Efficient injection of radiation-pressure-accelerated sub-relativistic protons into laser wakefield acceleration based on 10 PW lasers

Abstract

1We propose a hybrid laser-driven ion acceleration scheme using a combination target of a solid foil and a density-tailored background plasma. In the first stage, a sub-relativistic proton beam can be generated by the radiation pressure acceleration in the intense laser interaction with the solid foil. In the second stage, this sub-relativistic proton beam is further accelerated by the laser wakefield driven by the same laser pulse in a near-critical-density background plasma with a decreasing density profile. The propagating velocity of the laser front and the phase velocity of the excited wakefield wave are effectively lowered at the beginning of the second stage. By decreasing the background plasma density gradually from near critical density along the laser propagation direction, the wake travels faster and faster while it accelerates the protons. Consequently, the dephasing between the protons and the wake is postponed, and an efficient wakefield proton acceleration is achieved. This hybrid laser-driven proton acceleration scheme can be realized by using ultrashort laser pulses at the peak power of 10 PW for the generation of multi-GeV proton beams.

Theoretical Study of the Efficient Ion Acceleration Driven by Petawatt-Class Lasers via Stable Radiation Pressure Acceleration

“…p /c 2 ) 1/2 can be deduced from dγ p /dx ≈ πa 0 m e /λm p [26]. For a 0 = 100 and v p 0.73c (the corresponding E p 500 MeV) obtained in the laser-foil interaction stage, the sub-relativistic protons will be accelerated rapidly to relativistic speed in tens of microns.…”

“…To achieve quasi-monoenergetic ion beams, several mechanisms have been investigated, such as collisionless shock acceleration (CSA) [16][17][18][19][20], radiation pressure acceleration (RPA) [21][22][23][24][25], and RPA-wakefiled hybrid acceleration [26]. In one of the most-investigated mechanisms, light-sail mode of RPA, the acceleration of ions to ultrahigh energies is allowed, where a nanoscale solid foil could be continuously accelerated by an ultrashort, ultraintense laser pulse under the ideal conditions [21,22,27].…”

Polarized proton acceleration in ultraintense laser interaction with near-critical-density plasmas

“…In addition, the protons need to be preaccelerated to a sufficient energy in order to be injected into the wakefield. In the work of Liu et al it was shown that protons preaccelerated by the radiation pressure acceleration in a thin solid foil could be captured by the LWFA in an underdense gas [23].…”

Polarized proton acceleration in ultra-intense laser interaction with near critical density plasmas

“…Besides, the protons need to be pre-accelerated to a sufficient energy in order to be injected into the wakefield. In the research of M. Liu et al, with pre-accelerated by the radiation pressure acceleration (RPA) in a thin solid foil, the protons were captured by the LWFA in an underdense gas [23].…”