Synchrotron radiation from a cluster plasma in a circularly polarised laser field

An analytical model is developed for the generation of synchrotron radiation from a laser cluster plasma in the focal waist of an ultra-intense short circularly polarised laser pulse. The rotation of relativistic electrons around the ionised core of the cluster with a radius of rotation smaller than the laser wavelength leads to intense synchrotron radiation in the direction transverse to the laser wave vector. The parameters of the cluster plasma and laser pulse are determined at which, due to the small radius of curvature of the electron trajectory of the cluster shell, the intensity of synchrotron radiation exceeds the intensity of betatron radiation of the electron flux in the longitudinal (along the wave vector) direction.