Theoretical And Numerical Studies Of Interaction Between Ultra-short Intense Laser Pulses With Thin Solid Foils

In the field of plasma physics, the interaction between the ultra-short ultra-intense laserpulse and thin foil target has important research value，for its applications in acceleratingparticles and radiating short waves. In this thesis, using the theoretical analysis andone-dimensional particle numerical simulations, we aim to study the generation of attosecondx–ray pulses from the interaction between ultra-short ultra-intense laser pulses and thin foiltarget.In the single target scheme, the relativistic electron sheets driven by the ultra-relativisticintense laser pulse with intensity above10²²W/cm²irradiating the thin foil target, as well as theattosecond x–ray pulses induced by Thomson backscattering from electron bunch are studied inthis paper by one-dimensional particle-in-cell simulations and theoretical analysis. The resultsindicate that the intensity of the driving laser, density and thickness of foil target affect thevelocity of relativistic electron sheets and the wavelength of x–ray radiation. Increasing theintensity of driving laser or reducing the thickness and density of foil target properly canimprove the velocity of relativistic electron sheets and reduce the wavelength of attosecond x-raypulse. While the intensity of attosecond x-ray pulse can be influenced by the intensity of theprobing laser. A single attosecond pulse in X–ray band with wavelength1.168nm can beobtained through optimizing parameters. Especially, the scheme of probing laser pulse withdouble frequency can make the wavelength of coherent attosecond X-ray radiation decreaseobviously, even below0.4nm, and the energy of the scattered photons can achieve more than2KeV.In addition, by the theoretical model of the double layers scheme, we add an additionalthick foil located behind the first foil, which is thick enough to reflect the driving laser andeliminate the transverse momentum of electrons generated from the first foil pushed by drivinglaser. The Doppler shift factor due to the Thomson scattering effect of probe pulse and electronlayer is raised by the setting of the second thick target, so the wavelength of the attosecond X-rayradiation decreases obviously, and the energy of the scattered photons increases. When thedriving laser pulse with intensity above10²⁰W/cm²irradiates the first foil, with the reflector foilplaced in the position of electrons with maximumγ xin numerical simulation, the attosecondX–ray radiation with the wavelength0.833nm can be obtained. As the intensity of driving laser changes, the broadening of main peak with the change of the low-frequency portion in thespectrum of Thomson backscattering signal is discussed.Finally, the results from numerical simulations in single and double target schemes arecompared. It shows that the amplitude of the oscillation of the scattering spectrum in the doublelayer target scheme is much smaller than that in the single target technique, and the number ofthe frequency peaks decreases. Also, we find the maximum frequency and the photon energy ofscattering spectrum in the double target scheme increases compared with that in the single target,which shows that the double target scheme has more advantages to obtain shorter wavelengthradiation than the single target scheme.The thesis is organized as follows. The first chapter gives a brief introduction ofdevelopment of laser technique, the interaction of laser pulse with plasma and the generation ofhigh-order harmonics and attosecond pulses, as well as the research methods of interactionbetween the lasers and plasmas. In the second chapter, the theoretical model of attosecond x–raypulses generation from the interaction of laser pulse with single thin foil target, as well asnumerical simulations and the optimization of the relevant laser-target parameters are given.Then, in the third chapter, we study the theoretical model of attosecond x–ray pulses generationfrom the interaction of laser pulse with double thin foil targets, also numerical simulations, aswell as comparison between the single and the double target scheme. As the conclusion, in thelast chapter, we briefly summarize the total subject and give an expectation for the future work.