Attosecond keV x-ray pulses driven by Thomson scattering in a tight focus regime

The radiation of a relativistic electron interacting with a copropagating tightly focused high-power laser is investigated. High-order fields (HOFs) existing in a tight focus (a few micrometers or so) affect the dynamics of electrons rather significantly so as to enhance radiation intensity by several orders of magnitude. In the case of a co-propagating interaction geometry, the second-order field plays an important role in radiation enhancement. It is demonstrated that when HOFs are included, the radiation efficiency is increased by a factor of up to 100 000 for WQ = 2 and 5 μm, with a laser intensity of 2.2 × 10²⁰ W cm^-2, compared with that when HOFs are not included. The enhancement is larger for smaller electron energies and laser beam waists. It has also been shown that when an electron bunch interacts with a highintensity tightly-focused femtosecond laser pulse in a co-propagation geometry, attosecond (∼300 as) x-ray pulses can be produced. The photon energy can reach about 40 keV for an electron energy of 2 GeV. The physical scheme investigated in this work can be used for an ultrafast (attosecond or femtosecond) x-ray source in the range of 10-100 keV.