Demonstration of counter beam fast heating scheme by using a spherical CD shell target

We report fast heating of a shock-imploded core under counter beam configuration that published in recent [Y. MORI et al., Phys. Rev. Lett. 117, 055001 (2016)]. Experiments are performed by using a repetitive IFE driver HAMA [Y. MORI et al., Nucl. Fusion 53, 073011 (2013)]. Experiments results show that (i) a shock-imploded core with 70 micron diameter, originally deuterated polystyrene (CD) spherical shell of 500 micron diameter, is flashed by counter irradiating 110 fs, 7 TW laser pulses. The coupling efficiency from the laser to the core emission was inferred 13{\%}. A collisional Particle-In-Cell simulation code PICLS2D indicates a possibility that counter hot electron currents generate magnetic filaments in the imploded core. (ii) Fast electrons with energy bellow a few MeV might be trapped by these filaments in the core region supposed to be contributing to the observed X-ray flash and the high coupling efficiency. These results indicate a possibility that counter irradiating fast heating scheme can improve the energy coupling into the core by hot electrons those are limited to less 10{\%} for one-side irradiation fast heating conducted so far.