Experimental Studies On Kα Radiation Produced By The Interaction Of Ultra-short, Ultra-intense Laser Pulse With Solid Target

During the interaction of ultra-short and ultra-intense laser pulse with plasmas, high energy electrons will be produced near to critical-density surface. When the hot electrons knocked out inner-shell electrons of the cold material, Kαcharacteristic lines emission will be excited. Kαemission is closely correlated with the hot electrons'action. From Kαlines emission, we can find some useful information of hot electron, such as its production and transport in overdense plasmas. On the other hand, such Kαemission has widely potential applications, especially for chatacteristic pulse light source, owing to its compactness and high fluence. For the motivation referred above, we carried out the ITS code and experimental studies on the Kαcharacteristic lines emssion.In this paper, it was firstly started with the model and significance of the fast ignition and strong field. Secondly, the interaction of laser with plasma and the production of hot electrons were expatiated. Thirdly, the principle of caculation and its experiment setup of Kαline, and were introduced. Finally, the ITS code used to calculate the line intensity of Kα, and the experimental result were introduced.By using the ITS code, it were calculated the Kαline intensities of some solid targets. The result indicates that: 1) The line intensity of Kαdecreases as the angle with the normal direction of the target increases; 2) there is an optimal thickness which make the line intensity of Ka biggest; 3) when the temperature of hot electrons exceed a definite value, the line intensity of Kαhas a little fluctuation around a certain numerical value.Combined with the measurements of the yield of Kαphoton at the UI-US laser facility in the China Academy of Engineering Physics (CAEP), the conversion efficiency of hot electron'was calculated about multilayer target. The temperature of the hot electrons is diagnosed by characteristic lines emitting from a two-layer ?using the intensity ratio of Kαfluorescent target in combination with Monte-Carlo simulations. The temperatures of the hot electrons measured with this new method, are compared to our data measured by a magnetic spectrometer for the same shots. We find that a Monte Carlo model with a heuristic model for the electron injection gives a reasonable fit with our data. The results show that, by choosing appropriate fluorescent layer materials and the thickness, the temperature of the hot electrons inside the target can be measured by the intensity ratio of characteristic lines. ?...