Generation And Application Of The Laser Wakefield Accelerator Based Betatron Source

In the past decade,the compact laser-plasma accelerator based synchrotron-like Betatron X-ray source has made tremendous progress,which may revolutionize the field of X-ray detection.Betatron radiation,emitted by the relativistic electron beam in the laser wakefield accelerator(LWFA),has the advantages of high peak brightness which is comparable with that of the 3rd-generation synchrotron light source,?m-scaled source size and fs-scaled duration,which is a superior source for high-quality X-ray imaging and ideal probe for ultrafast science.However,two urgent problems that are poor stability and insufficient photon number in a single shot now limit the practical applications of the Betatron source and need to be solved.In-depth studies on these issues are carried out in the thesis:In Chapter 2 and 3,for improving the stability of the Betatron source,a highly stable Betatron source,with a photon count and pointing fluctuation below 5%,spectrum fluc-tuation below 10%and ?m-scaled effective source size(the root mean square position deviation of the source is 2 ?m in single-shot mode),is produced by combining ionization injection together with multiple-shot accumulation.Furthermore,utilizing this Betatron source,high-quality phase-contrast images of biological specimens with sub-5?m res-olution(4.2?m)have been obtained for the first time.These works pave the way for the application of high resolution phase-contrast imaging in biology and material science with stable Betatron sources using small scale high rep-rate lasers.In Chapter 4 and 5,for enhancing Betatron radiation,a density-depressed plasma structure and a bump-like plasma structure are used.By utilizing a tunable density-depressed plasma structure that is fabricated by the technology of laser plasma machining,the single-shot photon number of the Betatron X-ray is enhanced by a factor of 3,reaching up to 1× 109 photons/shot.By utilizing a tunable plasma structure with a density bump that is produced by a special gas source of a gas jet covered by a sharp knife,the single-shot photon number of the Betatron X-ray increases to 8 x 109 photons/shot with a sub-PW laser system for the first time.In Chapter 6,by using particle-in-cell simulations,preliminary explorations of EUV-band and coherent Betatron radiation generation are described.