Bunching Lens Technology For High Brightness Soft X-ray Source

Soft X-ray is the electromagnetic wave which photon energy ranges from 50 eV to 1500 eV and wavelength ranges from 0.83 nm to 24.8 nm. High brightness soft X-ray sources can be used to study the effect between soft X-ray and matters and ablation of the material, establish dark cavity model, it can also be used to calibrate soft X-ray detection systems,equipments and devices. Therefore all countries in the world are establishing higher brightness soft X-ray sources actively. The task of this paper is to design the soft X-ray lens, combine it with Z-pinch plasma radiation source, use the lens for the collection,transmission and convergence of soft X-ray, access high brightness soft X-ray source and study the transmission characteristics of lens under high power density incident soft X-ray condition.X-ray capillary is the basic component of the lens. In China, scientists have done a large number of researches on X-ray capillary in Beijing Synchrotron Radiation Facility 3W1B beam and other sources of radiation, but power density of the incident soft X-ray isn't high enough. In order to optimize soft X-ray lens design, first, we do research on measuring transmission efficiency with the power density range of 6×10~6-1.5×10~7 W/cm~2 for the X-ray capillary on Qiang-Guang I facility. It is shown that, for the capillary manufactured of glass DM308, basically, the power density of the soft X-ray that comes out of the capillary is linear with power density of the incidence soft X-ray; when the power density of the incidence soft X-ray is 1.2×10~7 W/cm~2, the average transmission efficiency is 16.3%. For the Z-Pinch radiation source, when the incident power density is below 1×10~8 W/cm~2, soft X-ray and plasma fragment can't destroy the X-ray capillary.According to the above results, we optimize lens design parameters through numerical simulation, the best design parameters are shown as follows: the lens consists of 2401 X-ray capillaries with external diameter of 0.60 mm and inside diameter of 0.45 mm, the distance between lens entrance and Z-pinch target is 200 mm, the total lens length is 410 mm and focal distance is designed to be 50 mm. We suppose Z-pinch plasma radiation source's luminous zone length is 20 mm, X-ray energy is E=1 keV and peak power is 0.5 TW, then the numerical simulation shows that the power density 8.96×10~8 W/cm~2 of soft X-ray with diameter of 2.5 mm can be obtained in the focal spot, the overall transmission efficiency of the lens is 11.71%.We make soft X-ray lens and combine it with high temperature plasma radiation which is produced on Qiang-Guang I facility. It is shown that, when the power density of the incident soft X-ray is 1.0×10 W/cm~2, the average transmission efficiency of lens is 9.6%, the power density at focal spot during focusing increases by a factor of 131, at the distance of 672 mm from the source the lens will give power density as the same of that of the source without lens produces at the distance of 58.8 mm. The power density 1.15×10~9 W/cm~2 of soft X-ray source without plasma fragment can be obtained at focal point. The lens can also be used repeatedly.