The ILIL-PW laser installation features a high power Chirped Pulse Amplification laser, with power up to 240 TW, and multi-purpose interaction area with radiation shielding. An overview of the ILIL-PW facility is shown in Figure 1, while a summary of the main laser parameters is given in the table of Table 1. The laser Front-end room and Power Amplifier room are located between the two experimental target areas. The Front-end pulse can be compressed and sent to the 10 TW Target area where two target chambers are available, currently featuring respectively a short focal length focusing from F/5 down to F/5 and a long focal length up to F/15. Alternatively, the uncompressed Front-end pulse can be delivered to the power amplifier room where it is further amplified and delivered to the Shielded target area where a separate, larger compressor is in place to compress the pulse. A vacuum transport line connects the compressor with an octagonal vacuum chamber inside the concrete shielded target area.
The 10-Hz front-end is shown schematically in the Figure below, with the oscillator producing 15 fs pulses atapproximately 6 nJ. A “booster” unit amplifies the oscillator pulse to the 10 J level and is followedby a stretcher that delivers a chirped pulse with a duration of 600 ps to the regenerative amplifier.The mJ energy pulse is further amplified by a 5-pass amplifier followed by a 4-pass amplifier, finally delivering 600 mJ at 800 nm.
The output pulses of the front-end are then transported to the final 4-pass amplifier, pumped by four Nd:YAG lasers (Titan6 by Amplitude Technologies) delivering a total of 24 J pulses (currently 12 J) at 532 nm at a maximum rep-rate of 5 Hz (currently 1Hz). The 800-nm pulse is thus amplified up to 7.9 J (currently 4.5 J) and compressed down to <25 fs. Pulse duration control is achieved through standard techniques based on acousto-optical devices (Dazzler and Mazzler) placed in the front-end to achieve control of spectral gain, phase, and amplitude. The pulse energy losses due to acousto-optics devices are compensated in the amplification stages. Pump fluence throughout the front-end system is kept below 1 J/cm2 to operate well below the Ti:Sa crystal damage threshold , yielding a typical energy extraction efficiency of less than 30%. This amplifier uses a water-cooled 50 mm x 50 mm x 30 mm Ti:sapphire crystal with anti-reflection coating on both faces. The amplified pulse is up-collimated to 65 mm before entering the attenuator, incorporating a rotating λ/2 waveplate and two high performance broadband 72° polarizers and allowing a precise energy control. The beam is then up collimated to its final 100 mm diameter before entering the final compressor.
The main consists of four 1480-groove/mm gratings and a retro-reflector. The throughout efficiency of the compressor is about 75% yielding a compressed pulse of 5 J (currently3.3 J). After compression, pulse duration of 25 fs can be achieved, corresponding to a pulse peak power of 240 TW (currently 130 TW).