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Large laser systems that deliver optical pulses with peak powers exceeding one Petawatt (PW) have been constructed at dozens of research facilities worldwide and have fostered research in High-Energy-Density (HED) Science, High-Field and nonlinear physics [1]. Furthermore, the high intensities exceeding 1018W/cm2 allow for efficiently driving secondary sources that inherit some of the properties of the laser pulse, e.g. pulse duration, spatial and/or divergence characteristics. In the intervening decades since that first PW laser, single-shot proof-of-principle experiments have been successful in demonstrating new high-intensity laser-matter interactions and subsequent secondary particle and photon sources. These secondary sources include generation and acceleration of charged-particle (electron, proton, ion) and neutron beams, and x-ray and gamma-ray sources, generation of radioisotopes for positron emission tomography (PET), targeted cancer therapy, medical imaging, and the transmutation of radioactive waste [2, 3]. Each of these promising applications requires lasers with peak power of hundreds of terawatt (TW) to petawatt (PW) and with average power of tens to hundreds of kW to achieve the required secondary source flux.

Overview of progress in construction and testing of the laser systems of ELI-Beamlines, accomplished since 2015, is presented. Good progress has been achieved in construction of all four lasers based largely on the technology of diode-pumped solid state lasers (DPSSL). The first part of the L1 laser, designed to provide 200 mJ

We have demonstrated the world's highest average power, fully diode-pumped, petawatt-class peak power laser, the High-repetition-rate Advanced Petawatt Laser System (HAPLS) [1-3]. These first commissioning results at 16J (stretched) at 3%Hz fully validate projected performance of 30J/30fs (>1PW) at 10Hz. The laser has been operated at this intermediate level at Lawrence Livermore National Laboratory to demonstrate integrated performance of all subsystems and provide benchmarking data to laser performance models before further increasing energy and peak power. Data was obtained during multiple campaigns, exceeding several hours of run time, and a snapshot of 60min of data is shown in Fig. 1. The average pump laser 1ω (1053nm) energy was 97J with an rms stability of 0.7%, 2ω (527nm) energy at the Ti:sapphire power amplifier was 62J, and the average stretched short pulse energy was 16J. A full-aperture diagnostic suite allows simultaneous, single-shot measurement of energy, spectrum, beam quality, and pulse duration at full repetition rate. Single-shot SPIDER retrieved pulse shapes (Fig. 1 inset) with an average pulse duration over 12000 consecutive shots of 28.6fs (rms=1.4fs). The mean pulse duration is consistent with the measured spectral bandwidth and is ∼1.2× the transform limit. All results shown are raw data without filtering or averaging, demonstrating the exceptional pulse characteristics, repeatability, and stability of the entire laser system.

The HAPLS laser system has been commissioned to its first integrated performance milestone, delivering laser pulses with 16J sub-30fs duration at a 3⅓Hz repetition rate. This first all-diode-pumped petawatt-class laser offers the average powers required for secondary source applications.

Phase 1 performance ramping of the HAPLS pump laser, a high-energy DPSSL based on Nd:glass, successfully produced 70J at 1053nm from a single aperture and 39J at 527nm using LBO frequency converter running at 3.3Hz repetition rate.

Initial performance ramping of the HAPLS pump laser, a high-energy DPSSL based on Nd:glass, produced 70J at 1053nm from a single aperture and 39J at 527nm using LBO frequency converter all at 3.3Hz repetition rate.

This paper presents our conceptual design for laser drivers used in Laser Inertial Fusion Energy (LIFE) power plants. Although we have used only modest extensions of existing laser technology to en...

A high average power diode pumped solid state laser is used to pump large aperture Ti:sapphire enabling high average power chirped pulse amplification. After compression, over a petawatt of peak power will be used to generate fusion ions and neutrons for materials testing of first wall and final optics candidates.

Hundred-joule, kilowatt-class lasers based on diode-pumped solid-state technologies, are being developed worldwide for laser-plasma interactions and as prototypes for fusion energy drivers. The goal of the Mercury Laser Project is to develop key technologies within an architectural framework that demonstrates basic building blocks for scaling to larger multi-kilojoule systems for inertial fusion energy (IFE) applications. Mercury has requirements that include: scalability to IFE beamlines, 10 Hz repetition rate, high efficiency, and 10 9 shot reliability. The Mercury laser has operated continuously for several hours at 55 J and 10 Hz with fourteen 4 x 6 cm 2 ytterbium doped strontium fluoroapatite amplifier slabs pumped by eight 100 kW diode arrays. A portion of the output 1047 nm was converted to 523 nm at 160 W average power with 73% conversion efficiency using yttrium calcium oxy-borate (YCOB).

Industrial and Scientific High Energy Laser Systems with output energies in the Joule to Megajoule range typically rely on flash lamps to energize the gain media. Especially in rep rated laser systems the advantage of low capital cost per lamp is outweighed by many disadvantages, such as low pump efficiency, heating of the gain medium, frequent maintenance requirement, significant capital cost for its pulsed power system, and laser performance stability. Diode Pumped Solid State Laser (DPSSL) systems represent a viable alternative. In this paper we will present an efficient, integrated power conditioning system developed for the High-Repetition-Rate Advanced Petawatt Laser System (HAPLS) that is being developed by LLNL for deployment in the international user facility Extreme Light Infrastructure Beamlines (ELI-Beamlines) in Czech Republic [1]. The High Energy Pump Laser of HAPLS is energized by 4 High Peak Power Laser Diode Arrays with total peak power of 3.2 MW that were developed by Lasertel and LLNL. The diode arrays deliver ∼1kJ at repetition rate 10Hz. Each diode array is comprised of 40 individual diode tiles where every tile generates >20 kilowatts of peak power. Each tile is driven by a single pulser that contains its own energy storage, control and high current drive circuitry. As part of the HAPLS laser the pulsers are operated at approximately 520A, a pulse width of 300μs at 10Hz. In another LLNL laser system basically identical pulsers are operated at 315A, 300us at 120Hz. The pulsers were designed to be operated in a support frame called a pulser crate. Each crate is designed to hold up to 45 pulsers in a volume similar to a desktop computer. Communication with the pulsers is by means of a one-way digital optical link which greatly simplifies the internal wiring. Each crate contains a “Brain Box” which in turn contains the front end processor (FEP), machine safety system (MSS) and energy storage dump subsystems. Providing flexibility and system balancing capability each pulser can be tailored to the diode tile: it has an internal Arbitrary Waveform Generator (AWG) on board that controls the shape of the diode current pulse. The AWG can vary the pulse shape in any combination of programmable increments with resolutions 1A and 1μs up to maximums of 1kA and 350μs. Under command of the crate controller each pulser can create its own distinct waveform and deliver that waveform when triggered.

We report on the operation of the Mercury laser with fourteen 4 × 6 cm 2 Yb:S-FAP amplifier slabs pumped by eight 100 kW peak power diode arrays. The system was continuously run at 55 J and 10 Hz for several hours, (2 × 10 5 cumulative shots) with over 80% of the energy in a 6 times diffraction limited spot at 1.047 μm. Improved optical quality was achieved in Yb:S-FAP amplifiers with magneto-rheological finishing, a deterministic polishing method. In addition, average power frequency conversion employing YCOB was demonstrated at 50% conversion efficiency or 22.6 J at 10 Hz.

Operation of the Mercury laser with two amplifiers has yielded 30 Joules at 1 Hz and 12 Joules at 10 Hz with over 8x10{sup 4} shots on the system. Static distortions in the Yb:S-FAP amplifiers were corrected by a magneto-rheological finishing technique.

This year fusion ignition and gain are expected on the National Ignition Facility at LLNL. The pathway to inertial fusion energy begins by addressing high average power operation of the diode pumped solid state laser system, target chamber, target injection and tracking, target mass production, blanket, and the balance of plant. To meet efficiency requirements, the power conditioning for the laser diodes must be compact and efficient. A diode pulser has been designed to meet these specifications, operate efficiently, and provide a means to minimizing cost and size for the estimated 4.4 million pulsers needed for a power plant.

Laser systems deployed in Inertial Fusion Energy power plants will usher in space qualified laser engineering and materials on a massive scale. Understanding subsystem efficiencies and component Mean Time Between Failure (MTBF) are critical for success.

We have commissioned a turnkey 500 mJ, 10 Hz front end laser. The system delivers temporally and spectrally tailored pulses to correct signal distortions within itself or subsequent amplifiers from single longitudinal mode to 250 GHz RF bandwidth.

The Mercury laser will be used to pump a high average power Ti:sapphire chirped pulse amplifier which will produce a compressed peak power >1 petawatt at 10 Hz.

We have produced over 500 mJ using a hybrid fiber-based master-oscillator system coupled with a Yb:S-FAP power amplifier. This system is designed with spatial, temporal, and spectral sculpting enabling broadband amplification correctable for gain narrowing.

The Mercury laser project is part of a national inertial fusion energy program in which four driver technologies are being considered including solid-state lasers, krypton fluoride gas lasers, Z-Pinch and heavy ions. Mercury's operational goals of 100 J, 10 Hz, 10% efficiency in a 5 times diffraction limited spot will demonstrate the critical technologies required for scaling the system to the multi-kilojoule level. Five one hour runs were conducted to assess system stability and reliability; energy fluctuations during the 55 J operations showed a 0.6% rms deviation. Current beam quality during average power operation is approximately 10 times diffraction limited. In the future, active wavefront control, and corrector plates for steady state thermal distortions will be implemented to achieve the 5 times diffraction limited spot.

The scope of the Mercury Laser project encompasses the research, development, and engineering required to build a new generation of diode-pumped solid-state lasers for Inertial Confinement Fusion (ICF). The Mercury Laser will be the first integrated demonstration of laser diodes, crystals, and gas cooling within a scalable laser architecture. This report is intended to summarize the progress accomplished during the first three years of the project. Due to the technological challenges associated with production of 900 nm diode-bars, heatsinks, and high optical-quality Yb:S-FAP crystals, the initial focus of the project was primarily centered on the R&D in these three areas. During the third year of the project, the R&D continued in parallel with the development of computer codes, partial activation of the laser, component testing, and code validation where appropriate.

We report on the progress in developing and building the Mercury laser system as the first in a series of a new generation of diode- pumped solid-state Inertial Confinement Fusion (ICF) lasers at Lawrence Livermore National Laboratory (LLNL). Mercury will be the first integrated demonstration of a scalable laser architecture compatible with advanced high energy density (HED) physics applications. Primary performance goals include 10% efficiencies at 10 Hz and a 1-10 ns pulse with 1 omega energies of 100 J and with 2 omega/3 omega frequency conversion.

We present the results of performance modeling of diode-pumped solid state laser beamlines designed for use in Laser Inertial Fusion Energy (LIFE) power plants. Our modeling quantifies the efficiency increases that can be obtained by increasing peak diode power and reducing pump-pulse duration, to reduce decay losses. At the same efficiency, beamlines that use laser slabs of Yb:YAG or Yb:S-FAP require lower diode power than beamlines that use laser slabs of Nd:phosphate glass, since Yb:YAG and Yb:S-FAP have longer storage lifetimes. Beamlines using Yb:YAG attain their highest efficiency at a temperature of about 200K. Beamlines using Nd:phosphate glass or Yb:S-FAP attain high efficiency at or near room temperature.

A LIFE laser driver needs to be designed and operated which meets the rigorous requirements of the NIF laser system while operating at high average power, and operate for a lifetime of >30 years. Ignition on NIF will serve to demonstrate laser driver functionality, operation of the Mercury laser system at LLNL demonstrates the ability of a diode-pumped solid-state laser to run at high average power, but the operational lifetime >30 yrs remains to be proven. A Laser Technology test Facility (LTF) has been designed to specifically address this issue. The LTF is a 100-Hz diode-pumped solid-state laser system intended for accelerated testing of the diodes, gain media, optics, frequency converters and final optics, providing system statistics for billion shot class tests. These statistics will be utilized for material and technology development as well as economic and reliability models for LIFE laser drivers.

The laser system has predicted performance of 8100-J at 16-Hz with 18% wallplug efficiency. This laser also has broad industrial applications including materials processing, and Chirped-Pulse-Amplification pump/amplifier sources which in turn can produce secondary radiation sources.

Several large scale laser applications require diode pumps for high efficiency and average power, but are sensitive to diode performance-cost tradeoffs. This paper describes approaches for addressing these issues, using the example of inertial fusion energy drivers.

Laser operations with two amplifiers activated produced 35 Joules at 1 Hz, 12 Joules at 10 Hz, and 8x104 total system shots. Static distortions in the Yb:S-FAP amplifiers were corrected by magneto rheological finishing technique.