Ion acceleration and high contrast PW interactions with near critical density plasmas at BELLA iP2

Advanced laser-driven ion acceleration mechanisms offer a promising route to high-quality proton beams and offer advantages over thermal-based Target Normal Sheath Acceleration (TNSA) [1]. Magnetic Vortex Acceleration, in principle, can produce lower divergence beams with a more favorable ion energy scaling with laser intensity. This regime can be accessed with thin (10’s 𝜇m) near-critical density plasmas that also offer significantly higher laser-electron energy coupling and laser pulse guiding in self-generated plasma channels [2]. This advanced regime requires high peak power and ultra-high contrast to preserve the integrity of the foam target prior to the main pulse interaction. This was facilitated by a re-collimating double plasma mirror system at the BELLA iP2 beamline [3] with a short focal length optic producing peak intensities of ~51021 W/cm2 with a ~5105 contrast improvement up to 1ps prior to the pulse peak. This presentation will discuss the experimental progress towards this regime, comparing the quality and characteristics of the ion beams produced to multi-dimensional particle-in-cell simulations.

[1] A. Macchi et al, Rev. Mod. Phys. 85, 751 (2013)

[2] J. Park et al, Phys. Plasmas 26, 103108 (2019)

[3] S. Hakimi et al, Phys. Plasmas 29, 083102 (2022)

This work was supported by the U.S. DOE-SC, FES, LaserNetUS, and HEP under contract number DE-AC02-05CH11231, DARPA via Northrop Grumman, NSF (PHY-2206777) and by the Czech Science Foundation project No. 22-42890L.