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(IF/1) Research on Imploded Plasma Heating by Short Pulse Laser for Fast Ignition

R. Kodama¹⁾, K. Mima¹⁾, Y. Kitagawa¹⁾, K. Fujita¹⁾, N. Miyanaga¹⁾, H. Nishimura¹⁾, N. Izumi¹⁾, H. Habara¹⁾, A. Sunahara¹⁾, Y. Sentoku²⁾, M. Heya³⁾, H. Fujita¹⁾, M. Mori¹⁾, H. Yoshida¹⁾, T. Jitsuno¹⁾, Y. Izawa¹⁾, M. Murakami¹⁾, K. Nishihara¹⁾, T. Yamanaka^1)
 
1) Institute of Laser Engineering of Osaka University, Osaka, Japan
²⁾ Institute of Laser Technology, Osaka, Japan
³⁾ Institute of Free Electron Laser, Osaka, Japan

Abstract.  Since the peta watt module (PWM) laser was constructed in 1995, investigated are heating processes of imploded plasmas by intense short pulse lasers. In order to heat the dense plasma locally, a heating laser pulse should be guided into compressed plasmas as deeply as possible. Since the last IAEA Fusion Conference, the feasibility of fast ignition has been investigated by using the short pulse GEKKO MII glass laser and the PWM laser with GEKKO XII laser. We found that relativistic electrons are generated efficiently in a preformed plasma to heat dense plasmas. The coupling efficiency of short pulse laser energy to a solid density plasma is 40% when no plasmas are pre-formed, and 20% when a large scale plasma is formed by a long pulse laser pre-irradiation. The experimental results are confirmed by numerical simulations using the simulation code ``MONET'' which stands for the Monte-Carlo Electron Transport code developed at Osaka. In the GEKKO XII and PWM laser experiments, intense heating pulses are injected into imploded plasmas. As a result of the injection of heating pulse, it is found that high energy electrons and ions could penetrate into imploded core plasmas to enhance neutron yield by factor 3$\sim$5.

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