218 / 2023-04-15 22:50:25

Experimental evidence of coronal plasma expansion inhibition with uranium-based hohlraum wall

hohlraum,coronal plasma,uranium,Thomson scattering

惯性约束聚变物理学 > 惯性约束聚变物理学-海报

Uranium-based hohlraums are known to have the advantages of lower M-band emission fraction and higher radiation temperature during main pulse, compared to traditional gold hohlraums. This research shows another potential advantage of uranium as an alternative hohlraum wall material. An experiment was conducted to study the temperature, density and motion characteristics of uranium coronal plasmas. The results show that the uranium-based hohlraum wall naturally has the effect of inhibiting the expansion of coronal plasmas, which benefits to symmetry control in a cylindrical hohlraum with multiple cones of incident lasers. The experiment adopts neopentane-filled, straight-through hohlraums (Φ2.8mm×2.0mm) without capsules insides. The hohlraum wall is set to be pure gold, or 5μm uranium lined with 0.1μm or 0.7μm uranium nitride as antioxidant coating. The plasma temperature, density, velocity and components are diagnosed by ultraviolet Thomson scattering from a region 500μm off the hohlraum wall. The X-ray emission images of coronal plasmas are recorded by an X-ray framing camera at 16° relative to the hohlraum axis. The motions of coronal plasmas are compared between gold and uranium at initial gas-fill pressure of 0.2atm and 0.3atm. Both cases show that the expansion velocity of uranium is ~10% less than gold, where the results from Thomson scattering and X-ray imaging are self-consistent. Besides, the thickness of the uranium nitride liners is shown to have little influence on the coronal plasma motion.