Radiation Source And Nuclear Reaction Driven By Laser Plasma Electron Acceleration

In recent years,the technology of laser plasma wakefield electron acceleration?LWFA?is becoming more and more mature,and the wakefield electron beam has characteristics of ultra-high density and femtosecond duration.Moreover,the electron beam can drive Betatron radiation and Thomson scattering source,and these sources have the characteristics of ultra-fast,ultra-brilliant and micro-meter class source size.Especially,these radiation sources have natural synchronization with driving laser pulse,which has incomparable advantages on ultra-fast pump detection.At present,Betatron radiation in high-energy output,polarization and controllability,and Thomson scattering based on plasma mirror in photon flux and how to realize nonlinear scattering are still relatively lacking.All of these factors limit the application of these table-top radiation sources to a certain extent.One of the research work of my dissertation is to enhance the radiation energy and control the Betatron polarization,and this work aims to enrich and expand the radiation source driven by LWFA electrons.In addition,the wakefield electron beam with high current intensity and the high density driven by laser plasma can also be applied to nuclear physics.The second part of my doctoral research work is the nuclear reactions driven by laser plasma acceleration electrons,which aims to combine laser plasma with nuclear physics,and to provide a new method to solve the difficulties in traditional nuclear physics.This dissertation includes the following five chapters:The first chapter is the introduction.As the basis of the whole dissertation,it introduces the basic concepts of plasma and LWFA,the research progresses of Betatron radiation and Thomson scattering based on wakefield electron beam,the generation methods of neutron source based on laser plasma and the basic concepts of isomer.The second chapter is the study of laser plasma wakefield electron acceleration and Thomson scattering.Firstly,it introduces the experiment of plasma wakefield electron acceleration driven by a 16 TW laser facility.Basing on ionization injection regime,by adjusting the laser focusing intensity,quasi-mono-energetic electron beam and stable electron beam with continues energy are obtained respectively.Then,it introduces the Thomson scattering source based on plasma mirror?PM?and stable electron beam.In this work,we acquire a Thomson scattering source with photon number?1.2×10⁷ for energy>200 ke V.At the end of this chapter,it introduces the scheme of focusing PM to enhance Thomson scattering.This method could be applied in experiment,and pushes the Thomson scattering based on PM to nonlinear region.The third chapter is the study of the optical control of the transverse motion of LWFA electron beam and the characteristics of Betatron radiation.Firstly,it introduces the study of an all-optical method for controlling the transverse motion of wakefield electron beam driven by laser pulse with asymmetrical focus.Such an all-optical method could be useful for the generation of synchrotron radiation with orbit angular momentum.the second part of this chapter introduces a theoretic method of achieving intense circularly polarized radiation via circularly polarized laser pulse driving LWFA in the regime of ionization injection.At the end of this chapter,it introduces a high efficiency method of achieving high energy Betatron radiation via accelerated electrons wiggling in an additional laser field.This method greatly increases the Betatron radiation energy and radiation efficiency.The fourth chapter is the study of nuclear reactions driven by laser plasma acceleration electrons.Firstly,it introduces the experimental study of photo-fission neutron source driven by LWFA electron beam.By optimizing the converter for photonuclear reaction to obtain the fast neutron.The fast neutron generation efficiency is about 1.1×10⁷/J which to best of our knowledge,is the highest compared with other laser neutron generation methods with the same laser energy.Finally,it introduces the experimental study of nuclear isomer excited by laser cluster interaction.By using a laser interaction with the Kr cluster,isomers of ⁸³Kr?E2=41 ke V,T1/2,2=1.83 h?are generated for the first time with efficiency of 3203±42 p/J.The results show that this new method is efficient to generate short lifetime isomers,which will benefit to the fields such as gamma ray laser.However,it is hard for traditional nuclear physics methods to accumulate shot lifetime isomers.The last chapter is the summary of the whole dissertation,which summarizes the key points of each chapter and highlights again the scientific and applied value of the work.