{"id":368,"date":"2018-08-22T14:16:01","date_gmt":"2018-08-22T05:16:01","guid":{"rendered":"http:\/\/www-wp22.ile.osaka-u.ac.jp\/?page_id=368"},"modified":"2018-12-17T15:03:49","modified_gmt":"2018-12-17T06:03:49","slug":"lfex","status":"publish","type":"page","link":"http:\/\/www-wp22.ile.osaka-u.ac.jp\/eng\/facilities\/lfex\/","title":{"rendered":"LFEX Petawatt Laser"},"content":{"rendered":"
The first phase of the FIREX (Fast Ignition Realization Experiment), referred to as FIREX-1, was drawn up with the aim of enhancing and refining existing heating lasers in order to heat fusion fuels up to 5\u201310 keV, the temperature range required for nuclear fusion. Consequently, construction of the heating LFEX (Laser for Fast Ignition Experiment) [2] began in the fiscal year 2003. The laser was designed to meet the following specifications: an output of 10 kJ in a 1\u201310 ps pulse width; a wavelength of 1.05 \u03bcm; a cone-focused spot diameter of 30 \u03bcm\u03c6. As such, the LFEX is a unique, ultra-high intensity laser, and is expected to be applied to experiments relating not only to nuclear fusion, but also to relativistic plasma interactions and laser-induced nuclear physics<\/p>\n
Initially, seed light from a femtosecond fiber oscillator with a suitable spectral band (90 fs, 100 MHz, electrically synchronized) is amplified by three-stage optical parametric amplification (OPCPA), yielding a chirped light output with an energy of at least 40 mJ, and a spectral width of 6 nm at 6 Hz. Then, the diameter is expanded from 10 mm to 25 mm, and the light is four-pass amplified by two glass rod amplifiers (diameter 50 mm). Furthermore, the light is branched into four beams, where each beam is amplified by each of two rod amplifiers and then directed into the main amplifier. The main amplifier is an amplifier composed of eight units connected in series; each unit contains laser glass slabs (LHG8, 46 cm \u00d7 81 cm \u00d7 4 cm) arranged in a 2 \u00d7 2 array structure (Fig. 1). The maximum aperture size is 40 cm \u00d7 40 cm, and the resulting beam size is 35 cm \u00d7 35 cm.<\/p>\n
After four-pass amplification, the laser light is then reflected by the end mirror and directed into a Faraday rotator, where the polarization is rotated. The Faraday rotator is combined with a thin-film polarizer to form an optical isolator to protect the amplifier from the light reflected off the target irradiated by a focused beam.<\/p>\n