Enhanced electron generation in near-critical density plasma lens*

The X-ray source based on ultraintense laser-plasma interactions has been widely applied in various fields. To meet the demand of high-resolution imaging for high-areal-density objects, the generation of bright micro-spot high-energy X-rays is urgently desired. 

Since the electrons accelerated in solid and gas plasmas are respectively limited in energy and yield, near-critical density (NCD) plasma lens is proposed based on the self-focusing effect to optimize the laser state, improve the energy conversion and get high-charge energetic electrons. By theoretical estimate and simulations, we prove that enhanced laser focusing in the self-formed NCD channel can contribute to the efficient energy absorption, thus producing near-μC multi-MeV electrons via direct laser acceleration mechanism. 

These findings offer a feasible access to the generation of micro-spot brilliant bremsstrahlung source, hopeful to realize the single-pulse transient imaging. Moreover, the production of tightly-focused, high-intensity laser pulse is of significant importance to related experimental researches and potential applications.