with a subluminal group velocity, making them suitable candidates to drive acceleration wakes for heavier particles. Furthermore, if carefully crafted, these pulses can also increase or decrease their group velocity while propagating [5].

In this work, we propose a plasma-based acceleration method for non-relativistic particles using pulses with increasing group velocities. At first, we investigated the acceleration using an external field with a non-relativistic group velocity analytically and in 2D particle-in-cell simulations using OSIRIS [6]. Finally, we show a study on how the acceleration changes when we make these non-relativistic pulses accelerate while propagating.