Impact Fast Ignition as Another Pathway to Laser Fusion M. MURAKAMI Institute of Laser Engineering, Osaka University, Japan In collaboration with ILE (Japan) T. Sakaiya, H. Saito, H. Azechi, K. Otani, T. Watari, K. Takeda, D. Ichinose, H. Hosoda, S. Fujioka, K. Shigemori, M. Nakai, H. Shiraga, H. Nagatomo, A. Sunahara, and K. Mima NRL (USA) M. Karasik, J. Gardner, J. Bates, D. Colombant, J. Weber, Y. Aglitskiy, A. Velikovich and S. Obenschain Outline of this talk １）Introduction & present status 2）Impact Ignition 3）Super-high velocity experiment 4) Integrate target experiment 1 Schematic picture and features of Impact Fast Ignition Target ILE Osaka Requirement for Ignition Impactor: Kinetic energy → Thermal energy 1 3 mi v 2 2 T ( T = 5 keV ) 2 2 v = 1000 km/s Momentum Pcore v 2 ( Pcore 2.2a core , a = 3, core = 200 g/cc) 5 3 = 5 g/cc Feature of Impact Fast Ignition (IFI) 1. Simple physics 2. High gain 3. Low cost Ref. M. Murakami and H. Nagatomo, Nucl. Instrum. Meth. Phys. Res. A 544, 67 (2005). Gain curve expected for Impact Fast Ignition 1kg/cc (1000 times the solid density) compression has been demonstrated Azechi et al., Laser& Particle Beams 1990 Density measurement with a Cu witness foil impactor X-ray Cu-foil UV emission from rear surface Of the witness foil Phys. Rev. Lett. 92 (2004) 195001 Suppression of RT instability Rayleigh-Taylor instability is suppressed by the radiation from ILE Osaka doped high-Z material. Suppression technique of Rayleigh-Taylor (RT) instability ・High-Z doping (CHBr): Ref. S. Fujioka et al., Phys. Rev. Lett. 92, 195001 (2004). t = 3.5 ns t = 2.6 ns CH 40 µmt CHBr(3%) 13.5 µmt 2D sim.: J.H.Gardner @NRL By controlling the Br-dope, we could optimize the acceleration performance. CHBr targets Laser energy: 1.5 kJ Reference: CH 2.5 mg/cm2 190 km/s (300 km/s) #29527 350 km/s #29517 CHBr 3% 300 mm 2 ns 2 ns #29529 #29535 400 km/s (600 km/s) CHBr 0.3% 400 km/s (550 km/s) 300 mm 2.5 mg/cm2 1.7 mg/cm2 We have observed a maximum velocity, 650 km/s, ever achieved The super-high velocity of 1000 km/s seems to be achievable with appropriate ablator/pulse design. Integrated experiment The impactor of hemispherical fuel impacts to the pre-compressed main fuel. ILE Osaka Experimental condition Main fuel: Laser: 2w, E = 3 kJ, 1.3 ns-Gaussian shape Target: CD shell 7 mmt, 500 mmf Impactor: Laser: 2w, I ~ 200 TW/cm2 , 1.3 ns-Gaussian shape Target: hemispherical CD 10 mmt, 500 mmf Experimental procedure The plastic scintillators were arranged in various directions. ILE Osaka Experimental setup (Top view) 2 3 Plastic scintillator 178 cm 52° 18 cm f × 2.5 cm Target chamber 25° 190 cm Pb 10 cm 80° 168° 4 311 cm 47 cm Pb Target 6 cm 1 Plastic scintillator 10 cm f × 5 cm Experiment results Neutrons are very likely to have thermal origin. ILE Osaka Energy (MeV) Neutron yield Distance: 47 cm Angle: 168° Angle( 168゜): 1.8 × 106 ±15% Angle( 25゜) : 1.6 × 106 ±13% Angle( 80゜) : 1.8 × 106 ±19% Angle( 52゜) : 2.0 × 106 ±13% X rays Signal (V) Distance: 190 cm Angle: 25° ・Neutron emission is isotropic. ・No significant energy shift. X rays Distance: 311 cm Angle: 80° Thermal neutrons X rays Distance: 178 cm Angle: 52° Flying time (ns) With the impact effect, neutron yield has been enhanced by a factor of about 100. Impact fast ignition has potential as an alternative approach to inertial fusion energy. Summary 1. Super-high velocity of 640 km/s has been achieved experimentally. v > 1000km / s 2. In-flight density of 0.2-0.8 g/cm3 has been achieved experimentally. > 3 - 5 g / cm3 3. In the first integrated experiment, it was observed that neutron yield is enhanced by a factor of 100 due to the impact effect. 4. These results show that the Impact Fast Ignition has a high potential as another path way to laser fusion.