1. About the possibility to build a 10-PW femtosecond laser for ELI-NP till 2015 Razvan Dabu National Institute for Lasers, Plasma and Radiation Physics Bucharest Workshop ELI-NP, Bucharest, March 11, 2011

2. A.Basic solution: High energy CPA in Ti:sapphire crystals. B. Back-up solution: CPA in mixed Nd doped glasses (silicate & phosphate glasses) Possible solutions for a 10-PW femtosecond laser system At present, both solutions involve technical difficulties and bottlenecks Workshop ELI-NP, Bucharest, March 11, 2011

3. Solution A – bottlenecks and technical difficulties: 1.Large size Ti:sapphire crystals. 2.Large size, high damage threshold compression gratings. 3.Broad bandwidth high damage threshold high reflection dielectric coatings. 4.Optically synchronized Front-End including high energy and high repetition rate Yb:YAG pump lasers for OPCPA. 5.High repetition rate pump lasers for power amplifiers (including technical solutions, large size LBO crystals for SHG, beam homogenizers). 6.Large size adaptive optics. Workshop ELI-NP, Bucharest, March 11, 2011

4. Solution B – bottlenecks and technical difficulties: 1. High energy short pulse amplification with sufficient bandwidth to generate pulses of ~ 100 fs pulse duration. 2. Pulse compression of high energy (>1 kJ) pulses (tiled system with high damage threshold multilayer dielectric gratings). 3. High intensity contrast (> 10^12) of the focused beams. 4. Thermal management of Nd:glass media for good repetition rate (1 pulse/min – 1 pulse/10 sec). 5. Large size mirrors. 6. Large size adaptive optics. Workshop ELI-NP, Bucharest, March 11, 2011

5. If we consider an optimistic probability of 80% for each of these 6 problems to be resolved in the next 2-3 years, the probability to overcome the whole system bottlenecks and technical difficulties is 26% until 2014. For 90% → 53% Moreover, there is an engineering question: it is possible to accomplish the laser system development in the remaining time till the end of 2015? It seems unlikely. Risk evaluation Workshop ELI-NP, Bucharest, March 11, 2011

6. I. There is an entity (Company, Research Institute, International Consortium, etc.) able to assume the risk to build till 2015 a laser system with the following specifications? Peak power ≥ 10 PW Central wavelength: in the range 700-1100 nm Pulse duration: < 150 fs Repetition rate: higher than 1 pulse/min (higher than 1 pulse/10 s?) Intensity contrast ≥ 10^12 Strehl ratio ≥ 0.6 Peak intensity of the focused beam ≥ 10^23 W/cm2. Delivery time ≤ 48 months under contract terms including: - milestones; - deliverables; - acceptance tests; - guarantee, penalties, repayment guarantee, etc. Workshop ELI-NP, Bucharest, March 11, 2011 Project implementation – version I

7. II. Two-stage project implementation (in the frame of an International Consortium managed by a Company with experience in femtosecond laser systems manufacturing?): First stage: contract for a 2- 4 PW (?) laser system development, based on already existing techniques at T 0 (project start moment), with the deadline on the end of 2013 - middle of 2014 year. Second stage: In the meantime (till 2014) and after 2014, R&D to build a multi-PW laser with the target to reach 10 PW in 2015 or later. Workshop ELI-NP, Bucharest, March 11, 2011 Project implementation – version II

8. CONCLUSIONS 1.Without delay: discussions with the potential producers to find out if there is some entity able to assume the risk of building a 10-PW laser system under a contract based on well established conditions. 2.In case of a negative answer, to apply the two-stage project implementation. Workshop ELI-NP, Bucharest, March 11, 2011