ABSTRACT
Performance of the novel high repetition rate HF-PW laser system of ELI ALPS is presented in its first operation phase at 400 TW and 700 TW levels. Long-term operation was tested at 2.5 and 10â Hz repetition rates, where an exceptional 0.66% and 1.08% shot-to-shot energy stability was demonstrated, respectively. Thorough spatio-spectral and temporal measurements confirmed high quality output pulses with a Strehl ratio of >0.9 after compression at both repetition rates. Amplified pulses with an unprecedentedly high 240 W average power were reached for the first time from a PW-class amplifier chain by using novel pseudo-active mirror disk amplification-based pump lasers.
ABSTRACT
With the recent advances in ultrahigh intensity lasers, exotic astrophysical phenomena can be investigated in laboratory environments. Collisionless shock in a plasma, prevalent in astrophysical events, is produced when a strong electric or electromagnetic force induces a shock structure in a time scale shorter than the collision time of charged particles. A near-critical-density (NCD) plasma, generated with an intense femtosecond laser, can be utilized to excite a collisionless shock due to its efficient and rapid energy absorption. We present electrostatic shock acceleration (ESA) in experiments performed with a high-density helium gas jet, containing a small fraction of hydrogen, irradiated with a 30 fs, petawatt laser. The onset of ESA exhibited a strong dependence on plasma density, consistent with the result of particle-in-cell simulations on relativistic plasma dynamics. The mass-dependent ESA in the NCD plasma, confirmed by the preferential reflection of only protons with two times the shock velocity, opens a new possibility of selective acceleration of ions by electrostatic shock.
