Invention and application of chirped pulse amplification technique in short pulse laser has been leading to unprecedented ultra high laser peak power. After more than three decade development, a few petawatt class lasers, whose pulse durations vary from a few femtoseconds to several picoseconds, have been built up around the world. The focused laser intensity goes beyond 1021W/cm2. The ultra-intense and ultra-short pulse laser has wide applications, such as high energy ion acceleration, laser wakefield acceleration, ultra fast x-rays, and fast ignition. The first multi hundred terawatt laser (SILEX-I) started operating in Laser Fusion Research Center, CAEP in 2004. This first high peak power laser facility was followed by an even larger scale laser facility “Xingguang-Ⅲ”, which is capable to output three synchronized laser pulses of femtosecond, picosecond, and nanosecond pulse durations. In 2016, the third ultra-high power laser “CAEP-PW”, of 4.9 petawatt and 18 femtosecond duration, was commissioned. The laser contrast of “CAEP-PW” reaches higher level thanks to the employment of the complete OPCPA technique. The contrast ratio is better than 1010 20 ps before the main pulse. After the setup of target area of CAEP-PW, the first experimental investigation started in June, 2017. The main results are reported in this presentation.
The basic experiments focused on the characterization of laser foil target interaction. A comprehensive diagnostics were fielded around the targets. A set of experimental data, including spatial resolved x-ray emission, the image of the coherent transition radiation, the harmonic spectra in reflective direction, the energy spectra and beam profile of accelerated ions, hot electron spectra, and transmitted laser energy fraction and distribution, were collected. From the complete data set, the on-target laser spot size, intensity, and prepulse level were estimated. It’s confirmed that the laser intensity reached 5×1020W/cm2 with a 5.8 µm focus (FWHM) and 30 femtosecond pulse duration. The high contrast laser guaranteed that laser transmission did not occur through the CH foil of thickness larger than 50 nm. When S-polarized laser was obliquely impinged on the 50 nm thick CH foil, the protons energy up to 40 MeV were observed in the laser direction, which was about two times higher than that in the target normal direction.
Key words: Multi petawatt, femtosecond laser, OPCPA, ion acceleration, laser plasmas interaction
Acknowledgement: This work was supported by the Science Challenge Project (No. TZ2017005) in China.
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|Working group||Laser-driven ion acceleration|