Secondary X-ray and gamma-ray sources

An important direction in the physics of ultrahigh power laser-matter interactions is the creation of secondary sources of high-power X-ray and gamma-ray radiation, including radiation of attosecond duration.

An original scheme for gamma-ray generation has been proposed by A. A. Gonoskov and A. V. Korzhimanov based on the interaction of a reflected laser pulse with an electron beam accelerated by that pulse. As a laser pulse propagates through the plasma, it generates a beam of electrons travelling behind the pulse. Once reflected at a certain point, the pulse will interact with accelerated electrons, thus making possible the generation of gamma-photons with energies of hundreds of megaelectron-volt. The brightness of such a source may reach outstanding values of the order of 1027 photons/(s × mm2 × mrad2).

A concept of giant attosecond pulse generation by the interaction of an ultrahigh power laser pulse with a solid target has been worked out by the same research team. An analytical model describing the process of generation of such pulses, the so-called relativistic electronic spring model, has been developed and shows excellent agreement with numerical simulation. In a certain range of intensities and angles of incidence of the optical pulse, the reflected pulse is a sequence of attosecond pulses whose amplitude is higher than that of the incident wave. By focusing a petawatt femtosecond optical pulse on a target with the surface in the form of a cylindrical groove, attosecond pulse intensities of the order of 1026 W/cm2 can be achieved.

The concept of achieving extreme intensities by focusing giant attosecond pulses: left – laser pulse is incident on a groove-shaped target, giant attosecond pulses combined coherently at the focal point are generated on target surface; right – numerical calculation of the generation and focusing of the giant attosecond pulses