Research On Electron Behavior In Laser-plasma Interactions

This thesis is focused on “research on electron behavior in laser-plasma interactions”,the main work I will introduce in this thesis is as following: Monoenergetic electronbeams with ultralow normalized emittance generated from high contrast laser-gasinteraction; Bright betatron X-ray radiation from a laser-driven-clustering gas target;Temperature diagnostic using photonuclear reactions for hot electrons in laser-plasmainteractions. It is composed of four parts. Firstly, we have briefly reviewed thedevelopment of intense ultra-short lasers and several popular research directions inthe laser-plasma fields. Secondly, we have introduced the study of electronacceleration in the laser-plasma interactions. Thirdly. we have recommended amethod in hot electron temperature diagnostic. Lastly, we have briefly shown somekinds of particle detectors. The experiment is carried out on “XL-II Laser System”,and the numerical simulations is based on the MCNP. Details are as following:The first part is composed of chapter one, which mainly reviews three aspects ofcontents. The first one introduces the development of the intense femtosecond lasers.The second one describes the definition of plasma and the process of the laser-plasmainteractions. The third one shows several popular research fields in laser-plasmaphysics, including laser wake-field acceleration, novel laser-driven radiations（such asbetatron radiation）.In the second part, high quality electron bunches are generated by using2TW,80fs,high contrast laser pulses interacting with Helium gas targets. In optimized condition,we get tens MeV monoenergetic electron beams with small energy spread and thenormalized emittance0.16π mm·mrad. Due to its ultra small emittance and high initialenergy, such bunch is very suitable for high current linear accelerators. In the third part, temperature of hot electrons produced in ultra-short ultra-intenselaser-plasma interactions could be measured by photonuclear diagnostic method. Theprocess of bremsstrahlung gamma photons generated by hot electrons interacting with⁶³Cu,¹⁰⁷Ag, and¹²C respectively, were simulated using the Monte Carlo N-ParticleTransport Code （MCNP）. According to the different cross sections, the activities ofdifferent samples were calculated. The activity ratios for¹¹C/⁶²Cu and¹¹C/¹⁰⁶Ag wereachieved with different electron temperatures. This method can realize thetemperature diagnostic of hot electrons in laser-plasma interactions.In the forth part, we have briefly shown some kinds of particle detectors. We discussthe principle of CR39, RCF, MCP and IP. The system of NaI scintillators detector wasintroduced in detail.