The Study On Electron Acceleration And Betatron Radiation Generated From Laser-gas Interactions

Laser driven wakefield acceleration has made great progresses in past decade,the generated energetic electron can be used to develop novel sources of radiation except for being considered seriously as possible seed for future compact X-ray free-electron –lasers and linear colliders.The thesis studies electron acceleration and x-ray radiation in laser-gas interactions,and the analysis of experimental results via PIC simulations.It is composed of 4 sections: 1st sections is about the generation and optimization of electeron from laser-wakefield accelerator,2nd section is about the enhancement of betatron radiation based on ionization injection,3rd section is about betatron radiation generated from self-moduation laser-wakefiled accelerator,4th is preliminary experiment research on the interaction of laser with near critical-density plasma and the formation of cluasters.Chapter 1 is the introduction past,we briefly introduce some fundamental physical concept and principle associated with ou experiments,as well as the the recnt progresses.It is composed of nonlinear optics during laser propagating in plasma,some laser-plasma accelerators and controllable injection schemes,and betatron radiation based laser-wakefield acceleration.Chapter 2 mainly introduces the experimental results generated from laser driven wakedfled accelerator and includes two parts.Part 1 introduces the study of laser wakefield electron acceleration deviationg from matching condition.We get electron bunch with current intensity up to 20 kA from experiment,and confireme its acceleration mechanism via PIC simulations.Part 2 introduces the ecperimental rsults based on laser-neitrogen gas interaction.We systematically study the characteristics and advantages of ionization injected electrons in a laser-plasma acclerator.Chaptor 3 introduces the enhancement of betatron radiation from ionization injected electrons in a laser-plasma accelerator.In the experimets,we get the betatron x-rays from ionization injection is about 10-flod than the self-injection case under similar laser conditions.The simulations suggest the fast ionization process and injection positin are beneficial for injected electrons catching up with laser pulse and effective betatron resonant oscillation in the laser fields.Chaptor 4 introduces the generation of betatron radiation from sub-ps high power laser-plasma interaction.We get two different type of critical energy x-ray spectra in experiments and analysed its generation mechanism.And,we also get large charge of electron bunches in the laser polarization direction,and make some preliminary analysis.Chaptor 5 introduces the studies on the formation process of clusters and the interaction of laser with near critical-density plasma.We systematically study the characteristics and formation time of clusters generated from pure xenon gas and hydrogen-xenon gas mixture.And,we also study the electron acceleration and x-ray radiation generated from hundred TW level laser pulse interacting with near-critical density plasma.