Experimental demonstration of high-charge electron beam acceleration in the undulating plasma bubble regime of LWFA

These experiments are based on new discovery of electron trapping/acceleration by an Expanding Phase-controlled Undulating Bubble (EPUB) [1]. Unlike other regimes of Laser Wakefield Acceleration (LWFA) relying on localized injections, the EPUB approach utilizes multiple injections of large electric charges inside the plasma controlled by bubble undulations. In the EPUB regime, super-ponderomotive effects accompanied by laser pulse steepening in the plasma induce bubble undulations controlled by the Carrier Envelope Phase (CEP) offset steepening [1,2]. In practical terms, the EPUB regime requires ultra-relativistic laser intensity (𝑎₀ ≫ 1), high plasma density (>10¹⁹ cm^-3), short pulse durations (<30 fs), and short plasma lengths (<3 mm). We will discuss the results of our experiments conducted at the ELI-NP 100 TW laser facility, including a multi-parameter study of the influence of the laser-plasma conditions (length, density, and laser beam polarization) on the properties of the electron and x-ray beams. This work is supported by the DOE NNSA award DE-NA0004127.