1. Introduction . The development of petawatt lasers has recently moved towards increased robustness, more stable pulse parameters, higher repetition rates and decreased pulse duration to obtain ultrahigh peak intensity on target. BELLA, the first rep-rated petawatt laser was implemented in Berkeley Lab, which after upgrades is able to produce 40 J pulses with 30 fs duration at 1?Hz [ 1 ]. Similar performance was achieved in HZDR, where the DRACO PW laser can produce 20 J with 30 fs pulse...