Multi-keV X-ray Sources And Their Applications On ShenGuangâ…¡ Laser Facility

Multi-keV x-ray sources are very important for the diagnostic of high density plasma relevance to Inertial Confinement Fusion (ICF) and High Energy Density Physics (HEDP). In this thesis, long pulse multi-keV x-ray sources and their applications in x-ray backlit imaging of indirect-drive capsule implosions and x-ray Thomson scattering of solid density (^lg/cc) CH plasma are research on ShenGuang II laser facility. Some important results are obtained.With the long laser pulse, the significant three-dimensional expansion of the plasma leads to that the longitudinal scale length of the x-ray emission region is finally determined by the laser spot size L and the emission volume is proportion to L³. Theoretical analysis show that x-ray flux can be enhanced by increasing the laser spot size because in the steady state the x-ray flux is proportion to L^5/3 under the same laser power. The scaling law is in reasonable agreement with the experimental data. It is also showed that shorter wavelength laser is more suitable for the multi-keV x-ray sources.The angular distribution of multi-keV x-ray sources produced with laser-heated thick disk can be described with the function of α+Pcos^γθ, which the index γ is close to 1/3 for K-shell x-ray sources and 1/2 for L-shell x-ray sources. The conversion efficiency (CE) of L-shell emission is obviously higher than the K-shell emission but lower than the M-shell emission because the number of the L-shell emission lines is greater than that of the K-shell emission lines but smaller than that of the M-shell emission lines. The CE of L-shell X-ray sources satisfy a power law, similar to the behavior of K-shell x-ray sources, decreases with the increasing of atomic number and photon energy.Efficient x-ray sources are achieved by thin foil with a single laser pulse. The enhancement of the CE should be due to the larger size of the hot underdense plasmas generated with thin foil. There is an optimized thicknessfor the thin foil that the CE will be the highest.With the efficient x-ray sources, two experiments are further performed to demonstrate the applications of the x-ray sources. Trajectories of indirect-drive capsule implosions of thick and thin shell are measured by x-ray backlit imaging on ShenGuang II laser facility. A method of optimizing x-ray photon energy for x-ray backlit imaging is given. X-ray Thomson scattering of solid density (^lg/cc) cold CH plasma with 4.75keV x-ray is demonstrated on ShenGuang II laser facility. The experimental feasibility of x-ray Thomson scattering is proved.