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For the purpose towards to ignition based on Laser inertial confinement fusion(ICF), the traditional indirect drive scheme proposed to create an extremely high hot-spot pressure up to ~350Gbar at stagnation phase and makes it ignited. On the other hand, the high compression ratio implosion(Cr~35) design was necessary while the driven pressure was just around 100Mbar and limited by ~300eV radiation temperature or peak laser power (Phot- spot~ Cr3*Pdriven). And then, hydrodynamic instability become serious and makes ignition difficult.
Hybrid drive that combined with indirect drive and direct drive was proposed few years ago[1]. The hybrid drive scheme can increasing driven pressure few times based on “snowplow” effect and make the implosion compression ratio decreased to 25 in numerical simulations and make the hybrid drive scheme become robust.
The experiment of driven pressure enhancement was performed on ShenGuang Laser facility. The target was a half-cylindrical hohlraum with 1500micro length and 2500micro diameter. 20 laser beams as indirect-drive beam with 15TW/3ns were inject into hohlraum and create 200eV radiation. 4 laser beams as direct-drive beam with 4TW/2ns and 2ns delay were interaction on the sample that mounted on the bottom of half-hohlruam. The sample was consisted with three layers: CH as an ablator, Al as an preheating barrier and Quartz as a window. The diagnostic using VISAR for shock velocity history measurement. The experimental result show that the indirect-drive shock velocity was 43.6km/s, hybrid-drive enhanced shock velocity was 83.8km/s, respectively. The experimental result compared with simulation well. The driven pressure of hybrid drive is up to 150Mbar and 3.6times than 200eV radiation driven only.
[1] X.T.He, et al. Phys.Plasmas 23,082706(2016)
