The direct drive laser is the key factor in hybrid drive inertial confinement fusion. Its drive asymmetry has a great influence on the ignition performance of nuclear fusion. Using the same laser power, the impacts of the direct drive laser focal spot size on the ignition performance of a hybrid drive model are studied. It is shown that the size of the laser focal spot is a key parameter to influence the ignition performance of the hybrid drive model. When the size of the laser focal spot is 1 500 μm, the neutron yield of the target is close to the one got by the one dimensional implosion. When the 1 400 μm laser focal spot is used, the neutron yield is 40% of the one got by the one dimensional implosion. However, it is failed to ignite for the 1 200 μm laser focal spot. The high drive asymmetry caused by the small laser focal spot can increase the adiabat in the fuel. The fuel compressibility will decrease when the adiabat is increased, which goes against creating the ignition condition. In this way, the ignition wave is weak. Meanwhile, the high drive asymmetry can lead a high perturbation of the fuel areal density. The perturbation growth of the fuel areal density can make the shell asymmetry grow greatly when the ignition wave is formed. Under the conditions of the weak ignition wave and the high fuel areal density perturbation, the fuel spike with a high density is hard to be ignited. Therefore, the positive feedback between the increase of hotspot temperature and the ignition is restrained. Meanwhile, the fuel spike can decrease the hotspot temperature. The fuel bubble can lead the hotspot expand rapidly. All these factors will make the ignition performance decrease when a small laser focal spot is used.

We report new progress in hybrid-drive (HD) ignition target design with a high-adiabat (>3.0) and high-velocity (>400 km·s^-1). First, two-shock indirect-drive (ID) radiation temperature with lower peak 200 eV ablates and pre-compresses the capsule. Later, direct-drive lasers of power 340 TW in flat-top pulse are absorbed near critical surface, combined with the radiation to drive the implosions. The "snowplow" effect in the HD heaps low ID corona density into a high HD plasma density at the radiation ablation front where maximal HD pressure reaches over 500 Mbar. Such high pressure further drives capsule imploding with peak velocity about 424.5 km·s^-1 and fuel aidabat about 3.4, and the high-velocity and high-adiabat lower the hotspot pressure required to ignition lower to about 200 Gbar at a low convergent ratio 23 to suppress hydrodynamic instabilities. 2D simulation also predicts the growth factor (GF) at hotspot is very small < 10, beneficial for a robust hotspot and further burn.