J-KAREN-P laser approached the diffraction-limited , bandwidth-limited Petawatt

The J-K AREN laser faci l i ty [1] del ivered a single-shot ontarget intensity of 1021 W/cm2 with a temporal contrast of ~1012. J-K AREN has been upgraded to J-K AREN-P to real ize petawatt (PW) peak-power pulses on target at a repetition rate of 0.1 Hz with an intensity capabil i ty of over 1022 W/cm2. Such progress in high-field science wil l give rise to new applications and breakthroughs, including relativistic particle acceleration, bright X -ray source generation, and nuclear activation. M any other interesting features can be investigated with PW and higherintensity laser pulses, including relativistic transparency and radiation friction. J-K AREN-P is shown schematical ly in Fig. 1. The output pulses with high temporal contrast and uniform spatial profi le from the power amplif ier [1] are up-coll imated and enter booster amplifier 1 (BA1), which uses an 80-mm-diameter Ti:sapphire crystal pumped with ~50 J from two commercial Nd:glass green lasers at a repetition rate of 0.1 Hz. The pulses from BA1 are then amplified in booster amplifier 2 (BA2), which uses a 120-mmdiameter Ti:sapphire crystal pumped with ~100 J from four commercial Nd:glass green lasers at 0.1 Hz. A deformable mirror is instal led in the laser chain to correct the wavefront distortion. The amplif ied pulses are up-coll imated to a diameter of ~250 mm, and final ly, compressed in the compressor consisting of four 1,480 grooves/mm gold-coated gratings of 565 × 360 mm2. A maximum output energy of 23 J was achieved with an incident pump energy of 47 J with a good conversion efficiency of 49% from BA1. The near-field beam profi le has a homogeneous and uniform spatial intensity distribution. The amplified spectrum from the Ti:sapphire amplif iers is red-shifted because of saturation. As a mitigating measure, the amplifier input spectrum is blue-shifted by tuning the phase-match setting of the BBO crystals in the OPCPA ampli fier. Figure 2 shows the measured dependence of the output broadband energy from BA2 on the total pump energy at a repetition rate of 0.1 Hz. A maximum output energy of 63 J is achieved with an incident energy of 92 J. The figure clearly shows that the experimental data fi t the simulation. Figure 3 shows the typical spatial profi le of the laser beam from BA2. The profile has a homogeneous and uniform intensity distribution (Fig. 3(a)). A fter BA2, the wavefront distortions are corrected using a deformable mirror. The beam is then sent into the pulse compressor. The measured spectrum has a bandwidth of ~50 nm (FWHM ). The recompressed pulse duration is obtained as less than 30 fs. The peak power is expected to be over PW at 0.1 Hz on target because the beam-line throughput from the laser room to the target chamber including the compressor is ~60%. With an f/1.3 off-axis parabolic mirror, according to measurements of the focal spot and encircled energy, a peak intensity of 1022 W/cm2 is achievable with a power level of 0.3 PW [2] (Fig. 3(a)). The contrast is measured with a third-order cross correlator for the laser pulse without pumping the booster amplifiers, as shown in Fig. 4. The contrast earlier than 200 ps before the main pulse is 3 × 10−12 (detection l imited). At 100, 50, 10, and 5 ps before the main pulse, the contrast is roughly 10−11, 6 × 10−10, and 8 × 10−9, respectively. Laser-driven acceleration via the interaction of short, intense laser pulses with matter is known as laser-plasma acceleration. Compared to radio-frequency accelerators, it features higher accelerating electric f ields, shorter acceleration distances, and shorter bunch lengths. Laser acceleration of protons [3] and electrons with the J-KAREN-P laser system is being tested. Currently, protons in excess of 50 M eV [4] are obtained with ~1021 W/cm2 and GeV-class electrons are obtained with ~1020 W/cm2. We wil l optimize the target and increase the laser intensity gradually while checking the total system. Laser-plasma acceleration can replace the front end of a conventional accelerator system and would help greatly in downsizing accelerator systems, especial ly for heavy ions [5] . A lso, in progress are experiments on (i) high-order harmonics from relativistic singularities [6,7] , (i i ) multi-M eV pure proton beam generation from micro-size hydrogen cluster targets [8] , and (i i i ) X -ray spectroscopy of laser-plasma interaction in the ultrarelativistic regime [9] . From national laboratories to university departments, ultrahigh-intensity lasers have evolved to become one of the most important scienti fic tools for studying matter in extreme states. The J-KAREN-P laser system is a leading faci l i ty in the provision and application of ultra-high-intensity lasers for the broad scienti f ic community. I t has been used in various pioneering and cutting-edge studies, which has resulted in high-impact discoveries for high-field science. Multi -PW lasers are now being constructed for specif ic applications in many fields ranging from proton therapy for cancer treatment to the simulation of astrophysical phenomena. The next generation of lasers wil l approach exawatt (EW =