Controlling the interaction of tightly focused 10-PW class lasers with multicomponent plasma via target parameters: Optimization of electron–positron pair and γ-photon sources

The interaction of multipetawatt lasers with plasma is a complex multiparameter problem, providing a wide field for fundamental research and opening up great opportunities for creating unique sources of high-energy electrons and positrons, dense pair plasma, and γ-photons. However, to achieve the high efficiency of such a source, it is necessary to use targets with optimized parameters, primarily density and size, for the given laser parameters. With the use of 3D QED-PIC modeling, it is shown that, when targets whose size is comparable with the laser wavelength are irradiated by laser beams with a total power of several tens of PW, the total initial number of target electrons may be regarded as the similarity parameter. In practice, this can significantly simplify the selection of the targets needed for controlling the interaction and, accordingly, for achieving the specified parameters of the developed electron–positron plasma and γ-photon sources. Based on the similarity parameter, various laser-plasma interaction modes are identified, the necessary conditions for their launch are determined, and the properties of the pair particle and γ-photon source are revealed. Moreover, qualitative estimates of the quantitative and energy characteristics of such a source are obtained, allowing it to be optimized for various laser beam configurations.