Backward-ion acceleration in critical density plasmas

We demonstrated a new ion acceleration mechanism using a uniform critical density plasma that yields very high ion energy despite the existence of a laser prepulse. In this model, when ultra-intense laser (UIL) propagates into a relativistically underdense plasma, the density and temperature gaps at the laser front excite the electrostatic field, which accelerates the electrons and subsequently the ions to the laser reflection direction. The maximum ion energies were found to be several times higher than those predicted by the TNSA mechanism.

The experiment was performed at the ELFIE 100TW laser facility at LULI, Ecole Polytechnique, France. The target comprised very low plastic foam materials with densities of 5 and 10 mg/cc inside a solid polyimide tube (S. Chen et al., Sci. Rep. 6 (2016) 21495). A chirped (uncompressed) pulse irradiates on the one side of target to create a homogenous critical density plasma over 200-µm length. Then another intense laser light (0.3 ps, 3x1019W/cm2) was injected into the plasma from the opposite side. The maximum proton energy was approximately 18 MeV under the conditions of the maximum prepulse contrast ratio of 10-3. Further, heavier particles such as carbon or oxygen present in the plasma were accelerated using the same acceleration field.

Zoom-Meeting
https://gsi-fair.zoom.us/j/96629963798

Meeting-ID: 966 2996 3798
Kenncode: 130302