S. Telford

The mercury project : A high average power, gas-cooled laser for inertial fusion energy development

Abstract 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 109 shot reliability. The Mercury laser has operated continuously for several hours at 55 J and 10 Hz with fourteen 4 × 6 cm2 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).

Compact, Efficient Laser Systems Required for Laser Inertial Fusion Energy

Abstract 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 ensure near-term feasibility, predicted performance meets or exceeds plant requirements: 2.2 MJ pulse energy produced by 384 beamlines at 16 Hz, with 18% wall-plug efficiency. High reliability and maintainability are achieved by mounting components in compact line-replaceable units that can be removed and replaced rapidly while other beamlines continue to operate, at up to ˜13% above normal energy, to compensate for neighboring beamlines that have failed. Statistical modeling predicts that laser-system availability can be greater than 99% provided that components meet reasonable mean-time-between-failure specifications.

ELI-Beamlines: development of next generation short-pulse laser systems

Overview of the laser systems being built for ELI-Beamlines is presented. The facility will make available high-brightness multi-TW ultrashort laser pulses at kHz repetition rate, PW 10 Hz repetition rate pulses, and kilojoule nanosecond pulses for generation of 10 PW peak power. The lasers will extensively employ the emerging technology of diode-pumped solid-state lasers (DPSSL) to pump OPCPA and Ti:sapphire broadband amplifiers. These systems will provide the user community with cutting-edge laser resources for programmatic research in generation and applications of high-intensity X-ray sources, in particle acceleration, and in dense-plasma and high-field physics.

A Laser Technology Test Facility for Laser Inertial Fusion Energy (LIFE)

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.

Engineering diode laser pumps for extremely large-scale laser systems

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.

HIGH AVERAGE POWER PETAWATT LASER PUMPED BY THE MERCURY LASER FOR FUSION MATERIALS ENGINEERING

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.

Full System Operations of Mercury: A Diode Pumped Solid-State Laser

Abstract Operation of the Mercury laser with two amplifiers has yielded 30 Joules at 1 Hz and 12 Joules at 10 Hz with over 8x104 shots on the system. Static distortions in the Yb:S-FAP amplifiers were corrected by a magneto-rheological finishing technique.

Compact, efficient, low-cost diode power conditioning for laser inertial fusion energy

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.

Power scaling of Ti:Sapphire amplifiers: Design of a high average power Temto-Petawatt laser

A large-aperture high-average-power gas-cooled Ti:sapphire slab pumped by the Mercury laser is the final amplifier in a chirped pulse amplification chain capable of producing a compressed peak power >1 petawatt and peak intensity >1023 W/cm2.

Commissioning results of the world's first diode-pumped 10Hz PW laser

We have demonstrated the worlds 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.